CHAPTER 4 - PRESENT WEATHER

Ch. 4 Pg. 1

ADDITIONAL MATERIAL TO STUDY: Chapter 9, paragraphs 9.2.1c, d, e, & f, present weather criteria for SPECI

4.1 Introduction

This chapter provides information concerning the identifying, recording, reporting, and coding of present weatherconditions.

4.2 Present Weather

Present weather includes precipitation, obscurations (obstructions to visibility), well-developed dust/sand whirls,squalls, tornadic activity, thunderstorms, sandstorms, and duststorms. The table below gives the abbreviationsused to report atmospheric phenomena.

Table 4-1. Notations for Reporting Present WeatherQUALIFIER WEATHER PHENOMENA

INTENSITY ORPROXIMITY

1

DESCRIPTOR

2

PRECIPITATION

3

OBSCURATION

4

OTHER

5

Light

Moderate (no symbol used)

+ Heavy

VC In the Vicinity

MI Shallow

PR Partial

BC Patches

DR Low Drifting

BL Blowing

SH Shower(s)

TS Thunderstorm

FZ Freezing

DZ Drizzle

RA Rain

SN Snow

SG Snow Grains

IC Ice Crystals

PL Ice Pellets

GR Hail (> 1/4 inch)

GS Small Hail and/or Snow Pellets (5/8SM)

FG Fog (

Ch. 4 Pg. 2

4.2.1 Precipitation

Precipitation is any form of water particles, whether in liquid or solid state, that fall from the atmosphere andreach the ground. Precipitation that reaches the ground can be an obscuration or obstruction to horizontalvisibility. The various types are:

a. Drizzle (DZ). Drizzle is a fairly uniform type of precipitation that is composed of fine drops with diametersof less than 0.02 inch (0.5 mm) that are very close together. Drizzle appears to float while following aircurrents. Unlike fog droplets, drizzle does fall to the ground.

b. Rain (RA). Rain comes in two forms. The first is in the form of drops larger than 0.02 inch (0.5 mm). Thesecond can have smaller drops, but unlike drizzle, they are widely separated. It does not fall to the groundlike drizzle.

c. Snow (SN). This type of precipitation contains crystals, most of which are branched in the form of six-pointed stars.

d. Snow Grains (SG). This precipitation contains very small, white, and opaque grains of ice similar instructure to snow crystals. It is the solid equivalent of drizzle. When the grains hit the ground, they do notbounce or shatter. They usually fall in small quantities, mostly from stratus, and never as showers.

e. Ice Crystals (Diamond Dust) (IC). Ice crystals are often so tiny that they seem to be suspended in the air. They may fall from a cloud or from clear air. Ice crystals are visible mainly when they glitter in the sunshineor other bright light. They are rarely more than the lightest precipitation, which occurs only at very lowtemperatures in stable air masses and are in the form of needles, columns, or plates.

f. Ice Pellets (PL). Ice pellets is a form of precipitation containing transparent or translucent pellets of icewhich are round or irregular in shape, rarely conical, and have a diameter of 0.2 inch (5 mm) or less. Thereare two types. The first is hard grains of ice consisting of frozen raindrops or largely melted and refrozensnowflakes. The second type consists of pellets of snow encased in a thin layer of ice which have formedfrom the freezing of droplets intercepted by pellets or of water resulting from the partial melting of pellets. The pellets usually rebound when striking hard ground and make a sound on impact.

g. Hail (GR). Hail is small balls or other pieces of ice falling separately or frozen together in irregular lumps.

h. Small Hail and/or Snow Pellets (GS). This type of precipitation consists of white, opaque grains of icewhich are round or sometimes conical. Their diameters range from 0.08 to 0.2 inch (2 to 5 mm). They arebrittle and easily crushed. When they fall on hard ground they bounce and often break up.

4.2.2 Obscurations

Obscurations or obstructions to visibility can be any phenomenon in the atmosphere that reduce horizontalvisibility. The various kinds are: (not including precipitation)

a. Mist (BR). A visible aggregate of minute water particles suspended in the atmosphere that reduces visibilityto less than 7 statute miles but greater than or equal to 5/8 statute miles.

b. Fog (FG). A visible aggregate of minute water particles (droplets) which are based at the earth's surfaceand reduce the horizontal visibility to less than 5/8 statute miles. Fog does not fall to the ground like drizzle. Fog with a qualifier (see paragraph 4.4.2) can be reported if the visibility is 5/8 mile or more.

c. Smoke (FU). Small particles produced by combustion that are suspended in the air. This phenomenonmay be present either near the Earths surface or in the free atmosphere. When viewed through smoke, thedisk of the sun at sunrise and sunset appears very red. The disk may have an orange tinge when the sun isabove the horizon. A transition to haze may occur when smoke particles have traveled great distances (25

Ch. 4 Pg. 3

miles or more) and, when the larger particles have settled out, the remaining particles have become widelyscattered through the atmosphere.

d. Volcanic Ash (VA). Fine particles of rock powder that have erupted from a volcano and remainsuspended in the atmosphere for long periods of time producing red sunsets and climatic modificationsthousands of miles away. Volcanic Ash is always reported when it is present regardless of the visibility.

e. Widespread Dust (DU). Fine particles of earth or other matter raised or suspended in the air by the windthat may have occurred at or away from the station.

f. Sand (SA). Particles of sand raised to a sufficient height that reduces visibility.

g. Haze (HZ). A suspension in the air of extremely small, dry particles invisible to the naked eye butsufficiently numerous to give it an opalescent appearance. This phenomenon resembles a uniform veil overthe landscape that subdues all colors. Dark objects viewed through this veil tend to have a bluish tingewhile bright objects, such as the sun or distant lights, tend to have a dirty yellow or reddish hue.

h. Spray (PY). An ensemble of water droplets torn by the wind from the surface of a large body of water,generally from the crest of waves, and carried a short distance into the air.

4.2.3 Other Weather Phenomena

a. Well-developed Dust/Sand Whirl (PO). An ensemble of particles of dust or sand, sometimes accompaniedby small pieces of litter, that is raised from the ground and takes the form of a whirling column with varyingheight, small diameter, and an approximate vertical axis.

b. Squall (SQ). The sudden onset of strong winds with speeds increasing by at least 16 knots and sustained at22 or more knots for at least one minute.

c. Funnel Cloud (FC). A violent, rotating column of air which does not touch the ground. It is one aspect oftornadic activity.

d. Tornado (+FC). A funnel cloud that touches the ground. It is one aspect of tornadic activity.

e. Waterspout (+FC). A funnel cloud that forms over a body of water and touches the water's surface. It isone aspect of tornadic activity.

f. Sandstorm (SS). Particles of sand carried aloft by strong winds. For the most part, the particles are foundat the lowest ten feet. Rarely do they rise to more than 50 feet above the ground.

g. Duststorm (DS). A severe weather condition characterized by strong winds and dust-filled air over a largearea.

4.3 Present Weather Reporting Order

When more than one type of present weather is reported at the same time, they are reported in the followingorder:

! Tornadic activity, i.e., Tornado (+FC), Waterspout (+FC), or Funnel Cloud (FC).! Thunderstorm(s) (TS) with or without associated precipitation.! Present weather in order of decreasing dominance, i.e., the most dominant type is reported first.

Precipitation will always be reported before obscurations.! Left to Right in Table (Column 1-5)

Ch. 4 Pg. 4

Reporting order of precipitation, obscurations, and other: (1) Precipitation in the order of decreasing dominance(maximum of 3 types within this group) with or without qualifiers; (2) Obscuration(s) in the order of decreasingdominance if more than one; (3) Other, excluding Funnel Cloud, Tornado, and Waterspout.

No more than three weather groups shall be used to report weather phenomena at or near the station.

4.4 Weather Observing Standards

Weather shall be defined by qualifiers. These qualifiers fall into two categories: intensity or proximity anddescriptors. Qualifiers may be used in various combinations to describe present weather phenomena. Morerefined definitions are as follows:

a. Intensity. Intensity qualifiers are the terms light, moderate and heavy. These terms vary in their meaningdepending on the type of precipitation they are describing. The coding of intensity for weather phenomenais placed in front of the associated weather and is used only once. Intensity shall be coded withprecipitation types, except ice crystals and hail, including those associated with a thunderstorm (TS) andthose of a showery nature (SH). No intensity is ascribed with the precipitation hail (GR), small hail (GS),or ice crystals (IC) and the obscuration of blowing dust (BLDU), blowing sand (BLSA), and blowingsnow (BLSN). Only moderate or heavy intensity is ascribed to sandstorm (SS) and duststorm (DS). Thefollowing tables establish criteria for these qualifiers:

Intensity Criteria

Light Up to 0.10 inch per hour; maximum 0.01 inch in 6 minutes.

Moderate 0.11 inch to 0.30 inch per hour; more than 0.01 inch to 0.03 inch in 6 minutes.

Heavy More than 0.30 inch per hour; more than 0.03 inch in 6 minutes.

Table 4-2. Intensity of Rain or Ice Pellets Based on Rate-of-Fall

Intensity Criteria

Light From scattered drops that, regardless of duration, do not completely wet an exposedsurface up to a condition where individual drops are easily seen.

Moderate Individual drops are not clearly identifiable; spray is observable just above pavementsand other hard surfaces.

Heavy Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray toheight of several inches is observed over hard surfaces.

Table 4-3. Estimating Intensity of Rain

Intensity Criteria

Light Scattered pellets that do not completely cover an exposed surface regardless ofduration. Visibility is not affected.

Moderate Slow accumulation on ground. Visibility reduced by ice pellets to less than 7statute miles.

Heavy Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3statute miles.

Table 4-4. Estimating Intensity of Ice Pellets

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Intensity Criteria

Light Visibility > 1/2 mile.

Moderate Visibility > 1/4 mile but

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10 SM VCSH 10SM VCSH

VCFG

Any type of precipitation, of any intensity, (e.g. Drizzle-DZ, Rain-RA, Snow-SN, Snow Grains-SG, Ice Pellets-PL, Hail-GR or GS), not occurring at the point of observation, but within 10 statute miles is reported as showersin the vicinity (VCSH). Simply, if its not falling on your head, report VCSH.

Obscurations are reported in the vicinity of the station (VC) when they are located between 5 and 10 statutemiles of the point of observation.

Example: VCFG is coded to report any type of fog observed between 5 and 10 statute miles of the station.

Present weather coded in the body of the report as VC may be further described in remarks, i.e., direction fromthe station, if known. For example, the two examples of VCSH above could be further described in remarks as:VCSH N; or the above VCFG could have a remark of: VCFG NE.

daleRain

daleSnow

daleFOG

1 "Glaze" is a coating of ice, generally clear and smooth, but with some air pockets. It is formedon exposed objects at temperatures below or slightly above 0C by the freezing of super-cooled drizzleor rain drops. Glaze is denser, harder, and more transparent than rime.

Ch. 4 Pg. 7

c. Descriptors. These are qualifiers that further describe weather phenomena and are used with certain typesof precipitation and obscurations. The descriptor qualifiers used are: shallow, partial, patches, low drifting,blowing, shower(s), thunderstorm, and freezing; they are defined below:

(1) Shallow (MI). The descriptor shallow shall only be used to further describe fog that has little vertical extent (less than 6 feet).

(2) Partial (PR) and Patches (BC). The descriptors partial and patches shall only be used to further describe fog that has little vertical extent (normally greater than or equal to 6 feet but less than 20 feet), and reduces horizontal visibility, but to a lesser extent vertically. The stars may often be seen by night and the sun by day.

(3) Low Drifting (DR). When dust, sand, or snow is raised by the wind to less than 6 feet, low drifting shall be used to further describe the weather phenomenon.

(4) Blowing (BL). When dust, sand, snow, and/or spray is raised by the wind to a height of 6 feet or more, blowing shall be used to further describe the weather phenomenon.

(5) Shower(s) (SH). Precipitation characterized by the suddenness with which they start and stop, by the rapid changes of intensity, and usually by rapid changes in the appearance of the sky.

(6) Thunderstorm (TS). A storm produced by a cumulonimbus cloud that is accompanied by lightning and/or thunder.

(7) Freezing (FZ). When fog is occurring and the temperature is below 0C, freezing shall be used to further describe the phenomena. It is only applied to fog (FG) and never to mist (BR). When drizzle and/or rain freezes upon impact and forms a glaze1 on the ground or other exposed objects, freezing shall be used to further describe the precipitation.

Descriptors precede certain types of precipitation or obscurations. To describe blowing snow, you combineBL from the descriptor list and SN from the precipitation list. (The Weather Phenomena Matrix contains allthe acceptable combinations that can be used.) Blowing is a description of the precipitation type snow. Nointensity is ever assigned to blowing snow.

Example: 4SM BLSN

When blowing snow is observed with snow falling from clouds, both phenomena are reported, e.g.,SN BLSN. If there is blowing snow and the observer cannot determine whether or not snow is also falling,then BLSN shall be reported.

Only one descriptor can be used for each grouping of weather phenomena reported. It is important to note thatthunderstorm (TS) and shower (SH) are descriptors of the precipitation rather than being a part of the weatherphenomena category. Therefore, you will never see TS and SH in the same group. This does not mean thatshowers do not occur when thunderstorms are reported, e.g., the report may be TS SHRA. Remember,thunderstorms can be treated as weather, even though it is a descriptor.

Example: TSRA or TS SHRA

Ch. 4 Pg. 8

Remember, a thunderstorm can occur without precipitation, it is the only descriptor that can be treated as presentweather and may be reported without precipitation.

Example: 10SM TS

When light precipitation is occurring along with a thunderstorm, following the rule of intensity before descriptorputs the before the TS.

REMEMBER, THE INTENSITY REFERS TO PRECIPITATION, NOT THE DESCRIPTOR. THERE ISNO SUCH THING AS A LIGHT THUNDERSTORM.

Example: 3SM !TSRA

Using the same principle, when a + is placed in front of a TS it is not an indication of a heavy thunderstorm. Again, the intensity symbol relates to the precipitation not the descriptor. An intensity symbol is never used withTS if it is reported alone.

There are restrictions on the use of descriptors. The most significant restriction is - Descriptors will never beused with Mist (BR). A descriptor such as patches (BC) or partial (PR) used to describe fog (FG) will alwaysimply that the visibility within the phenomena meets the less than 5/8 statute mile criteria.

4.5 Present Weather Reporting Procedures

As noted above, weather phenomena fall into three categories: precipitation, obscurations, and other phenomena. The categories shall be combined with the qualifiers to identify the present weather that is reported when it isoccurring at, or in the vicinity of, the station and at the time of observation. These are reported in the body of thereport, column 9 on the MF1M-10C form, with a remark made in Remarks, column 14 on the MF1M-10Cform, if further description is needed. With the exception of volcanic ash (which is always reported whenobserved) and low-drifting dust, sand, and snow, obscurations are reported only when the prevailing visibility isless than 7 statute miles or considered operationally significant.

Keep in mind if your prevailing visibility is reduced to less than 7 statute miles there needs to be a presentweather group showing the reason for this condition.

4.5.1 Precipitation

Precipitation of any form shall be reported in the body of the weather report whenever it is observed to beoccurring at the point of observation. Precipitation not occurring at the point of observation, but within 10 statutemiles, shall likewise be reported in the body of the report as showers in the vicinity. Precipitation observed at adistance from the point of observation (beyond 10 statute miles) shall be reported as distant from the station inRemarks.

4.5.1.1 Determining and Reporting Precipitation

Determine the type of precipitation occurring at the point of observation in accordance with the definitions inparagraph 4.2.1. Report precipitation using symbols found in Table 4-1. A SPECI observation is requiredwhenever freezing precipitation (FZRA, FZDZ) or Ice Pellets (PL) begin, end, or change intensity. A SPECIobservation is also required when Hail (GR) begins or ends.

Ch. 4 Pg. 9

4.5.1.2 Determining the Character of Precipitation

The character of precipitation can be determined by using the follow definitions:

a. Continuous. Intensity changes gradually, if at all.

b. Intermittent. Intensity changes gradually, if at all, but precipitation stops and starts at least once within anhour.

c. Showery (a descriptor). Precipitation changes intensity, or starts and stops abruptly.

4.5.1.3 Determining and Reporting the Intensity of Precipitation

Use the tables in this chapter to determine the intensity of precipitation. Report the intensity of precipitation usingthe symbols in Table 4-1.

No intensity symbol is used with Hail (GR), Small Hail (GS), or Ice Crystals (IC).

4.5.1.3.1 Intensity of Rain

Use Table 4-2 as a guide to estimate the intensity of rain on the rate-of-fall basis if a recording gauge is available. Estimate that portion of the rate-of-fall associated with the rain if other precipitation is also occurring. If arecording gauge is not available, use Table 4-3 to estimate the intensity.

4.5.1.3.2 Intensity of Drizzle, Freezing Drizzle, Snow, Snow Grains

If any of these phenomena are occurring alone, use Table 4-5 to determine intensity on the basis of visibility. Ifoccurring with other precipitation or obscuration, estimate intensity and then use Table 4-6 to determine if yourestimate is valid. You cannot use Table 4-6 to estimate visibility. Use some other means to estimate intensitybefore using Table 4-6; e.g., size of flakes, accumulation. The intensity assigned will not be greater than thatdetermined using visibility criteria if any of the above were occurring alone. With or without other obscuringphenomena, +SN cannot be reported if the visibility is 5/16 or greater and SN cannot be reported if visibility is5/8 or greater.

4.5.2 Obscurations

Obscurations should be reported in the body of the report only if prevailing visibility is reduced to less than 7statute miles (or considered operationally significant), with the exception of fog. If a descriptor qualifier is used todescribe fog (MIFG, PRFG, BCFG), prevailing visibility can be greater than 6 statute miles. A proximityqualifier (in the vicinity, VCFG) is used to report any type of fog observed between 5 and 10 statute miles fromthe point of observation. Fog, without the use of any qualifier, shall be reported when the horizontal visibility isless than 5/8 statute mile. To report freezing fog, the visibility must be less than 5/8 statute miles and thetemperature less than 0C.

Obscurations when present with precipitation will be in a separate group following the precipitation and enteredin order of dominance, e.g., RA BR HZ.

2 These are local phenomena usually formed by radiation cooling of the air. It often forms firstin low lying areas.

3 May be reported with prevailing visibility of 7 statute miles or greater.

Ch. 4 Pg. 10

4.5.2.1 Determining and Reporting Obscurations

Shallow Fog2 (MIFG)3, which is reported when visibility at 6 feet above ground level is 5/8SM or more and theapparent visibility in the fog layer is less than 5/8SM. This fog has a vertical extent of less than 6 feet. MIFG must be occurring within 5 statute miles of the point of observation in order to be reported. IfShallow Fog is occurring between 5 and 10 statute miles of the point of observation it is reported as VCFG.

Partial Fog (PRFG)3, is fog covering part of the station and which extends to at least 6 feet above the ground,but not more than 20 feet and apparent visibility in the fog is less than 5/8 statute mile. A substantial part of thestation is covered by fog while the remainder is clear of fog. PRFG must be occurring within 5 statute miles ofthe point of observation in order to be reported as PRFG. If Partial Fog is occurring between 5 and 10 statutemiles of the point of observation it is reported as VCFG.

Patches of Fog (BCFG)3, are fog patches that randomly cover the station and which extends to at least 6 feet,but less than 20 feet above the ground and apparent visibility in the fog is less than 5/8 statute mile. BCFG mustbe occurring within 5 statute miles of the point of observation in order to be reported as BCFG. If Patches ofFog are occurring between 5 and 10 statute miles of the point of observation it is reported as VCFG.

Freezing Fog (FZFG) is reported when the air temperature is 0.1C or colder. This fog may produce a depositof ice known as rime ice. It is composed of grains separated by air, sometimes adorned with crystallinebranches. The visibility must also be less than 5/8 statute miles to report FZFG.

Obscurations that stand alone, i.e., do not have a qualifier (descriptor) attached, will only be reported when thevisibility is less than 7 miles or deemed operationally significant by the observer. Volcanic Ash (VA) is alwaysreported when observed regardless of the visibility.

Ch. 4 Pg. 11

10SM PRFG 10SM BCFG

Patches Fog: Indicates that patches of fog randomly Partial Fog: Indicates that a substantial part of thecover the station. station is covered by fog while the remainder is clear of fog.

Vicinity Fog (VCFG) is coded to report any type of fog observed between 5 and 10 miles of the station. Thisfog layer must meet the criteria for fog, i.e., the apparent visibility in the fog layer is less than 5/8 statute miles. Like VCSH it is reported in column 9 (Present Weather) and a remark is put in column 14 (Remarks) to furtherdescribe its location. For example, an area of fog is observed 8 statute miles northeast of the station, it would bereported as: VCFG in column 9 (Present Weather) and the remark VCFG NE would be included in column14 (Remarks). VCFG is never used to report fog that is occurring more than 10 miles from the station, i.e.,VCFG DSNT ALQDS is never used. The two terms are in contrast with each other. VCFG means fog isobserved between 5 and 10 mile of your station, DSNT means fog is being observed more than 10 miles fromthe station. Likewise, VCFG is never used to report fog that is occurring at your station, that is, within 5 statutemiles of the point of observation. An area of fog observed 11 statute miles east through south of the station wouldbe report as, FG BNK DSNT E-S in column 14, no entry would be made in column 9 (Present Weather) forthis event..

Mist versus Freezing Fog: BR, (Mist) which is wimpy fog, is used to report fog when it reduces visibility from 6statute miles to 5/8 statute miles. BR is reported as long as the visibility remains above 1/2 statute milesregardless of how low the temperature goes. At 79.0F (61.7C) if the visibility was reduced by fog to 5/8statute miles BR (Mist) would be reported as Present Weather. Mist is never coded with any descriptor.

Freezing Fog versus Fog: FZFG is used to report fog when 1) it reduces visibility 1/2 statute miles or less and 2)when the temperature is -0.1C or lower. FG, (Fog) is used to report fog when it 1) reduces visibility below 5/8statute miles and 2) when the temperature is 0.0C or higher.

If any type of fog, including mist is observed, the following flow chart can be used as an aid in determining andreporting the various types of fog.

daleFog

daleFog

daleFog

daleFog

Ch. 4 Pg. 12

If FOG is Visible

Within10 Miles? NO

Report inRemarks, e.g.,

FG BNK DSNTE-S

YES

Within5 Miles? NO VCFG

1

YES

6 Feet Deepor More? NO MIFG

1

YES

Fairly Uniformin All

Directions?NO

Is in aContinuous

Mass?

NO BCFG1

YES PRFG1

YES

Visibility LessThan 7 Miles? YES

Visibility LessThan 5/8 Mile? YES

TemperatureBelow Freezing?(0.1C or less)

YES FZFG

NO NO NO

No Report BR FG

1 - Should be further described in Remarks, e.g., VCFG W-N, MIFG NW-E,BCFG S AND W, PRFG OVR RWY 18. MIFG, PRFG, and BCFG may bereported if the prevailing visibility is 7 statute miles or greater.

Blowing Snow (BLSN) is considered an obscuration. It is reported in column 9 (Present Weather). Snowparticles are raised and stirred violently by the wind to moderate or great heights. Visibility is poor (6 miles orless), and the sky may become obscured when the particles are raised to great heights.

Drifting Snow (DRSN) is snow particles raised by the wind to small heights above the ground (less than 6 feet). Visibility is not reduced to below 7 miles at eye level, although, obstructions below this level may veiled or hiddenby the particles moving nearly horizontal to the ground. This criteria can also be applied to Drifting Dust(DRDU) and Drifting Sand (DRSA).

Blowing Dust (BLDU) is dust raised by the wind to moderate heights above the ground and restricting horizontalvisibility to less than 7 miles.

Blowing Sand (BLSA) is sand raised by the wind to moderate heights above the ground, reducing horizontalvisibility to less than 7 statute miles.

Blowing Spray (BLPY) is water droplets torn by the wind from a substantial body of water, generally from thecrests of waves and is raised in such quantities as to reduce the visibility at eye level to 6 miles or less. Spray isnever reported as a stand alone obscuration but always contains the descriptor for blowing (BL) attached.

dale>

dale

Ch. 4 Pg. 13

4.5.3 Other Weather Phenomena

Other weather phenomena will be reported in the body of the report when they are occurring at the time of theobservation.

Duststorm (DS) is the same as blowing dust, except visibility is reduced between 5/8 to 5/16 statute miles.

Heavy Duststorm (+DS) is the same as blowing dust, except visibility is reduced to less than 5/16 statute miles.

Sandstorm (SS) is the same as blowing sand, except horizontal visibility is reduced between 5/8 to 5/16 statutemiles.

Heavy Sandstrom (+SS) is the same as blowing sand, except horizontal visibility is reduced to less than 5/16statute miles.

4.5.3.1 Tornadic Activity

A SPECI observation is required whenever these phenomena are observed to begin or disappear. This reportmay be a single-element SPECI. The report shall contain the following items, if they are known:

a. Type (+FC or FC) in Column 9 and spelled out in Column 14 (TORNADO, WATERSPOUT, orFUNNEL CLOUD).

b. Location with respect to the station.

c. Direction toward which the phenomenon is moving. If this is unknown, enter MOV UNKN in Column14.

Tornadic activity shall be coded as the first remark after the RMK entry. For example, TORNADO 6 NEwould indicate that a tornado was 6 statute miles northeast of the station.

These elements should also appear in the remarks of the next METAR if not previously reported in a routinereport.

4.5.4 Thunderstorm

A SPECI observation is required when a thunderstorm, with or without precipitation, begins or ends.The report should include:

a. Type (TS).

b. Location of each storm center with respect to the station.

c. Direction toward which the storm is moving. Omit if unknown.

The previous elements (a and c) should also appear in the remarks of the next METAR if not previouslyreported in a routine report.

The beginning of a thunderstorm is the earliest time thunder is heard or lightning is observed at the station whenthe local noise level is sufficient to prevent hearing thunder. The ending of a thunderstorm shall be reported 15minutes after the last occurrence of any of the criteria listed above.

Ch. 4 Pg. 14

Thunderstorms (TS) are always reported when they occur. If precipitation is occurring at the time of observationat the point of observation (falling on you head) when a thunderstorm is occurring they should be combined toform one group, e.g., TSRA or TSSN or TSPL etc. If precipitation of any type, (Drizzle-DZ, Rain-RA,Snow-SN, Snow Grains-SG, Ice Pellets-PL, Hail-GR or GS) of any intensity is occurring at the time ofobservation but is not occurring at the point of observation (not falling on your head) when a thunderstorm isoccurring but is within 10 statute miles of the point of observation they should be reported in two separategroups, e.g., TS VCSH.

When a thunderstorm (TS) is reported in column 9 (Present Weather) a remark in column 14 should be made toindicate the location of the thunderstorm with respects to the station. If the movement of the thunderstorm isknown this should also be included in the column 14 remark. For example, if thunder is heard at the time ofobservation, no precipitation was occurring with the thunderstorm, the thunderstorm is located southeast of thestation, movement is toward the northeast, this would be reported as follows:

Column 9 = TS Column 14 = TS SE MOV NE

Thunder is heard at the time of observation, rain was occurring at the point of observation (falling on your head),the thunderstorm is located northwest of the station, movement is toward the northeast, this would be reported asfollows:

Column 9 = TSRA Column 14 = TS NW MOV NE

Thunder is heard at the time of observation, hail (GS) was occurring 1 statute mile north of the station but not atthe point of observation (not falling on your head), the thunderstorm is located north of the station, movement ofthe thunderstorm is not known, this would be reported as follows:

Column 9 = TS VCSH Column 14 = TS N VCSH N or TS N MOV UNKN VCSH N

4.5.5 Lightning

A luminous phenomenon accompanying a sudden electrical discharge. There are four main types of lightning thatcan be distinguished:

a. CLOUD TO GROUND (CG). Lightning occurring between cloud and ground.

b. IN-CLOUD (IC). Lightning which takes place within the thunder cloud.

c. CLOUD TO CLOUD (CC). Streaks of lightning reaching from one cloud to another.

d. CLOUD-AIR (CA). Streaks of lightning which pass from a cloud to air, but do not strike the ground.

The frequency at which lightning is occurring is also reported. The frequency is based on the number of flashes oflightning occurring per minute. There are three frequencies used in reporting lightning:

a. OCCASIONAL (OCNL). Less than 1 flash per minute.

b. FREQUENT (FRQ). About 1 to 6 flashes per minute.

c. CONTINUOUS (CONS). More than 6 flashes per minute.

When lightning is observed the frequency, type of lightning and location are reported in the Remarks section ofthe observation (column 14 on MF1M-10C). The remark shall be coded in the formatFrequency_LTG(type)_[LOC]. The location and direction shall be reported as VC when 5 to 10 statute miles

Ch. 4 Pg. 15

of the point of observation. For example, frequent cloud to ground lightning occurring 6 statute miles northeast ofthe station would be reported as: FRQ LTGCG VC NE. When phenomena is beyond 10 statute miles of thepoint of observation it shall be reported as distant (DSNT) followed by the direction from the station. Forexample, lightning 25 statute miles west of the station would be coded in remarks as: LTG DSNT W.

When a lightning remark is made when a thunderstorm is also being reported, the lightning remark will berecorded first followed by the remark elaborating on the thunderstorm being reported in Present Weather(column 9).

4.6 Other Significant Weather Phenomena

Observers shall be alert to weather phenomena that are visible from the station, but not occurring at the station. Examples are fog banks, localized rain, snow blowing over runways, etc. They shall be reported when they areconsidered to be operationally significant. Volcanic eruptions shall also be reported in the remarks section of areport.

4.7 Coding of Present Weather Group(s)

No more than three weather groups shall be used to report weather phenomena at or near the station. If morethan one significant weather phenomena is observed, separate weather phenomena groups shall be included inthe report. Precipitation will always be reported before obscurations. If more than one form of precipitation isobserved, the appropriate abbreviations shall be combined in a single group with the dominant type ofprecipitation being reported first. In such a single group, the intensity refers to the first precipitation type. Theprecipitation that follows will be of equal or lesser intensity. The construction of the group is done withconsideration of columns 1 to 5 in Table 4-1 Notations for Reporting Present Weather, in sequence, i.e.,intensity, followed by descriptor, followed by weather phenomena. For example heavy freezing rain and snowwith fog and haze would be coded as: +FZRASN FG HZ

The same is true if there is more than one type of obscuration. It is entered in the order of dominance. Anobscuration that is coded with another present weather group(s) is separated from it by a space.

Examples: 3/4SM TSRA BR 1/4SM TS VCSH FG 3SM BR FU HZ

Question: What does an observer do if there are more than three weather groups, or more than three types of precipitation are occurring?

Answer: The observer will decide which three groups and/or precipitation types are more dominant than the rest, these three groups or precipitation types will then be coded in the METAR/SPECI report in their order of dominance, the rest will not be reported.

Example: Occurring: TS RA SN BR FU HZ

Thunderstorms are always reported when they occur. Moderate rain and snow (precipitation) are consideredpart of the group that is coded with the thunderstorm, i.e., TSRASN or TSSNRA. This is one of the threegroups that may be reported. The choice now falls between the mist, smoke, and haze. Each is considered aseparate group. The observer needs to decide which is the least significant or which two are the most dominant.

The observer decides that smoke (FU) is least dominant, on this occasion. The present weather for this METARreport could be: TSRASN BR HZ or TSSNRA HZ BR. The smoke is not used in the report.

Example: Occurring: TS RA SN DZ GS BR

Ch. 4 Pg. 16

Thunderstorms are always reported when they occur. This time four types of precipitation are occurring, butonly three may be reported. The observer must decide which of these is the least dominant.

The choice for this observation is: TSSNRAGS BR

The light drizzle was considered least dominate this time and was not reported.

QUESTION: What does an observer do if there are two or more types of precipitation that might seem impossible to combine to make a single group?

Example: Occurring: FZDZ GS or SHRA GS or SN IC GS or TS RA SN GR or RA GS

ANSWER: All precipitation (maximum 3 types of precipitation) must be combined into a single group. Precipitation types GR, GS, and IC must be included into a single group if observed with other precipitation. Intensity is not considered with these types of precipitation. If there are more than three types of precipitation observed at the same time, you can only report three. The least dominant would have to be eliminated from the report.

The choice for these observations is: FZDZGS SHRAGS

SNICGS TSSNRAGR RAGS

QUESTION: How would an observer report the following weather conditions: Dry Bulb below 0.1 Celsius, Visibility reduced to 5/16 statute miles due to light snow, Fog/Mist, and Blowing Snow.

ANSWER: Precipitation is always reported before obscurations. The obscurations are next to be reported in the order of decreasing dominance, that is the more dominant obscuration is reported first. If the observer determines that the dominate obscuration is the Blowing Snow he could report SN BLSN BR. The requirement for reporting BLSN is that it

reduces visibility to less than 7 statute miles. This means it could reduce it down to zero. It also means it could have a greater effect on visibility than the BR. BLSN being reported as the most dominate obscuration followed by BR indicates that the mist is effecting visibility to a lesser degree.

Likewise with the above scenario, if the observer determines that the dominate obscuration is the Fog/Mist he would report this as: SN FZFG BLSN

If the observer reports BR as the first obscuration this would be saying that it is the most dominant or is effectingvisibility to a greater degree than the BLSN. BR allowable range of effect on visibility is 6 statute miles to 5/8statute miles. Also reporting BLSN after the BR means that it (BLSN) is effecting the visibility to a lesser degree. That is why with the above scenario reporting present weather as SN BR BLSN would NOT be correct.

QUESTION: How would an observer report an obscuring phenomena that reduces visibility in one or more sectors, however, the phenomena does not meet the criteria for reporting sector visibility, that is, the sector or prevailing visibility is not less than 3 statute miles, or if the phenomena is a fog type obscuration but does not meet the criteria to be classified as shallow, partial, or patches of fog, that is, the apparent visibility in the fog layer is not less than 5/8 statute miles.

Ch. 4 Pg. 17

Example: Prevailing visibility is 10 statute miles, however, a surface based smoke layer is reducingnorth through northeast sectors to 5 statute miles.

ANSWER: The criteria for reporting sector visibility has not be met and so is not reported. The remarkVIS LWR N-NE will let others know your visibility to the north-northeast is different than yourprevailing visibility.

QUESTION: How would an observer report the following condition? Light snow, light ice pellets, and lightfreezing drizzle are occurring at the time of observation. However, the observer feels that, of thethree precipitation types, the light snow has a greater presents.

ANSWER: Remember, the construction of the groups is done with consideration of columns 1 to 5 in Table4-1 Notations for Reporting Present Weather, in sequence, that is, intensity, followed bydescriptor, followed by weather phenomena. This means, that, by default the light freezing drizzlewould be reported first, followed by the light snow, followed by the light ice pellets, i.e.,FZDZSNPL.

The Weather Phenomena Matrix, found on the following two pages gives combinations of weather phenomenaand qualifiers (intensity, proximity, and descriptor) that are to be used in METAR/SPECI reports.

Ch. 4 Pg. 18

Weather Phenomena Matrix

WX PHENOMENA QUALIFIER

Intensity or Proximity Descriptor1

Precipitation

Light

Moderate Heavy

+

Vicinity

VC2

Shallow

MI

Partial

PR

Patches

BC

LowDrifting

DR3

Blowing

BL

Shower(s)

SH

Thunder-storm

TS4

Freezing

FZ

Drizzle DZ DZ DZ +DZ - - - - - - - - FZDZ

Rain RA RA RA +RA - - - - - - SHRA TSRA FZRA

Snow SN SN SN +SN - - - - DRSN BLSN SHSN TSSN -

Snow Grains SG SG SG +SG - - - - - - - - -

Ice Crystals5 IC - IC - - - - - - - - - -

Ice Pellets PL PL PL +PL - - - - - - SHPL TSPL -

Hail5,6 GR - GR - - - - - - - SHGR TSGR -

Small Hail5,7 GS - GS - - - - - - - SHGS TSGS -

Unknown UP Automated Stations Only - No - - - - - - - -

Thunderstorms, Showers, Freezing, and their Intensity or Proximity - - - - - - -

TS - - TS - VCTS8 - - - - - - - -

TSRA - TSRA TSRA +TSRA - - - - - - - - -

TSSN - TSSN TSSN +TSSN - - - - - - - - -

TSPL - TSPL TSPL +TSPL - - - - - - - - -

TSGS - - TSGS - - - - - - - - - -

TSGR - - TSGR - - - - - - - - - -

SH - - - - VCSH9 - - - - - - - -

SHRA - SHRA SHRA +SHRA - - - - - - - - -

SHSN - SHSN SHSN +SHSN - - - - - - - - -

SHPL - SHPL SHPL +SHPL - - - - - - - - -

SHGR - - SHGR - - - - - - - - - -

SHGS - - SHGS - - - - - - - - - -

FZDZ - FZDZ FZDZ +FZDZ - - - - - - - - -

FZRA - FZRA FZRA +FZRA - - - - - - - - -

FZFG - - FZFG - - - - - - - - - -

Obscurations - - - - - - - - - - - -

Mist10 BR - BR10 - - - - - - - - - -

Fog11 FG - FG11 - VCFG12 MIFG13 PRFG14 BCFG15 - - - - FZFG16

Smoke FU - FU - - - - - - - - - -

Volcanic Ash17 VA - VA17 - - - - - - - - - -

Widespread Dust DU - DU - - - - - DRDU BLDU - - -

Sand SA - SA - - - - - DRSA BLSA - - -

Haze HZ - HZ - - - - - - - - - -

Spray PY - - - - - - - - BLPY - - -

Blowing Phenomena - - - - - - - - - - - -

BLSN18 - - BLSN - VCBLSN - - - - BLSN - - -

BLSA - - BLSA - VCBLSA - - - - BLSA - - -

BLDU - - BLDU - VCBLD - - - - BLDU - - -

Other - - - - - - - - - - - -

Sand/Dust Whirls PO - PO - VCPO - - - - - - - -

Squalls19 SQ - SQ - - - - - - - - - -

Funnel Cloud FC - FC - - - - - - - - - -

Tornado/Waterspout2 +FC - - +FC - - - - - - - - -

Sandstorm 21 SS - SS +SS VCSS - - - - - - - -

Duststorm 22 DS - DS +DS VCDS - - - - - - - -

FOOTNOTES ON REVERSE SIDE

Ch. 4 Pg. 19

Footnotes for Weather Phenomena Matrix

1 - Only 1 descriptor shall be included for each weather phenomena group, e.g., BCFG. Only 2 exceptions exist to this rule: VCSHand VCTS.

2 - Vicinity is defined as >0SM (not at point of observation) to 10SM of the point of observation for precipitation. Other thanprecipitation (VCFG, VCBLSN, VCBLSA, VCBLDU, VCPO, VCSS, VCDS), vicinity is 5SM to 10SM.

3 - Raised by wind to less than 6 feet above the ground.

4 - TS may be reported by itself if no precipitation is associated with the thunderstorm.

5 - No intensity is ever given to hail (GR/GS[snow pellets]) or ice crystals (IC).

6 - Largest hailstone observed has a diameter of 1/4 inch or more.

7 - Hailstone diameter is less than 1/4 inch. No remark is entered for hailstone size.

8 - VCTS shall only be used by automated stations. Not a manual entry. If thunder is heard, TS shall be reported.

9 - Showers (SH), when associated with the indicator VC, the type and intensity of the showery precipitation shall not be specified,i.e., +VCSHRA is not allowed; only VCSH would be reported. VCSH shall be used to report any type of precipitation not atpoint of observation, but >0 to 10SM.

10 - BR (mist) shall only be used when the visibility is at least 5/8SM, but not more than 6SM.

11 - For FG (fog) to be reported without the qualifiers VC12, MI13, PR14, or BC15 the visibility shall be less than 5/8 SM.

12 - VC is used to report any type of fog observed in the vicinity (5-10SM) of the station.

13 - MIFG (shallow fog) to be reported, the visibility at 6 feet above ground level shall be 5/8SM or more and the apparent visibilityin the fog layer shall be less than 5/8SM.

14 - PRFG (partial fog) indicates that a substantial part of the station is covered by fog while the remainder is clear of fog.

15 - BCFG (patches fog) indicates that patches of fog randomly cover the station.

16 - FZFG is any fog consisting predominately of water droplets at temperatures below 0C, whether it is depositing rime or not. The visibility must be less than 5/8 statute miles to report FZFG.

17 - Volcanic Ash is always reported in the body of the METAR/SPECI when present. Visibility is not a factor.

18 - SN BLSN indicates snow falling from clouds with blowing snow occurring. If the observer cannot determine whether or notsnow is also falling from clouds, then only BLSN shall be reported.

19 - SQ (squall) is a sudden increase in wind speed of at least 16 knots, the speed rising to 22 knots or more and lasting for at leastone minute.

20 - Tornadoes and Waterspouts shall be reported using the indicator "+", i.e., +FC.

21 - SS (sandstorm) reported if the visibility is > 5/16SM and < 5/8SM. Report +SS if the visibility is < 5/16SM.

22 - DS (duststorm) reported if the visibility is > 5/16SM and < 5/8SM. Report +DS if the visibility is < 5/16SM.

No more than three weather groups shall be used to report weather phenomena at or near the station. If more than one significant weatherphenomena is observed, separate weather phenomena groups shall be included in the report. If more than one form of precipitation isobserved, the appropriate abbreviations shall be combined in a single group with the predominant type of precipitation being reportedfirst. In such a single group, the intensity shall refer to the total precipitation and be reported with one or no indicator as appropriate, e.g.,RASN FG HZ.

U.S. DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATIONNational Weather Service - Observing Systems Branch1325 East-West HighwaySilver Spring, MD 20910 METAR\TA3\1/23/98

Ch. 4 Pg. 20

VISIBILITY PRESENTWEATHER

SKY CONDITION TEMP.(C)

DEWPOINT(C)

ALTIMETERSETTING

(Ins.)

REMARKS AND SUPPLEMENTAL CODED DATA TOTALSKY

COVER(0-8)SUR-

FACETOWER RUNWAY VISUAL RANGE

(Feet)

(7a) (7b) (8) (9) (10) (11) (12) (13) (14) (17)

Report if Occurring at the Station at the Time of Observation

Tornado/Waterspout . . . . . . . +FC Ice Pellets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PL Ice Crystals . . . . . . . . . . . . . . . . IC

Funnel Cloud . . . . . . . . . . . . FC Ice Pellet Shower(s) . . . . . . . . . . . . . . . . . . . . . . SHPL Hail . . . . . . . . . . . . . . . . . . . . . . GRThunderstorm . . . . . . . . . . . . TS Small Hail/Snow Pellets . . . . . . . . . . . . . . . . . . . GS Hail Shower(s) . . . . . . . . . . . . . SHGRRain . . . . . . . . . . . . . . . . . . . RA Small Hail/Snow Pellets Shower(s) . . . . . . . . . . SHGS Low Drifting Dust . . . . . . . . . . DRDURain Shower(s) . . . . . . . . . . . SHRA Snow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SN Low Drifting Sand . . . . . . . . . . DRSAFreezing Rain . . . . . . . . . . . . FZRA Snow Shower(s) . . . . . . . . . . . . . . . . . . . . . . . . . SHSN Low Drifting Snow . . . . . . . . . DRSNDrizzle . . . . . . . . . . . . . . . . . DZ Snow Grains . . . . . . . . . . . . . . . . . . . . . . . . . . . . SG Volcanic Ash . . . . . . . . . . . . . . VA

Freezing Drizzle . . . . . . . . . . FZDZPrecipitation Intensity Symbols

+ Heavy Light

Absence of intensity symbol indicates moderate. No intensity is assigned to Ice Crystals, Hail, or Small Hail/Snow Pellets.

Report These Obscurations Only If They Reduce Prevailing Visibility To Less Than 7SM (or are considered operationalsignificant) And Are Occurring At The Time of Observation

Mist . . . . . . . . . . . . . . . . . . . BR Widespread Dust . . . . . . . . . . . . . . . . . . . . DU Blowing Sand . . . . . . . . . . . . . . . . . . . . BLSA

Smoke . . . . . . . . . . . . . . . . . . FU Blowing Dust . . . . . . . . . . . . . . . . . . . . . . . BLDU Blowing Snow . . . . . . . . . . . . . . . . . . . BLSN

Haze . . . . . . . . . . . . . . . . . . . HZ Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SA Blowing Spray . . . . . . . . . . . . . . . . . . . BLPYReport These Obscurations Only If They Reduce Prevailing Visibility To Less Than 5/8SM At The Time Of Observation

Fog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FG Freezing Fog (when temperature is 0.1C or lower) . . . . . . . . . . . FZFGReport These Obscurations Only If They Reduce Prevailing Visibility From 3/8SM to 5/8SM At The Time Of Observation

Sandstorm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SS Duststorm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DS+ Is placed before phenomena if it reduces visibility to 5/16 or less

Report These Obscurations Only If They Are Occur Within 5SM Of the Point of Observation At The Time Of Observation

Shallow Fog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MIFG Partial Fog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PRFG

Patches of Fog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BCFG Sand/Dust Whirls (Dust Devils) . . . . . . . . . . . . . . . . . . . . . . POReport if Any Type of Precipitation of Any Intensity not Falling On Your Head But Occurring within 10SM At The Time

Of Observation

Showers in the Vicinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCSHReport if Not Occurring At The Point of Observation But Is Occurring At A Location That is Between 5 to 10SM From The

Point of Observation At The Time Of Observation

Fog in the Vicinity . . . . . . . . . . . . VCFG Blowing Snow in the Vicinity . . . . . . . . VCBLSN Sand/Dust Whirls (DustDevils) in the Vicinity . . . . . . . VCPOSandstorm in the Vicinity . . . . . . . VCSS Blowing Sand in the Vicinity . . . . . . . . . VCBLSA

Duststorm in the Vicinity . . . . . . . VCDS Blowing Dust in the Vicinity . . . . . . . . . VCBLDU

Report If There Is A Sudden Increase In the Average Wind Speed By At Least 16 Knots and Sustained at 22 Knots or MoreFor At Least 1 minute

Squall(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SQ

Ch. 4 Pg. 21

VISIBILITY PRESENTWEATHER

SKY CONDITION TEMP.(C)

DEWPOINT(C)

ALTIMETERSETTING

(Ins.)

REMARKS AND SUPPLEMENTAL CODED DATA TOTALSKY

COVER(0-8)SUR-

FACETOWER RUNWAY VISUAL RANGE

(Feet)

(7a) (7b) (8) (9) (10) (11) (12) (13) (14) (17)

Tornado/Waterspout . . . . . . . . . . . . . . . . . +FCFunnel Cloud . . . . . . . . . . . . . . . . . . . . . . . . FC

. . . . . . . . . TORNADO, FUNNEL CLOUD, or WATERSPOUT (location) (movement); e.g., TORNADO W MOV NE. FUNNEL CLOUD 6 NW would indicate that a funnel cloud was 6 statute milesnorthwest of the station. WATERSPOUT MOV N would indicatethat a waterspout had ended and moved north.

Thunderstorm . . . . . . . . . . . . . . . . . . . . . . . . . TS . . . . . . . . . TS (location) (movement); e.g., TS SE MOV NE would indicate thata thunderstorm was southeast of the station moving toward thenortheast.

Hail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GR . . . . . . . . . GR (size); e.g., GR 1 3/4 would indicate that the largest hailstoneswere 1 3/4 inches in diameter

Sand/Dust Whirls (Dust Devils) . . . . . . . . . PO . . . . . . . . . PO (location); e.g., PO SE would indicate that dust devils aresoutheast of the station (within 5 statute miles).

Showers in the Vicinity . . . . . . . . . . . . . . VCSH . . . . . . . . . VCSH (location); e.g., VCSH S AND W would indicate that thereare showers in the vicinity south and west of the station (within 10 statute miles).

Fog in the Vicinity . . . . . . . . . . . . . . . . . . VCFG . . . . . . . . . VCFG (location); e.g., VCFG W-N would indicate that there was fogin the vicinity west through north of the station (within 5 to 10 statutemiles).

Shallow Fog . . . . . . . . . . . . . . . . . . . . . . . MIFGPartial Fog . . . . . . . . . . . . . . . . . . . . . . . . PRFGPatches of Fog . . . . . . . . . . . . . . . . . . . . . BCFG

. . . . . . . . . MIFG, PRFG, or BCFG (location); e.g., MIFG NW-E would indicate thatshallow fog was northwest through east of the station (within 5 statutemiles). PRFG OVR RWY 18 would indicate that partial fog was overrunway 18. BCFG N and SE would indicate that patches of fog were northand southeast of the station.

Sandstorm in the Vicinity . . . . . . . . . . . . . VCSSDuststorm in the Vicinity . . . . . . . . . . . . VCDS

. . . . . . . . . VCDS or VCSS (location); e.g., VCSS N-SE would indicate thatthere was a sandstorm in the vicinity north through southeast of thestation (between 5 to 10 statute miles).

Blowing Snow in the Vicinity . . . . . . VCBLSNBlowing Sand in the Vicinity . . . . . . . VCBLSABlowing Dust in the Vicinity . . . . . . . VCBLDU

. . . . . . . . . VCBLSN, VCBLSA, or VCBLDU (location); e.g., VCBLSN Swould indicate that blowing snow was in the vicinity south of thestation (between 5 to 10 statute miles.

Sand/Dust Whirls (Dust Devils) in the VicinityVCPO. . . . . . . . .

VCPO (location); e.g., VCPO SE would indicate that dust devels are in thevicinity southeast of the station (between 5 to 10 statute miles).

OTHER FREQUENTLY USED REMARKS

Lightning..........(Frequency [OCNL, FRQ, or CONS]) LTG (type [CG, IC,CC, or CA]) (location); e.g., OCNL LTGCGIC NW would indicate thatoccasional cloud-ground and in-cloud lightning northwest of the station

Fog beyond 10 statute miles from station..........FG BNK DSNT E-Sindicates there is a distant fog bank east through south of the station.

Entries made in column 9 that requireappropriate remarks in column 14

PRESENT WEATHER REMARKS

Ch. 4 Pg. 22

REVIEW QUESTIONS

Ch. 4 Pg. 23

1. The intensity indicators for rain are?

a. Light (), Moderate (0), Severe (+)b. Thin (), Moderate ( ), Heavy (+)c. Light (), Moderate ( ), Heavy (+)d. Light (), Medium ( ), Heavy (+)

2. Volcanic ash is reported:

a. when visibility is less than 7 milesb. only during daylight hoursc. whenever it occursd. only if accompanied by fog or mist

3. Precipitation is:

a. any particle falling from the skyb. any form of water particles that falls from the atmosphere and reaches the groundc. any form of water found at the earths surfaced. water in any state (liquid, solid, vapor) moving through the atmosphere

4. The beginning of a thunderstorm will be reported when:

a. thunder is heardb. lightning is observed, but local noise prevents hearing thunderc. observe lightning at a distance, but no thunder is heardd. both a and b

5. The visibility at your station was reduced from 12 miles to 7 miles by mist, light snow, and haze. What minimum entry should you make in column 9 (Present Weather)?

a. BR SN HZb. SN BR HZc. SN BRHZd. SN

6. Occassional lightning is observed 8 miles north of the station, but thunder is not heard. What is reported inColumn 9 (Present Weather) and Column 14 (Remarks)?

a. Col. 9: nothing; Col. 14: OCNL LTG VC Nb. Col. 9: TS; Col. 14: OCNL LTG Nc. Col. 9: VCTS; Col. 14: OCNL LTG Nd. Col. 9: VCTS; Col. 14 OCNL LTG 8 N

REVIEW QUESTIONS

Ch. 4 Pg. 24

7. Light Drizzle (DZ) is reported when drizzle is occurring with fog and the visibility is:

a. 1/4 to 1/2 mile.b. less than 1/4 mile.c. less than 1/2 mile.d. any of the above.

8. The ending of a thunderstorm shall be reported minutes after the last occurrence of the event.

a. 5 minutesb. 10 minutesc. 15 minutesd. 30 minutes

9. Which of the following precipitation events does not require a SPECI report?

a. Ice pellets begin.b. Hail begins.c. FZRA changes to FZRA.d. SN changes to +SN.

10. Ice formed on exposed surfaces by freezing rain or freezing drizzle is known as:

a. glazeb. frost.c. rime.d. ice pellets.

11. Report thunderstorms occurring at your station when is/are observed within the past 15 minutes.

a. very dark CB overhead and lightning in all quadrantsb. heavy rain showers and 55 knot windsc. heavy rain showers and 1/2 inch haild. 3/4 inch hail 20 minutes earlier, but not at the time of the observation

12. Moderate snow (SN) is reported when snow is occurring alone and the visibility is less than:

a. 5/8 of a mile, but not less than 5/16 of a mile.b. 3/4 of a mile, but not less than 5/16 of a mile.c. 5/8 of a mile, but not less than 1/8 of a mile.d. 1 mile, but not less than 1/2 mile.

13. A light intensity symbol () is never used to report:

a. ice crystals.b. ice pellets.c. snow showers.d. freezing drizzle.

REVIEW QUESTIONS

Ch. 4 Pg. 25

14. Which of the following phenomena may be classified as having heavy intensity?

a. Hailb. Thunderstormc. Funnel cloudd. Sandstorm

15. If more than one obscuration is occurring at the same time the obscurations will be entered in Column 9 (Present Weather) in the order of:

a. their beginning.b. decreasing dominance.c. increasing dominance.d. intensity.

16. A complex weather situation, represented by light rain showers, light snow showers (dominant), and a thunderstorm is present. Entries are made in the following order:

a. TS RASNb. TSSNRAc. TS SNRAd. TSSHSNRA

17. The weather phenomena FZRASN indicates which type of weather is occurring at the station?

a. Light freezing rain and snow.b. Light freezing rain and moderate snow.c. Freezing rain and light snow showers.d. Light rain showers and snow.

18. The visibility at your station was reduced from 12 miles to 7 miles by mist, light snow, and smoke. Whatis the minimum entry that should be made in Column 9 (Present Weather)?

a. SNb. SN BR FUc. BRd. BR SN FU

19. Blowing dust is reducing the prevailing visibility to 5/8 statute mile, what would be recorded in Column9 (Present Weather)?

a. BLDUb. +BLDUc. DSd. +DS

REVIEW QUESTIONS

Ch. 4 Pg. 26

20. The visibility decreased from 1 mile to 1/2 mile in fog. At the same time, the temperature decreased from1.5C to 0.0C, what should be recorded in Column 9 (Present Weather)?

a. FZFGb. BRc. FGd. FZBR

21. If light snow and blowing snow are occurring at the same time and the observer can no longer determineif light snow is falling, what should be reported in Column 9 (Present Weather)?

a. BLSNb. SN BLSNc. SN BLSNd. BLSN

22. Steady rain is observed 4 miles NE to SE from the station, how should it be recorded?

a. Remarks: RA NE-SEb. Remarks: VCSHc. Column 9 (Present Weather): VCSHd. Column 9 (Present Weather): RA, and in Remarks: RA NE-SE

23. Heavy rain (+RA) is reported when the rate-of-fall is:

a. more than 0.01 inch to 0.03 inch in 6 minutesb. more than 0.11 inch to 0.30 inch per hourc. more than 0.30 inch per hourd. more than 0.20 inch per hour

24. When more than one type of present weather are reported at the same time, present weather shall be reported in the following order:

a. Tornadic activity, obscurations, precipitationb. Tornadic activity, thunderstorms, precipitation, obscurations, other weatherc. Thunderstorms, precipitation, obscurations, other weatherd. Tornadic activity, precipitation, thunderstorms, other weather

25. The intensity of snow occurring alone is determined according to:

a. the degree that it effects visibility.b. the rate of accumulation.c. whether it is showery or intermittent.d. the temperature of the dew point

26. Which of the following is a minus sign () used to show light intensity?

a. TSb. ICc. GSd. SG

REVIEW QUESTIONS

Ch. 4 Pg. 27

27. When is lightning reported in Column 9 (Present Weather)?

a. lightning is overheadb. lightning is observed and the wind gusts exceed 50 knotsc. hailstone size exceeds 3/4 inchd. lightning is never reported in Column 9

28. Sand raised by the wind to less than 6 feet is coded as:

a. BLSAb. MISAc. SHSAd. DRSA

29. The observer reports IC in Column 9 (Present Weather). Given this report, which of the following statements is correct?

a. The visibility is less than one mile.b. The sky may be clear.c. The air is unstable with rapidly changing weather conditions.d. The observer has made an error in Column 9.

30. Fog that covers a substantial part of the station and the prevailing visibility is 7 miles would be coded in thepresent weather as:

a. BRb. PRFGc. MIFGd. BCFG

31. Patches of fog randomly cover the station, but the prevailing visibility is 7 miles. What is reported in Column 9 (Present Weather)?

a. nothingb. BCFGc. BRd. VCFG

32. Proximity qualifier(s) is (are):

a. light, moderate, heavyb. vicinityc. weak, strong, violentd. light, moderate, strong

REVIEW QUESTIONS

Ch. 4 Pg. 28

33. The intensity of snow, occurring alone, is reported as moderate when the prevailing visibility is 1/2 to 5/16mile. When obscuring phenomena are also present, you could not report moderate snow if the prevailingvisibility is:

a. 0SMb. 1/2SMc. 1/4SMd. 3/4SM

34. Which of the following phenomena can be reported with an intensity qualifier?

a. drizzleb. fogc. small haild. smoke

35. Obscurations should be reported only when the prevailing visibility is less than 7 miles except for:

a. Volcanic Ashb. Partial Fogc. Patches of Fogd. All of the above

36. Rain showers of an unknown intensity are observed approximately 7 to 8 miles north of the station. Whatshould be recorded in Column 9 (Present Weather) and/or Column 14 (Remarks)?

a. Column 9: VCSH; Column 14: VCSH Nb. Column 9: nothing required; Column 14: VCSH 7-8 Nc. Column 9: VCSH; Column 14: RA SH UNKN Nd. nothing required in either column

37. Fog/mist is responsible for lowering the visibility to 5/8 mile. Light rain is also occurring, the present weatherwould be coded:

a. FG RAb. RA FGc. RA BRd. BR RA

38. A large are of fog is observed 6 miles NE-S of the station. What is reported in Column 9 (Present Weather)?

a. nothingb. VCFGc. PRFGd. BCFG

REVIEW QUESTIONS

Ch. 4 Pg. 29

39. The intensity of which of the following types of precipitation may be determined by visibility?

a. Ice crystalsb. Freezing rainc. Haild. Snow

40. Which of the following requires a special observation?

a. TS endsb. -SN beginsc. SHRA endsd. SG begins

41. The intensity of drizzle occurring alone must be determined by

a. total accumulation of water.b. degree to which the drizzle affects visibility.c. rate of accumulation of water.d. size of drops

42. An entry for a present weather group must be made when the prevailing visibility is

a. 15 miles or less.b. 10 miles or less.c. 6 miles or less.d. less than 10 miles.

43. Which report is in the correct order?

a. TSRAGRb. BR -RA HZc. -PLFZDZd. TSFGRA

44. Thunder is heard from a thunderstorm west of the station, moving NE, accompanied by frequent cloud-to-cloud lightning. It is reported in the remarks column (14) as

a. TS W MOV NE FRQ LTGCCb. FRQ LTGCC W TS W MOV NEc. CB TS W FRQ LTGCC MOV NEd. TS W MOV NE LTGCC.

45. The weather phenomena that are always written out in full in aviation weather reports in column 14 are:

a. thunderstorms, heavy rain, or rain showers.b. blowing dust and sand.c. hail and ice pellets.d. tornadoes, waterspouts, and funnel clouds.

REVIEW QUESTIONS

Ch. 4 Pg. 30

46. A light intensity qualifier is not used with

a. DZb. PLc. TSd. SN

47. One characteristic of patches of fog is that it

a. usually extends to great heights.b. hides the entire sky.c. is less than 20 feet deep.d. normally extends to about 40 feet vertically.

48. Haze, blowing sand, blowing snow, and smoke are coded as

a. Z, BS, BLSN, SNb. HZ, BS, BLSN, SKc. HZ, BLBN, BLSN, SKd. HZ, BLSA BLSN, FU

49. A thunderstorm with heavy rain showers and 3/4 inch hail is recorded as

a. +TSRAGRb. +TSRAGSc. +TSGRSHRAd. TSGRRASH+

50. Which condition below is classified as an obscuration to vision?

a. Blowing snow.b. Drifting snow.c. Light rain.d. Thunderstorm.

51. Precipitation is entered in column 9 in which order?

a. time each element beganb. decreasing dominancec. rate of falld. effect it has on visibility

52. Which of the following requires a special observation?

a. A tornado is reported by the police to have occurred 5 hours agob. visibility decreases to 3 milesc. volcanic eruptionsd. sky condition changes from BKN050 to BKN030