A Better Use of TAFs Southwest Aviation Weather Safety Workshop II A Better Use of TAFs Southwest Aviation Weather Safety Workshop II Leslie Wanek Aviation

A Better Use of TAFsA Better Use of TAFs SSouthwestouthwest

AAviationviation WWeathereather SSafetyafety Workshop II Workshop II

Leslie WanekLeslie WanekAviation Program LeaderAviation Program Leader

WFO PhoenixWFO PhoenixOctober 23-24, 2008October 23-24, 2008

Objectives for today…Objectives for today…

• TAF Review and TAF Review and TerminologyTerminology

• NWS TAF Writing NWS TAF Writing PhilosophiesPhilosophies

• Forecaster Best PracticesForecaster Best Practices

• Use of Cumulonimbus (CB) Use of Cumulonimbus (CB) & Vicinity (VC)& Vicinity (VC)

• TAF ExampleTAF Example

• Aviation Forecaster Written Aviation Forecaster Written DiscussionDiscussion

• 30-Hour TAF Format Change30-Hour TAF Format Change

TAF Review & TerminologyTAF Review & TerminologyTTerminal erminal AAerodrome erodrome FForecastorecast

• Terminal Aerodrome Forecasts, also known as Aerodrome Forecasts, are prepared by National Weather Service (NWS) Weather Forecast Offices (WFOs).

• The U.S. definition of terminal is an area within five (5) statute miles (SM) of the center of an airport’s runway complex.

• A NWS TAF will consist of expected meteorological conditions significant to aviation at an airport (terminal) for a specified time period.

• TAFs are a critical element of NWS aviation weather services because they are a key product in decisions on aircraft movement within the National Airspace System (NAS).

NWSI 10-813 November 2007NWSI 10-813 November 2007

TEMPOTEMPODefined as…Defined as…Temporary fluctuations in forecast meteorological Temporary fluctuations in forecast meteorological conditions which are expected to last less than one (1) hour in conditions which are expected to last less than one (1) hour in each instance and, in the aggregate, to cover less than half of the each instance and, in the aggregate, to cover less than half of the indicated period.indicated period.

• Used for high probability (greater than 50%) expectationsUsed for high probability (greater than 50%) expectations

• Will not be substituted to indicate a low probability event (less than 50%)Will not be substituted to indicate a low probability event (less than 50%)

• Will not exceed four (4) hoursWill not exceed four (4) hours


KABC 091125Z 091212 19008KT P6SM SCT010 BKN020 OVC090 KABC 091125Z 091212 19008KT P6SM SCT010 BKN020 OVC090 TEMPO 1215TEMPO 1215 2SM RA SCT010 BKN015 OVC040… 2SM RA SCT010 BKN015 OVC040…

Example…Example…

PROB30PROB30Defined as…Defined as…Probability of occurrence of a thunderstorm or other Probability of occurrence of a thunderstorm or other precipitation event, with associated weather elements as precipitation event, with associated weather elements as necessary (wind, visibility, and/or sky condition) whose necessary (wind, visibility, and/or sky condition) whose occurrences are directly related to, and contemporaneous with, occurrences are directly related to, and contemporaneous with, the thunderstorm or precipitation event.the thunderstorm or precipitation event.

• PROB30 groups only, indicating a 30% probability of the PROB30 groups only, indicating a 30% probability of the specified element occurringspecified element occurring

• PROB30 groups will not include forecasts of significant PROB30 groups will not include forecasts of significant weather in the vicinity (VC) or non-convective Low Level weather in the vicinity (VC) or non-convective Low Level Wind Shear (LLWS)Wind Shear (LLWS)

• Will not be used in the first nine (9) hours of every TAF valid Will not be used in the first nine (9) hours of every TAF valid period, including amendmentsperiod, including amendments


Low Level Wind Shear (LLWS)Low Level Wind Shear (LLWS)Defined as… Defined as… Wind Shear (WS), a change in horizontal wind speed Wind Shear (WS), a change in horizontal wind speed and/or directions, and/or vertical speed with distance, measured and/or directions, and/or vertical speed with distance, measured in a horizontal and/or vertical direction. WS is a vector difference, in a horizontal and/or vertical direction. WS is a vector difference, composed of wind direction and wind speed, between two wind composed of wind direction and wind speed, between two wind

velocities.velocities.

• LLWS in a NWS TAF will refer only to non-convective LLWS LLWS in a NWS TAF will refer only to non-convective LLWS from the surface up to and including 2K ft AGLfrom the surface up to and including 2K ft AGL

• Used only in FM groups (no TEMPO/PROB30), remains Used only in FM groups (no TEMPO/PROB30), remains prevailing until next FM change groupprevailing until next FM change group


KABC 220539Z 220606 KABC 220539Z 220606 21010KT21010KT 3SM BR SCT030 3SM BR SCT030 WS015/29065KTWS015/29065KT FM1100 24015KT 1SM TSRA BR OVC010CB FM1100 24015KT 1SM TSRA BR OVC010CB FM1830... FM1830...

Example…Example…

NWS TAF Writing PhilosophiesNWS TAF Writing Philosophies

• Keep in mind the varying degree of NWS TAF users, Keep in mind the varying degree of NWS TAF users, including… domestic and international commercial airlines, including… domestic and international commercial airlines, General Aviation (GA), Civilian and Military Operations, etc.General Aviation (GA), Civilian and Military Operations, etc.

AFC Ceiling (ft) Visibility (SM)

LIFR < 500 and/or < 1

IFR 500 to < 1000 and/or 1 to < 3

MVFR 1000 to 3000 and/or 3 to 5

VFR > 3000 and > 5

• Optimize timeliness and representativeness using the bestOptimize timeliness and representativeness using the best professional judgmentprofessional judgment

• Be aware of the potential operational impact of each forecastBe aware of the potential operational impact of each forecast element and it’s associated change in Aviation Flight Categoryelement and it’s associated change in Aviation Flight Category (AFC)(AFC)

• Know your airfield’sKnow your airfield’s restrictions andrestrictions and minimumsminimums

The Un-Amendable TAF…The Un-Amendable TAF…• Many pilots find TAFs are Many pilots find TAFs are

often written with such often written with such complexity that they lose complexity that they lose utilityutility

• NWS Verification statistics NWS Verification statistics indicate that PROB and indicate that PROB and TEMPO groups are overused TEMPO groups are overused and can hurt the value of the and can hurt the value of the forecastforecast

• The cost to an airline for The cost to an airline for adding fuel for an alternate adding fuel for an alternate can also be high, especially can also be high, especially for some carriersfor some carriers

• GA Pilot…it’s a go / no goGA Pilot…it’s a go / no go

Un-Amendable TAFUn-Amendable TAF

NWS TAF Writing PhilosophiesNWS TAF Writing Philosophies

Common Needs…Common Needs…• ClearClear• Concise Concise • Consistent Consistent • Relevant Relevant • TimelyTimely• AccurateAccurate

Through the TAF, NWS Forecasters have a great opportunityThrough the TAF, NWS Forecasters have a great opportunity

to enhance flight safety and save customers both time and money.to enhance flight safety and save customers both time and money.

Forecaster Best PracticesForecaster Best PracticesGoal:Goal: Avoid writing the un-amendable, ambiguous TAF and strive Avoid writing the un-amendable, ambiguous TAF and strivefor an effective, practical, user-friendly TAF by…for an effective, practical, user-friendly TAF by…

1.1. Establishing trends Establishing trends and writing to Aviation and writing to Aviation Flight Categories firstFlight Categories first

2.2. Add detail to the first 6 Add detail to the first 6 hours of the TAF, hours of the TAF, known as the critical known as the critical TAF periodTAF period

3.3. Limit the use of Limit the use of TEMPO groups to the TEMPO groups to the first 6 hoursfirst 6 hours

4.4. Avoid PROB30, which users have indicated can beAvoid PROB30, which users have indicated can be confusingconfusing

Use of Vicinity (VC) & Cumulonimbus (CB)Use of Vicinity (VC) & Cumulonimbus (CB)

• Used only in the initial time Used only in the initial time period or in from (FM) groups, period or in from (FM) groups, all of which forecast prevailing all of which forecast prevailing conditionsconditions

• Used in combination with fog Used in combination with fog (FG), showers (SH), and (FG), showers (SH), and thunderstorms (TS)thunderstorms (TS)

• Less stringent operational Less stringent operational impacts on users than PROB30 impacts on users than PROB30 groupsgroups

• CB = used to indicate CB = used to indicate instability in the atmosphereinstability in the atmosphere

Vicinity = Vicinity = A donut-shaped area between circles with radii of 5 A donut-shaped area between circles with radii of 5 andand10 SM from the center of the runway complex of an airport.10 SM from the center of the runway complex of an airport.

Forecast ExampleForecast Example

KTAF 231730Z 231818 14010KT P6SM SCT080KTAF 231730Z 231818 14010KT P6SM SCT080CBCB BKN200 BKN200 FM2100 17012G22KT P6SM FM2100 17012G22KT P6SM VCTSVCTS SCT050 SCT050CBCB BKN070 BKN070

TEMPOTEMPO 2224 VRB20G30KT 2224 VRB20G30KT TSRATSRA BKN030CB BKN030CB

Forecast Scenario:Forecast Scenario: A 70% chance for showers and thunderstorms A 70% chance for showers and thunderstorms is forecast for a zone in the afternoon, 18 – 00 UTC (local time 11amis forecast for a zone in the afternoon, 18 – 00 UTC (local time 11am – – 5pm). At a TAF site in that zone, a 30% chance for showers and 5pm). At a TAF site in that zone, a 30% chance for showers and thunderstorms is forecast for early afternoon and a 70% chance forthunderstorms is forecast for early afternoon and a 70% chance for late afternoon.late afternoon.

Public Zone (area) forecast reads…Public Zone (area) forecast reads…

PARTLY CLOUDY. SOUTH WIND 10 TO 15 MPH. SHOWERS ANDPARTLY CLOUDY. SOUTH WIND 10 TO 15 MPH. SHOWERS ANDTHUNDERSTORMS LIKELY IN THE AFTERNOON. CHANCE OFTHUNDERSTORMS LIKELY IN THE AFTERNOON. CHANCE OFRAIN 70 PERCENT.RAIN 70 PERCENT.

TAF reads…TAF reads…

AFD Aviation Discussion…AFD Aviation Discussion…AArearea F Forecastorecast D Discussioniscussion

• Change in Flight CategoriesChange in Flight Categories– VFR/MVFR/IFR/LIFRVFR/MVFR/IFR/LIFR

• Frontal PassageFrontal Passage– timing / causetiming / cause

• Precipitation TypePrecipitation Type– start/stopstart/stop

• Visibility ObstructionsVisibility Obstructions– smoke / hazesmoke / haze

• ThunderstormsThunderstorms– coverage / intensitycoverage / intensity

• WindsWinds– cross winds / LLWScross winds / LLWS

• AFD is one of the most used AFD is one of the most used products the NWS issuesproducts the NWS issues

• Routinely issued 2-4 times/dayRoutinely issued 2-4 times/day

• Insight into Forecasters’ Insight into Forecasters’ thought processthought process

• Basic weather discussion (in Basic weather discussion (in non-technical wording), non-technical wording), identifying weather-related identifying weather-related items which may affect the items which may affect the operations of an airport operations of an airport terminalterminal

• Provide users a better Provide users a better understanding of expected understanding of expected weather during Critical TAF weather during Critical TAF PeriodPeriod

AFD Aviation Discussion…AFD Aviation Discussion…www.aviationweather.gov/testbed/afdwww.aviationweather.gov/testbed/afd

30-Hour TAF Format Change30-Hour TAF Format Change

What is it?What is it?• In response to request by long haul operations for better service, In response to request by long haul operations for better service,

the International Civilian Aviation Organization (ICAO) made the International Civilian Aviation Organization (ICAO) made provisions for a 30-hour TAF in Annex 3 for the Meteorological provisions for a 30-hour TAF in Annex 3 for the Meteorological Service for International Air Navigation, Amendment 74.Service for International Air Navigation, Amendment 74.

• Will likely impact TAF software de-coders worldwide since each Will likely impact TAF software de-coders worldwide since each change group will now have a date (applies to ALL locations, even change group will now have a date (applies to ALL locations, even those not providing 30-hour TAFs).those not providing 30-hour TAFs).

When is it?When is it?• New format is expected to start for the US and most other New format is expected to start for the US and most other

countries 00Z on the Nov 5th 2008 (5pm local MST on Nov 4th). countries 00Z on the Nov 5th 2008 (5pm local MST on Nov 4th).

• However some countries may delay etc…so vendors will need However some countries may delay etc…so vendors will need to be able to decode both formats for some period of time.to be able to decode both formats for some period of time.


Old Format…Old Format…KABC 152335Z KABC 152335Z 160024160024 13018KT P6SM BKN020 13018KT P6SM BKN020

TEMPO TEMPO 08120812 17025G45KT 1SM TSRA SCT010CB BKN020 17025G45KT 1SM TSRA SCT010CB BKN020 FM0100 15015KT P6SM BKN020FM0100 15015KT P6SM BKN020

New Format…New Format… KABC 152335Z KABC 152335Z 1600/17061600/1706 13018KT P6SM BKN020 13018KT P6SM BKN020

TEMPO TEMPO 1608/16121608/1612 17025G45KT 1SM TSRA SCT010CB 17025G45KT 1SM TSRA SCT010CB FM170100 15015KT P6SM BKN020FM170100 15015KT P6SM BKN020

New Format for 24-Hour TAF Locations…New Format for 24-Hour TAF Locations…KABC 152335Z KABC 152335Z 1600/17001600/1700 13018KT P6SM BKN020 13018KT P6SM BKN020


32 U.S. locations will go to 30 Hour32 U.S. locations will go to 30 Hour

Where is it produced?Where is it produced?


The NOAA Aviation Services Branch (ASB) has a 30 The NOAA Aviation Services Branch (ASB) has a 30 hour testbed…where vendors and users can go to hour testbed…where vendors and users can go to download further material and practice TAFs…download further material and practice TAFs…

www.weather.gov/os/aviation/taf_testbed.shtmlwww.weather.gov/os/aviation/taf_testbed.shtml

Where to find more information…Where to find more information…

Closing RemarksClosing Remarks

– TAF terminologyTAF terminology– NWS TAF Writing Philosophies and Forecaster NWS TAF Writing Philosophies and Forecaster

Best PracticesBest Practices– Example TAFsExample TAFs– AFD Aviation DiscussionAFD Aviation Discussion– Upcoming 30-Hour TAF Format ChangeUpcoming 30-Hour TAF Format Change

Questions or comments after today…you can reach me at Questions or comments after today…you can reach me at [email protected]@noaa.gov

Thank you!Thank you!

Additional Resources & References…Additional Resources & References…• ““TAF Writing Tips from Medford, OR”. James Reynolds, WFO HastingsTAF Writing Tips from Medford, OR”. James Reynolds, WFO Hastings

• COMET Distance Learning Aviation Course DLAC2 Modules 1-2COMET Distance Learning Aviation Course DLAC2 Modules 1-2

• ““TAF Writing Philosophy”. Bill South, WFO Key WestTAF Writing Philosophy”. Bill South, WFO Key West

• ““TAF Best Practices from Phoenix, AZ”. Leslie Wanek, NWS PhoenixTAF Best Practices from Phoenix, AZ”. Leslie Wanek, NWS Phoenix

• ““Practical TAF Writing”. Karen Oudeman, NWS JacksonPractical TAF Writing”. Karen Oudeman, NWS Jackson

• ““Writing Better Aviation AFDs (or) Do you know who your customerWriting Better Aviation AFDs (or) Do you know who your customerreally is?” Dustin Harbage & Brian Schoettmer, WFO Jacksonreally is?” Dustin Harbage & Brian Schoettmer, WFO Jackson

• ““Aviation AFD Guidance, An Airline Perspective”. Ken Widelski, WFO Aviation AFD Guidance, An Airline Perspective”. Ken Widelski, WFO LubbockLubbock

• ““The 30-Hour TAF, What When and Where?”, Mike Graf; NOAA The 30-Hour TAF, What When and Where?”, Mike Graf; NOAA Aviation Aviation Services BranchServices Branch

• NATIONAL WEATHER SERVICE INSTRUCTION 10-813, TERMINAL NATIONAL WEATHER SERVICE INSTRUCTION 10-813, TERMINAL AERODROME FORECASTS. November 2007AERODROME FORECASTS. November 2007

• Cartoon: Adapted fromCartoon: Adapted from www.CartonStock.com www.CartonStock.com; Artist: Hagen, Ralph ; Artist: Hagen, Ralph

Low Level Wind ShearLow Level Wind Shear(non-convective)(non-convective)

The format of the non-convective low-level wind shear group isThe format of the non-convective low-level wind shear group isWShwshwshws/dddffKT, where: WShwshwshws/dddffKT, where:

• WSWS = Indicator for non-convective LLWS= Indicator for non-convective LLWS • hwshwshws = Height of the top of the WS layer in hundreds of hwshwshws = Height of the top of the WS layer in hundreds of

feet AGL feet AGL

• dddddd = True direction in ten degree increments at the = True direction in ten degree increments at the indicated heightindicated height

• ffff = Speed in knots of the forecast wind at the indicated = Speed in knots of the forecast wind at the indicated heightheight

• KTKT = Unit indicator for wind= Unit indicator for wind

Documents

A Better Use of TAFs Southwest Aviation Weather Safety Workshop II A Better Use of TAFs Southwest Aviation Weather Safety Workshop II Leslie Wanek Aviation