Meteorological Concepts for Soaring in the Western U.S. Dan Gudgel Meteorologist/Towpilot/CFIG

Meteorological Concepts for Soaring in the Western U.S.

Dan Gudgel

Meteorologist/Towpilot/CFIG

Presentation Points

1. Weather Information Sources2. Meteorology Points3. Synoptic Scale Weather Patterns4. A Forecast Funnel5. Miscellaneous Info

1. Weather Information Sources

Weather Data

• Internet (use “search engines”)•Site addresses change frequently for this medium•Customize access list for efficient data retrieval

• Review AC-006, Aviation Weather• Review AC-45E, Aviation Weather Services

• Other Information Sources

Internet Weather Data

• Upper Air Temperature Soundings• Observed and Forecast Weather Charts• Model Forecasts• Satellite Imagery

•Education / Explanations•Soaring Category Info

National Weather Service

<http://www.weather.gov>• NWS National Homepage

•Select area of interest (‘clickable’ map)• All Western Region NWS Offices listed

• Numerous weather links•Current weather•Forecast models•Satellite images•Aviation Wx Center•Other sites

Forecast Systems Laboratory<http://www-frd.fsl.noaa.gov/mab/soundings>

•Forecast Upper Air Temperature Soundings•40Km grid resolution•Out to 16 Hours•Spot forecasts (By airport)

Unisys Weather<http://weather.unisys.com/index.html>

• Upper Air Temperature Soundings• Constant Pressure Charts• Model Forecast Charts• Education / Explanations

National Center for Atmospheric Research (NCAR) [et al.]

<http://www.rap.ucar.edu/weather/>

• Upper Air Data (Temperature/Relative

Humidity/Wind Info)

• Other weather data

Other Weather Info SourcesFor the Aircraft Category

• Fixed base operators• Soaring Society of America• Associated sites

• Other Sources• Newspapers• NWS Weather Radio• FAA DUATS

2. Meteorology Points

• Atmospheric Soundings• Great Basin Applications

• Convection concepts• Climate Aspects• Local Influences

Altitude

Temperature

Dry Adiabatic Lapse Rate5.4 deg F/1000 Ft

Average Lapse Rate 3.5 deg F per 1000 Ft

Sounding Basics

• Small day-to-day changes can make big differences in a soaring day's characteristics

• Spot observation versus need to assess task area air mass, including discontinuity lines

• Altitude noted by Pressure-850 mb 5000 Feet (MSL)-700 mb 10,000 Feet-500 mb 18,000 Feet

Sounding Sources

•University of Utah Upper Air Link http://

www.met.utah.edu/jhorel/html/wx/skewt.html•Unisys Weather Upper Air Link

http://weather.unisys.com/upper_air/skew/index.html

Lapse Rate Definitions

Altitude

Temperature

Dry Adiabatic Lapse Rate5.4 deg F/1000 Ft

Average Lapse Rate 3.5 deg F per 1000 Ft

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Lapse Rates

Dryand

Moist

Adiabatic

Definitions - Stable/UnstableDry Atmospheric Conditions

Altitude

Temperature +

+

d

A B

A - Temperature decreasing greater than Dry Adiabatic Lapse Rate denotes unstable atmospheric conditions

B - Temperature not decreasing as fast as Dry Adiabatic Lapse Rate denotes more stable atmospheric conditions

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Temperature Inversions Surface-Based and Aloft

Altitude Altitude

Temperature Temperature

Surface-Based

Aloft

Wind Shear

•Wind velocity is a change in speed and/or direction•Temperature inversions are boundaries of air layers•Shear zone may not be deep or turbulent but...

•Each layer of air can have a differentcharacteristics:

- Wind velocity- Moisture- Parameter gradients

Altitude

Temperature +

+

Wind

Wind

SHEAR

ZONE

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Profiles• A mixed atmosphere is near-adiabatic (left)• Subsidence from high pressure “caps”

convection but high enough to facilitate soaring over terrain (right)

TemperatureTemperature

Alt. Alt.

d d

19

Surface-Based Inversion Established with Time

d

Alt.

Temperature(0600 LT) (0100 LT) (2000 LT) (1700 LT) Time of Day

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Surface-Based Inversion Erosion with Time

d

Alt.

Temperature

(0600 LT) (0900 LT) (1100 LT) (1400 LT)Time of Day

Cloud Base / Moisture Layers

•T / DP Closure Possible Cloud Layers

•Moist Adiabatic Lapse Rate

Altitude

Temperature

Cloud Layer

Cloud Layer

DewPoint

Temperature

The Drying Process

Rising,CoolingCondensing

Sinking, HeatingDrying

OwensValley

SierraNevada

GreatBasin

San Joaquin Valley

5K Ft

Moisture, DeficitAir

MSL

WhiteMtns5000 Ft MSL

10000 Ft MSL

De-Stabilizing ProcessColder Air Advection above, and/or

Warm Air Advection below will de-stabilize

• Delta-T increase!

• Moisture presence also de-stabilizes

Altitude

Temperature

Warming

Cooling

T Increasing

d

Basin Thunderstorm / Microbursts

• Develop Adjacent cells• Classic short duration• 60Kt+ Sink Rates• Regardless of cell size• Wind shifts• Degrade ceiling and visibility

25

Mojave Desert Downburst

Courtesy of Caracole Soaring, California City, CA)

Microburst Sounding

Thunderstorm Activity (#1)

• Presence of "cap"; and "penetration" of cap (observed time vs. forecast time?)

• Winds aloft•Cell movement•Anvil spread

Thunderstorm Activity (#2)

• Air mass Thunderstorms•Favored spots

• Outflow

Radar

30

Classic Supercell Thunderstorm

0 5 10Nautical miles

Light Rain

Moderate/Heavy Rain & Hail

Supercell Thunderstorm(top view)

Anvil Edge

Gust Front

WSR-88D Radar Image

N

Hook echo

Hook echo

National Weather Service www.weather.gov

Convection CirculationTemperature Differences

• Uneven heating leads to differing air density and ultimately supports a thermal circulation

• Terrain/slope contributions• Surface heating capacity = f(ground and lower air

mass moisture content)

Elevated Thermal SourceGreat Basin Mountains

• Mountain slopes normal to incoming energy

• Less attenuation•Air density•Moisture•Pollutants

• Less mass of air to heat for greater buoyancy

Climate and Other Influences

• Climate and Terrain Considerations• Modifying Influences and Contributions• Thunderstorm Indices

Climate and TerrainGreat Basin

• Time of year•Diurnal temperature spread

• Humidity factors• Terrain rising aspects (and TAS)

Sunset / Sunrise / Normal TempsReno, NV

• Sunrise / Sunset•June 1 5:34 AM PDT / 8:20 PM PDT•July 1 5:35 AM PDT / 8:30 PM PDT•Aug 1 5:58 AM PDT / 8:12 PM PDT•Sep 1 6:27 AM PDT / 7:30 PM PDT

• Normal Maximum/Minimum Temperatures•June 81.5 / 44.3 (T=37.2F)•July 91.0 / 49.3 (T=41.7F)•Aug 89.7 / 47.2 (T=42.5F)

Great Basin Temps

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The Drying Process

Rising,CoolingCondensing

Sinking, HeatingDrying

OwensValley

SierraNevada

GreatBasin

San Joaquin Valley

5K Ft

Moisture, DeficitAir

MSL

WhiteMtns5000 Ft MSL

10000 Ft MSL

Washoe Zephyr

Mono Lake

Modified Basin Air

Mono Lake Shear

Carson Sink

Major Modifying Influences(#1)

• Washoe Zephyr• Nevada Sinks• Mono Lake Shear• Basin Air• Terrain "Holes"

Topaz Flow

Mono Lake

Mammoth Lakes

June Lake

Mammoth Pass

Major Modifying Influences(#2)

• Topaz Flow• Mammoth Lakes• June Lake

Pressure PatternsFavorable for Great Basin Soaring

• High location (aloft)-Ridge aloft east of task area (or far west)

• Low pressure (aloft)-Not strong or close enough to bring strong gradient wind

• De-stabilizing Influences-Split flow in the upper wind field with weak trough

•Allows for Instability aloft but good surface heating

• Thermal Trough (surface)-Through interior CA (better if along the coast!)

Pressure Gradients(#1)

Stable Air Movement to the Western Great Basin

•Great Basin to Interior California* 4 mb Reno to Sacramento delta-P inhibits Washoe Zephyr development

Pressure Gradients(#2)

Stable Air Movement to the Western Great Basin

•South CA Coast to Desert Interior* Depth of marine layer greater than 1500' MSL* 3+ mb Los Angeles (LAX) to Daggett (DAG)

•Central CA Coast to Desert Interior* 6+ mb San Francisco to Las Vegas* Depth of marine layer greater than 2000' MSL

Thermal DetractorsMacro-scale Level

Cirrus Anvil from ThunderstormsCirrus

•Around jet stream cores•Small pressure perturbations / waves

Convective Cloud Cover•More than 50% sky cloud cover

Other•Relative Humidity gradients

Thermal EnhancersGreat Basin

Rising terrain steps to southeast of Minden•Minden to Patterson/Bridgeport +2000'•Patterson to Whites +1000' and more

Convergence / Shear•Mono Lake Shear Line•Flying “M” Shear Line

Small air basins•Fixed volume of air to heat (valley vs. plain)

Other•Summer wave or wave-encouraged cloud streets

46

Mojave Desert Shearlines

47

Mono Lake Shear Line

• Mono Lake Shear Line “Typically” present• Example: 6/13/99

48

Mono Lake Shear Line

49

Mono Lake Shear Line

50

Flying “M” Shear Line

• Flying “M” Shear Line “Typically” present• Example: 6/14/99

51

Flying “M” Shear Line

52

Flying “M” Shear Line

53

Mountain Wave

54

Mountain Wave

55

Mountain Wave

• Wave Presence for Long Distance Flight• Example: 6/15/99

Moisture SurgesWarm Season Sources

• Southwest U.S. Monsoon-Low level and/or mid-level

• Significantly deep trough developing moisture field due to the dynamics

-But a southwest flow is generally a very dry flow• East Pacific hurricane activity

-Mid/High Clouds with a major hurricane release of its accompanying moisture

57

East vs. West Great Basin

• Time of Year Sub-Tropical Moisture Progression– Parawon UT (Late June/Early July)– East NV (Mid-Late July)– West NV (Late July/Early August)

• Slower Thermal Processes– Dry west; Slower start per moisture-deficit– More attenuation; CA and local “Haze”– West NV, slightly lower terrain

• West Great Basin Enhancements– Shear line influences prevalent within 50 s.m. of the Sierra

Nevada Front

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Soaring = f(Moisture Changes)

• Moisture Contribution– Dew Points rise to the southeast over the Great Basin

• La Nina/El Nino Influences– La Nina

• Dry south; Thunderstorms develop less frequently

– El Nino• Moist ground delays (thermal) soaring season• Upon initiation, more thunderstorm activity

– Other Climatic Oscillations’ Impact?• Arctic Oscillation, Pacific Decadal, Madden-Julian Oscillation

Hypothesis: Annual Climate Changes Impact Soaring

Infrared Satellite Imagery• Cloud top temperature• Good delineator for high clouds

Water Vapor Satellite Imagery• Moist and dry air boundaries• Active convection often along interface• Determine Raob representativeness of task area?

3. Synoptic-Scale Weather Patterns

Weather Types Favorable to Long Distance Soaring

Type #1: Four-Corner High Type #2: Strong Ridge Type #3: Low Center, Trough, Short-wave Proximity Type #4: Building Ridge Aloft

11

17

23

5

0

5

10

15

20

25

1 2 3 4

Summer 2000 Map Types

Type #1: The Four-Corner High

• High pressure centered aloft near the Four Corner area of the Southwest U.S.

• Most recognized, "Classic" long flight pattern• Good low level heating de-stabilizes the air mass

-Light surface wind-Lower layer warm air advection

• Monsoon moisture tap ... therefore usually not a long-lived pattern

• Good soaring ... but days get truncated with afternoon TSTMs... often widespread

Type #1: 6/18/88

ASI to Keeler and return

6/18/88 Raobs

• WMC 94/50• RNO 90/58• TPH 83/52• LAS 98/78

Type #2: Strong Ridge

• Light wind• Low level heating• Thermal trough well to the west of task area• Impulse aloft over ridge axis; or,• Ridge axis aloft east of the task area

Type #2: 8/9/96Long-lived, extraordinary patternNumerous 1000Km flightsOver a 4-day period

8/9/96

WMC 98/48

RNO 95/53

TPH 95/61

LAS 99/80

Type #3: Low Center, Trough, or Short Wave Proximity

• Ridge axis to the east; Trough axis proximity• De-stabilizing by cold air advection aloft• But light wind and/or split in the jet aloft• Thermal trough closer to NV; but...• Low level Zephyr washout delayed• Still able to heat lower levels• Prevalent pattern for long distance soaring!

Type #3: 7/7/88Flight of 350 miles

7/7/88 Raobs

WMC 84/54RNO 84/49TPH 90/56LAS 103/77

Type #3(a): Proximity of Low Pressure Center

Low off Southern California coast provides cooler air aloft upstream to de-stabilize

Elevated heat source influence contributions

Type #3(a): 6/19/93

1000Km flights from TruckeeAnd Minden area

6/19/93 Raobs

WMC 86/47RNO 88/57TPH 86/54LAS 94/72

Type #4: Building Ridge Aloft2 Examples / Next 4 Slides

Temperature trend upward•Surface temps climbing faster than aloft•Subsidence not strong•Large diurnal temperature spread in transition

Light wind aloft•Height gradient small

Suppression of westerly washout

Type #4: 6/13/88500 Mile Flight

6/13/88 Raobs

WMC 81/42RNO 81/27 (!!!)TPH 78/MLAS 95/70

77Map Types also varied as season passed!

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17

23

5

0

5

10

15

20

25

1 2 3 4

Summer 2000 Map Types

4. Weather Forecasting

• Forecast Funnel• Soaring Indices• Automated Soaring Forecasts

•Dr. Jack and BLIPMAP•Other Automated Forecasts

• NWS IFPS (Gridded Data)

A Glider Pilot’s Forecast FunnelA Process of Soaring Forecast Refinement

• Site Climate• Outlook Forecasts• Extended and Zone

Forecasts (2-7 Day)• Persistence• Flight Day

Soaring Indices(#1)

Great Basin

• Thermal Index

- Lift = f(T)

Soaring Indices (#2)

Great Basin

• Soaring Index

- Lift = f(Convection Altitude and T)

Soaring Indices (#3)

Great Basin

• Vertical Totals [T(deg C) 850 mb to 500 mb]

- Upper 20s average to good- 30 to 34 very good- 35+ excellent (too unstable many times)

Instability Indices(#1)

Great Basin

• K-Index

•Uses Vertical Totals and 2 fixed reference levels T(C) + 850 dew point(C) - 700 dew point depression(C)•5+ = some cumulus possibilities•Thunderstorms increase in the 10-15 range

Instability Indices (#2)

Great Basin

• Lifted Index (LI) and Showalter Index (SI)

•Lower layer moisture influences on the convection process / thunderstorm indicator

• > 10 stable (weak convection)• < -4 too unstable (severe weather)

85

Thermal Lift Indices Work

• Thermal Index (Williams/Higgins)

• Maximum Lift (Lindsay/Lacy)

• Soaring Support (Aldrich/Marsh)

• Soaring Index (Armstrong-Hill)

86

Wave Strength Forecasting

Wave Nomogram (Herold/Armstrong)

87

Traditional Soaring Forecasts

• Persistence• Nowcasting

– Soundings– Satellite– Analysis

• Algorithm Use

Altitude

Temperature

Warming

Cooling

T Increasing

d

88

Thermal Index Prediction (TIP)Dr. John W. (Jack) Glendening

• Estimate for the Current Day Thermal Soaring Potential

• Two Day Thermal Soaring Outlook

• Several Sites• Mountain Top

Experiment (Walker Ridge)

URL: http://www.drjack.net/TIP/index.htmlURL: http://www.drjack.net/TIPEX/index.html

89

Boundary Layer Information Predictor

Maps(BLIPMAP)

•Single Time or Sequence

URL: www.drjack.net/BLIPMAP/index.html

•Thermal Soaring Parameters (over a geographic region)

-Numerical Model Outputs•General Air Mass Lift

90

Wind Information Predictions (WINDIP)

(Simple Mountain Wave Prediction)

• “Alert” WINDIP E-Mail List

• Assumptions

• Longer Forecast Time PredictionsURL: http://www.drjack.net/WINDIP/index.html

91

Linear Wave Interpretation Page (LWIP)

• Description

• Interpretation

• Notes

• Links

URL: http:// www.drjack.net/LWIP/index.html

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Automated Thermal Soaring Forecasts

• Two Parts:

1.Pure Model Output (top portion)

2.NWS Forecast Temps as base (lower portion)

• Limitations• NWS Websites

Walt Rogers (WX), MIC CWSU ZLA

URL: http://www.weather.gov/***** where ***** is NWS Office Name, I.e., Hanford, Oxnard, etc.

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Interactive Forecast Preparation System (IFPS)

• Man-Machine Mix

•“Flagship” Products Not Text -Forecasters Edit Gridded Data•Graphical Products -Customer Requested Output

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Gridded Data

Graphical Display of Requested Weather Parameter(s)

5. Miscellaneous Information

• Aero-medical Considerations

Aeromedical ConsiderationsSoaring good enough that...

Oxygen requirements

Water

Sun protection

Meteorological Concepts for Soaring in the Western U.S.

Dan GudgelMeteorologist/Towpilot/CFIG

134 South Olive StreetLemoore, CA 93245(w)559-584-3752 ext.223(h)559-924-7134

<dgudgel@cnetech.com>