SSA EducationTutorial Jan2006

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Meteorological Concepts for Soaring in the Western U.S. : 

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

Presentation Points: 

Presentation Points Weather Information Sources Meteorology Points Synoptic Scale Weather Patterns A Forecast Funnel Miscellaneous Info

1. Weather Information Sources: 

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: 

Internet Weather Data Upper Air Temperature Soundings Observed and Forecast Weather Charts Model Forecasts Satellite Imagery Education / Explanations Soaring Category Info

National Weather Service: 

National Weather Service <> 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: 

Forecast Systems Laboratory <> Forecast Upper Air Temperature Soundings 40Km grid resolution Out to 16 Hours Spot forecasts (By airport)

Unisys Weather: 

Unisys Weather <> Upper Air Temperature Soundings Constant Pressure Charts Model Forecast Charts Education / Explanations

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

National Center for Atmospheric Research (NCAR) [et al.] <> Upper Air Data (Temperature/Relative Humidity/Wind Info) Other weather data

Other Weather Info Sources: 

Other Weather Info Sources For the Aircraft Category Fixed base operators Soaring Society of America Associated sites Other Sources Newspapers NWS Weather Radio FAA DUATS

2. Meteorology Points: 

2. Meteorology Points Atmospheric Soundings Great Basin Applications Convection concepts Climate Aspects Local Influences

Sounding Basics: 

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: 

Sounding Sources University of Utah Upper Air Link Unisys Weather Upper Air Link

Lapse Rate Definitions: 

Lapse Rate Definitions

Lapse Rates: 

Lapse Rates Dry and Moist Adiabatic

Definitions - Stable/Unstable: 

Definitions - Stable/Unstable Dry 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

Temperature Inversions: 

Temperature Inversions Surface-Based and Aloft

Wind Shear: 

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 different characteristics: - Wind velocity - Moisture - Parameter gradients Altitude Temperature + + Wind Wind SHEAR ZONE


Profiles A mixed atmosphere is near-adiabatic (left) Subsidence from high pressure “caps” convection but high enough to facilitate soaring over terrain (right) Temperature Temperature Alt. Alt. d d

Surface-Based Inversion Established with Time: 

Surface-Based Inversion Established with Time d Alt. Temperature (0600 LT) (0100 LT) (2000 LT) (1700 LT) Time of Day

Surface-Based Inversion Erosion with Time: 

Surface-Based Inversion Erosion with Time d Alt. Temperature (0600 LT) (0900 LT) (1100 LT) (1400 LT) Time of Day

Cloud Base / Moisture Layers: 

Cloud Base / Moisture Layers T / DP Closure Possible Cloud Layers Moist Adiabatic Lapse Rate

The Drying Process: 

The Drying Process Rising,Cooling Condensing Sinking, Heating Drying Owens Valley Sierra Nevada Great Basin San Joaquin Valley 5K Ft Moisture, Deficit Air MSL White Mtns 5000 Ft MSL 10000 Ft MSL

De-Stabilizing Process: 

De-Stabilizing Process Colder Air Advection above, and/or Warm Air Advection below will de-stabilize Delta-T increase! Moisture presence also de-stabilizes

Basin Thunderstorm / Microbursts: 

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

Mojave Desert Downburst: 

Mojave Desert Downburst Courtesy of Caracole Soaring, California City, CA)

Microburst Sounding: 

Microburst Sounding

Thunderstorm Activity (#1): 

Thunderstorm Activity (#1) Presence of "cap"; and "penetration" of cap (observed time vs. forecast time?) Winds aloft Cell movement Anvil spread

Thunderstorm Activity (#2): 

Thunderstorm Activity (#2) Air mass Thunderstorms Favored spots Outflow



Classic Supercell Thunderstorm: 

Classic Supercell Thunderstorm 0 5 10 Nautical miles Light Rain Moderate/Heavy Rain & Hail Supercell Thunderstorm (top view) Anvil Edge Gust Front WSR-88D Radar Image Hook echo National Weather Service

Convection Circulation: 

Convection Circulation Temperature 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 Source: 

Elevated Thermal Source Great 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 Other Influences Climate and Terrain Considerations Modifying Influences and Contributions Thunderstorm Indices

Climate and Terrain: 

Climate and Terrain Great Basin Time of year Diurnal temperature spread Humidity factors Terrain rising aspects (and TAS)

Sunset / Sunrise / Normal Temps: 

Sunset / Sunrise / Normal Temps Reno, 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: 

Great Basin Temps

The Drying Process: 

The Drying Process Rising,Cooling Condensing Sinking, Heating Drying Owens Valley Sierra Nevada Great Basin San Joaquin Valley 5K Ft Moisture, Deficit Air MSL White Mtns 5000 Ft MSL 10000 Ft MSL

Major Modifying Influences(#1): 

Major Modifying Influences(#1) Washoe Zephyr Nevada Sinks Mono Lake Shear Basin Air Terrain "Holes"

Major Modifying Influences(#2): 

Major Modifying Influences(#2) Topaz Flow Mammoth Lakes June Lake

Pressure Patterns: 

Pressure Patterns Favorable 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): 

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): 

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 Detractors: 

Thermal Detractors Macro-scale Level <Cirrus Anvil from Thunderstorms <Cirrus Around jet stream cores Small pressure perturbations / waves <Convective Cloud Cover More than 50% sky cloud cover <Other Relative Humidity gradients

Thermal Enhancers: 

Thermal Enhancers Great 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

Mojave Desert Shearlines: 

Mojave Desert Shearlines

Mono Lake Shear Line: 

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

Mono Lake Shear Line: 

Mono Lake Shear Line

Mono Lake Shear Line: 

Mono Lake Shear Line

Flying “M” Shear Line: 

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

Flying “M” Shear Line: 

Flying “M” Shear Line

Flying “M” Shear Line: 

Flying “M” Shear Line

Mountain Wave: 

Mountain Wave

Mountain Wave: 

Mountain Wave

Mountain Wave: 

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

Moisture Surges: 

Moisture Surges Warm 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

East vs. West Great Basin: 

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

Soaring = f(Moisture Changes): 

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: 

Infrared Satellite Imagery Cloud top temperature Good delineator for high clouds

Water Vapor Satellite Imagery: 

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: 

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

Type #1: The Four-Corner High: 

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: 

Type #1: 6/18/88 ASI to Keeler and return

6/18/88 Raobs: 

6/18/88 Raobs WMC 94/50 RNO 90/58 TPH 83/52 LAS 98/78

Type #2: Strong Ridge: 

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: 8/9/96: 

Type #2: 8/9/96 Long-lived, extraordinary pattern Numerous 1000Km flights Over 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: 

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: 7/7/88: 

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

7/7/88 Raobs: 

7/7/88 Raobs <WMC 84/54 <RNO 84/49 <TPH 90/56 <LAS 103/77

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

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: 

Type #3(a): 6/19/93 1000Km flights from Truckee And Minden area

6/19/93 Raobs: 

6/19/93 Raobs <WMC 86/47 <RNO 88/57 <TPH 86/54 <LAS 94/72

Type #4: Building Ridge Aloft: 

Type #4: Building Ridge Aloft 2 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: 6/13/88: 

Type #4: 6/13/88 500 Mile Flight

6/13/88 Raobs: 

6/13/88 Raobs <WMC 81/42 <RNO 81/27 (!!!) <TPH 78/M <LAS 95/70


Map Types also varied as season passed!

4. Weather Forecasting: 

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 Funnel: 

A Glider Pilot’s Forecast Funnel A Process of Soaring Forecast Refinement Site Climate Outlook Forecasts Extended and Zone Forecasts (2-7 Day) Persistence Flight Day

Soaring Indices(#1): 

Soaring Indices(#1) Great Basin Thermal Index Lift = f()T)

Soaring Indices (#2): 

Soaring Indices (#2) Great Basin Soaring Index Lift = f(Convection Altitude and )T)

Soaring Indices (#3): 

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): 

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): 

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)

Thermal Lift Indices Work: 

Thermal Lift Indices Work Thermal Index (Williams/Higgins) Maximum Lift (Lindsay/Lacy) Soaring Support (Aldrich/Marsh) Soaring Index (Armstrong-Hill)

Wave Strength Forecasting : 

Wave Strength Forecasting Wave Nomogram (Herold/Armstrong)

Traditional Soaring Forecasts: 

Traditional Soaring Forecasts Persistence Nowcasting Soundings Satellite Analysis Algorithm Use

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

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: URL:

Boundary Layer Information Predictor Maps(BLIPMAP): 

Boundary Layer Information Predictor Maps(BLIPMAP) Single Time or Sequence URL: Thermal Soaring Parameters (over a geographic region) -Numerical Model Outputs General Air Mass Lift

Wind Information Predictions (WINDIP): 

Wind Information Predictions (WINDIP) (Simple Mountain Wave Prediction) “Alert” WINDIP E-Mail List Assumptions Longer Forecast Time Predictions URL:

Linear Wave Interpretation Page (LWIP): 

Linear Wave Interpretation Page (LWIP) Description Interpretation Notes Links URL: http://

Automated Thermal Soaring Forecasts: 

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:***** where ***** is NWS Office Name, I.e., Hanford, Oxnard, etc.

Interactive Forecast Preparation System (IFPS): 

Interactive Forecast Preparation System (IFPS) Man-Machine Mix “Flagship” Products Not Text -Forecasters Edit Gridded Data Graphical Products -Customer Requested Output

Gridded Data: 

Gridded Data Graphical Display of Requested Weather Parameter(s)

5. Miscellaneous Information: 

5. Miscellaneous Information Aero-medical Considerations

Aeromedical Considerations: 

Aeromedical Considerations Soaring good enough that... <Oxygen requirements <Water <Sun protection

Meteorological Concepts for Soaring in the Western U.S. : 

Meteorological Concepts for Soaring in the Western U.S. Dan Gudgel Meteorologist/Towpilot/CFIG 134 South Olive Street Lemoore, CA 93245 (w)559-584-3752 ext.223 (h)559-924-7134 <>

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