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Meteorological Concepts for Soaring in the Western U.S. Dan Gudgel Meteorologist/Towpilot/CFIG Presentation Points 1. Weather Information Sources 2. 3. 4. 5. Meteorology Points Synoptic Scale Weather Patterns A Forecast Funnel 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 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 • Atmospheric Soundings • Great Basin Applications • Convection concepts • Climate Aspects • Local Influences Average Lapse Rate 3.5 deg F per 1000 Ft Altitude Dry Adiabatic Lapse Rate 5.4 deg F/1000 Ft Temperature 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 Average Lapse Rate 3.5 deg F per 1000 Ft Altitude Dry Adiabatic Lapse Rate 5.4 deg F/1000 Ft Temperature Lapse Rates Dry and Moist Adiabatic 14 Definitions - Stable/Unstable Dry Atmospheric Conditions + A B A - Temperature decreasing greater than Dry Adiabatic Lapse Rate denotes unstable atmospheric conditions Altitude ( d Temperature + B - Temperature not decreasing as fast as Dry Adiabatic Lapse Rate denotes more stable atmospheric conditions Temperature Inversions Surface-Based and Aloft Altitude Altitude Aloft Surface-Based Temperature 16 Temperature 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 + Wind Altitude SHEAR ZONE Wind Temperature + Profiles • A mixed atmosphere is near-adiabatic (left) • Subsidence from high pressure “caps” convection but high enough to facilitate soaring over terrain (right) Alt. Alt. (d (d Temperature 18 Temperature Surface-Based Inversion Established with Time (d Alt. (0600 LT) Temperature (010019 LT) (2000 LT) (1700 LT) Time of Day Surface-Based Inversion Erosion with Time (d Alt. Time of Day Temperature 20 (0600 LT) (0900 LT) (1100 LT) (1400 LT) Cloud Base / Moisture Layers • T / DP Closure Cloud Layer -Possible Cloud Layers • Moist Adiabatic Lapse Rate Altitude Cloud Layer Dew Point Temperature Temperature The Drying Process Sinking, Heating Drying Moisture, Deficit Air 10000 Ft MSL Rising,Cooling Condensing 5000 Ft MSL 5K Ft Sierra Nevada White Mtns Owens Valley MSL San Joaquin Valley Great Basin De-Stabilizing Process Colder Air Advection above, and/or Warm Air Advection below will de-stabilize Cooling ( d • Delta-T increase! • Moisture presence also de-stabilizes T Increasing Altitude Warming Temperature 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 Courtesy of Caracole Soaring, California City, CA) 25 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 Classic Supercell Thunderstorm N Light Rain Moderate/Heavy Rain & Hail Gust Front Hook echo Anvil Edge Supercell Thunderstorm Hook echo (top view) Nautical miles 0 5 10 WSR-88D Radar Image 30 National Weather Service www.weather.gov 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 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 Terrain Considerations • Modifying Influences and Contributions • Thunderstorm Indices Climate and Terrain Great Basin • Time of year •Diurnal temperature spread • Humidity factors • Terrain rising aspects (and TAS) Sunset / Sunrise / Normal Temps Reno, NV • Sunrise / Sunset •June 1 •July 1 •Aug 1 •Sep 1 5:34 AM PDT / 8:20 PM PDT 5:35 AM PDT / 8:30 PM PDT 5:58 AM PDT / 8:12 PM PDT 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 37 The Drying Process Sinking, Heating Drying Moisture, Deficit Air 10000 Ft MSL Rising,Cooling Condensing 5000 Ft MSL 5K Ft Sierra Nevada White Mtns Owens Valley MSL San Joaquin Valley Great Basin Major Modifying Influences(#1) • • • • • Washoe Zephyr Nevada Sinks Mono Lake Shear Basin Air Terrain "Holes" Washoe Zephyr Carson Sink Mono Lake Shear Mono Lake Modified Basin Air Major Modifying Influences(#2) • Topaz Flow • Mammoth Lakes • June Lake Topaz Flow Mono Lake Mammoth Pass June Lake Mammoth Lakes 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) 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 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 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 46 Mono Lake Shear Line • Mono Lake Shear Line “Typically” present • Example: 6/13/99 47 Mono Lake Shear Line 48 Mono Lake Shear Line 49 Flying “M” Shear Line • Flying “M” Shear Line “Typically” present • Example: 6/14/99 50 Flying “M” Shear Line 51 Flying “M” Shear Line 52 Mountain Wave 53 Mountain Wave 54 Mountain Wave • Wave Presence for Long Distance Flight • Example: 6/15/99 55 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 • 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 57 Soaring = f(Moisture Changes) Hypothesis: Annual Climate Changes Impact Soaring • 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 58 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 Summer 2000 Map Types 25 23 20 Type #1: Four-Corner High Type #2: Strong Ridge Type #3: Low Center, Trough, Short-wave Proximity Type #4: Building Ridge Aloft 17 15 11 10 5 5 0 1 2 3 4 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: 8/9/96 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 • 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 Flight of 350 miles 7/7/88 Raobs <WMC 84/54 <RNO 84/49 <TPH 90/56 <LAS 103/77 Type #3(a): Proximity of Low Pressure Center <Low off Southern California coast provides cooler air aloft upstream to destabilize <Elevated heat source influence contributions Type #3(a): 6/19/93 1000Km flights from Truckee And Minden area 6/19/93 Raobs <WMC 86/47 <RNO 88/57 <TPH 86/54 <LAS 94/72 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: 6/13/88 500 Mile Flight 6/13/88 Raobs <WMC 81/42 <RNO 81/27 (!!!) <TPH 78/M <LAS 95/70 Summer 2000 Map Types 25 23 20 17 15 11 10 5 5 0 1 2 3 4 Map Types also varied as season passed! 77 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 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) Thermal Lift Indices Work • Thermal Index (Williams/Higgins) • Maximum Lift (Lindsay/Lacy) • Soaring Support (Aldrich/Marsh) • Soaring Index (Armstrong-Hill) 85 Wave Strength Forecasting Wave Nomogram (Herold/Armstrong) 86 Traditional Soaring Forecasts • Persistence • Nowcasting – Soundings – Satellite – Analysis • Algorithm Use Cooling d T Increasing Altitude Warming Temperature 87 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.html URL: http://www.drjack.net/TIPEX/index.html 88 Boundary Layer Information Predictor Maps(BLIPMAP) •Thermal Soaring Parameters (over a geographic region) -Numerical Model Outputs •General Air Mass Lift •Single Time or Sequence URL: www.drjack.net/BLIPMAP/index.html 89 Wind Information Predictions (WINDIP) (Simple Mountain Wave Prediction) • “Alert” WINDIP E-Mail List • Assumptions • Longer Forecast Time Predictions URL: http://www.drjack.net/WINDIP/index.html 90 Linear Wave Interpretation Page (LWIP) • • • • Description Interpretation Notes Links URL: http:// www.drjack.net/LWIP/index.html 91 Automated Thermal Soaring Forecasts Walt Rogers (WX), MIC CWSU ZLA • Two Parts: 1.Pure Model Output (top portion) 2.NWS Forecast Temps as base (lower portion) • Limitations • NWS Websites URL: http://www.weather.gov/***** 92 where ***** is NWS Office Name, I.e., Hanford, Oxnard, etc. Interactive Forecast Preparation System (IFPS) •“Flagship” Products Not Text -Forecasters Edit Gridded Data •Graphical Products -Customer Requested Output • Man-Machine Mix 93 Gridded Data Graphical Display of Requested Weather Parameter(s) 94 5. Miscellaneous Information • Aero-medical Considerations Aeromedical Considerations Soaring good enough that... <Oxygen requirements <Water <Sun protection 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 <[email protected]>
