meteorological concepts for soaring in the western u.s. dan gudgel meteorologist/towpilot/cfig
TRANSCRIPT
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
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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
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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
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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
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Mojave Desert Shearlines
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Mono Lake Shear Line
• Mono Lake Shear Line “Typically” present• Example: 6/13/99
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Mono Lake Shear Line
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Mono Lake Shear Line
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Flying “M” Shear Line
• Flying “M” Shear Line “Typically” present• Example: 6/14/99
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Flying “M” Shear Line
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Flying “M” Shear Line
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Mountain Wave
54
Mountain Wave
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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
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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)
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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
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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
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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