ChicagoLand Glider Council Soaring Weather and Data Analysis Soaring Weather and Data Analysis Greg Chisholm Greg Chisholm December 19, 2000 December 19, 2000 ChicagoLand Glider Council Al McDonald Photo Weather Data and Analysis 1
Outline ● The internet - so much data – so little time ● The internet - so much data – so little time ● Brief introduction ● Brief introduction ● Introduce SkewT/LogP ● Introduce SkewT/LogP ● Examples ● Examples ● Discussion on how to improve our page ● Discussion on how to improve our page ChicagoLand Glider Council Weather Data and Analysis 2
What’s out there! Meteo-Speak Sounding diagrams provide a important means for determining the stability of the Sounding diagrams provide a important means for determining the stability of the ■ ■ atmosphere above a specific location. By using the concept of an air parcel, lifting it atmosphere above a specific location. By using the concept of an air parcel, lifting it or lowering it and comparing the resulting parcel conditions to the conditions of the or lowering it and comparing the resulting parcel conditions to the conditions of the surrounding environment as defined by the balloon sounding. surrounding environment as defined by the balloon sounding. Parcels of unsaturated air tend to follow the dry adiabat lines as they ascend or Parcels of unsaturated air tend to follow the dry adiabat lines as they ascend or ■ ■ descend. The saturation adiabats lines show how parcels saturated with water descend. The saturation adiabats lines show how parcels saturated with water vapor will ascend or descend. Descending parcels will tend to unsaturate vapor will ascend or descend. Descending parcels will tend to unsaturate immediately. The mixing ratio lines relate to the amount of water vapor in a parcel in immediately. The mixing ratio lines relate to the amount of water vapor in a parcel in grams of water vapor per kilograms of dry air. Parcels of air attempt to maintain a grams of water vapor per kilograms of dry air. Parcels of air attempt to maintain a constant mixing ratio as they ascend or descend. Generally, a parcel will rise, constant mixing ratio as they ascend or descend. Generally, a parcel will rise, following the dry adiabat until it saturates. This occurs when dry adiabat crosses following the dry adiabat until it saturates. This occurs when dry adiabat crosses the initial mixing ratio line. This is considered the LCL. If lifting continues, the the initial mixing ratio line. This is considered the LCL. If lifting continues, the parcel cools following the saturation adiabat. If the parcel descends, it will always parcel cools following the saturation adiabat. If the parcel descends, it will always follow the dry adiabat as it will immediately unsaturate if saturated. By then follow the dry adiabat as it will immediately unsaturate if saturated. By then comparing the parcel temperature to the environment, you can determine whether it comparing the parcel temperature to the environment, you can determine whether it is stable (parcel cooler) or unstable (parcel warmer). An unstable parcel will is stable (parcel cooler) or unstable (parcel warmer). An unstable parcel will accelerate upwards and is the primary means for thunderstorm development. A accelerate upwards and is the primary means for thunderstorm development. A stable parcel will decelerate and eventually descend. This is the typical atmospheric stable parcel will decelerate and eventually descend. This is the typical atmospheric condition and it the primary condition in high pressure areas. The descending air condition and it the primary condition in high pressure areas. The descending air desaturates the atmosphere and leads to clearing skies and calm conditions desaturates the atmosphere and leads to clearing skies and calm conditions ChicagoLand Glider Council Weather Data and Analysis 3
What we want ● Top and strength of the lift ● Top and strength of the lift ● Thermal Indices ● Thermal Indices ● Cloud base estimates ● Cloud base estimates ● Perturbations, i.e., ● Perturbations, i.e., ✸ Clamp ✸ Clamp ✸ Sea Breeze Front ✸ Sea Breeze Front ● Conditions over our airfield and changes over time ● Conditions over our airfield and changes over time “Thermals are a product of instability - their height depends on “Thermals are a product of instability - their height depends on the depth of the unstable layer and their strength depends on the the depth of the unstable layer and their strength depends on the degree of instability. To arrive at an estimate of the thermal degree of instability. To arrive at an estimate of the thermal height and strength, a thermal index (TI) is computed ...” (Extract height and strength, a thermal index (TI) is computed ...” (Extract from SSA's Soaring Flight Manual) from SSA's Soaring Flight Manual) ChicagoLand Glider Council Weather Data and Analysis 4
Kevin Ford’s Offering - Abbreviated ChicagoLand Glider Council Weather Data and Analysis 5
Partial output for an ILX request ChicagoLand Glider Council Weather Data and Analysis 6
Introduction – SkewT/LogP ● Temperature as a function of height (denoted ● Temperature as a function of height (denoted by pressure) by pressure) ● Pressure is plotted horizontally on an inverse ● Pressure is plotted horizontally on an inverse log scale = LogP log scale = LogP ● Temperature is plotted with a skew to the ● Temperature is plotted with a skew to the right = SkewT right = SkewT ● Dry and saturation adiabats are drawn to aid ● Dry and saturation adiabats are drawn to aid analysis analysis ● Winds as a function of height are also plotted ● Winds as a function of height are also plotted ● Additional esoteric meteo-stuff is provided ● Additional esoteric meteo-stuff is provided ChicagoLand Glider Council Weather Data and Analysis 7
GOES SkewT ChicagoLand Glider Council Weather Data and Analysis 8
Thermal Soaring and the SkewT – Valley Soaring Association – P.J. Kelley ● Want to predict height and strength of ● Want to predict height and strength of thermals thermals ● Most SkewT diagrams are too complicated for ● Most SkewT diagrams are too complicated for our use our use ✸ especially since we’re only interested in the bottom ✸ especially since we’re only interested in the bottom 25% 25% ✸ For example -- 0-50K’ + pressure/alt + temperature ✸ For example -- 0-50K’ + pressure/alt + temperature + dry adiabat + sat. adiabat + mixing ratio + + dry adiabat + sat. adiabat + mixing ratio + dewpoint + hodogram + wind) dewpoint + hodogram + wind) ● Note: the following is provided by soaring ● Note: the following is provided by soaring pilots for soaring pilots – meteorologists be pilots for soaring pilots – meteorologists be warned warned ChicagoLand Glider Council Weather Data and Analysis 9
Blank Soaring SkewT ChicagoLand Glider Council Weather Data and Analysis 10
Building Your Own SkewT 1) Plot the forecast high temperature for the day, e.g., 86°F., 1) Plot the forecast high temperature for the day, e.g., 86°F., at airfield elevation at airfield elevation 2) Plot the forecast temperatures aloft, e.g., 2) Plot the forecast temperatures aloft, e.g., 3,000’, 260/8, no temp 3,000’, 260/8, no temp ■ ■ 6,000’, 270/7, +12°C ≅ +53°F 6,000’, 270/7, +12°C ≅ +53°F ■ ■ 9,000’, 300/15, +7°C ≅ +45°F 9,000’, 300/15, +7°C ≅ +45°F ■ ■ 12,000’, 290/15, -2°C ≅ +28°F 12,000’, 290/15, -2°C ≅ +28°F ■ ■ 3) Connect the dots 3) Connect the dots 4) The top of the thermals is the intersection of the dry 4) The top of the thermals is the intersection of the dry adiabat for today’s high and the temperature aloft plot adiabat for today’s high and the temperature aloft plot (sounding) (sounding) ChicagoLand Glider Council Weather Data and Analysis 11
Example 12K ′ ,28 ° F 1. Forecast Hi 2. Temps aloft 3. Connect dots 4. Intersection = Top 9K ′ ,45 ° F This Day’s 6K ′ ,53 ° F Thermal Top Forecast Hi ChicagoLand Glider Council Weather Data and Analysis 12
Thermal Strength ● Thermal Index (RAOB based ala Kevin Ford) ● Thermal Index (RAOB based ala Kevin Ford) ✸ At any altitude below the top of the lift, the difference ✸ At any altitude below the top of the lift, the difference between between ✜ the dry adiabatic temperature (i.e., the intersection of ✜ the dry adiabatic temperature (i.e., the intersection of the adiabat eminating from the forecast high the adiabat eminating from the forecast high temperature/field altitude point on the graph and the temperature/field altitude point on the graph and the altitude of interest), for the day’s forecast high temp. altitude of interest), for the day’s forecast high temp. and and ✜ the sounding temp. ✜ the sounding temp. ● Thermal Index (time dependant) ● Thermal Index (time dependant) ✸ ..., the difference between ✸ ..., the difference between ✜ the dry adiabat temperature (i.e., the intersection of ✜ the dry adiabat temperature (i.e., the intersection of the adiabat eminating from the ground the adiabat eminating from the ground temperature/field altitude point on the graph and the temperature/field altitude point on the graph and the altitude of interest), and altitude of interest), and ✜ the sounding temperature ✜ the sounding temperature ChicagoLand Glider Council Weather Data and Analysis 13
Kevin Ford Example ChicagoLand Glider Council Weather Data and Analysis 14
Recommend
More recommend
