A Generalized Approach to Precip Type Forecasting.
-
Upload
ashlynn-bennett -
Category
Documents
-
view
227 -
download
0
Transcript of A Generalized Approach to Precip Type Forecasting.
![Page 1: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/1.jpg)
A Generalized Approach to Precip Type Forecasting
![Page 2: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/2.jpg)
Temperature of the Atmosphere
• The key aspects are diagnosing the temperature of the entire atmosphere.
• Think about warm (above freezing) layers and cold layers (below freezing).
• What is the surface temperature?– If it is well above freezing, rain is likely.– If it is near or below freezing, frozen (or freezing
rain) is likely.
![Page 3: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/3.jpg)
Examples of Freezing Rain
• Note the large warm layer from ~900mb-750mb and the shallow cold layer near and at the surface.
• Surface temperature is also below freezing.
![Page 4: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/4.jpg)
Freezing Rain
Once again, note large warm layer, (~900mb-680mb) shallow near surface cold layer, and subfreezing surface temperature.
![Page 5: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/5.jpg)
Examples of Sleet
• Note smaller (less depth) and cooler warm layer between ~830mb-760mb and deeper cold layer near the surface.
• Surface temp is below freezing.
![Page 6: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/6.jpg)
Sleet
• Once again, note shallow and cooler warm layer and deep cold layer near surface.• Also note the rather cold temperatures at the surface.
![Page 7: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/7.jpg)
Examples of Snow
• Note the entire atmosphere is below freezing.• Temperatures are quite cold (<-20C) high in the cloud layer and at the surface. • Note: A cloud layer is located where the temperature dewpoint spread is ≤4C.
![Page 8: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/8.jpg)
Snow
• Entire atmosphere is below freezing.• Cold high in cloud layer (<-20C) and near surface
![Page 9: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/9.jpg)
Examples of Rain
• Note large layer above freezing and surface temp is well above freezing.
![Page 10: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/10.jpg)
General “Rules of Thumb”• Large warm layer, (>3C) shallow near surface cold
layer, and surface temp below freezing = freezing rain.
• Small and cooler (1-3C) warm layer, deep near surface subfreezing layer, and surface temp <0C = sleet.
• Entire atmosphere below freezing = snow– Exceptions!
• It can snow when the surface temp is above freezing as long as it is below freezing just above the surface.
• It can rain when the entire atmosphere is below freezing (when there is a shallow cloud layer close to the surface)
• Large warm layer and surface temp above freezing = rain.
![Page 11: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/11.jpg)
The 540 Thickness Line• Another very general “rule of thumb”– If the 1000-500mb thickness is below 540dm snow
is possible. If it is above, rain is more likely.
The thick blue line is the 540dm (5400m) line.
![Page 12: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/12.jpg)
What is the precip type?
![Page 13: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/13.jpg)
What is the precip type?
![Page 14: A Generalized Approach to Precip Type Forecasting.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649dbf5503460f94ab3b0b/html5/thumbnails/14.jpg)
What is the precip type?