METC 330 Exam 3 pt 5

decoding 850 mb heights you add a

1

typical 850 mb height

150 Dm (1 mile)

850 mb uses

temp forecasting, moisture/humidity, low level jets, placing fronts

the 850 mb level is just above/within the boundary layer, meaning

it represents air that mixes w/ the surface during the day

the 850 mb should not be used in the western US bc

elevation is high, many stations are above 3000 ft (meaning 850 mb level may be in boundary layer or underground making data inaccurate)

850 mb chart to forecast afternoon high temps

1. assume well mixed atmo

2. Bring 850 mb temp down to surface using DALR

3. add seasonal adjustment

summer seasonal adjustment

+15 C

Spring fall adjustment

+12 C

WInter adjustment

+9 C

Forecast high temp =

850 mb temp + seasonal adjustment

Forecasting LE snow

look at cold air at 850 mb moving over warmer lake water (is air cold/moist enough for LES)

Uses for TS forecasting

strong low level jet, moisture advection

Strong low level Jet

brings warm air + moisture, adds wind shear, increases chance of strong storms, wind gusts and tornadoes

moisture advection

shows how moisture is moving into an area, helps determine if enough moisture for t storm