Penn State Weather Camps Basic Weather Forecasting Guidelines

Basic Forecast Guidelines Climatology Forecast = averages for today Persistence Forecast = yesterday’s valuesyesterday’s values

Basic Forecast Guidelines Climatology – Persistence – Modified Persistence What causes temp to change? ◦Cloud cover:  Day Vs. Night ◦Precipitation:  When it rains T’s tend to be higher/lower? Why? ◦Wind and Fronts:  Direction ◦ N vs. S  Speed ◦ Day Vs. Night

Basic Forecast Guidelines What causes rain? ◦Need clouds!  Will any ole cloud do? ◦Moisture supply  Bodies of H20 – Moisture content of air (Td) ◦Upward motion:  How affect clouds/precip.?  Mechanisms for “lift” ◦ Fronts – Topography – Low Pressure – Jet stream dist. ◦Intability (convection):  Warm down low … cold up high!

Basic Forecast Guidelines Climatology – Persistence – Modified Persistence Extrapolation/trend Forecast = Look upstream to see what the wind’s bringing in ! ◦Satellite IR - Satellite VIS - Radar - sfc. map 1 - sfc. map 2Satellite IR Satellite VIS Radarsfc. map 1 sfc. map 2 Thunderstorms/Moist Convection ◦Triggers ? ◦Fuel  LI LI  Cape Cape

Basic Forecast Guidelines The “Models” ◦Simulate future state of atmosphere ◦Higher resolution / lower resolution The “Models” ◦Lower Res. (GFS)Lower Res. (GFS) ◦Higher Res. (NAM)Higher Res. (NAM) ◦Higher Res. (HRRR)Higher Res. (HRRR) Clouds Forecasting … ◦SoundingsSoundings ◦Cloud forecasting ICloud forecasting I ◦Cloud forecasting II – NAMCloud forecasting II – NAM ◦Cloud forecasting II – HRRRCloud forecasting II – HRRR

Your competition !!! ◦The National Weather ServiceThe National Weather Service ◦The Weather ChannelThe Weather Channel ◦AccuweatherAccuweather ◦The guy or gal to your left and right