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The Story Behind the Weather - By Forecaster John Ensworth M.S. - 

The Discussion of Weather Events Daily for Philadelphia and Pennsylvania

  last updated: 09/14/2003 02:20 PM

    Wow, a nice day!  If you remember back to the drought years of recent, it is easier not to get down about the very wet, cloudy and cool spring this has been.   The current visible satellite picture shows very clear skies across all of New England and the East Coast.  There is a plume of thin cirrus (high ice clouds) streaming southeast across the state, but the sun will warm us nicely into the upper 70's today. 

The national surface map valid at 8am shows the weekend's storm system far to the northeast in the Nova Scotia area. The yellow lines across the map are isobars (lines of equal surface barometric pressure adjusted to sea level (so we can ignore changes due to the topography of the US and only concentrate on the weather causes)) are streaming out of the northwest to the south east over us.  The wind closely follows these yellow lines rotating counterclockwise around low pressure systems and clockwise around high pressure systems.  The next rain producer (that will arrive Tuesday afternoon and into Wednesday) can be seen getting it's act together in the southern plains. 

Jumping forward 24 hours to Tuesday morning at 8am, we see the next surface system getting closer (with a cool front slipping down from Canada to our north)...

And finally, by Tuesday at 8pm, we are sitting again under the rain shield north of the low pressure system with east (on shore) winds, cool temperatures and wetness everywhere.   

An interesting point to note is that these systems are originating in the Colorado/New Mexico/Texas area and are moving east then north towards us.  The previous few systems started in the northern plains (around Montana and the Dakotas) and slid east and southeast towards Pennsylvania.   Does this speak for a change in pattern that will give us a warmer, more seasonal end of the Spring?  Stay tunes...

Meteorologist John Ensworth, M.S. 

(This page sometimes contains sources from AccuWeather.com   www.accuweather.com ).