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

The Discussion of Weather Events Daily for Philadelphia and Pennsylvania

 Last updated: 10/17/2003 09:35 AM
 

Good Afternoon Philadelphia!   

    I'm glad to announce that these discussions will continue until at least the end of November.  

We have clouds, and lots of them.  The front that stalled here a day or so ago is sitting just to our south.  Moist warm air from the south -above the surface- is flowing up over the cool air and generating tons of cloudiness. 

This satellite view, an Infrared Satellite Image, shows temperature instead of reflectivity (or what looks white like the visible satellite above). Blue colored regions are cold higher cloud tops, reds are warm temperatures.  You can see the Great Lakes are warmer than the surrounding land (north of the cool front) and you can see the warmer southern Atlantic ocean - where the Gulf Stream is. We have many middle and high clouds streaming over Pennsylvania as this system gains strength again. 

Temperatures are in the upper 40's and lower 50's near Philadelphia this morning, 

and winds near the front (all of our state) are nearly calm (nice change over the last two days!). 

This means we don't have much of a wind chill, which is a cooling effect on the human body as wind removes heat as if the temperature were lower than it is. 

The Weather channel shows the front sitting right on Philadelphia with a low deepening over Arkansas and western Tennessee. Rain is forming north of the front and ahead of the low. 

Weatherunderground.com has the front significantly further south - with the low further south as well.   I like the pattern of precipitation around the Weather Channel's analysis better.  Different meteorologists see fronts a bit differently sometimes. 

Checking for winter precipitation, we see it is all rain over the state (and light, but approaching us). 

The upper air pattern responsible for all this fun is the newly digging (deepening trough - marked in red) trough over the Mississippi Valley.  Remember, you look for storms and strengthening Low pressure systems and fronts on the right side of a trough.  We are becoming located on the right side of the trough!

By 2am tonight (Saturday morning) the trough will move to the east...

And the low races up towards us, the front slides to the east, and a wave of rain is passing (from midday today through Saturday morning).

Then by Saturday night 8pm, the trough has moved off the east coast and the western ridge is BIGGER!

And the lows and front and rain is all off the coast. Then we settle in for a dry spell. 

So stay dry and warm as best as you can...

And I'll see you tomorrow morning!

Meteorologist  John Ensworth

Surface Station sky cover color key: