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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 02:32 PM
 

Good Morning Philadelphia!  

[The server this page resides on continues to be down today... so no one will be able to see this live.  I'll, again, quickly recap what is happening, and wait for the big diagnosis to return when the power is back on!  Update, the UPS is out and one was ordered Thursday. Yikes. ]

Rain is the story still.  According to the National Weather Service, Philadelphia has recorded more than a trace of rain 100 days this year so far.  Normally we only have 115 days of measurable rain.  As they point out, though, we are only 12% above normal.  We've been spared the heaviest rains many times. 

Looking at the totals, we've had 2.58" of rain this month do date, where last year we had only seen a trace of rainfall. We are about 3.50" above normal this year, but about a foot over how much had fallen by this time last year. Wow. 

This current round of storms and showers had dumped locally (very locally) up to 4-5" of rain in places (the reds on the map). Around Philadelphia, we've received about 0.10" to 0.50"of rain. It's more water, but not record breaking. 

The Weather Channel has a new-ish trough to our west and a cold front oozing down from Canada...

While the NWS (National Weather Service) has our old friend, the dead front, still in place with a Low still near Philadelphia. They have a cold front oozing down from the northwest as well. 

Either way, the story is similar.  Very humid tropical air is continuing to flow northward on the west side of the Bermuda High over the ocean, and on the east side of the low pressure regions to our west giving us a LOT of water available in the atmosphere to fall in very  heavy rain showers. 

Our upper atmospheric trough is still there (marked in red) with more mini-troughs (short waves) marked in blue.  The short waves will rotate around the big trough and kick off storms and showers when they pass over a warm moist lower atmosphere.  Because of this, the NWS has issued a flood watch for many locations up the east coast. 

By early morning Tuesday, the trough and slowly approaching front are still players in the area making the days and nights wet, on and off. 

The surface map is still not significantly different by Tuesday night either. 

But the change is coming. By Wednesday morning, the trough over us begins to weaken and break up.  There are pieces of the growing ridge (marked below) gaining strength as a trough builds (deepens) on the west coast. 

Thursday morning, the upper air pattern looks as different as it has in a long time.  We should have a nearly zero chance of rain by then!

Friday morning and there is a trough 'like' feature setting up on the east coast, but the central US has the big ridge streghtening (marked in red). 

And that ridge parks itself over the Ohio valley putting us on the down wind side of a ridge, not a trough.  Expect warmer/hotter and drier weather by the end of the week!

I'll be connected via modem for the next 2 days (and the server will still be down until about the time I get back from vacation).

Hopefully the servers will be working soon and I'll be able to post live again. 

Until then, keep looking up and stay dry!

Meteorologist  John Ensworth

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