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: 09/14/2003 02:38 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 will be ordered Thursday. Yikes. ]

With yesterday's batch of rain and thundershowers, we received another 0.77 inches of precipitation.  The water keeps coming (remember that multi-year drought we just finished?)...

It's morning again and the showers have calmed down.  Much of the precipitation is driven by sunlight as well as upper level energy (the short waves described in the last week's set of discussions) that is also shown a few maps down. 

The surface map shows a surface low near us (just to our NE) and the sort-of front / boundary to our east.  Most of the heaviest rain should be to our east now because of this drift of the front, but as long as it is nearby, we can still get some shower and thunderstorm activity, again, mainly in the afternoon and early evening. 

The upper air map (showing winds blowing primarily from west to east across the US at about 18,000 feet, or at the place where the atmospheric pressure is about half of what it is at the surface) shows the big eastern US trough in red, and the little bubbles of cool air traveling in the flow marked in blue.  When the ground is warm in the afternoon, and the air is moist, and there is a surface boundary where air is coming together, and when one of these goes overhead, you can get rain.  That'll be the story with the showers/thunderstorms to come through the weekend.  

It's definitely moist and mainly cloudy in the east (except right near Philadelphia for now). 

There are (as usual) warmer temperatures to the east of the Appalachians, but the soupiest warmest air is off the coast and to our south.  The blue dashed line shows a mainly land formed (not frontal formed) change in temperatures currently. 

Winds are light over us, but blowing from the north over the Ohio valley (sort of how you would expect air to flow behind a frontal system). 

Now, into the future.  Saturday morning shows the trough not significantly changed over the east. 

And rain and showers are still possible everywhere to the right of the trough. 

Sunday morning, the trough is a bit more shallow! Things are changing...

And the chances of rain drop to chance levels, rather than all rain...all the time. 

On Monday morning, the trough is broader and the 'uphill' right side of the trough is even more off to the east.  

And the rain chances begin to retreat eastward (but still  exist around Philadelphia). 

Then Tuesday shows the trough tilting and shifted, again, a bit further east. 

And the chances of rain are all but gone (I think there should be some green coloration on the map below, the trough isn't gone yet, and they did include the words). 

Wednesday morning, the trough looks very different with the Bermuda High (that big area over the southwest Atlantic) begins to dominate the southeastern US.   The heat should return with this development as well. 

I'll be connected via modem for the next 5 days (and the server will still be down until about the time I get back from vacation).  But I'll keep this up, just in a, possibly, reduced manner). 

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

Surface Station sky cover color key: