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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: 11/20/2003 06:23 PM
Good Morning Philadelphia!
I'm glad to announce that these discussions will continue until at least the end of this Year!. I have the needed server space.
In short: Dry and warm through the weekend, then rain and cold weather (snow?) coming late Monday/Tuesday.
Rainfall from this last shot of precipitation is shown in the map below. You can see a broad area of one inch rainfall from W. Virginia and Virginia up into New York.
Locally, we received much rainfall in the 1 to 1.5" region. That was a good dumping of liquid!
But winter is not here yet, the snow on the ground as of Nov 19th is still confined to Canada. You'll have to wait for a trough to come and sit in the east.
The infrared satellite picture shows the temperatures of whatever the satellite is first seeing from space. Warmer temperatures are colored red and cold ice crystals in cloud tops are colored blue/green. You can see the relatively hot Gulf Stream as a red stream of water. The Great Lakes are also fairly warm while the higher elevations of the Appalachians show up as a cooler ribbon of land.
The trough that was expected to cut-off from the westerlies has not yet and is just moving off to the east. A shallow ridge to the west will warm us up right away and we won't see a slug of cold air until that new trough out west swings eastward, makes a few blizzards from Colorado to Michigan, then heads for us next week.
On the surface map, the low is sliding to the northeast pretty quickly.
Rain is still wrapping around the low and along its front, but it is out of our area. The air at the surface is moving 'mostly' along the black lines from west to east. This map implies that Indiana, Ohio and western PA has southwest winds while we still have northwest winds behind the Low.
And on the surface wind map, we DO see that pattern. Cool. No?
The southwest winds are bringing warmer temperatures into the states to the west, while we still have half a day of cooler northern winds.
Friday afternoon 1pm, the high to the south oozes eastward and a boring front is sitting to our northwest.
Saturday morning we cool a bit with the front drifting south near Philadelphia, but not much weather will come of this.
Enjoy the dry nice weather and get ready for a real shot of winter in the middle of next week.
I'll see you here Friday AM!
Meteorologist John Ensworth
Surface Station sky cover color key:
Flight category definitions:| Category | Ceiling | Visibility | |
|---|---|---|---|
| Low Instrument Flight Rules LIFR* (magenta circle) |
below 500 feet AGL | and/or | less than 1 mile |
| Instrument Flight Rules IFR (red circle) |
500 to below 1,000 feet AGL | and/or | 1 mile to less than 3 miles |
| Marginal Visual Flight Rules MVFR (blue circle) |
1,000 to 3,000 feet AGL | and/or | 3 to 5 miles |
| Visual Flight Rules VFR+ (green circle) |
greater than 3,000 feet AGL | and | greater than 5 miles |
| *By definition, IFR is ceiling less than 1,000 feet
AGL and/or visibility less than 3 miles while LIFR
is a sub-category of IFR. +By definition, VFR is ceiling greater than or equal to 1,000 feet AGL and visibility greater than or equal to 3 miles while MVFR is a sub-category of VFR. |
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