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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: 10/31/2003 09:31 AM
Good Morning Philadelphia!
I'm glad to announce that these discussions will continue until at least the end of November.
In Short: For Trick-or-Treat-ing tonight, winds will be fairly light, temperatures will be in the lower 60's to mid 50's as the kids run around under mostly clear skies. You gotta like it!
The BIG story nationwide is the switch in the upper air pattern that HAS happened.
We now have an upper atmospheric ridge overhead and temperatures are warming. The west coast is now under a tremendous trough. Wow, what a change over the last many months.
(The 500mb map shows winds (blowing parallel to the black lines) as they move over the US from west to east at roughly 18,000feet.)
We are in the region between two big high pressure systems (so you would expect air to be slowly moving clockwise around the Highs).
Skies are mostly clear as a result of the high pressure on the east coast.
And warm air is moving up on the winds (next frame) circulating around the Highs (there are already upper 70s F air out in the Ohio Valley at this time of the morning!).
Here are the surface winds... they are nearly calm under the High pressure region, and moving clockwise around the highs (winds out of the southwest) in the states to our west and southwest.
With the ridge overhead, high pressure at the surface, and warm temperatures, there isn't much to worry about in the weather. Taking a quick peek at Saturday morning, there is a front stalling over the Great Lakes, but we are still under the high pressure zone.
High temperatures Friday will approach 70 F in Philadelpha!
And by Sunday afternoon, even if New York is colder, we still are near 70 F for a high. Not much change.
Picking a random day early next week (Tuesday afternoon), you can see the ridge is STILL here on the east coast. In fact, this doesn't look very different from the map for this morning at the top of the discussion. Quiet nice weather!
Have a happy Halloween and I'll see you again Saturday morning for a short and sweet discussion (I always like at least a thunderstorm or frost to spice things up, but I'll settle for some quiet weather...for now).
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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