Tag Archives: Explosive Cyclogenesis

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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Deep Storm Monday Through Tuesday

Update Sun 3/12 7:39 PM — Several of this afternoon’s higher resolution models show enough cold air being brought in to this system by early Tuesday morning that the precipitation will be falling here as snow. Surface temperatures above freezing will limit or prevent accumulation. Solar effects (insolation) through clouds and high March sun angle will further prevent accumulation on dark roadways.

Still a very dynamic system that needs to be watched.

Previously Posted Sun 4:38 PM —

This week’s weather will start out with a coastal storm that is expected to first give us rain Monday through at least early Tuesday as it moves northward. This storm is then expected to retrograde toward Cape Cod and undergo “explosive cyclogenesis“. (yes, the “bombogenesis” as they like to call in on TV.)

Extremely low central surface pressure with blocking high pressure in the North Atlantic will result in very high winds and heavy rains and inland snow to New England. We will be indirectly affected by this storm in it’s advanced form.

It appears that the light rain tonight will move in later tonight (Sun), after midnight. Monday will be increasingly rainy and windy.

Here’s the NAEFS forecast for 11 PM Monday night —

Today’s 12z NAEFS model forecast for Monday night. Coastal low (1) will sling back rain into our area on easterly winds. The upper level low (2) will pull the surface low to the coast as its normal northeastward movement will be blocked by strong high pressure ridge (3) in the North Atlantic.

By Tuesday evening, the low has retrograded close to the Massachusetts coastline and undergone the extreme cyclogenesis. Notice it’s still raining here!

NAEFS model forecast for Tuesday evening show the surface low (1) and the upper low-blue (2) have become almost vertically stacked. Strong cyclonic flow around this storm (white arrows) will bring cold windy conditions with continued rain. Notice the 32º surface line (white on my maps) is well west of us in central PA. keeping it rain for us. (Click on image for a larger view.)

By Wednesday, things dry out here and it will become milder towards the end of the week. Another rainstorm, faster moving, affects us next weekend.