Wednesday, November 7, 2012

November 7, 2012: Winter Storm Athena Brushes Baltimore

What's In A Name?

Yes, the winter storm has received a name...courtesy of The Weather Channel (TWC).  While not officially sanctioned by the National Weather Service, TWC meteorologists took the unusual step of rolling out a naming convention for Nor'easters.   They have decided to name Nor'easters that generate impacts and cause disruption.   Personally I feel this is a good move and is long overdue.   We have been naming hurricanes since the 1950s and many Nor'easters are just as damaging and far-reaching as hurricanes.   I find it interesting that the NWS Buffalo has been officially naming Lake Effect snowstorms for many years now.  Time will tell if NWS, and other forecasting agencies, adopt TWC's somewhat daring naming convention.

A Brush With Athena

As of 2 pm today, Athena is a moderately intense Nor'easter, moving northward over the Atlantic about 150 miles east of Atlantic City, NJ.   The storm is rapidly deepening and expanding.   Moderate-heavy precipitation is occurring along the Delmarva, NJ and NY.   You can see the precipitation in relationship to the surface pressure field (isobars) in this image:


Note that the precipitation covers more area over the ocean than shown here, because weather radar along the coast has limited viewing range.

Not all the precipitation is rain.  A band of moderately heavy snowfall (1"/hr) has set up over NJ.  The snow band has developed in the "classic" location about 200 miles north and west of the storm's center, on the cold air side of the storm, in a region where a mid-level front is developing:

The light green colors represent intermittent light rain over north-central Maryland;  however, because the air beneath cloud base is dry, much of it is evaporating before reaching the surface.

Baltimore Region Impacts

Yesterday I was not calling for much, if any, snowfall in our region, and this appears to be verifying.  The NWS has scaled back their snow accumulation totals for the Baltimore region...down to a dusting around the city, up to an inch in the far northern suburbs.   Only the back edge of the precipitation shield is scraping by Baltimore, because the storm is so far out to sea.   The precip shield has expanded a bit southwestward through the day as the storm intensifies.  But there is not a lot of moisture to work with on the back edge.  And air cold enough for sustained snow has not filtered in from the north.

The storm will continue to intensify this evening, but will also continue moving away to the north.  The precipitation shield should retreat east of Baltimore after midnight.   Winds will remain breezy at times, with peak gusts in the 20-30 mph range.  Tomorrow will become partly cloudy as the storm moves further away, but the breeze will continue.   Tomorrow's the breeze will be sustained by a developing pressure gradient between the storm, and high pressure advancing in from the west.  Wind gusts should not exceed about 25-30 mph.

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