Friday, March 09, 2012

Weather History: Seabreeze & Backdoor Fronts In March

Yesterday marked the 12th anniversary of the earliest 80 degree day in Philadelphia's recorded history...while we did reach 70 and that's an impressive accomplishment, it's still ten degrees shy of the record for the day.   In putting together the post, I bounced around a couple of different ideas -- one was to talk about the day itself and how warm it got -- that's run of mill.  I thought it would be kinda neat, though, to show the progression of a seabreeze (some would argue a backdoor) front in the month of March, especially since one of these on this level don't quite have as much of a contrast across the region since temperatures typically don't get to 80 in March all that often.

The warm-up to 80 in Philadelphia was part of a two day "torch"...the 9th also hit a record-setting 73 in Philadelphia that included some thunderstorms in the afternoon.  However, the 8th was the peak of the heat for just about everyone except Atlantic City and the Shore (which had their warm day on the 9th).  Temperatures by 1 PM were pushing into the 80's in York, mid and upper 70's across much of the Philly metro, but you can see the Shore hanging in the 60's with a wind off the Atlantic.  Over the course of the next several hours, those east and southeast breezes off of the chilled Atlantic would work their way west.

By 3 PM, which was pretty close to the peak heat of the day -- temperatures flirted with 80 in a number of spots around Philadelphia and were in the 80's in Central Pennsylvania.  Belmar was down to 55, with 50's common across the New York metro.

As the oomph of the March sun was diminishing towards sunset, the seabreeze and cooling were able to make inroads to the west.  Temperatures dropped to the 60's at Trenton and Mount Holly by 5 PM, into the lower 50's in Belmar.

And by 7 PM, temperatures dropped into the 40's and lower 50's at the Shore and below 60 in Trenton, Millville, Mount Holly, and Dover, with Philadelphia down to 62 as winds nudged to the southeast during the 5 PM hour.  Philly dropped into the 50's an hour later and bottomed out around 43 early in the morning on the 9th before rebounding back to 73.  It's not often in March you see this type of setup fire through -- temperatures in the 70's in Reading at 7 PM while Belmar is 46 degrees.  You'll see it in April...sometimes early May...but not in early March.

One could argue this was part backdoor front as well -- reanalysis data shows a very weak high near Nova Scotia that nudged some easterly winds into the New England, which worked their way down the coast.  The influence of this high was rather weak and as the cold front approached the next day southwest winds were able to take back over and send the region back into the 70's.

One of the uglier backdoor fronts occurred in April 2003 where temperatures went from the upper 80's on the 16th to the 40's on much of the 17th.  Thankfully, the March warm up, cool down, and warm up in 2000 wasn't ugly on the order of April 2003, except if you like snow.