Tuesday, March 20, 2012

Bermuda High Strength, Miami Style Temps In March

Today's mid 70's repeat (thanks to a bit extra sunshine and the timely burnoff of fog) provided the region a taste of Miami in March as humidity levels were pretty high. It's weird when I can actually calculate a heat index on a March day (I could today...it was 76 at 4 PM).  It's not quite Miami-like considering their average high today is 81 but it's still North Florida style weather here in Philadelphia in March.

We've had heat in March -- it's a bit more rare to get the humidity (or whatever amount of it there is) to go with it for the ride.  However, the pattern aloft is supportive of warmth and supportive of humidity.  High pressure aloft across the Carolinas and Southeast, with a broad south to southwest flow in the atmosphere pumping moisture northward from the Gulf of Mexico, pumping up atmospheric heights across the Mid Atlantic to summertime levels and allowing for temperatures and dew point values to jump.  In 1998, our dew point values when the worst of the 80 degree days hit the region in March reached 63 on the 31st...humidity can be a factor even this early in the year...just not that often.

Consequently, the strong trough in the Western US has helped keep the Eastern US ridge in place...and helped feed into it as the pattern aloft is somewhat stuck in place, with little to break or bog down the ridge of high pressure.  The result is uber warmth surging northward into Minnesota, Manitoba, Ontario, and Michigan.  Minneapolis recorded its earliest 80 degree day on record.  International Falls had a low on Monday of just 60 degrees, smashing its warmest March morning on record...and Rochester, MN on Sunday surpassed the record high for the date not only at Midnight...but at their lowest temperature point for the day!

This afternoon, warmth pretty much engulfed the eastern 40% of the country -- generally along and east of the Mississippi River to the East Coast and more record highs are being knocked out throughout this territory, including some all-time records for March.   You know it's warm when they're selling ice cream outdoors in Toronto in March!

I overlayed the temperature/mid level map so you can see the outline of the March "Supertorch" perfectly -- it is essentially where the mid level ridge is setting up shop, with the core or warmest of the warm generally on the western edges of the ridge, particularly where the south-southwest flow is the strongest aloft and at the surface ahead of the surface cold front that separates "less warm" from really warm.

In our future, the warmest days will be on Thursday and Friday as the ridge begins to break down ever-so-slightly and the influence of the jet orientation aloft becomes west-southwest over us.  Those days are our best chances to hit 80.  At this point, the potential back door front that we talked about last night is looking like it will approach or cross the region on Friday but the front's cooling effects may not be felt until Friday night and Saturday.   The warmest of the warm is still ahead of us and has the potential to knock out a few more records before we're all done.