Earlier in my Spring Outlook I wrote the reasons why I expected much of March to be colder than average. I see absolutely no reason to adjust that prediction (though some moderation is possible by the weekend) as a strong blocking pattern in the upper wind pattern continues to hold sway over the Eastern North American continent. This blocking pattern in conjunction (and mainly the result of) with an an extremity negative Arctic Oscillation /AO/. Word from the Weather Prediction Center /WPC/ today confirms that with following discussion;
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1102 AM EDT TUE MAR 19 2013
VALID 12Z FRI MAR 22 2013 - 12Z TUE MAR 26 2013
MULTI-DAY MODEL AVERAGES DEPICT A SPLIT FLOW OVER NORTH AMERICA AT
THE MEDIUM RANGE, WITH CONTINENTAL POLAR AND ARCTIC AIR FEEDING
INTO THE CENTRAL AND EASTERN STATES, AND A PACIFIC JET DIVING
THROUGH THE WEST AND ACROSS THE DEEP SOUTH. THE EXTREME AMPLITUDE
AND PERSISTENCE OF THE NORTHERN STREAM OWES TO THE NEAR-RECORD
NEGATIVE ARCTIC OSCILLATION--EXPECTED TO BOTTOM OUT AT THE SHORT
RANGE.
Note the latest projection of the AO for the rest of March. The extremely negative AO is projected this week, ironically bottoming-out right around the first day of spring!
What do I mean by "strong blocking pattern" in the upper wind pattern? See Map -1
Map -1
First Day of Spring? More Like the First Day of Winter!
On March 20, 2013, at precisely 7:02 A.M. EDT, the Sun will cross directly over the Earth's equator. This moment is known as the vernal equinox in the Northern Hemisphere.
Ironically; the following projection /Map -2/ of the upper air pattern /5,000 ft/ Thursday morning the first full day /24 hrs/ of spring across North America in the east is a pitiful rendition of a spring time weather map. Actually, if one were to look at it and asked; what first calendar day of a season does this look like? "Winter" would be pretty much the unanimous reply! Note; I highlighted the -15c /+5f/ air pockets at 5,000 ft...one where it should be over the polar region and the other where it shouldn't...over the Great Lakes and Southeast Lower Michigan /black dot/. Note; the freezing line 0c /32f/ extends far south into the Southeast Gulf states.
Temperatures across Southeast Lower Michigan are/will be more typical mid January through the remainder of the week with again; some moderation due this weekend. With that moderation; latest models are intimating another storm system to form over the mid Mississippi Valley with its sights set on the Ohio Valley and possibly the southern Lakes region early next week. We also know the errors of the models lately have been in this area; so prudence will prevail at this time. ;-)
Map - 2
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian
