4th Warmest Winter at Philadelphia

Preliminary data from the National Weather Service indicate that the winter of 2011-12, ending today, was the 4th warmest at Philadelphia since official climate records began in 1872. The average temperature of 40.7° was 0.3° warmer than the previous 4th warmest winter in 1997-98. As was the case in New York, the 12th of February was the only day this month with below-average temperatures.

The previous 10 warmest winters at Philadelphia were:

1932 43.3
1890 42.3
2002 41.3
1998 40.4
1933 39.9
1880 39.7
1991 39.1
1913 39.0
1937 38.9
1949 38.8  

Second Warmest Winter in New York Since Records Began in 1869

Preliminary figures from the National Weather Service indicate that the winter of 2011-12, ending today, was the second warmest in climate records extending back 143 years at Central Park in New York City. The winter average temperature of 40.5° was 0.4° above the previous second warmest in 1931-32. Each of the 3 winter months was well above the long-term average. In February, only one day, the 12th, with a high of 32° and a low of 20°, was below average.

Three of the winters this century are now in the top 10 warmest list. The previous warmest winters at Central Park were:

41.5    2001-02               
40.1    1931-32                  
39.6    1997-98                        
39.2    1990-91                  
38.7    1998-99                  
38.5    1948-49 & 1889-90      
38.1    2005-06 & 1852-53      
38.0    1879-80                
37.9    1982-83 & 1936-37      
37.8    1996-97 & 1932-33       

Washington's Warmest Winters Update: Leap Year Leap Clinches 3rd Place

March 1, 12 PM Update: The National Weather Service confirms that this winter was the 3rd warmest in history at Washington, as reported previously at CapitalClimate (see below). It was also the warmest on record for the shorter period of record beginning in 1962 at Washington Dulles and the 7th warmest at Baltimore:

FOR WASHINGTON DC...MEASURED AT REAGAN NATIONAL AIRPORT...DCA...

THE AVERAGE WINTER TEMPERATURE OF 43.4F RANKS AS THE 3RD WARMEST
WINTER... DEC-FEB...ON RECORD BEHIND ONLY THE WINTERS OF
1931-32... 44.6F AND 1889-90...44.3F.

FOR BALTIMORE MD...MEASURED AT BWI THURGOOD MARSHALL AIRPORT...BWI...

THE AVERAGE WINTER TEMPERATURE OF 40.7F RANKS AS THE 7TH WARMEST
WINTER ON RECORD...THE WARMEST WINTER SINCE 1949-50. THE WARMEST
WINTER IN BALTIMORE WAS 1931-32...45.3F.

FOR DULLES AIRPORT...IAD...

THE AVERAGE WINTER TEMPERATURE OF 40.1F RANKS AS WARMEST ON
RECORD...BREAKING THE PREVIOUS WARMEST WINTER OF 39.8F SET IN
2001-02. THE PERIOD OF RECORD AT DULLES GOES BACK TO 1962. 

1 AM Update: Woot! A high temperature of 56° just before 11 pm rounds up the winter average to 43.4°.

10 PM Update: A temperature of 55° at this hour puts the winter average within 0.005 of rising by another 0.1° to 43.4°.

5 PM Update: The exact final result may depend on how the National Weather Service accounts for leap year, but today's preliminary high as of 4 pm is 52°, which virtually locks in the winter average at 43.3°. Since a further rise of 2° on southerly winds through the evening is not out of the question, the average could actually bump up, as noted below.

Original post:
With a 2 pm temperature of 51°, following a jump of 6° in the previous hour, and an overnight low of 40° on Leap Day, Washington, DC has maintained a 2011-12 winter average temperature of 43.3°, which edges out 2001-2002 by 0.1° as the 3rd warmest winter in over 140 years of climate history. A further increase of just 3° in this afternoon's temperature would raise the final seasonal average by another 0.1°. On the other hand, because of rounding, it would require a highly-unlikely drop of at least 7° in the daily low (to 33°) before midnight to reduce the average by 0.1°.

Although March snow is not completely out of the question (see "Not the March of the Penguins"), this winter is also the 3rd least snowy on record.

Images (click to enlarge): Washington's 10 warmest winters vs. 2011-12 average to date (through 4 pm February 29) and 10 lowest seasonal snow totals, CapitalClimate charts from National Weather Service data

Unanticipated Consequences: Hurricane Irene Claims Another Life

Hurricane Irene was 6 months ago, but its effects linger. From today's high-fiber edition of WaPo:

Calvert man is crushed by fallen tree’s root ball
By Carol Morello, Sunday, February 26,7:27 PM

A Calvert County man died Saturday afternoon when a root ball the size of a small car rolled onto him while he was cutting up a toppled tree, authorities said.

Brian W. Buck, 50, of Lusby was working on an oak tree that fell last August during Hurricane Irene, said Lt. Steve Jones of the Calvert County Sheriff’s Office. When a large log rolled into the hole where the tree once stood, Buck jumped into the hole to retrieve the log.

A root ball estimated to weigh more than 10 tons then rolled into the hole, crushing Buck. A backhoe operator was summoned to lift the root ball, Jones said. Buck was pronounced dead at the scene.

Washington's Warmest Winters Update: 4th Place Tied, 3rd Within Reach; 2 of 4 Warmest Winters Within Last 11 Years

PM Update, February 24: Last night's area forecast discussion said:

ALMOST THROUGHOUT THIS WINTER BOTH HIGH AND LOW TEMPS HV BEEN UNDERFCST 
BY THE MDLS SO WL STAY ON THE WARM SIDE 

So, right on schedule, the 24-hour forecast of 75° was busted by 18° in the wrong direction with a high of 57°. Nevertheless, the winter average temperature to date remains tied for 3rd warmest. Although it will be colder over the weekend, temperatures at or near 60° by Wednesday should be enough to clinch undisputed possession of 3rd place. [Chart updated above.]

PM Update, February 20: Today's high and low, if it holds through midnight, have already exceeded Sunday's forecast by 2° each. Along with upwardly revised forecasts for the rest of the week (including 68° on Thursday), the projected winter average is now slightly edging out 2002 for sole possession of 3rd place.

Original post:
As noted earlier, Washington has been having an exceptionally warm winter. Temperatures in the past week have confirmed that trend, consistently outperforming even above-average forecasts. This excess culminated on Saturday, when the high of 59°, exceeded the extended forecast by 9°. Although today's high of 45° was well below Monday's National Weather Service forecast of 51°, it was also well above the forecast of upper 30s made less than 24 hours in advance. Altogether, the week's daily highs averaged 3.3° above the temperatures forecast last Monday.

The winter average temperature to date now stands at 42.9°, tied with 1950 for 4th warmest in Washington climate history. Projecting forward using the forecast for the next week, the temperature will have to average just 3° above normal for the last 3 days of the month in order for the winter to tie with 2002 for 3rd place. Regardless of the exact final result, it's likely that 2 of the 4 warmest Washington winters will have occurred in the last 11 years.

Image (click to enlarge): Washington's 10 warmest winters vs. 2011-12 average to date and projected through end of February, CapitalClimate chart from National Weather Service data

Snowfall Scarce Following February 50s; Washington Snow Rare Immediately After Warm Temperatures

The weather-wise are all a-Twitter over the prospect of snowfall in the Washington, DC region on Sunday, but the situation is giving forecasters fits. There's a good reason for that, since warm-February snows, while not impossible, are rare.

Since official records were kept at or near the current location at National Airport beginning in 1930, there have been only 8 instances in which 2" or more of snow fell in the calendar day following a day with temperatures of 50° or higher. With today's high of 54° and a similar reading expected tomorrow, there is a considerable climatological obstacle to overcome. In fact, there have been only 5 cases in which a 2"+ snowfall followed a day with a high above 53°.

The most recent instance of significant snow following 50°+ temperatures was on Feb. 22, 2001, when 2.8" of snow followed a previous day's high of 57°. That was preceded by a 3.6" snowfall on the same date in 1986, following a temperature of 56°.

The full list of February 2"+ snowfalls on the day after 50°+ temperatures is:

Date     Snowfall Temperature
2/16/1937 5.6       52
2/14/1940 2.5       53
2/17/1945 2.6       60
2/11/1955 2.5       63
2/17/1967 5.7       63
2/8/1974  4.0       50
2/22/1986 3.6       56
2/22/2001 2.8       57 

Image (click to enlarge) Washington, DC 2"+ snowfalls on the day following temperatures of 50° or higher, CapitalClimate chart from National Weather Service data, background image © Kevin Ambrose (www.weatherbook.com)

Washington's Warmest Winters: 2012 in Fifth Place, Fourth Feasible

PM Update, February 14: With today's high of 56° and low of 37° exceeding the 24-hour forecast by 8° and 5° respectively, the winter average temperature to date is holding at 42.7°.

Original post:
With a little over 2 weeks left in meteorological winter, Washington's current seasonal average temperature of 42.7° is now ahead of 1998 as the 5th warmest winter in records dating back to 1871. A projection of the final winter average based on the forecast temperatures for tomorrow through February 20 and climatological averages through the rest of the month would give a result of 42.5°, enough to still tie with 1998. If the temperature averages at least 3.7° above climatology for the 21st through the 29th, that would be enough to push the winter average to a tie with 1950 as the 4th warmest. Given that the month to date is averaging 4.6° above average so far, and the 8-14 day forecast indicates a nearly 50% chance of above-average temperatures (vs. a climatological expectation of 33%), this seems to be a feasible result.

The monthly averages and departures from climatology for the winter so far:

December 45.0° (+5.3°)
January  40.7° (+4.7°)
February 42.7° (+4.6°) 

Image (click to enlarge): Washington's 10 warmest winters vs. 2011-12 average to date and projected through end of February, CapitalClimate chart from National Weather Service data