Abnormally Late Into Season Without Highs Below Freezing

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
832 PM CST MON DEC 10 2012 /932 PM EST MON DEC 10 2012/

...UNUSUALLY LATE INTO THE SEASON WITHOUT A HIGH TEMPERATURE BELOW
FREEZING...

EVERYDAY SO FAR THIS COOL SEASON CHICAGO AND ROCKFORD HAVE HAD HIGH
TEMPERATURES AT OR ABOVE 32 DEGREES EVERYDAY. ON AVERAGE...CHICAGO
SEES THEIR FIRST DAY WHERE TEMPERATURES NEVER REACH THE FREEZING
MARK AROUND NOVEMBER 22ND...WHILE THE ROCKFORD AVERAGE FIRST DATE
WHEN HIGH TEMPERATURES FAILS TO REACH FREEZING IS NOVEMBER 11TH.
SOME OF THE REASONS FOR THE 11 DAY DISPARITY BETWEEN CHICAGO AND
ROCKFORD INCLUDE THE WARMING EFFECTS OF LAKE MICHIGAN AND CHICAGO`S
URBAN HEAT ISLAND. THIS WAS PARTICULARLY THE CASE PRIOR TO THE
OFFICIAL OBSERVATION SITE BEING RELOCATED FROM DOWNTOWN CHICAGO TO
MIDWAY AIRPORT BACK IN 1942.

HERE ARE THE RANKINGS FOR LATEST FIRST COMPLETELY SUB-FREEZING DAYS
FOR BOTH CHICAGO AND ROCKFORD...AS WELL AS HOW THAT METEOROLOGICAL
WINTER (DECEMBER THROUGH FEBRUARY) STACKED UP VERSUS THE CURRENT 30
YEAR NORMALS IN BOTH SNOWFALL AND TEMPERATURES...

     CHICAGO      WINTER AVG TEMP   DEC-FEB SNOWFALL
1)  01/01/1924      27.8 (+1.4)       14.8 (-13.6)
2)  12/28/1971      28.0 (+1.6)       26.7 ( -1.7)
3)  12/25/1918      33.1 (+6.7)       17.2 (-11.2)
4)  12/24/2001      32.5 (+6.1)       18.9 ( -9.5)
5)  12/22/1998      30.3 (+3.9)       32.5 ( +4.1)
6)  12/21/1939      29.5 (+3.1)       22.0 ( -6.4)
7)  12/18/1921      28.8 (+2.4)        6.9 (-21.5)
8)  12/17/1987      24.7 (-1.7)       39.6 (+11.2)
    12/17/1999      29.4 (+3.0)       27.0 ( -1.4)
10) 12/16/1878      23.9 (-2.5)       MISSING
11) 12/13/1915      27.7 (+1.3)       19.9 ( -8.4)
    12/13/1961      23.2 (-3.2)       50.0 (+21.6)
    12/13/2004      28.5 (+2.1)       22.6 ( -5.8)
14) 12/12/1922      27.8 (+1.4)       14.8 (-13.6)
15) 12/11/1912      29.3 (+2.9)       11.6 (-15.6)
    12/11/1994      28.4 (+2.0)       20.5 ( -7.9)
16) 12/10/2011      32.6 (+4.2)       19.5 ( -8.9)
    12/10/1954      32.1 (+3.7)       21.2 ( -7.2)


    ROCKFORD    WINTER AVG TEMP   DEC-FEB SNOWFALL
1) 12/23/2001     30.9 (+7.2)       13.2 (-16.0)
2) 12/20/1998     27.4 (+3.7)       12.6 (-16.6)
3) 12/16/1999     26.1 (+3.2)       28.3 ( -0.9)
4) 12/13/1915     23.6 (-0.1)       15.1 (-14.1)
   12/13/1943     28.5 (+4.8)       24.6 ( -4.6)
6) 12/11/1912     25.5 (+1.8)       29.0 ( -0.2)
7) 12/09/1922     24.0 (+0.3)       13.4 (-15.8)
   12/09/1947     23.8 (+0.1)       11.2 (-18.0)
   12/09/1961     19.5 (-4.2)       39.9 (+10.7)
   12/09/2011     30.0 (+6.3)       21.3 ( -7.9)

GIVEN THE CURRENT FORECASTS IT SEEMS QUITE LIKELY THAT HIGHS WILL
REACH AT LEAST FREEZING AND LIKELY QUITE A BIT WARMER THROUGH
DECEMBER 15TH...WHICH WOULD MOVE THIS YEAR UP TO RANKED AT LEAST 4TH
IN ROCKFORD AND AT LEAST 11TH IN CHICAGO. CURRENT LONGER RANGE
OUTLOOKS FROM THE CLIMATE PREDICTION CENTER SUGGEST THAT
TEMPERATURES DECEMBER 16TH THROUGH 24TH ON THE WHOLE WILL REMAIN
ABOVE AVERAGE...WHICH IS NOT TO SAY THAT THERE WONT BE A COUPLE COLD
DAYS...BUT OVERALL IT LOOKS LIKE THE MILD START TO WINTER WILL
CONTINUE.

GOING THIS FAR INTO THE SEASON WITHOUT HAVING HAD A BELOW FREEZING
DAY DOES NOT NECESSARILY MEAN THAT THE REST OF THE WINTER WILL BE
MILD OR SNOWFALL BELOW AVERAGE AND SHOULD NOT BEE USED AS A
PREDICTIVE TOOL FOR THE SEASON. HAVING SAID THAT...

IN ROCKFORD...OF THE 10 YEARS THAT HAD NOT SEEN A HIGH TEMPERATURE
BELOW FREEZING BY DECEMBER 9TH...6 OF THEM ENDED UP WITH MUCH ABOVE
AVERAGE TEMPERATURES FOR THE WINTER AND MUCH BELOW AVERAGE SNOWFALL.
ONLY 1 OF THE 10 YEARS ENDED UP SNOWIER AND COLDER THAN NORMAL.

IN CHICAGO...IT IS A VERY SIMILAR STORY WITH THE MAJORITY OF YEARS
THAT HADNT SEEN A HIGH TEMPERATURE BELOW FREEZING YET ENDING UP
WARMER AND LESS SNOWY THAN NORMAL (MANY OF THEM SIGNIFICANTLY SO).
CHICAGO DID HAVE A COUPLE OF VERY NOTABLE EXCEPTIONS...INCLUDING THE
WINTER OF 1961-62 WHEN THE FIRST SUBFREEZING DAY WAS NOT UNTIL
DECEMBER 13TH...YET THAT WINTER WENT ON TO SEE 50 INCHES OF SNOW
(JUST FROM DEC-FEB) AND AVERAGED WELL BELOW NORMAL TEMPERATURES.
INTERESTINGLY...THE WINTER OF 1998-99 DIDNT SEE A HIGH TEMPERATURE
BELOW FREEZING UNTIL DECEMBER 22ND YET ONE OF THE BIGGEST SNOWSTORMS
IN CHICAGO HISTORY OCCURRED AROUND THE NEW YEAR THAT WINTER. SO
WHILE STATISTICALLY SPEAKING YEARS WITH SIMILAR LATE FIRST
SUBFREEZING DAYS HAVE OVERWHELMING ENDED UP WARMER AND LESS SNOWY
THAN AVERAGE...THERE IS NO GUARANTEE THAT THIS WINTER WILL BE THE
SAME AS 1961-62 PROVES!

$$

IZZI


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