896
NOUS44 KBMX 230722
PNSBMX
ALZ011>015-017>050-240230-
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
122 AM CST MON NOV 23 2009
...FREEZE AND FROST PRODUCT ISSUANCES END FOR THE YEAR ON
THANKSGIVING DAY...
AS PART OF NORMAL PROCEDURE...THE NATIONAL WEATHER SERVICE IN
BIRMINGHAM ISSUES FROST ADVISORIES...AND FREEZE WATCHES AND
WARNINGS...TO COINCIDE WITH THE END OF THE GROWING SEASON IN THE
FALL AND THE BEGINNING OF THE NEXT GROWING SEASON IN THE SPRING.
ON THURSDAY...THANKSGIVING DAY...WE WILL END THE ISSUANCE OF FROST
ADVISORIES...AS WELL AS FREEZE WATCHES AND WARNINGS FOR THE FALL
SEASON. THESE PRODUCTS WILL RESUME ON OR AFTER MARCH 15TH.
HARD FREEZE WATCHES AND WARNINGS WILL STILL BE ISSUED WHEN
TEMPERATURES ARE EXPECTED TO BE 15 DEGREES OR COLDER ANYWHERE
IN CENTRAL ALABAMA. THESE WATCHES AND WARNINGS WILL BE ISSUED WITH
THE NORMAL HEADING OF NPWBMX.
THE MAIN REASON FOR THIS DATE IS THAT THE MEDIAN AVERAGE OF THE
FIRST FALL FREEZE DURING THE 30 YEAR CLIMATOLOGICAL NORMALS PERIOD
OF 1971 TO 2000. THE MEDIAN IS DEFINED AS THE MIDDLE VALUE OF AN
ORDERED SET OF VALUES. IN OTHER WORDS...50 PERCENT OF THE TIME
FREEZING TEMPERATURES OCCUR BEFORE THE GIVEN DATE AND 50 PERCENT OF
THE TIME FREEZING TEMPERATURES OCCUR AFTER THE GIVEN DATE. TYPICALLY
THE FIRST FREEZE OCCURS TOWARD THE MIDDLE OF OCTOBER IN THE
NORTHWEST...TO THE SECOND WEEK OF NOVEMBER FOR THE SOUTHERN SECTIONS
OF CENTRAL ALABAMA.
THROUGH NOVEMBER 22...THERE HAS NOT BEEN A WIDESPREAD SIGNIFICANT
FREEZE ACROSS ALL OF CENTRAL ALABAMA. THAT BEING SAID...NUMEROUS
SPOTS HAVE ALREADY DROPPED BELOW FREEZING A COUPLE OF TIMES THIS
YEAR. DESPITE THE LACK OF WIDESPREAD FREEZING TEMPERATURES...THERE
HAVE BEEN A COUPLE OF WIDESPREAD FROST EVENTS.
TAKING A LOOK AT SOME NUMBERS FOR 2009...BIRMINGHAM HAS ONLY DROPPED
TO 35 DEGREES THIS FALL...ON OCTOBER 18TH. THE MEDIAN AVERAGE DATE
FOR THE FIRST FREEZE AT BIRMINGHAM IS NOVEMBER 10TH. BY NOVEMBER
19TH...BIRMINGHAM HAS HAD A FREEZE 90 PERCENT OF THE TIME. BY
NOVEMBER 30TH...BIRMINGHAM HAS HAD A FIRST FREEZE 99 PERCENT OF THE
TIME. THERE WAS ONE YEAR...1931...IN WHICH BIRMINGHAM DID NOT HAVE A
FREEZE FOR THE FALL SEASON OR BEFORE DECEMBER 31ST. THIS IS
BASED ON OBSERVATIONS FROM 1900 TO 2009.
MONTGOMERY HAS REACHED THE FREEZING MARK AT LEAST ONCE THIS FALL
SEASON. ON NOVEMBER 20TH...MONTGOMERY DROPPED TO 31 DEGREES. THE
MEDIAN AVERAGE DATE FOR THE FIRST FREEZE AT MONTGOMERY IS NOVEMBER
13TH. BY NOVEMBER 17TH...MONTGOMERY HAS HAD A FREEZE 75 PERCENT OF
THE TIME AND BY NOVEMBER 29TH...MONTGOMERY HAS HAD A FREEZE 90
PERCENT OF THE TIME. BY DECEMBER 11TH...MONTGOMERY HAS HAD A FIRST
FREEZE 99 PERCENT OF THE TIME. THERE WERE TWO YEARS...1923 AND
1931...IN WHICH MONTGOMERY DID NOT HAVE A FREEZE FOR THE FALL SEASON
OR BEFORE DECEMBER 31ST. THIS IS BASED ON OBSERVATIONS FROM 1900 TO
2009.
THE FIRST FREEZE THAT COOL SEASON WAS NOT UNTIL JANUARY 10...1932 IN
BIRMINGHAM AND JANUARY 31...1932 IN MONTGOMERY.
16/JRA
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