Warm and Mostly Dry September 2009

Despite the cool snap for the last three days of the month, September 2009 will most likely be the 6th warmest on record statewide. For the Twin Cities, September 2009 wound up being 11th warmest at 66.5 degrees for the average temperature. It was the 3rd driest September on record for the Twin Cities, going back to 1891. International Falls had the 4th warmest September on record going back to 1897.

While much of the eastern half of Minnesota experienced dry weather for the month of September, western Minnesota had near normal precipitation.

Below is a Public Information Statement from the La Crosse National Weather Service about the warm and dry weather.


CLIMATE REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI                                
655 AM CDT THU OCT 1 2009

...SEPTEMBER 2009 WAS WARMER AND DRIER THAN NORMAL IN ROCHESTER MN...

THE AVERAGE MONTHLY TEMPERATURE WAS 62.6 DEGREES.  THIS WAS
3.7 DEGREES ABOVE THE NORMAL OF 58.9 DEGREES.  THE AVERAGE HIGH 
TEMPERATURE WAS 73.8 DEGREES.  THIS WAS 4.6 DEGREES ABOVE THE 
NORMAL OF 69.2 DEGREES. THE AVERAGE LOW TEMPERATURE WAS 51.4 DEGREES. 
THIS WAS 2.7 DEGREE BELOW THE NORMAL OF 48.7 DEGREES.  THE HIGHEST 
TEMPERATURE FOR THE MONTH WAS 82 DEGREES ON BOTH THE 15TH AND THE 
18TH...AND THE LOWEST TEMPERATURE WAS 40 DEGREES ON THE 30TH. 
A TOTAL OF ONLY 1.28 INCHES OF PRECIPITATION FELL. THIS WAS 1.84 
INCHES BELOW THE NORMAL OF 3.12 INCHES. THE GREATEST 24-HOUR 
PRECIPITATION TOTAL WAS 0.64 INCHES AND THAT PRECIPITATION FELL 
FROM THE 24TH THROUGH THE 25TH.   

THE AVERAGE WIND SPEED FOR THE MONTH WAS 6.5 MILES AN HOUR.  
THE FASTEST SUSTAINED WIND WAS 35 MILES AN HOUR ON THE 27TH...
AND THE FASTEST WIND GUST WAS 48 MILES AN HOUR ON BOTH THE 27TH AND 28TH.

...RECORDS...

THE MONTH BEGAN VERY DRY...WITH NO MEASURABLE PRECIPITATION FOR
THE FIRST 20 DAYS OF THE MONTH...WITH THE FIRST MEASURABLE RAIN 
FALLING ON THE 21ST. THE 20 DAYS WITH JUST A TRACE OF PRECIPITATION
WAS THE LONGEST STRETCH OF NON MEASURABLE /LESS THAN A 0.01 INCH/ 
PRECIPITATION DAYS TO BEGIN A SEPTEMBER. THE PREVIOUS RECORD WAS
18 DAYS IN 1998.

PRECIPITATION RECORDS FOR THE ROCHESTER AREA ARE AVAILABLE FROM
1886 TO 1920 AND FROM 1929 TO 2009. 
...DISCUSSION...

THE UPPER MIDWEST WAS DOMINATED BY PERSISTENT HIGH PRESSURE FOR 
THE FIRST 3 WEEKS OF THE MONTH. THIS STAGNANT PATTERN ALLOWED THE 
AREA TO SET RECORDS FOR THE LONGEST STRETCH OF PRECIPITATION-FREE 
DAYS FOR MANY LOCALES. THIS ALSO RESULTED IN LIGHT WINDS FOR A 
LENGTHY PERIOD OF TIME. 
THE WEATHER PATTERN SHIFTED TO END THE MONTH. SEVERAL DISTURBANCES 
AND COLD FRONTS MOVED THROUGH THE REGION...ON THE 21ST AND 22ND...
ON THE 25TH...AND AGAIN ON THE 27TH. THIS LAST ONE WAS THE STRONGEST 
OF THE FRONTS...RESULTING IN VERY STRONG WINDS AND THE FIRST THREAT 
FOR ANY FROST. WIND GUSTS DURING THE EVENING OF THE 27TH REACHED 48 
MPH AT THE ROCHESTER AIRPORT...AND AGAIN PEAKED AT 48 MPH THE NEXT 
DAY. THE COLD AIRMASS ARRIVING BEHIND THIS POTENT FRONT SENT LOW 
TEMPERATURES DOWN TO 41 DEGREES BY THE MORNING OF THE 30TH. PATCHY
FROST WAS SEEN AROUND THE REGION WHERE TEMPERATURES WERE A BIT 
COOLER THAT MORNING.