Heat Bursts Affected Rock and Jefferson Counties Wed June 8, 2011

NOUS43 KMKX 081721
PNSMKX
WIZ046-047-051-052-056>060-062>072-082100-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1220 PM CDT WED JUN 8 2011

...HEAT BURSTS AFFECTED SOUTH-CENTRAL AND SOUTHEAST WISCONSIN
WEDNESDAY MORNING...

A LINE OF RAIN SHOWERS MOVING THROUGH SOUTHERN WISCONSIN GENERATED
LOCALIZED HEAT BURSTS. THESE HEAT BURSTS PRODUCED GUSTY WINDS OF 40
TO 55 MPH ALONG WITH SIGNIFICANT INCREASES IN TEMPERATURES AND
DECREASES IN RELATIVE HUMIDITY.

MUCH OF THE RAIN EVAPORATED BEFORE IT REACHED THE GROUND SINCE THE
BASE OF THE CLOUDS WAS SOME 10 TO 12 THOUSAND FEET ABOVE THE GROUND.

THE EVAPORATED RAIN COOLED THE AIR BELOW CLOUD BASE.  THIS
RAIN-COOLED AIR ACCELERATED TOWARD THE GROUND DUE TO THE EFFECTS OF
GRAVITY SINCE COOL AIR IS HEAVIER THAN WARM AIR.

EVENTUALLY...THE GLOBS OF RAIN-COOLED AIR WARMED UP DUE TO GRAVITY
AND COMPRESSIONAL EFFECTS AS THEY NEARED THE GROUND.

ONCE THE GLOBS OF AIR REACHED THE GROUND THEY HAD WARMED UP ENOUGH
TO PRODUCE SIGNIFICANT INCREASES IN TEMPERATURES AT GROUND LEVEL.
ADDITIONALLY...GUSTY WINDS AND LOWER RELATIVE HUMIDITIES RESULTED.

BELOW ARE THE CHANGES IN TEMPERATURE...DEWPOINTS...AND RELATIVE
HUMIDITIES AT THREE MESO-NET SCHOOL SITES AND THE SULLIVAN WEATHER
OFFICE...AS THE HEAT BURSTS MOVED THROUGH...ALONG WITH MAXIMUM WIND
GUSTS.

THREE NUMBERS ARE PROVIDED....TEMP/DEWPOINT/RELATIVE HUMIDITY

                                              BEFORE        AFTER         MAX WIND GUSTS
MILTON                               76/65/69        92/46/21      42 MPH
WHITEWATER                   78/66/67        89/49/26      55 MPH
FT. ATKINSON                   76/64/67        88/43/21      35 MPH
SULLIVAN WEATHERX    75/67/76        82/59/46      32 MPH

HEAT BURSTS ARE MORE COMMON OVER THE GREAT PLAINS STATES WHERE THERE
ARE MORE INSTANCES OF HIGHER CLOUD BASES. THEY CAN OCCUR AT ANY TIME
OF THE DAY. THEY HAVE BEEN KNOWN TO INCREASE TEMPERATURES FROM THE
70S AND 80S TO THE 100 TO 105 DEGREE RANGE.

$$

KAPELA/CRAVEN

 



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