FROM: Bob Weisman, Earth Sciences
St. Cloud State University
DATE: 2 October 2000
SUBJECT: Driest September Since 1952 Further Fuels Drought
Saint Cloud September 2000 weather summary
The localized drought in east central Minnesota continued
through September in St. Cloud. The Saint Cloud Municipal Airport only
received 0.93 inches of rainfall during September, more than 2.2 inches
below normal. This low rainfall tied 1923 for the 9th driest September
on record and was the driest September since 1952, the driest September
in 108 years of St. Cloud weather records (see table below). There were no
really large rainfall events during the past month. The rainiest day was on
the 9th when St. Cloud received .35 inch from thunderstorms.
The St. Cloud area missed a potential major rainfall event on the
22nd and 23rd. A storm system set up an inverted trough, a focus of ongoing
research by the National Weather Service Sioux Falls Office and SCSU. This
feature distorted the normal frontal rainfall distribution, so only the
northwestern and the southeastern parts of Minnesota received significant rain.
Instead, the parched region from St. Cloud to the northern Twin Cities
suburbs got less than 0.2 inch.
The dry September left St. Cloud with a 2000 growing season (Apr 1-
Sep 30) of 12.46 inches, nearly 8 inches below normal. This is the 6th lowest
growing season rainfall in St. Cloud in the 109 years of records (see table
below). Combined with the rainfall deficit from last fall (2.1 inches), St.
Cloud is now more than 10 inches of rainfall behind during the growing
season since September of last year. Also, note that 3 of the last
10 years (1992, 1996, 2000) rank in the 7 driest growing seasons to date.
The average temperature during September 2000 in St. Cloud was 57.6
degrees, which was very close to normal. This means that the cold
outbreak of September 20-27 (highs of 61 or colder on 6 days; lows in
the 20's on 3 mornings) was balanced by 8 days with highs in the 80's
including 3 days in a row twice (Sept 16-18 and Sept 28-30). Note, however,
that the average high (71.9 deg) was 2.8 degrees above normal while
the average low (43.2 deg) was 2.2 degrees below normal. This range of
temperatures can be attributed to the dry conditions: less water vapor
in the air means more of the sun's heat gets through during the day
and more of the earth's warmth escapes at night. The "jaw dropper"
of temperature range occurred on the 16th with an afternoon high of
85 after a morning low of 35. Four other days had a high at least
40 degrees warmer than the low.
The growing season came to an abrupt halt in St. Cloud with a
28 degree low on the morning of September 21. Whatever survived
stopped 3 days later thanks to a record cold low of 24 on the 24th.
While the first frost was close to the normal date of September 26, the
late start to the growing season with the last frost coming with a record
low of 28 on May 19, led to a frost-free season which was more than 2 weeks
shorter than normal and a freeze-free season which was more than a month
shorter than normal (see table below). The late freeze was also indicative
of the rather cool conditions which dominated large portions of May and
June.
SUMMARY FOR SEPTEMBER 2000 SEP 2000 NORMAL
TEMPERATURE
Average high temperature ( F) 71.9 69.1
Average low temperature ( F) 43.2 45.4
Average temperature ( F) 57.6 57.3
Warmest high for this month ( F) 89 on the 9th
Coolest high for this month ( F) 50 on the 23rd
Mildest low for this month ( F) 61 on the 9th
Coldest low for this month ( F) 24 on the 24th (broke record;
see below)
Records broken:
Daily high temperature: 88 (tie) on the 18th (1984 and 1998)
Daily low temperature: 24 on the 24th (old record: 25 in 1942)
PRECIPITATION (in)
September .93* 3.14
Greatest in 24 hours (Sept 2000) .35 on the 9th
Growing season rainfall (Apr 1-Sep 30) 12.46** 20.32
*-(tie) 9th driest Sept on record (see below)
**-6th driest growing season thru Sep 30 (see below)
GROWING SEASON STATISTICS
Temperature cutoff last day in spring first day in fall no of days
32 degrees
2000 May 19 Sept 21 125
normal May 10 Sept 26 142
28 degrees
2000 May 19 Sept 21 125
normal April 28 Oct 8 161
ST. CLOUD PRECIP--SEPTEMBER (108 YEARS; AVG = 2.95 IN; SDEV = 1.88 IN)
WETTEST DRIEST
10.72 IN 1926 0.07 IN 1952
9.48 IN 1985 0.68 IN 1943
7.12 IN 1900 0.74 IN 1922
6.60 IN 1929 0.78 IN 1932
6.55 IN 1983 0.80 IN 1919
6.49 IN 1914 0.81 IN 1893
6.28 IN 1986 0.84 IN 1918
6.12 IN 1934 0.90 IN 1935
6.10 IN 1921 0.93 IN 1923
5.99 IN 1980 0.93 IN 2000 <-- TIED 9TH DRIEST;
DRIEST IN 48 YRS
===========================================================================
GROWING SEASON PRECIP: APR 1-SEP 30
AVG = 19.95 SDEV = 4.99; 111 YRS; 108 GOOD YRS
10 DRIEST GROWING SEASONS - APR 1-SEP 30
10.52 1922
10.58 1976
11.29 1931
11.57 1996
12.33 1910
12.46 2000 <--6TH DRIEST; 3RD YR IN 1991-2000
12.47 1992
13.82 1930
14.16 1950
14.17 1933
10 WETTEST GROWING SEASONS - APR 1-SEP 30
26.71 1906
26.73 1912
27.17 1990
27.44 1928
27.98 1926
28.77 1985
28.83 1903
29.76 1897
30.70 1905
30.90 1965
31.17 1986
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