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News and Information

Minnesota WeatherTalk Newsletter for Friday, September 16, 2011

To: MPR Morning Edition Crew
From: Mark Seeley, University of Minnesota Extension
Dept of Soil, Water, and Climate

Subject: Minnesota WeatherTalk Newsletter for Friday, September 16, 2011

-Fire weather
-Widespread frost and freeze
-Weekly Weather Potpourri
-MPR listener question
-Almanac for September 16th
-Past Weather

Topic: Fire weather

The spread of the Pagami Creek Fire in the BWCA this week was certainly assisted by the weather. A dry air mass with dewpoints only in the 20s and 30s F (15-20 degrees less than normal for this time of year) dominated the landscape earlier this week. Then modest southerly winds turned to strong northwesterly winds with gusts from 30 to 40 mph, allowing flames to jump gaps in the forest and ignite other canopies and understory materials. Fortunately light rains over the 13th and 14th abated faster and further spread of the fire, still one of the largest (over 100,000 acres) in Minnesota history.

The MODIS sensor aboard NASA's Terra Satellite captured the Pagami Creek Fire as it grew earlier this week and produced some pyrocumulonimbus cloud forms. You can view the images at...

Topic: Widespread frost and freeze on September 15th, and again on the 16th

The dry air, cloudless sky, and low wind dropped the temperatures Thursday morning to record setting values in many Minnesota communities. Some new records were set or tied, including:

19 degrees F at International Falls
19 degrees F at Embarrass
19 degrees F at Wannaska
23 degrees F at Waskish
24 degrees F at Park Rapids
28 degrees F at Browns Valley
25 degrees F at Bemidji and Fosston
28 degrees F at Crookston (tied record low)
20 degrees F at Hibbing
23 degrees F at Kabetogama
24 degrees F at Orr
21 degrees F at Crane Lake
22 degrees F at Tower
36 degrees F at MSP Airport (tied record low)
31 degrees F at Forest Lake
29 degrees F at Eau Claire, WI
27 degrees F at Little Falls
31 degrees F at Rochester
26 degrees F at Wadena
28 degrees F at Waseca
29 degrees F at Zumbrota and Theilman

The reading of 19 degrees F at International Falls, Wannaska and Embarrass is only 2 degrees F warmer than the statewide record for September 15th of 17 degrees F at Bigfork in 1964. That reading was also lowest in the nation for September 15th. Because of the number of record setting low temperature values it is safe to say that September 15, 2011 was one of the coldest in Minnesota history (along with 1873, 1964, and 1984).

Light to calm winds and clear skies over northern sections of the state allowed record low temperatures to occur again on the morning of Friday, September 16th. Those reporting new record lows included:

Hibbing with 22 degrees F
Crane Lake and International Falls with 23 degrees F
Ely, Kabetogama, and Orr with 23 degrees F
Bigfork with 25 degrees F

In addition observers at Ely and Dultuh reported traces of snowfall on September 14th, very early at both locations.

Weekly Weather Potpourri:

NOAA scientists announced this week that globally August of 2011 was the 8th warmest since 1880. this combines the land and ocean temperature records. Exceptions were Scotland and Northern Ireland which recorded one of their coolest months of August. You can read more at...

NOAA-National Hurricane Center was tracking Hurricane Maria well off the coast in the North Atlantic Ocean. It was perhaps expected to bring heavy rains and winds to coastal Canada early in the weekend. In the western Pacific Ocean Tropical Storm Roke was producing winds up to 60 mph with sea waves of 18 ft over the waters south of Japan. Another Tropical Storm (Sonca) was producing winds up to 70 mph and sea waves up to 14 ft in the waters southeast of Tokyo. It was expected to dissipate early next week.

The BBC reported this week that Karachi, the commercial hub of Pakistan, and surrounding areas were hit by torrential monsoon rains and flooding this week. Millions of people have been displaced by the floods. You can read more at...

NASA scientists reported this week that a meteor, probably between the diameter of a baseball and a basketball, was the cause of a beautiful light show witnessed by many observers across the southwestern USA on Wednesday night (Sept 14) this week. The meteor exhibited some brilliant blue, green, and orange colors as it burned up in the Earth's atmosphere. You can read more about it at...

MPR listener question: Is it unusual to have serious wildfires in Minnesota during September?

Answer: Actually, many of our worst historical fires have occurred during the fall season. The great Hinckley Fire of 1894 was in September, and the great Cloquet Fire of 1918 was in October. In the Pioneer Era wildfires were common in the fall season as the prairie grasses dried out. But in the modern era the frequency of wildfires in Minnesota is highest during April and May and then tails off through the summer, picking up again in October. Fall wildfires are far more common in years with summer-long drought. This year northern St Louis, Lake, and Cook Counties have been in drought all summer long. During the months of December, January and February wildfires are almost non-existent.

Almanac for September 16th:

The average MSP high temperature for this date is 71 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 52 degrees F (plus or minus 8 degrees standard deviation).

MSP Local Records for September 16th:

MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 1955; lowest daily maximum temperature of 50 degrees F in 1916; lowest daily minimum temperature of 38 degrees F in 1873; highest daily minimum temperature of 74 degrees F in 1955; record precipitation of 1.97 inches in 1997; no measurable snowfall has been recorded on this date.

Average dew point for September 16th is 49 degrees F, with a maximum of 71 degrees F in 1992 and a minimum of 29 degrees F in 1937.

All-time state records for September 16th:

Scanning the state climatic data base: the all-time high for this date is 101 degrees F at Montevideo (Chippewa County) in 1891. The all-time record low for this date is 17 degrees F at Karlstad (Kittson County) in 1973. The all-time record precipitation amount for this date is 7.07 inches at Red Wing (Goodhue County) in 1992. No measurable snowfall on this date in Minnesota.

Past Weather Features:

Temperatures were in the 20s and 30s F on September 16, 1873. There were multiple killing frosts that month, bringing an early end to the growing season in southern Minnesota counties.

A September heat wave dominated the state on September 16, 1891. Many communities reported temperatures in the 90s F, including 92 degrees F in the Twin Cities. Montevideo saw 9 consecutive days with high temperatures of 90 F or greater (Sep 15-23), including 101 degrees F on the 16th and 100 degrees F on the 18th. It was their hottest September on record.

A 4-day heat wave gripped the state over September 15-18, 1955. Many observers reported temperatures in the 90s F during the day and lows in the 60s and 70s overnight. Fortunately by the 19th temperatures fell off into the 40s and 50s F.

Between 4:00 and 5:00 am on the morning of September 16, 1962 two tornadoes touched down in Olmsted County. The first struck near Rochester, and was on the ground for 1 mile. It destroyed four homes and damaged seven others, leaving 34 people injured. This tornado was rated F-4 (winds 207-260 mph). The second, weaker tornado (F-2, winds 113-157 mph) struck near Pleasant Grove in Olmsted County. It was on the ground for 4 miles and destroyed five barns, while damaging two homes. These storms were very unusual for the early morning hours.

Freezing temperatures invaded northwestern Minnesota counties on September 16, 1973. Many observers in the Red River Valley reported temperatures in the teens and 20s F. Fortunately most of the rest of the state was under cloud cover and spared from any frost.

Two rounds of thunderstorms brought flash flooding to eastern parts of the state on September 16, 1992. Red Wing reported over 7 inches of rainfall, Farmington over 6 inches, and Hastings over 5 inches. Many other observers reported 4-5 inches of rainfall which flooded roads and some basements.

Word of the Week: Calm

A demeanor of the atmosphere around us that produces no perceptible wind. For well over a century the definition of a calm was when smoke is observed to rise vertically or the sea surface is mirrorlike. In the modern context with instrumentation to measure wind speed, a calm is generally defined by a wind speed of less than 3 knots (3.5 mph).

In the Twin Cities calm conditions comprise but a small fraction of the annual wind distribution, less than 7 percent of all observations show calm conditions. The peak time for calm conditions occurs at night. During the summer months, calm conditions may prevail from midnight to 6 am about 20 percent of the time or 1 day in 5. However, during the other seasons overnight calms occur only about 10 to 15 percent of the time. During the daytime hours, calms are very infrequent, most often less than 5 percent of the time.


Increasing cloudiness and warmer temperatures over the weekend. There will be a chance of showers and thunderstorms late Saturday and into Sunday. Mild much of next week with a chance for showers Tuesday and Wednesday.

Further Information:

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