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News and Information

Minnesota WeatherTalk Newsletter for Friday, July 22, 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, July 22, 2011

-State Climate Office Opens Again
-New Seasonal Climate Outlook
-Many weather records broken this week
-Weekly Weather Potpourri
-MPR listener question
-Almanac for July 22nd
-Past weather

Topic: State Climate Office Open Again

With state employees back to work this week, it was a great relief to have the State Climatology Office back in operation. Welcome back to Jim Zandlo, Greg Spoden, and Pete Boulay, our outstanding DNR climatologists. The Climatology Working Group web site ( is now back in operation too, with access to the state database, current weather, publications, and various web tools.

Topic: New Climate Outlook

The NOAA-Climate Prediction Center released a new seasonal climate outlook on Thursday this week. The outlook for Minnesota calls for a weather pattern that favors above normal temperatures in the eastern and southern portions of the state during the August through October period. So perhaps Minnesota crops will be spared from early frost. The precipitation outlook favors wetter than normal conditions in the western regions of the state during this same period. In this context crops should not be lacking for water as they go through their reproductive growth period, and further flows on many western Minnesota watersheds are likely to remain higher than normal for much of the summer.

Topic: New climate normals (1981-2010) available easily online

Jan Null, climatologist with Golden Gate Weather Services in California has placed the nation's new climate normals on their web site in a user friendly manner. You can click on any state and retrieve a tabular listing of monthly and annual normals for temperature, precipitation, and snowfall. Some noteworthy examples show the Twin Cities annual precipitation normal increased to 31.16 inches, while the seasonal snowfall normal decreased slightly to 53.9 inches. At Duluth the seasonal snowfall normal increased from 84.3 inches to 86.1 inches. Caledonia in Houston County remains the wettest spot in the state with an annual precipitation normal of just under 37 inches, while Wolf Ridge Environmental Learning Center near Finland (Lake County) is the snowiest spot with a seasonal normal of 89.6 inches. You can view the new normals at...

Topic: Many weather records were broken this week

Despite the near absence of 100 degrees F temperature readings, the period from July 16 to July 20 was one of the hottest five day periods in Minnesota history in terms of human comfort. The only weather observer to report a three-digit air temperature was Blue Earth with 102 degrees on the 20th. But some observers reported Heat Index Values of 100 degrees F or higher on five consecutive days. At Moorhead, dewpoints hit 80 degrees F or higher everyday from the 16th to the 20th, topping out at 88 degrees F on July 19th with a Heat Index of 134 degrees F, both tentatively new statewide records.

The Twin Cities endured for the first time a period of three consecutive days with dewpoints hitting 80 degrees F or higher. On July 19th a new all-time dewpoint level was achieved with a reading of 82 degrees F, topped by a sub-hourly reading of 84 degrees F. These new records will have to be certified by the State Climate Office. Preliminary data also indicate a new Heat Index record of 124 degrees F was reached in the Twin Cities on the 19th.

Even far northern areas reached uncharted dewpoint and Heat Index values during this period. Hallock hit a dewpoint of 84 degrees F with a Heat Index of 111 degrees F on the 19th, while Winnipeg, Manitoba (Canada) reported a dewpoint of 77 degrees F and a Heat Index of 109 degrees F, both new records.

Those without air conditioning suffered as overnight low temperatures set records for warmth as well, with many observers reporting minimum temperatures that ranged from 77 degrees F to 82 degrees F. The Heat Index at midnight on July 20th in the Twin Cities was still 100 degrees F, perhaps the only time it has been so high that late at night.

The heat and humidity dominated the weather in many other states this week causing some cattle and poultry mortality in the Dakotas, and some human mortality in other states. For the most part Minnesota citizens took precautions and looked after each other, as well as looking after farm animals and pets.

In summary the heat wave this week will be noted for its amplitude (many places reporting Heat Index values from 110 to 120 F), it's longevity (5-days in many places), and it's widespread distribution (nearly the whole state was under the heat dome). The harbor at Grand Marais was one of the few spots to escape, as they saw mostly temperatures in the 80s F during the day and 50s and 60s F at night.

Weekly Weather Potpourri:

In tropical weather news this week, Typhoon Ma-on brought heavy rains to parts of Japan, while Hurricane Dora spun off the coast of Mexico, and moved off the southern coast of Baja California as it weakened. Tropical Storms Bret and Cindy remained at sea over the North Atlantic and continued to move east away from the USA.

On Tuesday of this week a second dust storm (another one struck on July 5th) struck the Phoenix, AZ area bringing a massive cloud of dust up to 3000 feet high across the city. The airport was closed for a time and people had to stay indoors.

The United Kingdom Meteorological Office announced a new subscription service which provides users with tropical weather forecast out to 15 days, including strike probabilities for tropical storms and hurricanes. The service is designed for those who need to assess risk to transportation and operations that are conducted in the tropical latitudes. You can read more about this new service at...

Researchers at MIT have developed a model to estimate maximum tree height for different environmental conditions. They claim the model works accurately if local meteorological data on temperature, precipitation, solar radiation, and humidity are available. You can read about this model and its application at....

MPR listener question: I have heard that during Heat Waves there are few tornadoes reported. Is this generally true?

Answer: Yes, most of the time Heat Waves are produced by static high pressure systems which tend to bring atmospheric stability. There are exceptions. For example this week the high water vapor content of the air combined with surface heating by the strong sun produced some convective thunderstorms which delivered intense rainfalls (3-5 inches in some parts), and even a tornado near Karlstad (Kittson County) on July 20th. Still, on a national scale there has been a relative absence of tornadoes (about a dozen reports in the past week) during the massive Heat Wave which has encompassed so many states.

Almanac for July 22nd:

The average MSP high temperature for this date is 84 degrees F (plus or minus 8 degrees standard deviation), while the average low is 64 degrees F (plus or minus 6 degrees standard deviation).

MSP Local Records for July 22nd:

MSP weather records for this date include: highest daily maximum temperature of 105 degrees F in 1934; lowest daily maximum temperature of 64 degrees F in 1992; lowest daily minimum temperature of 49 degrees F in 1947; highest daily minimum temperature of 77 degrees F in 1984; record precipitation of 2.69 inches in 1997; no measurable snowfall has been recorded on this date.

Average dew point for July 22nd is 60 degrees F, with a maximum of 76 degrees F in 1952 and a minimum of 40 degrees F in 1925.

All-time state records for July 22nd:

Scanning the state climatic data base: the all-time high for this date is 111 degrees F at Beardsley (Big Stone County) in 1934; the all-time low is 31 degrees F at Meadowland (St Louis County) in 1985. The all-time record precipitation amount for this date is 10.84 inches at Fort Ripley (Crow Wing County) in 1972. No measurable snowfall on this date in Minnesota.

Past Weather Features:

July 21, 1884 about 2:00 pm an F-4 tornado (winds 206 mph or greater) traveled 30 miles across portions of Rock and Nobles Counties in southwestern Minnesota. Many farms around Luverne and Adrian were destroyed and two people were killed.

July 22, 1934 marked the middle of a six-day heat wave in Minnesota. Over two dozen cities reported daytime highs of 100 degrees F or greater. New Ulm reported six consecutive days of 100 F readings. The heat was quite damaging to the corn crop.

July 21-22, 1972 brought one of the largest flash floods in state history to central Minnesota. Portions of Crow Wing, Morrison, Aitkin, and Mille Lacs Counties saw over 10 inches of rain, with individual observers reporting over a foot. The flash flooding covered over 1500 square miles and closed dozens of state and county roads and highways.

Word of the Week: Humidex

This term refers to the Canadian analogy to our National Weather Service Heat Index. It describes the combined effects of temperature and humidity (dewpoint) on the human body, and is scaled similarly to what our National Weather Service uses. Environment Canada reported many cities in Manitoba and Ontario saw record high Humidex readings this week ranging from 101 to 109 degrees F, as they too suffered from unusual dewpoints near 80 degrees F, and air temperatures in the low 90s F.


Near normal temperatures over the weekend and into next week, with a chance for showers and thunderstorms on Saturday (some perhaps may reach severe levels). It will be windy late Saturday and early Sunday, then generally nice through Tuesday. Chance for showers and thunderstorms again by late Tuesday and Wednesday next week.

Further Information:

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