To: MPR's Morning Edition From: Mark Seeley, Univ. of Minnesota Extension, Dept of Soil, Water, and Climate Subject: Minnesota WeatherTalk for Friday, September 21, 2007 HEADLINES: -MPR's Jet Streaming Podcast this week -Frosts and heavy rains continue -Another state record proposed -Weekly Weather Potpourri -Frequency of September Snow in the Twin Cities -Almanac for September 21st -The Morristown Tornado -Equatorial Oscillation -Outlook Topic: On this week's "Jet Streaming" podcast This week's podcast, available at the MPR web site, includes a discussion about educational programs in the atmospheric sciences sponsored by the American Meteorological Society (AMS). Our guest is Dr. Jim Brey from the AMS Education Office in Washington, D.C.. He explains the philosophy behind some of their successful teacher education programs and how to get involved. We also announce an open invitation for classroom teachers and students to participate in one of our Jet Stream podcasts. In addition we answer a listener question about rating hurricane strength. You can find more at.... http://minnesota.publicradio.org/radio/programs/morning_edition/ or http://minnesota.publicradio.org/radio/podcasts/jet_streaming/ Topic: Frosts and heavy rains continue this month..... Three mid-month frosts (12th, 13th and 15th) brought an end to the growing season for most areas around the state. The most intense and widespread frost occurred on Saturday morning, September 15th when Embarrass reported the nation's low of just 18 degrees F. Elsewhere around the state there were many reports of low temperatures in the 20s F, even across southern Minnesota where Lamberton reported 29 degrees F, Redwood Falls 28 degrees F, Byron 28 degrees F, Grand Meadow 29 degrees F, and Preston 28 degrees F. Some of these low temperatures were record setting for the date, including 32 F at Rochester, 31 F at Albert Lea, 21 F at Cambridge, 29 F at Jordan, 21 degrees F at Hibbing, and 36 degrees F in the Twin Cities (MSP Airport). These cold mornings have accelerated the fall leaf color change. In addition, episodes of heavy rains and thunderstorms have continued this month, fueled by dewpoints in the 60s and 70s F. September 18 and 19 brought heavy amounts of rainfall to many parts of the state and in a narrow band across NE Minnesota radar estimates of 3 to 5 inch amounts occurred, temporarily flooding Highway 169 north of Grand Rapids. Some observers reported record setting amounts of rainfall for the date, including Moose Lake with 2.58 inches, Tower with 2.18 inches, Leech Lake with 2.72 inches, and Bruno with 3.64 inches. Tower has reported over 11 inches of rainfall so far this month. Such intense rainfalls in the northern sections of the state are rare for September. Yet more flash flooding was reported in western and central counties of Minnesota on Thursday morning, September 20th, when 2 to 4 inch rains were detected by Doppler radar across the region, and even more heavy rainfall came on Friday morning, the 21st with 3-4 inch rainfall amounts across sections of central Minnesota. Topic: Another new state record precipitation measurement is sought.... The NCDC and NOAA committee on climate extremes will decide soon if another precipitation record was set in Minnesota during the month of August. The observer from Hokah (Houston County) already reported a new all-time 24-hr rainfall record last month with a measurement of 15.10 inches. Now it appears that the monthly total rainfall for August measured at Hokah, an incredible 23.86 inches, may qualify as a new all-time state monthly record as well, surpassing the 17.9 inches of rainfall received in the Twin Cities during July, 1987. Topic: Weekly Weather Potpourri..... Significant acres of tea crops were destroyed by hail in Kenya this week. Tea is a major income crop there and officials estimate it will take up to two months for the crop to recover fully in growth. A study released this week in Geophysical Research Letters documents that the rapid loss of permafrost in the high latitudes of the northern hemisphere is being tempered by peatlands and forests over significant areas. The insulating effects of peatlands and forests are beneficial in this regard. But forest fires and drying out of the peatlands can cause accelerated permafrost loss. Scientists argue that preservation of the northern boreal forests and peatlands needs to be given more attention. NASA's Ikhana unmanned aircraft is being deployed to gather thermal-infrared images over wildfires burning in Oregon, Washington, and California. The aircraft can be remotely controlled and fly for 20 hours or longer. The images will be used to map and study wildfires. A paper released this week by Dr. Ben Santer and colleagues at the Lawrence-Livermore National Lab documents that greenhouse gas increases have produced an increase in the bulk moisture content of the atmosphere over the Earth's oceans. This at least partiallly explains a net increase in atmospheric water vapor, another greenhouse gas and a "feedback" mechanism that further amplifies the warming effect of the other greenhouse gases. The bulk increase in atmospheric water vapor since 1988 is estimated at 0.41 kilograms/cubic meter of air. This finding may help explain some of the observed changes in the hydrologic cycle over various landscapes. Hurricane Dean which struck Mexico's Yucatan region last month inflicted so much coastal damage that the tourism industry will be affected for some time. Both Carnival and Royal Caribbean Cruise lines announced this week that they will not call on the Puerto Costa Maya region until spring of 2009 when the damages there are expected to be repaired. It appears that this Mexican resort area will suffer serious economic consequences in tourism as a result. MPR listener question: I heard Cathy Wurzer mention reports of snowfall in NE Minnesota last week. Having moved from Winnipeg, Canada to the Twin Cities 14 years ago, I have never seen a September snow here. We used to get a few in Winnipeg. How often does the Twin Cities see a September snowfall? Answer: In the modern National Weather Service records for the Twin Cities which date back to 1891, there are 13 reports of September snowfalls of a trace or greater, three of which came in September of 1942. In the older Pioneer Era records for the Twin Cities (1820-1890) there were only 4 reports of a trace of snowfall in September. The most recent measurable amount of snowfall was September 24, 1985 when 0.4 inches was reported at MSP International Airport. I am sure you saw more frequent September snows in Winnipeg. Twin Cities Almanac for September 21st: The average MSP high temperature for this date is 70 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 51 degrees F (plus or minus 8 degrees F standard deviation). MSP Local Records for September 21st: MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 1937; lowest daily maximum temperature of 46 degrees F in 1913 and 1995; lowest daily minimum temperature of 32 degrees F in 1974 (30 degrees F in 1866 of the Pioneer Era); highest daily minimum temperature of 66 F in 1891 and 1908. Record rainfall for this date is 2.07 inches in 1986. Average dew point for September 21st is 46 degrees F, with a maximum of 69 F in 1924 and a minimum of 22 degrees F in 1974. All-time state records for September 21st: The state record high temperature for this date is 101 degrees F at Wheaton (Traverse County) in 1937. The state record low temperature for this date is 13 degrees F at Alborn (St Louis County) in 1934. The state record precipitation for this date is 3.95 inches at Lamberton (Redwood County) in 1968. Record snowfall for this date is 0.5 inches at International Falls (Koochiching County) and Walker (Cass County) in 1974 and at Park Rapids (Hubbard County) in 1995. From "Minnesota Weather Almanac":(from bookstores or write the author) This Sunday, September 23 (4:51 am our time) brings the autumnal equinox as the midday sun passes over the equator on its migration into the southern latitudes for our winter season. Days will begin to grow shorter more rapidly, as much as 20-25 minutes each week. In addition, Monday, September 24th marks the 108th anniversary of the famous Morristown tornado in Rice County. Shortly after 5:00 pm that date in 1900 an EF-2 tornado (winds 113-157 mph) formed over Rice County and sped eight miles across the landscape at an estimated 60 mph toward Morristown. There were many eyewitnesses to this storm as it was seen from some distance away. Many people sought shelter in Gattske's Saloon, being one of the few brick buildings in town. But the building walls were collapsed by the mighty wind and killed seven people. In addition, a hog farmer north of town lost many of his stock to the storm. This remains the worst tornado in history to hit Rice County. Words of the Week: Equatorial Oscillation (EO) There has been a good deal of online discussion this week about research into a pressure pattern over the Pacific Ocean Basin that appears to show a north-south orientation and oscillating pattern of high and low pressure between the equatorial latitudes and mid-latitudes. This oscillating behavior is different from the west-east orientation of the pressure pattersn associated with El Nino (warm water) and La Nina (cold water) events. Positive phase EO patterns are associated with relatively high pressure in the tropical zones of the Pacific and relatively low pressure in the north. Negative phases are the oppositve pattern. Like other teleconnections associated with atmospheric pressure patterns the phases of the EO seem to have some correlation to the weather pattern across the North American continent, especially in the winter season. In the negative phase, relatively higher pressure sets up a blocking pattern in the North Pacific, bringing more northwesterly flow to the mid-continent. Further research may lead to the use of the EO as a forecasting tool, much like the Climate Prediction Center presently uses El Nino and La Nina, as well as the Arctic Oscillation and North Atlantic Oscillation Indices. Outlook: Weekend weather will be mostly sunny and warm with 70s and 80s for daytime highs. Winds will pick up again on Sunday with the approach of a weather disturbance. There will be an increasing chance for showers and thunderstorms late Sunday and into Monday. Wednesday and Thursday look to be cooler and drier.