No more weather-drama

3-D volumetric scan of the strong thunderstorms that passed just north of the Twin Cities late yesterday. The red-shaded areas show the maximum "DBZ", the most intense echoes producing heavy rain and hail. You can see evidence of strong "wind shear", rapidly changing wind speed/direction with altitude that caused the storms to tilt over slightly. This shear produced favorable conditions for "supercell" thunderstorms that spawned at least 4 separate tornadoes over central and west central Minnesota.

The storms reached their maximum intensity near Spicer, dropping a couple of confirmed tornadoes that produced damage, flash flooding and funnel clouds were observed in the St. Cloud area, and extreme rainfall amounts of 5-6" (6 weeks worth!) were reported near Brainerd, Merrifield and Pillager. For a complete rainfall & damage report from last night's severe storm outbreak scroll down towards the end of my column.

Yesterday was busy, a rare severe-weather day filled with watches and warnings. Surprisingly, in spite of a fairly early start to the severe weather, SPC never issued any tornado or severe storm watches, which was a bit odd. Many of the ingredients were present for an outbreak, dew points near 70, strong wind shear, sufficient instability, and a cool frontal boundary approaching from the Dakotas. The gun was loaded, and sure enough storms fired during the afternoon, intensifying right up until the dinner hour.

For central Minnesota the threat was isolated tornadoes, but farther north, deeper into the cool air, the risk was flash flooding as storms kept redeveloping over the same counties. One storm would dump 1-2" of rain and then dissipate, but another storm would redevelop over the same spot, a classic "train echo" effect. Much like the cars of a train pass over the same section of track, this train echo weather pattern can result in 3-5 storms passing over the same geography within a short period of time, less than 4 hours, resulting in some astounding rainfall amounts, more than 6" near Pillager. Keep in mind that average rainfall for the ENTIRE month of June is 4". When rain comes down that furiously there's no way the ground can soak it up, it quickly runs off into streets, streams and rivers, resulting in a risk of flash flooding. It's good to remember that flooding claims more lives every year than hurricanes and tornadoes combined. It doesn't make news the way a hurricane or tornado outbreak does, but it's extremely dangerous, especially when roads flood after dark. People want to get home (understandable). They're sitting up high in an SUV, and they honestly believe they can make it to the other side. But there's no way to estimate water depth, especially at night. All it takes is 2 feet of rapidly moving water to push that big, heavy SUV downstream. So you're suddenly in command of a 4-wheel drive BOAT, with little chance of getting out (safely) to higher ground. More than half of all flood deaths occur in vehicles, at night, as drivers underestimate the depth of raging water, and pay a terrible toll for their mistake.

The cool front that squeezed out 1-2" of rain on the St. Cloud area, but a meager .04" in the drought-stricken Twin Cities area (more fell over the northern suburbs) is now sweeping into Wisconsin. Cool, dry, refreshing exhaust on the backside of this Canadian air will punch holes in any leftover cloud cover, resulting in a partly sunny sky much of today with a noticeable drop in humidity. Winds will blow from the west, gusting past 30 mph at times, a potentially bad-hair afternoon. But the sun should be out, you can unplug the air conditioner (for the next 2-3 days, in fact) so no big deal.

Thursday will feel more like mid September (again) with temperatures struggling just to climb out of the 60s. A sunny start will give way to patchy afternoon clouds, a few wind-whipped showers and sprinkles popping up over the Minnesota Arrowhead, where the mercury probably won't climb out of the 50s and dazed locals will be wandering around in jackets and sweatshirts....possibly wondering when they were abducted and parachuted into the Yukon Territories. What on earth?

4-Panel WRF/NMM model. An autumn-like storm anchored over Hudson Bay will pump unseasonably cool air southward into Minnesota - Thursday highs may be as much as 10-15 degrees cooler than average. Temperatures slowly moderate to more typical, summerlike levels over the weekend as winds turn more to the south.

Normally a forecast of 6 dry days in a row would be interpreted as "good news". But with drought conditions spreading westward from the Twin Cities metro I have mixed feelings. True, last night's soaking helped the soil moisture situation over parts of central and northern Minnesota, but the southeastern third of our great state is still too dry - lake water levels are down, farmers are being impacted. A counterclockwise wind flow around an unusually strong storm (unusually far south) will pump a healthy dose of autumnal air south of the border. A weak bubble of high pressure keeps us sunny, cool and comfortable through the end of the week. By Sunday winds turn around a little more to the south, the mercury (finally) rises above 80 - Sunday still looks like the warmer, more lake-friendly day of the weekend (but both days look pretty incredible right now). The next opportunity for rain/storms? Next Tuesday and Wednesday look stormy and wet, but until then, smooth sailing. No wailing sirens, no quality time crawling around in the basement, no mad dashes to safety. I'm happy to report the weather will be a pleasant afterthought for the next 6 days. No worries....


File: Altocumulus. These clouds are too high (and thin) to produce precipitation. This time of year they're often seen on the backside (cool/stable) side of a cool front, or an approaching warm front.
Doppler Rainfall Estimates from last night's storms. The tornado-producing storms tracked northeast toward St. Cloud and the Brainerd Lakes area. Another (smaller) area of severe storms blossomed over southwestern Minnesota; these storms moved toward the southeast. The end result? Much of central and southeastern Minnesota missed out, almost entirely, on the rain. This isn't the first time this has happened this summer; a bit odd, yes. Wish I had a great (scientific) explanation for this one.

Rainfall Amounts, close-up image. The greater St. Cloud area soaked up 1-2" of rain (almost 2 weeks worth!) The heaviest amounts fell farther north, near Brainerd and Aitkin, where Doppler estimates showed some 4-5"+ rainfall amounts. The NWS issued flash flood warnings for the region, it may take 2-3 days for stream water levels to return to normal after last night's gushing torrent.

Paul's Outlook for the greater St. Cloud area:

Today: Plenty of sun, windy and less humid. Winds: West 15-30. High: 75

Tonight: Clearing, unusually cool for mid July. Low: 54

Thursday: Sunny start, clouds increase during the afternoon - still on the breezy, chilly side. Winds: NW 15-25. High: 71 (holding in the 60s up north)

Friday: Bright sun, less wind. High: 74

Saturday: Sunny and warmer, a fine summer day. High: near 80

Sunday: Generous sunshine, a few degrees warmer, a bit more humidity. High: 83

Monday: Fading sun, still dry. High: 84

Tuesday: More clouds arrive, growing chance of showers/T-storms. High: 81

* Here is more information on last night's heavy rainfall and severe weather reports, courtesy of the National Weather Service. Check out the funnel cloud sightings near St. Cloud (mainly on the north side of town) and the damage reports from the Spicer area.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE DULUTH MN
953 PM CDT TUE JUL 14 2009

...PUBLIC INFORMATION STATEMENT...


PRELIMINARY HEAVY RAIN TOTALS FROM TUESDAY JULY 14TH.

RAIN ACCUMULATION

6.30 INCHES8N PILLAGER

6.00 INCHES5NE DEER WOOD

5.00 INCHES 1S MERRIFIELD

4.20 INCHES5N BRAINERD

4.00 INCHES NISSWA

3.25 INCHES2N MOTLEY

2.75 INCHES 5SW GRAND RAPIDS

1.60 INCHESCLOQUET

1.50 INCHES NATIONAL WEATHER SERVICE DULUTH

0903 PM     HEAVY RAIN       5 N PILLAGER            46.40N 94.48W
07/14/2009  M6.30 INCH       CASS               MN   TRAINED SPOTTER

0515 PM     HAIL             1 E MERRIFIELD          46.47N 94.15W
07/14/2009  M1.75 INCH       CROW WING          MN   TRAINED SPOTTER

0515 PM     HEAVY RAIN       1 E MERRIFIELD          46.47N 94.15W
07/14/2009  M5.00 INCH       CROW WING          MN   TRAINED SPOTTER

MAX/MIN TEMPERATURE AND PRECIPITATION TABLE FOR MINNESOTA
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
730 PM CDT TUE JUL 14 2009

VALUES REPRESENT 12 HOUR HIGH...18 HOUR LOW
AND PRECIPITATION OVER THE LAST 24 HOURS




:            STATION           MAX     MIN     24-HR
:             NAME             TEMP    TEMP    PCPN
AXN : ALEXANDRIA MN ARPT     :  76  /   58  /   0.35
STC : ST CLOUD MN ARPT       :  79  /   58  /   1.19
MSP : MINNEAPOLIS MN ARPT    :  80  /   65  /   0.04
RWF : REDWOOD FALLS MN ARPT  :  84  /   67  /     T
DLH : DULUTH AIRPORT         :  62  /   54  /   0.18
INL : INTERNATIONAL FALLS    :  71  /   41  /   0.94
HIB : HIBBING ARPT           :  63  /   45  /   0.56
GNA : GRAND MARAIS MN        :  58  /   47  /   0.03
RST : ROCHESTER MN ARPT      :  77  /   62  /     T

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
930 PM CDT TUE JUL 14 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
  ..REMARKS..

0415 PM     FUNNEL CLOUD     4 NE BENSON             45.36N 95.55W
07/14/2009                   SWIFT              MN   TRAINED SPOTTER

0423 PM     TORNADO          4 SW GILCHRIST          45.41N 95.37W
07/14/2009                   POPE               MN   TRAINED SPOTTER

  SPOTTER REPORTED TORNADO ON THE GROUND

0436 PM     TORNADO          6 NNE SWIFT FALLS       45.49N 95.39W
07/14/2009                   POPE               MN   LAW ENFORCEMENT

  TORNADO REPORTED NEAR SCANDINAVIAN LAKE

0440 PM     TORNADO          SPICER                  45.23N 94.94W
07/14/2009                   KANDIYOHI          MN   LAW ENFORCEMENT

  LAW ENFORCEMENT REPORTED A TORNADO ON THE GROUND IN
  SPICER WITH DEBRIS SEEN AT A LOCAL SHOPPING MALL.

0450 PM     TORNADO          3 NE SPICER             45.26N 94.89W
07/14/2009                   KANDIYOHI          MN   PUBLIC

  TORNADO TRACKED ACROSS GREEN LAKE

0508 PM     HAIL             5 SW EVANSVILLE         45.96N 95.75W
07/14/2009  M0.88 INCH       DOUGLAS            MN   TRAINED SPOTTER

0545 PM     FLASH FLOOD      STAPLES                 46.36N 94.80W
07/14/2009                   TODD               MN   LAW ENFORCEMENT

  EVACUATIONS FOR HOMES ON 5TH ST. POWER SHUT OFF TO
  STAPLES HIGH RISE APTS ON 4TH ST.

0552 PM     FUNNEL CLOUD     2 E RICHMOND            45.45N 94.48W
07/14/2009                   STEARNS            MN   TRAINED SPOTTER

0625 PM     FUNNEL CLOUD     2 N ST CLOUD            45.58N 94.17W
07/14/2009                   STEARNS            MN   TRAINED SPOTTER

  HAVE RECEIVED MULTIPLE REPORTS OF FUNNEL CLOUDS IN THE ST
  CLOUD AREA.

0630 PM     FLOOD            ST CLOUD                45.55N 94.17W
07/14/2009                   STEARNS            MN   LAW ENFORCEMENT

  CO SHERIFF REPORTED LOCALIZED FLOODING PROBLEMS MAINLY
  URBAN AREAS IN STREETS

0635 PM     FLASH FLOOD      4 WNW DUELM             45.58N 94.01W
07/14/2009                   BENTON             MN   TRAINED SPOTTER

  SPOTTERS WERE NORTH OF DUELM LOOKING WEST.

0715 PM     HEAVY RAIN       ST JOSEPH               45.57N 94.32W
07/14/2009  M2.80 INCH       STEARNS            MN   CO-OP OBSERVER

  RECIEVED 2.8 INCHES OF RAIN FROM AFTERNOON THUNDERSTORMS.


0731 PM     HEAVY RAIN       3 N ST CLOUD            45.60N 94.18W
07/14/2009  M3.00 INCH       BENTON             MN   TRAINED SPOTTER

0825 PM     HAIL             4 SSW WARMAN            46.01N 93.33W
07/14/2009  M0.50 INCH       KANABEC            MN   TRAINED SPOTTER