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March 20-23 Severe Threat


Jim Martin

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE DES MOINES IA

717 PM CDT TUE MAR 22 2011

IAC001-121-175-230030-

/O.CON.KDMX.TO.W.0011.000000T0000Z-110323T0030Z/

UNION IA-ADAIR IA-MADISON IA-

717 PM CDT TUE MAR 22 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR MADISON...SOUTHEASTERN

ADAIR AND NORTH CENTRAL UNION COUNTIES UNTIL 730 PM CDT...

AT 714 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO JUST

SOUTHWEST OF WINTERSET. THIS TORNADO WAS LOCATED NEAR

WINTERSET...OR 23 MILES NORTHEAST OF CRESTON...MOVING EAST

AT 55 MPH.

LOCATIONS IMPACTED INCLUDE...

EAST PERU.

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BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE DES MOINES IA

731 PM CDT TUE MAR 22 2011

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* TORNADO WARNING FOR...

NORTHEASTERN MADISON COUNTY IN SOUTH CENTRAL IOWA...

NORTHERN WARREN COUNTY IN SOUTH CENTRAL IOWA...

* UNTIL 800 PM CDT

* AT 728 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS

STORM WAS LOCATED NEAR WINTERSET...OR 19 MILES WEST OF INDIANOLA...

AND MOVING EAST AT 45 MPH.

* LOCATIONS IMPACTED INCLUDE...

INDIANOLA...NORWALK...CARLISLE...BEVINGTON...ST. MARYS...

MARTENSDALE...CUMMING...SPRING HILL...ACKWORTH...HARTFORD AND

SANDYVILLE.

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Sounds like SPC is working on a new MD (#251).

MESOSCALE DISCUSSION 0251

NWS STORM PREDICTION CENTER NORMAN OK

0800 PM CDT TUE MAR 22 2011

AREAS AFFECTED...SERN IA...NERN MO AND W-CNTRL IL

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 230100Z - 230200Z

THREAT FOR SEVERE STORMS COULD SHIFT INTO SERN IA...NERN MO AND

POSSIBLY W-CNTRL IL THIS EVENING. WW 53 WILL LIKELY NEED TO BE

REPLACED BY ANOTHER WW BEFORE 02Z. HOWEVER...OVERALL SEVERE THREAT

DOES NOT APPEAR AS GREAT AS EARLIER THIS EVENING.

TREND HAS BEEN FOR STORMS TO EVOLVE INTO LINES ACROSS S-CNTRL IA AS

COLD FRONT OVERTAKES THE DRYLINE...AND SOME SWD DEVELOPMENT INTO NRN

MO IS POSSIBLE AS THIS PROCESS CONTINUES. DISCRETE SUPERCELLS IN

WARM SECTOR HAVE WEAKENED AS THE BOUNDARY LAYER STABILIZES AND

STORMS CROSS ONTO THE COOL SIDE OF WARM FRONT. SURFACE HIGH PRESSURE

ANCHORED OVER SERN CANADA EXTENDING INTO THE GREAT LAKES WILL TEND

TO INHIBIT NWD PROGRESSION OF WARM FRONT CURRENTLY EXTENDING ACROSS

SRN IA. INSTABILITY DECREASES WITH ERN EXTENT THROUGH WARM SECTOR

ACROSS SERN IA...NERN MO AND W-CNTRL IL DUE TO WIDESPREAD CLOUDS

EARLIER TODAY. WITH ONSET OF NOCTURNAL COOLING...BOUNDARY LAYER WILL

LIKELY REMAIN RELATIVELY STABLE...AND THIS SHOULD SERVE AS A

LIMITING FACTOR FOR A MORE ROBUST SEVERE THREAT.

NEVERTHELESS...FORCING ASSOCIATED WITH NEWD EJECTING VORT MAX AND

ATTENDANT COLD FRONT MAY BE SUFFICIENT TO MAINTAIN LINE OF STORMS

THROUGH SERN IA AND NERN MO NEXT FEW HOURS. STORMS WILL REMAIN

EMBEDDED WITHIN STRONG VERTICAL SHEAR SUPPORTIVE OF SUPERCELLS AND

BOWING SEGMENTS. WHILE AN ISOLATED TORNADO OR TWO CANNOT BE RULED

OUT...SEVERE THREAT APPEARS TO BE TRANSITIONING TO ISOLATED DAMAGING

WIND AND HAIL.

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Very nice funnel, tough to tell with the building in the way if it extended all the way to the surface though.

Multiple chasers reported it on the ground, and it apparently did some damage in town. Hopefully video will be up soon on YT.

I guess I should stop writing off these seemingly marginal chase ops just because of distance. :lightning:

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 54

NWS STORM PREDICTION CENTER NORMAN OK

835 PM CDT TUE MAR 22 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

PARTS OF SOUTHERN IOWA

LARGE PART OF NORTHERN MISSOURI

EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 835 PM

UNTIL 200 AM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHEAST OF OTTUMWA

IOWA TO 5 MILES SOUTH SOUTHEAST OF CHILLICOTHE MISSOURI. FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU4).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO

WATCH NUMBER 53. WATCH NUMBER 53 WILL NOT BE IN EFFECT AFTER 835

PM CDT.

DISCUSSION...LINE OF SEVERE THUNDERSTORMS WILL MOVE EWD ACROSS WATCH

AREA THRU THE EVENING. WITH VERY STRONG SHEAR PROFILES...MARGINAL

BUT SUFFICIENT INSTABILITY IS AVAILABLE TO MAINTAIN THE THREAT OF

EMBEDDED SUPERCELLS/TORNADOES WITHIN THE LINE. IN ADDITION DAMAGING

WINDS ARE LIKELY...PARTICULARLY IN BOWING SEGMENTS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

450. MEAN STORM MOTION VECTOR 24035.

...HALES

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Looking ahead to Thursday... we'll watch a beautiful low-amplitude but potent shortwave trough go to waste over the Southern Plains because of the surface ridge building down from the Great Lakes. The good juice never even gets pushed past the Gulf Coast with this current cold front, yet it won't be able to return at all into NW TX by Thursday afternoon.

This perpetual eastern troughing thing is getting old real fast.

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Interesting news just from my north evidently there was some localized significant damage at my uncles and aunts: lost 2 trees, a shed and the tin roof off another shed. I wonder what was going on inside the little storm you can see at the beginning of this frame.

http://www.weather.com/weather/map/interactive/Badger+IA+USIA0056?animation=true

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And with that we're now under a severe thunderstorm warning for strong winds. Was expecting more of a hail threat here, and not wind, so this is interesting....

UNTIL 1215 AM CDT.

* AT 1109 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. THESE STORMS WERE LOCATED APPROXIMATELY ALONG A

LINE EXTENDING FROM 7 MILES WEST OF LONG GROVE TO BLUE GRASS TO

ELIZA TO MORNING SUN...OR ALONG A LINE EXTENDING FROM 11 MILES

NORTHWEST OF DAVENPORT TO 9 MILES SOUTHEAST OF DURANT TO 8 MILES

SOUTHEAST OF MUSCATINE TO 7 MILES SOUTHWEST OF WAPELLO...AND MOVING

EAST AT 50 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO

MANNON...BUFFALO...TOOLESBORO...ANDALUSIA...NEW BOSTON...

ELDRIDGE...HAMLET...MILLERSBURG...JOY...TAYLOR RIDGE...OAKVILLE...

ROCK ISLAND...REYNOLDS...ROCK ISLAND ARSENAL...MILAN...OAK GROVE...

KEITHSBURG...BETTENDORF...MOLINE QUAD-CITY AIRPORT...RIVERDALE...

MOLINE...ALEDO...EAST MOLINE...PRINCETON...COAL VALLEY...

MATHERVILLE...HAMPTON...CORDOVA...SHERRARD...SILVIS...BODEN...LE

CLAIRE...SHALE CITY...SEATON...PORT BYRON...RAPIDS CITY...CABLE...

COLONA...WARNER...VIOLA...CLEVELAND...OSBORN...ORION...BURGESS...

LYNN CENTER...NEW WINDSOR...ANDOVER...ERIE...GENESEO...ALPHA...

CAMBRIDGE...NORTH HENDERSON...WOODHULL...PROPHETSTOWN...LYNDON...

ATKINSON...HOOPPOLE...ANNAWAN...KEWANEE AND GALVA.

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I noticed there was a gust front out ahead of the main line, but figured it wasn't impacting the surface given the ambient conditions. Maybe the inversion is so shallow that the winds are able to reach the surface easier?

The 3z RUC sounding for DVN has a pretty stout inversion in the 950-900 mb layer.

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getting some more stratiform rain now behind themain line as it loses some of its punch on the north end.

Yeah the line north of I-80 is really beginning to wane. Doubt we'll see more than a 30-40mph wind gust here.

South of I-80 there could still be some strong gusts. The warm front down there could still cause a brief "spin up" as well.

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Actually sort of impressed by the winds here. Only gusting to 40-45mph, but the fact that we went from due east winds to strong westerlies in a matter of minutes is very interesting. Also of note, our pressure rose from 999.4mb to 1004.2mb over the past 5 minutes.

That type of rise/fall couplet will definitely help drive stronger wind gusts.

It's interesting how the base velocity images from DVN look "wavy." There appear to be multiple gust fronts, and the radar is indicating winds (or at least scatterers) are reversing their direction at times. I wonder if the convection is acting upon that inversion and inducing a gravity wave type thing. The presentation on radar is very similar.

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That type of rise/fall couplet will definitely help drive stronger wind gusts.

It's interesting how the base velocity images from DVN look "wavy." There appear to be multiple gust fronts, and the radar is indicating winds (or at least scatterers) are reversing their direction at times. I wonder if the convection is acting upon that inversion and inducing a gravity wave type thing. The presentation on radar is very similar.

Yeah the appearance of those waves look similar to the waves we saw in the blizzard. The strong winds here lasted about 10 minutes, which is longer than a normal gust front. With a normal gust front you get a few strong gusts at the beginning, and then lighter winds. With this the winds stayed strong, if not even stronger for up to 10+ minutes.

Edit: Very heavy rain falling right now. Thought we were getting small hail, but as it turns out it's just very large drops within the downpour.

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Had a brief gust to 52mph here on the leading edge but not much more than a garden variety thunderstorm outside of that brief gust. This seems to be more of a warning for the first borderline storm of the year type deal, plus its occurring later in the evening. Looking forward to much more of this as we get further into Spring. Interestingly, will be fun to see how much snow we now get Friday Night into Saturday. I lol'd a bit last week when one of our local meteorologists said he was confident we were done with snow. I thought to myself its way, way to early to make that claim and he's gonna get burned.

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Yeah the appearance of those waves look similar to the waves we saw in the blizzard. The strong winds here lasted about 10 minutes, which is longer than a normal gust front. With a normal gust front you get a few strong gusts at the beginning, and then lighter winds. With this the winds stayed strong, if not even stronger for up to 10+ minutes.

Edit: Very heavy rain falling right now. Thought we were getting small hail, but as it turns out it's just very large drops within the downpour.

Notice the change in appearance north of I-80 and south. Almost right where the warm front is.

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Notice the change in appearance north of I-80 and south. Almost right where the warm front is.

Yeah the line north of the front is basically gone now. Just an area of anvil rains with embedded thunder. There's actually a decent amount of lightning here right now, but it's all aloft/intra-cloud. It's funny how this almost seems like a typical decaying severe weather setup here, but temps are only about 10 degrees away from this being freezing rain.

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