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Severe Weather Update

12:35 pm in Extreme Weather, Severe Storms, The Ozarks by Ted Keller

Radar at 1:25 pm

Good news, the tornado threat, what there was, has lessened but a severe thunderstorm watch may be in the works for this afternoon.

Morning storms have changed the environment across much of the Ozarks to lessen the tornado threat. The 5% area ala the SPC is now in Kansas. There is still a marginal (2%) threat for the area.

The storms in question are now approaching Vernon and St Clair counties. This area is under a flash flood warning from morning storms and this additional rainfall could lead to some high water in spots.

A severe thunderstorm watch may be hoisted for a large portion of southwest Missouri shortly as this storm area continues to move ESE. Large hail and isolated severe wind gusts are the main threat.

Be sure to watch for updates on KOLR News at 5, 6 & 10 and Ozarks Fox News at 9 pm tonight for the latest!

A Mini Bowing Thunderstorm Line

10:13 am in Extreme Weather, Storm Summaries, The Ozarks by Ted Keller

Storm Reports as of 10:35 Sunday

A cluster of thunderstorms which started in Kansas Saturday evening, crossed into Missouri and left a swath of wind damage!

The bowing refers to the shape of the mini line of storms as it advances. This is shown clearly in the embedded loop of radar from early Sunday morning (below).

This line produced scattered wind damage reports from southern Crawford County in Kansas into Dade and eventually Greene County.  There were lots of reports of small limbs down and outdoor objects such as potted plants “displaced”.  The Springfield National Weather Service reported a wind gust to 51 ph at 2:10 am.  There were likely some severe wind gusts (59 mph or higher ) with this storm line.  Several minor power outages were reported with this storm line as well.

Storm Reports Collected by the National Weather Service

PRELIMINARY LOCAL STORM REPORT…SUMMARY
NATIONAL WEATHER SERVICE SPRINGFIELD MO
633 AM CDT SUN AUG 15 2010
..TIME…   …EVENT…      …CITY LOCATION…     …LAT.LON…
.DATE…   ….MAG….      ..COUNTY LOCATION..ST.. …SOURCE….
            ..REMARKS..1224 AM     TSTM WND DMG     4 SW FRONTENAC          37.41N 94.73W
08/15/2010                   CRAWFORD           KS   LAW ENFORCEMENT
            FRONT PORCH PULLED FROM HOUSE. TIME ESTIMATED.1224 AM     TSTM WND DMG     2 S PITTSBURG           37.38N 94.70W
08/15/2010                   CRAWFORD           KS   LAW ENFORCEMENT
            FOUR TREES REPORTED DOWN ON THE SOUTH SIDE OF PITTSBURG.
            TIME ESTIMATED.0140 AM     TSTM WND GST     LOCKWOOD                37.39N 93.95W
08/15/2010  E60.00 MPH       DADE               MO   LAW ENFORCEMENT
            50 TO 60 MPH WIND GUST ESTIMATED BY DEPUTY IN THE CITY OF
            LOCKWOOD.0140 AM     TSTM WND GST     GREENFIELD              37.42N 93.84W
08/15/2010  E60.00 MPH       DADE               MO   LAW ENFORCEMENT

            50 TO 60 MPH WIND GUST ESTIMATED AT THE DADE EOC.0145 AM     TSTM WND DMG     GREENFIELD              37.42N 93.84W
08/15/2010                   DADE               MO   LAW ENFORCEMENT
            SEVERAL TREES DOWN IN GREENFIELD…A FEW WITH A DIAMETER
            UP TO 18 INCHES.

0145 AM     TSTM WND DMG     LOCKWOOD                37.39N 93.85W
08/15/2010                   DADE               MO   LAW ENFORCEMENT

            TWO TREES DOWN ACROSS THE ROAD NEAR THE INTERSECTION OF
            HIGHWAYS 160 AND 39.

0200 AM     TSTM WND GST     EVERTON                 37.34N 93.70W
08/15/2010  E60.00 MPH       DADE               MO   LAW ENFORCEMENT

            50 TO 60 MPH WIND GUSTS ESTIMATED BY SPOTTER IN EVERTON.

0210 AM     NON-TSTM WND GST 5 SSE WILLARD           37.23N 93.40W
08/15/2010  M51.00 MPH       GREENE             MO   OFFICIAL NWS OBS

            51 MPH WIND GUST WITH THE OUTFLOW BOUNDARY AHEAD OF MAIN
            COMPLEX OF THUNDERSTORMS.

0217 AM     NON-TSTM WND GST NIXA                    37.04N 93.29W
08/15/2010  E50.00 MPH       CHRISTIAN          MO   AMATEUR RADIO

            50 MPH WIND GUST WITH THE PASSAGE OF THE OUTFLOW
            BOUNDARY.

0255 AM     TSTM WND DMG     SSE STRAFFORD           37.27N 93.12W
08/15/2010                   GREENE             MO   AMATEUR RADIO

            10 FOOT SECTION OF WOOD FENCING BLOWN DOWN…A FEW TREE
            LIMBS UP TO THREE INCHES IN DIAMETER BLOWN DOWN. TIME
            ESTIMATED.

0258 AM     TSTM WND DMG     2 WNW FAIR GROVE        37.39N 93.19W
08/15/2010                   GREENE             MO   AMATEUR RADIO

            FOUR INCH DIAMETER DOGWOOD TREE BLOWN DOWN.

0300 AM     TSTM WND DMG     1 N STRAFFORD           37.29N 93.12W
08/15/2010                   GREENE             MO   AMATEUR RADIO

            14 INCH DIAMETER TREE DOWN ON POWER LINE. PART OF FARM
            ROAD 84 BLOCKED IN THIS AREA.

0318 AM     NON-TSTM WND GST AVA                     36.95N 92.66W
08/15/2010  M38.00 MPH       DOUGLAS            MO   AMATEUR RADIO

            38 MPH WIND GUST MEASURED WITH OUTFLOW BOUNDARY PASSAGE.
            FLAG POLE AT AVA POLICE DEPARTMENT BLOWN DOWN.

A Wild Outbreak of Tornadoes

7:05 pm in Severe Storms, Storm Summaries by Ted Keller

No Place on Earth

can put the ingredients together for an outbreak of tornadoes quite like the central U.S. and the outbreak of May 10th, 2010 certainly reminds us of this fact.

Rope Tornado Near Yukon, OK. Photo by Chris Novy.

The outbreak came together as extremely unstable air was pulled northward ahead of a dry line.  At the same time, a very strong but compact area of intense air level winds (shortwave/jet max) moved over the area.

The alignment of the upper level winds and unstable air was going to last for only about six hours and in a relatively small area.  But in that time and space frame, numerous supercell thunderstorms quickly evolved, most into tornado-barring cells.

At this writing, the National Weather Service in Norman, Oklahoma has indentified ten areas where tornadoes likely tracked on this day.  More tornadoes occurred in Kansas and northeastern Oklahoma. This will be refined more as survey crews finish their painstaking task.  The death toll stands at five. 

NWS Reviews:

The Set Up

Low Wall Cloud, Multiple Vorticies. Photo by Allan Detrich.

It was a situation typical to the Great Plains but with the volume cranked way up.  It starts when a “trough” of low pressure develops over the western U.S.  This encourages steady southerly winds to blow over the central U.S. drawing humid air from the Gulf of Mexico northward.  On this day the dew points, a measure of moisture in the atmosphere, were quite high and this humidity helps to make the air unstable.  In fact, all else being equal, higher dew points will generally lead to more violent storms.

Unstable air is produced whenever you can warm the air at or near the surface of the earth while keeping things relatively cool aloft.  Moisture adds to the instability because when water vapor condenses back into visible cloud droplets, the energy in took to evaporate this water is released into the atmosphere.

Now on top of all of this, the jet stream winds, fueled mostly by differences in temperature from south to north, were howling!  These winds do several things.  The overall increase in wind speed with increasing height provides structure for developing thunderstorms and allows them to become “supercells”.  Also, the speed and directional changes in the wind close to the earth’s surface provide a spinning which the updrafts of a thunderstorm inherit.

Sometimes, the “wind shear” can be too strong and developing storms will get “sheared” off.  The winds on the outbreak day were strong enough to be a concern for this happening BUT the instability was so strong that the updrafts which make up a thunderstorm rose violently and were able to survive, even flourish, in this environment!

Chasing These Storms

The wind speeds were very high in the atmosphere leading to storms traveling over 60 mph!  This “storm motion” made these storms difficult to chase. Still, there were some shots.  The multiple-vortex tornado shot by Andy Gabrielson is stunning!

Some local chaser friends of mine Jason Blum, Dave Toner and Cody Hudson got themselves into a dangerous situation near Arkansas City, KS.  Their vehicle goes down a steep embankment.  Then the tornado passes nearly on top of them!

The Ozarks Missed This

Some may wonder since weather moves from west to east why the Ozarks didn’t see at least a weaker version of what happened out west, especially considering how fast the jet stream was.  The answer is that we were in much more stable air.  I watched as these storms literally fell apart while racing eastward.  The fast jet stream winds actually outpaced the ability to draw unstable air out ahead of the system.  Later on, we actually did have a tornado warning or two west and northwest of Springfield but this was mostly due to the incredible wind shear working on even the weakest updraft to see if can be coaxed into rotating.

Storm Chase Results from May 1st

10:05 am in Storm Chasing, Storm Summaries by Ted Keller

A high risk for severe thunderstorms and long-tracked tornadoes existed for much of central and eastern Arkansas the afternoon of May 1st, 2010.  I went down there to chase this event.  When storms started firing, there were lots of them, most ended up tornado-warned.  Folks were anticipating the worst.  But in the end, very few tornadoes were produced.

Here’s my account of the chase and a bit about why so few tornadoes occurred on this day despite much anticipation.

We drove down via Willow Springs, MO to see the damage caused by an EF1 tornado Friday evening.  The Hillbilly Junction sustained roof damage as did an antique store just up a hill and to the east.  This was the last of five tornadoes produced by a supercell which started in Boone County, Arkansas.

We were a caravan of three with Dustin Elkins and Bo Hessee also driving.  We eventually wove our way down to White Hall which is just north of Pine Bluff.  Here, other chaser friends of ours had gathered including Dena Sanders and Brian DePriest.  The Tornado Intercept Vehicle (TIV) was there as were other chasers.

Boundary Moving Slowing North This Day

Of much interest early on was the very obvious boundary visible on radar stretching WSW/ENE south of Little Rock.  It was thought that this boundary would be able to supply more focused and localized storm relative helicity to storms forming along it.  Indeed several storms west of Little Rock did appear to have an increase in rotation while crossing this boundary.  But the storm motion was taking them across and not along this feature.  If a storm could have traveled along it, it might have produced the longer-track type of tornado which was feared on this day.

Storms became very numerous in southern Arkansas by the 6 o’clock hour.  In fact, too numerous really.  It became difficult to know which storm to chase!  We initially decided to get northeast of the Arkansas River toward the flat rice lands in and around Stutgartt.  But as supercells became tornado-warned in southern Arkansas, we decided to change the plan, back track a bit and try to get one of the southern storms.  While on the way, storms started firing north and south of Pine Bluff which eventually became tornado-warned.  The decision of the day was to not chase these storms and instead press on to the most southeast of all of the supercells which was going to cross highway 65 near Gould, AR.  The reasons we didn’t pursue the Pine Bluff storms were 1) we would have to travel back through the city of Pine Bluff, 2) the river crossing were limited and 3) there was too much rain, drizzle and just plain bad visibility east of these storms.

Radar Image w/Mesocyclone Indicator at 7:46 pm

So, on down highway 65 we traveled.  We were racing against dark really.  We got into position ahead of the well defined cell which had a great hook echo.  One more adjustment southeast to Gould was required due to the slight right turn the storm (and many supercells) started to take.

We saw some great formations and a likely wall cloud but as the storm passed just to our west, no tornado ever formed.  Reed Timmer and the Dominator crew was coming though Gould and we followed them briefly north chasing the same storm but eventually the chase was abandoned.

I’m waiting on the archived SPC data for this day to appear but I suspect that the reason more tornadoes were not generated on this day were due to low values of low level rotation and generally weaker than needed low level winds.

I am compiled a video log of the chase which should be finished by Thursday.

Storm Report, Strange Weather

10:41 am in Forecast Discussion by Ted Keller

Snow Cover on 3/22/10 Using MODIS

O.K., after a sick and draining Saturday, I have the energy to discuss this winter (spring?) storm!  My apologies for missing “Upstream” Friday night and what have likely been a special edition on Saturday too.  I also wasn’t able to attend a NWS conference on Saturday morning. I hate being sick!

Anyway, there are three aspects to this storm which people are asking a lot about 1) isn’t it too late in the season for this 2) how can we have just been in the sixties and are forecast to be back that warm in a few days and 3) what’s with the big differences in precipitation type and totals over short distances in the Ozarks?

Well, first off, big March snows are not unheard of at all.  The last one I remember was in the late nineties and although I don’t have an exact date handy, I can tell you it occurred the same weekend that the men MSU (SMSU) Bears went to the NCAA playoffs.  It was a Saturday night…I believe portions of the Ozarks received over 10 inches!   Another big storm occurred sometime in the late eighties (again, I don’t have access to detailed records here at home, this is all by personal recollection).  That storm just about shut this town down and you should know it was seventy degrees only a few days after this storm!  Finally, the small difference in average snowfall between February and March should tell you something about March snow potential.

You think you’re in shock over this, think about what the folks in Kansas were feeling last year in late March.

"Cut-off" Low at 7am Sunday at 500 mb.

As for this “winter sandwich” we seem to be in, with warmth on both sides of the storm, this is best explained by the “cutoff” nature of this weather system and by the fact that spring is simply an extreme time of year.  Because the cold air was drawn into a circulation that cut itself off from the main jet stream flow, it will only be a matter of moving the cold core to experience a rapid temperature recovery.

This same closed-off and slow-moving structure explains how the precipitation was laid down.  Greene County, which was correctly forecast to be “on the line”,  certainly lived up to this with 6″ plus snow/sleet totals over the extreme western portion of the county to rain and freezing rain in the eastern portion (I have about a 1/4″ of ice on my trees here in eastern Springfield). Nightfall determined precipitation type here in Greene county as temperature adjusted down a bit.

 A transition from rain to sleet to ice to snow is not unheard of in most winter storms.  In non-low pressure storms involving a front, this is usually much more noticeable and is responsible for nearly all of the worst ice storms.  But low pressure type storms such as this weekend’s are usually moving too fast and have narrow mixed zones so that mixed precipitation is not usually an issue.  But as we already know, this storm “cut off” and was slow-moving, allowing a everything to exaggerate.  The ice and the quick transition to heavy snow totals are the two aspects to this storm that I think were largely unexpected.

Because of the heavy rains and a snowpack which is expected to melt quickly later in the week, river flooding will likely be an issue for some.

I’m thinking about an “Uptream” later today, probably in the early evening as I’ll be working the late shows tonight. Send in photos and storm reports!

Link to MODIS Satellite images.

The “Storm of the Century 2″, March 12, 2006 Tornadoes

4:05 pm in Storm Summaries by Ted Keller

Looking NNE from Seymour on 3/12/06. From video shot by Matt Gingery.

In terms of shear numbers and intensity, this outbreak was much worse than the May 4th, 2003 outbreak.

16 different tornadoes tracked through the area indicated on the maps below.  This total does not count the rest of Missouri, Arkansas, Oklahoma, Kansas and Illinois.

Tornado Tracks

 

Tornado Tracks

Radar at 9:31 pm 3/12/06

Doppler Radar: it can sense whether raindrops or hail are moving away or toward the radar site. This principle also works in an environment without storms because radar beams can actually bounce off of large cloud droplets and turbulent pockets in the atmosphere.  Doppler codes winds that are blowing toward the radar with green, wind blowing away as red.

The first image captured at about 6:00 pm shows winds near the surface of the earth coming from the SSW.  Two hours later at 8:00 pm, the winds had turned slightly or backed  to the SSE.

This turning of the wind in the lowest layer of the atmosphere has been shown to have a profound impact on the potential for thunderstorms to produce tornadoes.

This can also be seen in the Conway profiler data.  Note not only the backing winds but also the incredible overall wind speeds which increased rapidly with height.  This kind of wind profile helps to give supercell thunderstorms longevity.

Doppler at 6 pm

Doppler at 8 pm Conway, MO Profiler on 3/12/06

Conway, MO Profiler on 3/12/06

Eerie Similarity: The map below is actually two maps superimposed: one shows the track (heavy red line) of the May 4th, 2003 tornado while the other shows the track (thin red line) of the March 12th, 2006 tornado.  The tracks are exactly on top of each other near Verona and never drift more than a mile from each other until the very end.  The 2003 storm turned left near the end of its track and struck Battlefield while the 2006 storm maintained more of a straight line.  These maps were created by the Springfield National Weather Service Office and can be found in their original form here (2003) and here (2006).

Thick Red: 5/4/03, Thin Red: 3/12/06

Tornado Tracks OK/AR 3/12/06

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