Author Topic: US Tornadoes 16-18 Oct 2007  (Read 8071 times)

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Offline Mike

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US Tornadoes 16-18 Oct 2007
« on: 17 October 2007, 01:58:11 PM »
Big day ahead on the plains in Oklahoma if the models stay as they are for wednesday arvo and evening.  Another low pressure area is moving into the region and there's a moderate risk of damaging tornadoes if things go as the models suggests.  Bet the seasoned chasers JD et al were there for this!

Quote is from Reed Timmer of http://www.tornadovideos.net/ who is planning the chase....and I have added the WRF models to salivate over!!!!

'The WRF is forecasting an environment  of 1500-3000 J/kg CAPE, zero CIN, and 200+ m2/s2 0-1 km helicity for the entire warm sector east of a sharp dryline, with dewpoints in the upper 60s to around 70 in central OK!  The hodographs look very favorable for strong tornadoes, with INTENSE low-level shear.  Shown below are some forecast panels from this evening's WRF model, with the area of highest tornado threat shaded in red'

Mike
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Offline Michael Bath

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RE: US Tornadoes 16-18 Oct 2007
« Reply #1 on: 19 October 2007, 06:02:37 AM »
The 16th turned out to be a bit of a dud with just some modearte sized hail reports. Today has been fairly active across Missouri with 10 tornado reports so far, and a couple in other states. Biggest hail reported has been 2.5 inches in Kansas - along with a funnel.

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Offline Mike

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RE: US Tornadoes 18-19 Oct 2007
« Reply #2 on: 20 October 2007, 09:03:22 AM »
They still have warnings out.  reports of some people already injured from tornadoes.  Storm Prediction Centre link here - http://www.spc.noaa.gov/products/watch/ and some graphics and the like here at http://www.crh.noaa.gov/jkl/

The first loop is from 2324 to 0029 UTC and the second loop is from 2335 to 0045 UTC - (thanks to Reed Timmer for the loop times and damage list) indication of their movement to the E/NE - confirmed is thus:

0045 UTC -- 10 NW Hopkinsville -- Hopkins Co. -- Confirmed damage with injuries.
0100 UTC -- Nortonville -- Hopkins Co. -- Several buildings with severe damage.
0109 UTC -- 2 S Dawson Springs -- Caldwell Co. -- Confirmed tornado along Dawson Springs Road.  Individuals trapped in a mobile home.  Emergency responders enroute.

Jackson, Kentucky radar has all the counties to the west/east under tornado watch at the moment until at least 0500am.  Go to  http://radar.weather.gov/radar.php?rid=jkl&product=N0R&overlay=11101111&loop=no

Radar image at the above link was taken around 0220am and the areas affected under severe thunderstorm/tornado watch.

Mike




« Last Edit: 20 October 2007, 10:33:46 AM by Mike »
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Offline Mike

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Re: US Tornadoes 16-18 Oct 2007
« Reply #3 on: 21 October 2007, 04:10:44 AM »
Around 29 tornadoes and one confirmed fatality thus far with this outbreak in the eastern states of the US.  Three YouTube videos of a supercell that formed in Pensacola Florida, and the tornado are available to view via  http://tornadovideos.net - very good quality and shows rotation of the storm, funnels and more..quite a nasty event this one and we'll have to wait a few days for all the reports, photos and the like to come in to see actually how much damage was done.
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Offline Mike

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Re: US Tornadoes 16-18 Oct 2007
« Reply #4 on: 22 October 2007, 04:10:25 AM »
Here's the storm report from NOAA on the Oct 18 2007 system.

A powerful fall storm system affected a large part of the Midwest on October 18.  Strong low pressure developed out of a deep upper level trough which moved from the Rockies into the Plains overnight, and was strengthened by mid-level jet stream winds in excess of 100 mph.  Surface low pressure developed over the central Plains and quickly deepened to 982 mb and moved northeast into southern Minnesota by early evening. 

Round #1 of severe weather struck central and southeast Illinois during the early morning hours as a 60 mph low-level jet stream brought deep moisture and warm air northward into the area.  Additionally, a mid-level shortwave moved quickly northeast helping to produce widespread showers and thunderstorms.  Intense storms developed just after midnight in west-central Illinois producing strong winds which damaged trees and power lines from Scott county eastward into Sangamon county.  These storms weakened as they moved northeast into a more stable airmass.  New storms erupted around 4 AM in southeast Illinois and developed quickly to the northeast and intensified over the next couple of hours.  Between 4 and 6 AM winds in excess of 60 mph damaged trees and power lines from Effingham eastward through Lawrenceville, and northward through Martinsville, Robinson, and Paris.  In addition to the strong winds these storms were very efficient rain producers, with between 2 and 4 inches of rain falling within one to two hours over a large part of southeast and east central Illinois.

The system’s warm front pushed north of the area by the early morning hours, and the "dry slot" moved in from the west, shutting off precipitation and bringing mostly sunny skies by morning.  The morning sunshine allowed the atmosphere to destabilize ahead of the approaching cold front to the west.  Early afternoon temperatures rose well into the 70s, with dewpoints in the 60s.  With a moderate risk of severe storms for the eastern half of the state, a special 18Z weather balloon was launched from the Lincoln office.  Data showed very strong low-level lapse rates and sufficient moisture in the lower levels to produce a moderately unstable airmass .  Additionally, wind fields were very strong aloft.  Surface winds of 25-35 mph increased to 75 mph at mid-levels, and 125 mph at upper levels.  While the wind direction did not change much with height, the speed difference created an impressive amount of vertical shear which was sufficient to create supercell thunderstorms.  By late afternoon the atmosphere had continued to destabilize as the cold front/dry line plowed in from the west.  Thunderstorms erupted around 5 PM between the I-55 and I-57 corridor and moved to the northeast at 40 to 60 mph.  Frequent lightning, very heavy downpours, hail, and damaging straight line winds accompanied many of these storms.  The activity continued until around 7:30 PM.  Many locations along and east of the I-57 corridor sustained damage to trees and power lines. 

There were no tornadoes associated with this activity, likely due to a lack of directional wind shear locally.  Violent tornadoes did develop later in the evening as these storms pushed into Indiana .  Over 4 dozen tornadoes were reported over a 2 day period across the central U.S.


And just for something different - the difference between chasing with big bucks and being a 'spotter' reporting from fixed locations? Prime mover with 5cm doppler vs banged up SUV !!!  (Photos courtesy Reed Timmer attending the National Weather Service open day in Norman OK.)

Mike

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Offline Jimmy Deguara

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Re: US Tornadoes 16-18 Oct 2007
« Reply #5 on: 22 October 2007, 06:52:54 AM »
Mike,

29 confirmed reports seriously does makes this a really significant event particularly for a late season situation. This did happen a few years ago as well.

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Jimmy Deguara
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Offline Mike

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Re: US Tornadoes 16-18 Oct 2007
« Reply #6 on: 22 October 2007, 12:55:09 PM »
Indeed, Jimmy.  2007 has been a monster season as you had encountered whilst over there, the US weather is just so unpredictable. 

Would the La Nina cycle there as well be having this affect on their tornado outbreaks so late in the season? 

I view the US weather maps on and off and the amount of complex weather systems producing storms through the central plains right through to the eastern states is just amazing, but don't know enough about which state gets what weather and when!

Four dozen tornadoes in two days just beggars belief.  From the previous frontal system that came through during the 15/16Oct dropped off slightly, but the second front that came through obviously carried some serious storms with it in the latter days of last week.

The full SPC report for the 18th is here http://www.spc.noaa.gov/climo/reports/071018_rpts.html - it's got so much info a link was needed -  sadly several deaths now confirmed. 

Will be looking for further post-storm event reports with much interest.

Mike
Darwin, Northern Territory.
StormscapesDarwin.com
Lightning Research 2010/14