All Weather News

Very Significant November Tornado/Straight Line Wind Event Unfolding

17 Nov 2013, 10:52 am

Sunday morning, November 17, 2013

* Major, potentially historic mid-November tornado outbreak and straight-line wind damage scenario shaping up for Ohio Valley and portions of the Great Lakes today. 

* PDS (Particularly Dangerous Situation) Tornado Watches already issued for much of Illinois, Indiana and Michigan and into Ohio.  When conditions are especially volatile SPC issues a PDS Tornado Watch, calling for a high risk of large, damaging, violent EF2+ tornadoes

 

Almost Unprecedented. I can’t remember the last time I saw a “High Risk” pop up in mid-November. A “Moderate Risk” is usually a threshold for significant tornadoes – High Risk means a high confidence of several large, long-tracked, EF-2 or stronger tornadoes capable of significant damage and injury. As is always the case with a tornado scenario, it’s impossible, hours in advance, to know precisely where a tornado will touch down. All we know is that conditions are very ripe, in fact the maps resemble something out of May. Extreme wind shear (changing wind speed/direction with altitude) will combine with moderate instability and a rich, deep layer of Gulf moisture to fire of supercell thunderstorms, the spinning storms that show up on Doppler and are capable of large hail and tornadoes.

 

This is the newest PDS watch issued late this morning.

* EFFECTIVE THIS SUNDAY MORNING AND EVENING FROM 1120 AM UNTIL
     800 PM EST.

   ...THIS IS A PARTICULARLY DANGEROUS SITUATION...

   * PRIMARY THREATS INCLUDE...
     SEVERAL INTENSE TORNADOES LIKELY
     NUMEROUS DAMAGING WIND GUSTS LIKELY WITH SEVERAL SIGNIFICANT
       GUSTS TO 80 MPH POSSIBLE
     SEVERAL LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER LIKELY
Click here for details from the SPC:

 

This is the PDS watch area issued earlier in effect until 4pm CST.

Details: THE NWS STORM PREDICTION CENTER HAS ISSUED A * TORNADO WATCH FOR PORTIONS OF EASTERN IOWA ILLINOIS NORTHWEST INDIANA NORTHEAST MISSOURI SOUTHEAST WISCONSIN LAKE MICHIGAN * EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 840 AM UNTIL 400 PM CST. …THIS IS A PARTICULARLY DANGEROUS SITUATION… * PRIMARY THREATS INCLUDE… SEVERAL INTENSE TORNADOES LIKELY SEVERAL LARGE HAIL EVENTS LIKELY WITH A FEW VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE SEVERAL DAMAGING WIND GUSTS WITH A FEW SIGNIFICANT GUSTS TO 80 MPH POSSIBLE THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES SOUTH SOUTHEAST OF SCOTT AFB ILLINOIS TO 40 MILES NORTHEAST OF MADISON WISCONSIN. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE. PRECAUTIONARY/PREPAREDNESS ACTIONS… 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.

 

 

Timing Today’s Squall Line. I want to emphasize that the vast majority of cities will experience severe thunderstorms, with straight-line winds over 60 mph and 1-2″ diameter hail. Most locations will NOT see a tornado. But conditions are ripe, especially over Indiana and far southern Michigan, for a few significant tornadoes. If you’re tracking these storms on Doppler it’s the isolated cells out ahead of the main squall line that need to be watched most carefully for tornado formation. The squall line itself may produce straight-line wind damage, but the greatest risk of large and violent tornadoes will be 50-150 miles out in front of this line of heavy weather.

Paul Douglas/Senior Meteorologist- Alerts Broadcaster

 

Alerts Broadcaster provides severe weather and natural hazard intelligence to businesses worldwide through Alerts, Briefings, and Business Continuity Consultation.  Alerts Broadcaster meteorologists are working  24×7  to provide analysis and perspective that is crucial to your company’s severe weather response. Contact us to learn how Alerts Broadcaster can help protect your organization, staff and patrons: http://www.alertsbroadcaster.com/contact/

Leave a comment

Your email address will not be published. Required fields are marked *