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Major Severe Weather Outbreak November 17


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DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0659 AM CST SUN NOV 17 2013  
 
VALID 171300Z - 181200Z  

 
...THERE IS A HIGH RISK OF SVR TSTMS OVER PARTS OF  
ILLINOIS...INDIANA...WESTERN OHIO...AND SRN MICHIGAN...  
 
...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK  
AREA...FROM MUCH OF KENTUCKY AND EASTERN MISSOURI NEWD INTO THE LWR  
GRT LKS...  
 
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE HIGH AND MDT  
RISK AREAS...FROM PARTS OF THE LWR MS VLY NEWD TO THE MID ATLANTIC  
STATES/WRN NEW ENGLAND...  
   
..SYNOPSIS
 
 
SVR WEATHER OUTBREAK...WITH SIGNIFICANT TORNADOES AND  
WIDESPREAD DMGG WINDS...EXPECTED OVER THE OH VLY AND SRN  
GREAT LKS REGION TODAY/TNGT...  
 
POTENT CNTRL PLNS SHORTWAVE TROUGH...WITH MID-LVL WIND SPEEDS AOA  
100 KTS...WILL SWEEP E ACROSS THE NRN OZARKS/MID MS VLY LATER  
TODAY...AND ENE ACROSS THE OH VLY BY EARLY TNGT...BEFORE TURNING  
MORE NEWD ACROSS LWR GRT LKS/NRN APPALACHIANS EARLY MON. THE SYSTEM  
WILL BE ACCOMPANIED BY A RAPIDLY DEEPENING SFC LOW THAT SHOULD TRACK  
FROM SE IA THIS MORNING INTO NRN LWR MI BY EARLY TNGT. COLD FRONT  
TRAILING S AND SW FROM THE LOW...NOW EXTENDING THROUGH NW MO AND FAR  
ERN KS...SHOULD ACCELERATE E/SEWD THROUGH THE DAY...OVERTAKING  
PRE-FRONTAL TROUGH/DRY LINE OVER MO...AND REACHING WRN OH/N CNTRL KY  
THIS EVE. THE FRONT SHOULD CONTINUE RAPIDLY E ACROSS THE LWR GRT  
LKS...THE MID ATLANTIC STATES...AND WRN NEW ENGLAND LATER TNGT/EARLY  
MON.  
 
COMBINATION OF VERY STRONG TO INTENSE WIND FIELD WITH APPRECIABLE  
SFC-BASED INSTABILITY OVER A FAIRLY WIDE AREA WILL YIELD A BROAD  
SWATH OF SVR WEATHER FROM ERN PORTIONS OF THE MID MS VLY TO THE  
MID-ATLANTIC STATES AND NORTHEAST. THE GREATEST/MOST CONCENTRATED  
SVR THREAT...INCLUDING POTENTIALLY STRONG AND/OR LONG-TRACK  
TORNADOES...SHOULD FOCUS OVER THE OH VLY AND ADJACENT PARTS OF THE  
MIDWEST BEGINNING LATER THIS MORNING AND CONTINUING THROUGH EARLY  
TNGT.  
 
...MID MS/OH/LWR TN VLYS NEWD TO LWR GRT LKS/WRN NEW ENGLAND TODAY  
THROUGH EARLY MON...  
LATEST OBSERVED DATA SHOW SFC LOW ALREADY STARTING TO DEEPEN OVER S  
CNTRL IA...WITH LOW-LVL MOIST AXIS BECOMING BETTER DEFINED ACROSS  
CNTRL MO...ALONG AND E OF PRE-COLD-FRONTAL TROUGH. AT UPR  
LVLS...SATELLITE SUGGESTS THAT EXIT REGION OF CNTRL PLNS JET STREAK  
WILL CONTINUE EWD ACROSS IA/NRN MO THROUGH MID-MORNING...AND INTO  
NRN/CNTRL IL BY MIDDAY.  
 
COMBINATION OF INCREASING ASCENT/MID-LVL COOLING WITH THE JET  
STREAK...CONTINUED LOW-LVL MOISTURE INFLOW /WITH SFC DEWPOINTS  
RISING INTO THE 60 F/...AND MODEST SFC HEATING SHOULD SUPPORT TSTM  
DEVELOPMENT ALONG AND AHEAD OF MERGING COLD FRONT/TROUGH BY MID TO  
LATE MORNING OVER ERN MO AND CNTRL/NRN IL. OTHER STORMS SHOULD  
CONTINUE TO INCREASE IN ZONE OF STRENGTHENING WAA FROM ERN IA INTO  
FAR NRN IL/SRN WI.  
 
INTENSITY OF LOW TO MID-LVL WIND FIELD...PARTICULARLY WITH 700 MB  
SPEEDS INCREASING TO BETWEEN 50 AND 70 KTS...IN CONJUNCTION WITH  
SUBSTANTIAL SFC-BASED BUOYANCY /SBCAPE RANGING FROM 500-1000 J PER  
KG/...WILL YIELD AN ENVIRONMENT VERY FAVORABLE FOR LONG-LIVED  
DISCRETE TO SEMI-DISCRETE SUPERCELLS...BEGINNING IN FAR ERN MO...AND  
THEN CONTINUING ENE ACROSS MUCH OF IL...IND...FAR SRN WI...SRN MI  
AND WRN OH THROUGH THE REMAINDER OF THE DAY.  
 
WHILE STRENGTH OF SHEAR /RELATIVE TO DEGREE OF LOW-LVL CONVERGENCE  
AND BUOYANCY/...AND DESTRUCTIVE INTERFERENCE BETWEEN STORMS MAY  
PROVE TO BE LIMITING FACTORS...SETUP NONETHELESS APPEARS CAPABLE OF  
SUPPORTING A FEW LONG-TRACK/POTENTIALLY STRONG TORNADOES. WITH  
TIME...ESPECIALLY THIS EVE AS LINEAR FORCING INCREASES ALONG  
STRENGTHENING COLD FRONT...THE STORMS SHOULD EVOLVE INTO SEVERAL  
BROKEN LINES...WITH EMBEDDED LEWPS AND RESIDUAL SUPERCELL  
CIRCULATIONS CONTINUING TO POSE A RISK FOR DMGG WIND EWD INTO THE  
NRN AND CNTRL APPALACHIANS. WHILE TIME OF DAY WILL BE  
UNFAVORABLE...STRENGTH OF WIND FIELD/DCVA...AND PRESENCE OF EXITING  
CONVECTIVE BAND SUGGEST AT LEAST A CONDITIONAL RISK FOR DMGG WINDS  
EARLY MON EWD INTO PARTS OF NEW ENGLAND AND THE MID-ATLANTIC STATES.  
 
FARTHER S...MID-LVL WARMING ON S SIDE OF AMPLIFIED MIDWESTERN JET  
STREAK MAY SOMEWHAT HINDER STORM DEVELOPMENT/DELAY SVR THREAT IN  
VERY MOIST/MODERATELY-SHEARED ENVIRONMENT AHEAD OF COLD FRONT OVER  
THE LWR TN AND LWR MS VLYS. NEVERTHELESS...AT LEAST A LOW  
CONDITIONAL THREAT FOR SVR STORMS /INCLUDING A FEW SUPERCELLS WITH A  
TORNADO OR TWO/...WILL EXIST IN THIS REGION THROUGH EARLY  
TNGT...ESPECIALLY IN ANY AREAS RECEIVING ENHANCED AFTN SFC HEATING.  
 
..CORFIDI/PETERS.. 11/17/2013  
 

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Guys - please try to keep the weather discussion on topic and only weather related. If you need to reach out to people individually do so in PM and lets try to stay away from how the NFL will handle the severe weather threat. Want to try and keep this thread as clutter free as possible. 

 

Thanks

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MD out:

mcd2010.gif

 

 

MESOSCALE DISCUSSION 2010
NWS STORM PREDICTION CENTER NORMAN OK
0747 AM CST SUN NOV 17 2013

AREAS AFFECTED...PARTS OF CENTRAL/ERN MO...SERN IA...AND WRN/CENTRAL
AND NRN IL

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 171347Z - 171515Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...TSTMS ARE EXPECTED TO DEVELOP SWD FROM CENTRAL/ERN IA INTO
NRN/CENTRAL MO BY MID-LATE MORNING WITH ACTIVITY THEN MOVING QUICKLY
EWD INTO MUCH OF IL THROUGH THIS AFTERNOON. STORMS WILL BECOME
ORGANIZED WITH THE POTENTIAL TO EVOLVE INTO LONG-LIVED DISCRETE TO
SEMI-DISCRETE SUPERCELLS. THREATS FOR TORNADOES...HAIL AND DAMAGING
WINDS WITH THESE INITIAL STORMS SUGGEST A TORNADO WATCH MAY NEED TO
BE ISSUED BY MID-LATE MORNING.

DISCUSSION...MORNING VISIBLE SATELLITE IMAGERY SHOWED CONVECTIVE
CLOUDS ALONG A PRE-FRONTAL CONVERGENCE ZONE EXTENDING FROM SWRN-NERN
MO INTO SERN IA NEAR THE SURFACE LOW. MEANWHILE...RADAR IMAGERY
SHOWED A NARROW BAND OF REFLECTIVITY EXTENDING FROM SWRN IA INTO
NWRN MO /INVOF KANSAS CITY MO/...WITH THIS LIKELY INDICATING THE
PRESENCE OF THE COLD FRONT AND STRONG DEEP LAYER FORCING FOR ASCENT
ADVANCING EWD INTO THIS REGION. STORMS...MAINLY ELEVATED...ARE
ONGOING OVER CENTRAL/ERN IA ALONG AND N OF A BOUNDARY EXTENDING FROM
SWRN-NERN IA.

THE DEGREE OF FORCING ADVANCING EWD ACROSS THE DISCUSSION AREA
COMBINED WITH STRONG DEEP LAYER AND LOW LEVEL SHEAR ALREADY PRESENT
OVER MO/IL /E.G. 0-1 KM BULK SHEAR NEAR 50 KT/ IS EXPECTED TO
SUPPORT TSTM DEVELOPMENT SWD FROM CENTRAL/ERN IA INTO NRN/CENTRAL MO
AS LOW LEVEL CONVERGENCE INCREASES WITH THE COLD FRONT OVERTAKING
THE PRE-FRONTAL TROUGH.

..PETERS/CORFIDI.. 11/17/2013
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8 AM CST obs in NE IL:

 

ILZ005-006-012>014-019>023-171500-  
NORTHEAST ILLINOIS  
 
CITY SKY/WX TMP DP RH WIND PRES REMARKS
 
CHICAGO-OHARE CLOUDY 65 61 87 S21G30 29.40F  
CHICAGO-MIDWAY CLOUDY 65 61 87 S21G31 29.42F  
AURORA CLOUDY 64 61 90 S18G24 29.41F  
LANSING* CLOUDY 63 60 88 S25G33 29.46F  
WAUKEGAN CLOUDY 61 60 97 S16 29.38F  
DUPAGE AIRPORT CLOUDY 64 61 90 S21G32 29.40F  
WHEELING CLOUDY 64 60 87 S17G30 29.41F  
NORTHERLY ISL N/A 64 60 87 S15 N/A 

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