If you read convective outlooks as much as I do (especially during severe storm season), you’ll likely encounter a reference to a “shortwave,” which is an abbreviated way to mentioning a shortwave trough (area of low pressure) in the atmosphere. Shortwaves can help create thunderstorms.
Meteorologist Jason Myers published an excellent, short video explanation of shortwaves. Check it out, it’ll only take you 65 seconds!
Update: The NWS has canceled the tornado watch for northern Indiana and northwestern Ohio counties.
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 501
NWS STORM PREDICTION CENTER NORMAN OK
155 PM EDT WED SEP 10 2014
THE NWS STORM PREDICTION CENTER HAS ISSUED A
* TORNADO WATCH FOR PORTIONS OF
WEST CENTRAL THROUGH EASTERN INDIANA
SOUTHEAST LOWER MICHIGAN
WESTERN AND NORTHERN OHIO
LAKE ERIE
* EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 155 PM
UNTIL 900 PM EDT.
* PRIMARY THREATS INCLUDE...
A FEW TORNADOES LIKELY
SCATTERED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES NORTHEAST OF TOLEDO
OHIO TO 20 MILES EAST OF BLOOMINGTON INDIANA. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU1).
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.
TORNADO WATCH 501 IS IN EFFECT UNTIL 900 PM EDT FOR THE
FOLLOWING LOCATIONS
INC001-003-005-009-011-013-021-029-031-033-035-041-047-053-055-
057-059-063-065-067-069-071-075-079-081-093-095-097-103-105-109-
119-133-135-137-139-145-151-159-161-169-177-179-183-110100-
/O.NEW.KWNS.TO.A.0501.140910T1755Z-140911T0100Z/
IN
. INDIANA COUNTIES INCLUDED ARE
ADAMS ALLEN BARTHOLOMEW
BLACKFORD BOONE BROWN
CLAY DEARBORN DECATUR
DELAWARE DE KALB FAYETTE
FRANKLIN GRANT GREENE
HAMILTON HANCOCK HENDRICKS
HENRY HOWARD HUNTINGTON
JACKSON JAY JENNINGS
JOHNSON LAWRENCE MADISON
MARION MIAMI MONROE
MORGAN OWEN PUTNAM
RANDOLPH RIPLEY RUSH
SHELBY STEUBEN TIPTON
UNION WABASH WAYNE
WELLS WHITLEY
MIC059-091-115-110100-
/O.NEW.KWNS.TO.A.0501.140910T1755Z-140911T0100Z/
MI
. MICHIGAN COUNTIES INCLUDED ARE
HILLSDALE LENAWEE MONROE
OHC003-011-017-021-033-037-039-043-051-063-065-069-077-091-095-
101-107-109-113-123-125-135-137-143-147-149-159-161-171-173-175-
110100-
/O.NEW.KWNS.TO.A.0501.140910T1755Z-140911T0100Z/
OH
. OHIO COUNTIES INCLUDED ARE
ALLEN AUGLAIZE BUTLER
CHAMPAIGN CRAWFORD DARKE
DEFIANCE ERIE FULTON
HANCOCK HARDIN HENRY
HURON LOGAN LUCAS
MARION MERCER MIAMI
MONTGOMERY OTTAWA PAULDING
PREBLE PUTNAM SANDUSKY
SENECA SHELBY UNION
VAN WERT WILLIAMS WOOD
WYANDOT
BULLETIN - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WARNING NATIONAL WEATHER SERVICE NORTHERN INDIANA 133 PM EDT WED SEP 10 2014 THE NATIONAL WEATHER SERVICE IN NORTHERN INDIANA HAS ISSUED A * SEVERE THUNDERSTORM WARNING FOR... NORTHERN GRANT COUNTY IN CENTRAL INDIANA... WESTERN HUNTINGTON COUNTY IN NORTHEAST INDIANA... SOUTHERN WABASH COUNTY IN NORTH CENTRAL INDIANA... * UNTIL 215 PM EDT * AT 131 PM EDT...A SEVERE THUNDERSTORM WAS LOCATED NEAR LA FONTAINE...AND MOVING NORTHEAST AT 55 MPH. HAZARD...60 MPH WIND GUSTS. SOURCE...RADAR INDICATED. IMPACT...EXPECT DAMAGE TO ROOFS...SIDING AND TREES. * LOCATIONS IMPACTED INCLUDE... ANDREWS...HANFIELD...SERVIA...LANDESS...LINCOLNVILLE...BANQUO... PLEASANT PLAIN...MOUNT ETNA AND LANCASTER. THIS INCLUDES INTERSTATE 69 IN INDIANA BETWEEN MILE MARKERS 269 AND 276. PRECAUTIONARY/PREPAREDNESS ACTIONS... FOR YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A BUILDING.
Geography and severe weather probabilities remained pretty much the same when the National Weather Service Storm Prediction Center issued its updated “Day 1 Convective Outlook” at 12:28 p.m. EDT.
SPC meteorologists expect Thunderstorms, some severe, to develop near a cold front from the southern Great Lakes southwestward through the lower Ohio and mid-Mississippi valleys into the Ozarks. Damaging winds will be the primary threat this afternoon through early tonight.
Some risk will exist for isolated tornadoes in addition to locally damaging wind through late afternoon from eastern Illinois east-northeastward into parts of Ohio and Lower Michigan.
The next update is due out by 4 p.m. EDT.
The National Weather Service Storm Prediction Center is monitoring trends in the area indicated on the map above for any increase in thunderstorm activity late this morning through early afternoon and for a conditional tornado threat, according to a “Mesoscale Discussion” it issued at 11:34 a.m. EDT.
A leading shortwave trough is currently moving across northern Illinois and will continue rapidly northeastward across Indiana, northwestern Ohio and Lower Michigan.
Around 10:30 a.m. EDT, a weak thunderstorm showed brief supercell characteristics over central Illinois. This suggests the environment is close to being favorable for at least brief tornadoes.
A limiting factor is extensive cloud cover ahead of the leading band of precipitation, but partial heating is occurring across southwestern Indiana.
It is unclear whether atmospheric destabilization will be sufficient for further supercell development today before the aforementioned shortwave trough moves through. Once that wave passes, early potential for severe storms should be largely over, with any additional and primarily wind threat focusing southwestward along the trailing cold front.
Nearly the entire state of Indiana has a slight risk of severe weather between 9 a.m. EDT today and 8 a.m. EDT tomorrow, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center issued at 8:56 a.m. EDT today. The slight risk area also includes about half of the 37-county warning area of the northern Indiana NWS office and all of IMO SKYWARN quadrant two.
The primary threat is damaging straight-line thunderstorm winds or gusts of 58 mph or stronger, although an isolated tornado cannot be ruled out. As you can see on the maps at right, the probability of damaging straight-line winds in northeastern Indiana is 15 percent, which is about 7.5 times the average probability for this time of year (2 percent). The probability of a tornado is 2 percent, which is about 20 times the average probability for this time of year (0.1 percent).
The severe weather risk is conditional, because it depends largely on sunshine. If cloud cover remains heavy all day, the threat of severe weather will be much lower than if the area sees sunshine. This is because the sun’s heating of the earth’s surface would increase atmospheric instability.
SKYWARN storm spotter activation might be needed this afternoon and early this evening, according to a “Hazardous Weather Outlook” issued by the northern Indiana NWS office at 5:27 a.m. EDT.
Residents of the slight risk area should be sure they have a reliable way to be aware of any watches or warnings the NWS might issue today, such as a weather alert radio. You can also keep up to date on weather developments by subscribing to this blog, following the northern Indiana NWS office on Twitter (@NWSIWX) and/or liking the northern Indiana NWS office on Facebook.
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The northern Indiana National Weather Service office has postponed until Thursday the weekly weather radio test that it normally conducts on Wednesdays between 11 a.m. and noon EDT time, due to the threat of severe weather as well as transmitter problems at South Bend.
The severe risk is lower although the flood risk has increased. Moderate rain most of the morning. Storms poss. la http://t.co/uGOsyZry4k
— NWS Northern Indiana (@NWSIWX) September 10, 2014
The National Weather Service has issued a flash flood watch for most of northern Indiana and northwestern Ohio from early this afternoon through this evening.
A flash flood watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation.
Are you severe weather ready? With the potential for severe weather on Wednesday, now is the time to prepare! http://t.co/cG38r37iPC
— NWS Northern Indiana (@NWSIWX) September 9, 2014
