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September 1st and Beyond Severe Thread


andyhb

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Could it affect storm motion though? Might the cell start to turn more easterly? The latest MCD seemed to indicate the severe potential overnight being further south than the region the cell appears to be heading toward.

It's possible but I have my doubts. The stronger cells all seem to be west/northwest of the outflow boundaries, so they're essentially cut off from the better boundary layer inflow. I think that should keep them moving more east-northeasterly as opposed to east or east-southeasterly. Also, effective bulk shear values really drop off southeast of where the ongoing storms are. The LL wind fields over eastern Iowa look pretty paltry as well. I think the storms will continue trekking more north of due east for most of the night unless something much better organizes. We would need some serious cold pool generation to get the storms much further southeast of where they're currently trekking.

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Looks like the cell over far northeastern Iowa is closer to the outflow boundary now, so it looks like it's growing upscale/forward propagating now. Should mean a pretty decent wind threat over southwestern Wisconsin over the next hour or two if the trend continues.

Maybe that's why the severe thunderstorm watch was issued over the southern tier of counties in WI. That said, I am going to have to be skeptical that we will get anything until I see it.

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It's possible but I have my doubts. The stronger cells all seem to be west/northwest of the outflow boundaries, so they're essentially cut off from the better boundary layer inflow. I think that should keep them moving more east-northeasterly as opposed to east or east-southeasterly. Also, effective bulk shear values really drop off southeast of where the ongoing storms are. The LL wind fields over eastern Iowa look pretty paltry as well. I think the storms will continue trekking more north of due east for most of the night unless something much better organizes. We would need some serious cold pool generation to get the storms much further southeast of where they're currently trekking.

we *might* get that with the further north and east complex going into WI but most of it is still behind the OFB and getting new storm generation to the immediate south due in part of the boundary and it won't happen with the stuff east of DSM (good cold pool that is). I was kind of suprised they issued the blue box for the counties in northern IL, unless stuff develops further south overnight which it doesn't look like right now.

Tomorrow afternoon/evening will be our time here.

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we *might* get that with the further north and east complex going into WI but most of it is still behind the OFB and getting new storm generation to the immediate south due in part of the boundary and it won't happen with the stuff east of DSM (good cold pool that is). I was kind of suprised they issued the blue box for the counties in northern IL, unless stuff develops further south overnight.

Yeah it was surprising. The good ingredients really drop off south of highway 20 due to lack of mid and upper support. The instability is about the only thing decent in place, but the evening inversion kills that though lol. Everything settles a little further southward tomorrow so hopefully we can get something decent along the I-80 corridor.

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Yeah it was surprising. The good ingredients really drop off south of highway 20 due to lack of mid and upper support. The instability is about the only thing decent in place, but the evening inversion kills that though lol Everything settles a little further southward tomorrow so hopefully we can get something decent along the I-80 corridor.

Ya the moisture and instability are there but crappy mid-level winds and no good LLJ isn't helping.

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Good morning!

SEVERE WEATHER BULLETIN

ISSUED BY ENVIRONMENT CANADA

AT 10:42 AM EDT SATURDAY 3 SEPTEMBER 2011.

---------------------------------------------------------------------

WATCHES/WARNINGS IN EFFECT FOR SOUTHERN ONTARIO...

SEVERE THUNDERSTORM WATCH FOR:

=NEW= ELGIN COUNTY

=NEW= LONDON - MIDDLESEX COUNTY

=NEW= SIMCOE - DELHI - NORFOLK

=NEW= OXFORD COUNTY - BRANT COUNTY

=NEW= HURON COUNTY - PERTH COUNTY

=NEW= WATERLOO REGION - WELLINGTON COUNTY

WINDSOR - ESSEX COUNTY - CHATHAM-KENT

SARNIA - LAMBTON COUNTY.

SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON..

THIS IS AN ALERT TO THE POTENTIAL DEVELOPMENT OF SEVERE

THUNDERSTORMS WITH LARGE HAIL, DAMAGING WINDS OR HEAVY

RAINFALL..MONITOR WEATHER CONDITIONS AND LISTEN FOR UPDATED

BULLETINS.

---------------------------------------------------------------------

==DISCUSSION==

A COLD FRONT IS EXPECTED TO SWEEP ACROSS SOUTHWESTERN ONTARIO THIS

AFTERNOON. A VERY HOT AND HUMID AIRMASS OVER THESE REGIONS WILL

PROVIDE SUFFICIENT ENERGY FOR STRONG THUNDERSTORMS TO DEVELOP THIS

AFTERNOON OVER THE ABOVE REGIONS. SOME OF THESE THUNDERSTORMS MAY

BECOME SEVERE WITH LARGE HAIL, DAMAGING WINDS, AND TORRENTIAL

DOWNPOURS.

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the storms look pretty crappy right now..

MESOSCALE DISCUSSION 2107

NWS STORM PREDICTION CENTER NORMAN OK

1224 PM CDT SAT SEP 03 2011

AREAS AFFECTED...NRN IL INTO SWRN LOWER MI AND NRN IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 031724Z - 031830Z

THE THREAT FOR A FEW SEVERE STORMS CAPABLE OF MAINLY DAMAGING WINDS

IS EXPECTED TO INCREASE THIS AFTERNOON. CONVECTIVE TRENDS ARE BEING

MONITORED FOR A POSSIBLE WATCH.

THE RE-DEVELOPMENT AND/OR RE-INTENSIFICATION OF TSTMS IS CURRENTLY

BEING OBSERVED ALONG AN EWD-SURGING...RESIDUAL GUST FRONT FROM NEAR

MKE SWWD TO JUST SW OF MLI. STRONG DIABATIC HEATING COUPLED WITH

BOUNDARY LAYER DEW POINTS OF 65-70 F WITHIN IMMEDIATE DOWNSTREAM AIR

MASS IS RESULTING IN A WEAKENING CAP WITH MLCAPE VALUES OF 2000-2500

J/KG. THIS SHOULD SUPPORT THE CONTINUED INTENSIFICATION OF STORMS

THIS AFTERNOON.

REGIONAL VAD/PROFILER DATA INDICATE THAT DISCUSSION AREA RESIDES

ALONG SRN FRINGE OF STRONGER MIDLEVEL WIND FIELD /AND RESULTANT

DEEP-LAYER SHEAR/ ATTENDANT TO PRIMARY UPPER TROUGH MOVING INTO THE

UPPER GREAT LAKES. BUT...GIVEN THE LARGELY UNIDIRECTIONAL WIND

FIELD AND STEEPENING OF LOW-LEVEL LAPSE RATES...SOME RISK FOR BOWING

LINE SEGMENTS CAPABLE OF MAINLY DAMAGING WINDS WILL EXIST AS STORMS

PROGRESS EWD ACROSS THE REGION.

..MEAD.. 09/03/2011

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Southern Lower Michigan is slowly becoming a loaded gun for latter this evening. Under a monster Cap ATM allowing us to bake in the sun for hours. CAPE should surge upwards into the 2000-3000 area. Shear is kinda Meh, still wouldn't rule out a few weak supercells that blow up in front of the main show. ...But regardless most def looking forward to a solid light show latter this evening.

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