Robert Dewey
EF5
Of course, now that I said that, tomorrow will feature yet another busted forecast :lol:
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8/18/04 FCST: Midwest/Great Lakes
- Thread starter nickgrillo
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Of course, now that I said that, tomorrow will feature yet another busted forecast :lol:
Robert Dewey
EF5
ETA 00Z still seems on track. The 500mb vort that was evident on the 18Z ETA is now gone, and the front appears to have slowed down by a couple of hours, putting the timing close to what he 12Z ETA had. Lapse rates also appear a bit lower this go around - from 6.7C/KM (850-500) to 6.2C/KM.
CAPE does climb to near 3000J/KG tomorrow afternoon, but there is no real significant trigger around, so I don't see a real big thunderstorm threat (unless some outflow boundaries from todays storms linger around). Main show should be late tomorrow evening across western lower, extending hrough the early night across the east. ETA drops CAPE of significantly between 21Z and 00Z, but this is due to how the ETA handles SFC moisture (it pretty much scours things out around and after 00Z). Adjusting for this change in moisture (averaging the 21Z and 00Z dewpoints), I still come out with CAPE values around 1800J/KG through 03Z across many locations, before the front comes through. Forcing along the front is also very strong - as evident by the 700-500mb vertical velocity field, and the SFC wind/moisture convergence. Dry air intrusion is also very intense - with <30% slamming into the region... Given that... I am Still expecting a line of severe thunderstorms, as helicities are now lower than the previous ETA runs - 150m2/s2 to 200m2/s2...
As for a derecho event... I think it's still possible given the intensity of the of the 500mb height falls (i.e. rapid intensification), good wind fields, and very strong forcing. I believe 1800J/KG would be enough to sustain a serious line of storms through the night time hours WED into THU... Not really sure how to calculate speed of the storms if they were to form into a derecho type event, but it does seem that it could outrun the cold front and perhaps arrive a bit sooner than expected across central/eastern lower MI...
Robert Dewey
EF5
Havn't seen any big changes in the 12Z ETA...
Still expecting a decent line of storms to roll through pretty much all of lower MI this evening/thru the night time hours. Not sure why SPC has most of lower MI in only a 15%, since this does appear to be a good setup for a line of storms with damaging winds. Past few model runs have been showing CAPE values of 1250-1800J/KG between 03-06Z across various locations in southern lower MI (slight inversion is evident, but that diminishes as good convergence/column saturates), coupled with good wind fields (shear is pretty much line-normal to the expected squall line), 700-300mb dry punch, and very strong convergence/forcing along the front.tom hanlon
EF2
Looks like things are falling apart somewhat. Indianapolis and/or N Indiana NWS AFD or HWO mentioned feedback as a possible issue.
I am going to make it a casual chase day and park myself in W OH or E IN and see what satellite and radar show me.
Not expecting much but you gotta try.
Some models showed a high SWEAT index in S IN today. So I am hesitant to head to far N. Especially with SPC downgrading the northern risk.
I 70 at the IN/OH line or perhaps a hundred miles N of there. Depends on how things build today.
Late summer is spent chasing mathematical anomolies.. so it goes.
Tom
Robert Dewey
EF5
I believe they were talking about the GFS model for FRI when it comes to convective feedback. The SFC low today is real, and can be seen on the SFC analysis (the strength can be seen by the OBS in MN - temps in the 50's and winds gusting to 40knts!)...
I still think there is a good chance for severe storms, but they will be very late this evening or tonight. So really, not much to chase...Jeremy Lemanski
EF3
DTX Downplaying the threat a ton in there afternoon dis.
Something that really bugs me is when they issue the afternoon dis. at 1.40pm when storms could fire. Why not wait til around 3 or 4 like you usually would and see whats happening before making any bold statements.?
Robert Dewey
EF5
GRRs discussion at 1:15pm doesn't look bad. DTX definately downplaying though...JHadorn
EF4
Right now there are currently CAPE values in the 2000 - 2800 (I hope I read it right) range here in SE Nebraska, but it appears that there's a fairly strong cap in place. They are talking thunderstorms possible later tonight and tomorrow.
Le sigh.Wendy Johnson
Tornado Warning for Menominee County in Michigan. Any confirmation of a tornado on the ground or was this just pick up on radar?tom hanlon
EF2
You were correct about the feedback
I read that through rather quickly on my way out the door. Just the word Feedback as I skimmed the discussion.Similar threads
