snowstormcanuck Posted August 30, 2012 Share Posted August 30, 2012 This is usually true near/shortly after landfall but heaviest precip often tends to shift along/west of track by the time storms make it here. Models haven't been showing it as much for this event, possibly because this is more of a ridge rounder and not really phasing with another system (just a guess)? Yeah, you're right. Thinking back to Frances in 2004 and Katrina in 2005, that was the case. And I'd concur that the lack of phasing might be keeping the models from forming a deformation zone once it reaches the midwest (lotsa dry air being fed into the northern flank of the storm by that blocky ridge). I gotta say though, looking at the GFS with its blob like 6-hour precip bombs, it's got me thinking it's sufferring from convective feedback. Not sure how must weight it's QPF distribution can be given. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 30, 2012 Share Posted August 30, 2012 lol 18z GFS dumps on central/northern IL but doesn't get up to the IL/WI border. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted August 30, 2012 Share Posted August 30, 2012 HPC holding steady for the moment, but it looks like Chicago may get nada out of Isaac. of course HPC is often wrong in the 5 day timeframe. Link to comment Share on other sites More sharing options...
Chicago WX Posted August 31, 2012 Share Posted August 31, 2012 Latest HPC QPF discussion DAYS 2 AND 3... ...ISAAC... ALTHOUGH ISAAC CONTINUES TO WEAKEN...ISAAC'S INFLUENCE REMAINS QUITE EXPANSIVE AND IS MOVING SLOWLY...IN FACT MORE SLOWLY THAN ANTICIPATED WHICH HAS THE BEEN THE MODEL TREND THE LAST COUPLE DAYS. THE LATEST NHC TRACK FORECAST...WHICH FORMED THE BASIS FOR THE DAY 2/3 QPF...IS ALMOST 50 PERCENT SLOWER COMPARED TO FORECASTS GENERATED A COUPLE DAYS AGO. THE 12Z GUIDANCE WHICH CONFORMS BEST TO THE LATEST NHC TRACK...ABOUT MIDWAY BETWEEN THE 12Z ECMWF/UKMET AND A LITTLE OF THE GFS WHEN WE CONSIDER DAY 3...SEEMS TO RESPOND TO THE SLOWER TRACK BY PRODUCING HIGHER QPF THROUGH THE PERIOD MAINLY FROM THE LONGER DURATION. THIS IS ESPECIALLY NOTICEABLE BEGINNING WITH THE MIDDLE OF DAY 2 (12Z SAT) OVER CENTRAL MISSOURI...AND THEN CONTINUES THROUGH THE REMAINDER OF THE PERIOD. OTHER THAN USING A BLEND OF THE 12Z ECMWF/UKMET QPF AND NHC TRACK FORECAST AS GUIDES...AMOUNTS WERE GENERALLY INCREASED ABOVE GUIDANCE TO ACCOUNT FOR THE INADEQUATE RESOLUTION OF THE MODELS AND LOW QPF BIASES THAT OFTEN ACCOMPANY DECAYING TROPICAL EVENTS SUCH AS POTENTIAL INCREASES IN NOCTURNAL DEVELOPMENT AS THE BOUNDARY LAYER BEGINS TO DECOUPLE...AND MORE EFFICIENT RAINFALL PRODUCTION VIA WARM RAIN PROCESSES AND DROP-SIZE DISTRIBUTIONS FOCUSED TOWARD THE SMALL SIZE OF THE SPECTRUM. THE FINAL DAY 2 VALUES ARE CLOSEST TO THE UKMET AND CANADIAN WITH SPATIAL ADJUSTMENT ALSO MADE...WHILE THE DAY 3 TOTALS ARE BETWEEN THE UKMET/ECMWF/CANADIAN. HIGHER TOTALS ARE ANTICIPATED LOCALLY. HOWEVER...CONFIDENCE IN DETERMINING EXACTLY WHEN AND WHERE IS LESS THAN IDEAL GIVEN THE ABOVE MENTIONED CONCERNS. FROM A LARGER PERSPECTIVE...MOISTURE ANOMALIES SUCH AS PW REMAIN IMPRESSIVELY HIGH...WITH VALUES NEARING 3.5 STANDARD DEVIATIONS ABOVE NORMAL...WHICH SHOULD NOT BE TOO SURPRISING GIVEN THE REGIME. ADDITIONALLY...AS ISAAC LOSES ITS TROPICAL CHARACTERISTICS...CONVERSION TO A MORE BAROCLINIC SYSTEM WITH A WARM FRONTAL BAND SEEMS INEVITABLE...WHICH IS DEPICTED WITHIN THE GUIDANCE. DETERMINING HOW MUCH QPF TO INSERT FOR THIS PROCESS ALONE IS DIFFICULT TO DETERMINE...BUT WOULD NOT BE SURPRISED TO SEE AMOUNTS HIGHER THAN FORECAST GENERATED AND MOVE MORE QUICKLY AS MOISTURE IS RAPIDLY TRANSPORTED DOWNSTREAM...THUS SEEDING NEW DEVELOPMENT. ACCORDINGLY...SLIGHT AND MODERATE EXCESSIVE RAINFALL AREAS WERE HIGHLIGHTED AND SHOULD ALIGN WELL WITH THE LATEST DAY 1 QPF AND EXCESSIVE RAINFALL FORECASTS. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 lol 18z GFS dumps on central/northern IL but doesn't get up to the IL/WI border. looks pretty believable to me...feeling pretty confident in an inch or so up here...not that I need it, it's been really wet Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 31, 2012 Share Posted August 31, 2012 looks pretty believable to me...feeling pretty confident in an inch or so up here...not that I need it, it's been really wet I was going to try to golf on Saturday so hopefully it can hold off as long as possible. Link to comment Share on other sites More sharing options...
Geos Posted August 31, 2012 Share Posted August 31, 2012 lol 18z GFS dumps on central/northern IL but doesn't get up to the IL/WI border. That map is funny, but at the same time it is not. Would like to see that D3 area wiped out near the border. Although this area has benefited from lake rains. Hopefully the steering currents can lift that low a bit north of its forecasted track. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 31, 2012 Share Posted August 31, 2012 Link to comment Share on other sites More sharing options...
Geos Posted August 31, 2012 Share Posted August 31, 2012 Low wouldn't have to shift very far north of its track to get this area. That's one of the sharpest cutoffs in qpf I've seen on the GFS! Looks like Quincy to Peoria to Joliet would be ground zero for the heaviest rain in this case. Just across this county which is about 20 miles from N to S (as the crow flies), there is 3" in the SE corner and < 0.10" in the farthest northern fringe. Link to comment Share on other sites More sharing options...
Chicago WX Posted August 31, 2012 Share Posted August 31, 2012 Just as a frame of reference, here's the 1981-10 normal precipitation totals in September for a few sites in Indiana. We'll see how many can get to or surpass their normals this Saturday and Sunday. Bloomington BMG: 3.72" South Bend SBN: 3.53" Indianapolis IND: 3.12" Evansville EVV: 3.05" Muncie MIE: 3.01" Fort Wayne FWA: 2.80" Lafayette LAF: 2.66" Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 Just as a frame of reference, here's the 1981-10 normal precipitation totals in September for a few sites in Indiana. We'll see how many can get to or surpass their normals this Saturday and Sunday. Bloomington BMG: 3.72" South Bend SBN: 3.53" Indianapolis IND: 3.12" Evansville EVV: 3.05" Muncie MIE: 3.01" Fort Wayne FWA: 2.80" Lafayette LAF: 2.66" Chad still going 1-3" for the area. Interestingly he thinks the highest amounts may be north, which would be more in line with the GFS. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 Chad still going 1-3" for the area. Interestingly he thinks the highest amounts may be north, which would be more in line with every 4 runs of the GFS. FYP...you're locked and loaded...best might be west of you but not north Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 FYP...you're locked and loaded...best might be west of you but not north Yeah I think I'm in a pretty good spot. Maybe not in the heaviest band but should get a nice soaking. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 Yeah I think I'm in a pretty good spot. Maybe not in the heaviest band but should get a nice soaking. I'm really liking Champaign, which will be fun since they have the home opener Saturday....and they really need the rain Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 PWAT of 2.42" at Little Rock and 2.49" at Shreveport on the 00z soundings. Link to comment Share on other sites More sharing options...
Fickle Heights Posted August 31, 2012 Share Posted August 31, 2012 Chad still going 1-3" for the area. Interestingly he thinks the highest amounts may be north, which would be more in line with the GFS. Chad's got a narrative to maintain. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 lol, NAM just went from .10 to 5"+ over southern Iowa Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 Chad's got a narrative to maintain. lol...it does seem to be conservative given that this thing won't be zipping along. 2-5" area wide is probably a good bet with locally higher amounts. Link to comment Share on other sites More sharing options...
SchaumburgStormer Posted August 31, 2012 Share Posted August 31, 2012 lol, NAM just went from .10 to 5"+ over southern Iowa Looking like a Nowcast event... Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 One thing that is noticeable in the precip plots...you can see the pullback closer to the center at night. The showers/storms that are farther away from the center tend to fade away at night. Link to comment Share on other sites More sharing options...
Stebo Posted August 31, 2012 Share Posted August 31, 2012 Nothing like the brick wall at the Michigan border . Good luck to those who cash in on some excitement though Link to comment Share on other sites More sharing options...
Stebo Posted August 31, 2012 Share Posted August 31, 2012 The NAM still isn't impressive. Has that little "explosion" over a small chunk of Iowa and just sorta drifts eastward. I don't really think big rains make it into Ohio. The convective feedback issues probably will make modeling pretty useless. It will either hit you or it won't. Using the NAM at this juncture for something still 2-3 days out is like throwing a dart at a dart board. You are better off not looking at it. Link to comment Share on other sites More sharing options...
snowlord81 Posted August 31, 2012 Share Posted August 31, 2012 Im not real confident in the any model QPF right now. They change every single run and there has been no consistency for days. I really dont know what to expect with this. If you ask me though, the GGEM has been the most consistent model the last few days. This is def. not a forecast I'd like to have to make for the public. Link to comment Share on other sites More sharing options...
Hoosier Posted August 31, 2012 Author Share Posted August 31, 2012 GGEM hammers LAF. Even some good precip into southern/eastern MI. Link to comment Share on other sites More sharing options...
PatrickSumner Posted August 31, 2012 Share Posted August 31, 2012 GGEM hammers LAF. Even some good precip into southern/eastern MI. My question is...based on the last guidance, when does it look like the heaviest rain will fall? From what I can see...Saturday night and Sunday... Link to comment Share on other sites More sharing options...
Chicago WX Posted August 31, 2012 Share Posted August 31, 2012 2-5" area wide is probably a good bet with locally higher amounts. Seems like a good call. Link to comment Share on other sites More sharing options...
Geos Posted August 31, 2012 Share Posted August 31, 2012 Looks like the GFS is suggesting lake enhanced rain for Alek! - bulls eye southern end of LM. I might have gotten closer to the 0.5" line. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 It would be much more interesting if we were dealing with lake temps from 3 weeks back and a true cold core low Link to comment Share on other sites More sharing options...
Chicago WX Posted August 31, 2012 Share Posted August 31, 2012 I'm really liking Champaign, which will be fun since they have the home opener Saturday....and they really need the rain Agreed about Champaign. Think the totals in IL will be the most impressive in this region. Purdue's home opener is a 3:30pm start tomorrow, which could make it a little more interesting (rain taking a bit longer to get this far east). Real grass at Ross-Ade Stadium too. Link to comment Share on other sites More sharing options...
A-L-E-K Posted August 31, 2012 Share Posted August 31, 2012 love these long vectors Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.