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Isaac Heavy Rain Event


Hoosier

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Let your tropical weenie out, what's your call for strength upon landfall? And where?

I like the Grand Isle, LA area. For landfall intensity, I'll go conservative with 90 mph but would not be surprised if it's stronger (could just as easily see a 100+ mph storm). For all the progress that's been made, intensity forecasting is still pretty tough.

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I like how that track looks, the mean track looks to take it right around here, but then again I have yet to even see the GFS place S Wisconsin in a big rain zone, it's always been just to the south, so I'm wondering if this projected path is too far west for what the mean models say.

I think the rain placement will depend on where the front hangs up. That tropical moisture is really going to pile up along it! Hopefully the 12z EURO is having a bad run.

Edit: we still have lots of runs to go yet!

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IND

FOCUS FOR THE EXTENDED REMAINS SOLELY ON ISSAC AND THE POTENTIAL IMPACTS IT COULD BRING TO THE OHIO VALLEY THIS WEEKEND. 12Z MODELS ARE ZEROING IN ON A LANDFALL SOMEWHERE FROM CENTRAL LOUISIANA EAST THROUGH THE MOBILE-PENSACOLA AREA EARLY WEDNESDAY. AFTER THAT HOWEVER...WIDE VARIANCE REMAINS IN REGARDS TO EXACTLY WHAT TRACK THE REMNANTS OF ISSAC TAKE AND TIMING OF POTENTIAL IMPACTS TO THE REGION. AS ISSAC CHURNS THROUGH THE GULF OF MEXICO THIS AFTERNOON...STILL QUITE A BIT OF VARIANCE FROM MODEL RUN TO MODEL RUN ON TRACK AND TIMING OF THE REMNANTS INTO THE REGION. AT THIS POINT...CONFIDENCE CONTINUES TO GROW ON ISSAC PAYING THE REGION A VISIT OVER THE WEEKEND.

EMPLOYING ADDITIONAL DETAILS ON SPECIFIC IMPACTS AND TIMING HOWEVER REMAINS DIFFICULT AT THIS POINT IN TIME WITH SOME NEW CONCERNS BEING INTRODUCED WITH SOME OF THE 12Z MODEL RUNS. OP GFS REMAINS CONSISTENT WITH A LOOPING WESTERN TRACK FROM A CENTRAL LOUISIANA LANDFALL WEDNESDAY AND LIFTING INTO THE MID MISSISSIPPI VALLEY BY SATURDAY MORNING. GGEM...00Z ECMWF AND NAM REMAIN EAST WITH A LANDFALL SOMEWHERE BETWEEN NEW ORLEANS AND BILOXI. CURRENT OFFICIAL NHC TRACK RIGHT IN THE MIDDLE OF THE ABOVE GUIDANCE ON TRACK. BOTH THE 00Z ECMWF AND 12Z GGEM BRING ISSAC INTO THE OHIO VALLEY BY LATE FRIDAY INTO SATURDAY AND DEPART IT EAST MORE QUICKLY AS IT BECOMES ABSORBED IN THE FASTER FLOW ALOFT ALONG THE US-CANADIAN BORDER AND MOVES AWAY TO THE NORTHEAST. THE OP GFS PRESENTS A TROUBLING NEW WRINKLE ON ITS 12Z RUN WITH THE TROPICAL REMNANTS CURLING INTO THE REGION FROM THE WEST...BUT NEVER LINKING UP WITH THE STRONGER UPPER LEVEL FLOW. THIS RESULTS IN THE REMNANTS OF ISSAC REMAINING CUTOFF AND SPINNING SLOWLY THROUGH THE OHIO AND TENNESSEE VALLEYS INTO LABOR DAY WHICH COULD OPEN CENTRAL INDIANA TO THE POSSIBILITY OF AN EXTENDED PERIOD OF SUSTAINED HEAVY RAINFALL ENCOMPASSING MUCH OF THE HOLIDAY WEEKEND. A CLOSER LOOK AT THE INDIVIDUAL GFS ENSEMBLE MEMBERS HOWEVER SHOW THAT THE CUTOFF SOLUTION IS NOT FAVORED AT THIS POINT...AND THE ENSEMBLE MEAN CONTINUES TO MIMIC THE 00Z ECMWF WITH ISSAC PULLING AWAY FROM THE REGION BY LATE SUNDAY.

AT THIS TIME...WILL CONTINUE THE TREND OF SLOWLY BUMPING UP TO HIGH CHANCE POPS IN THE LATE FRIDAY TO SUNDAY PERIOD AND KEEP THE MENTION OF THUNDERSTORMS FOR THE ENTIRE FORECAST AREA. GREATEST POTENTIAL FOR WIDESPREAD RAINFALL COMES SATURDAY AND SATURDAY NIGHT WITH THE REMNANTS IN CLOSEST PROXIMITY TO THE REGION. PRECIP WATER VALUES IN EXCESS OF 2.5 INCHES OR 200% OF NORMAL AND FREEZING LEVELS AT 15-16KFT STRONGLY SUGGESTIVE OF WARM RAIN PROCESSES AND SUPPORTIVE OF HEAVY RAINFALL. AS HAS BEEN MENTIONED...IF THE EVENTUAL TRACK TAKES ISSAC RIGHT OVER CENTRAL INDIANA OR TO THE WEST AND NORTH OF THE FORECAST AREA...POTENTIAL FOR SEVERE WEATHER AND TORNADOES VIA LOW TOPPED SUPERCELLS WILL EXIST. WILL CONTINUE TO MONITOR THE TRACK OF ISSAC CLOSELY OVER THE NEXT SEVERAL DAYS.

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A couple of players to watch before this occurs, 1. how strong the ridge is over our area Wed-Friday, 2. where the ridge axis sets up, and 3. how quickly the trough moves Eastward to pick the remnants up.

If the ridge is too strong or locks in over the Great Lakes this thing could get locked in South of us and not move up here.

If it is weaker and/or locks in just East of the region then Isaac would slide up the backside of the Ridge.

If the trough is too quick moving in, it would pick up Isaac too soon and places South of I-70 would get the brunt of it.

If the trough is too slow moving in than places South of I-80 and especially I-70 could completely miss out.

A lot of variables in play here and things could change several times between now and then. The Euro solution is probably too strong with the ridge in the region which is a tendency the Euro has to over do ridges.

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Looks like some of the ensembles have shifted the heaviest precip a bit farther north and west, will be interesting to see if this holds.

gefs_precip_total_conus_d5_10.png

Yeah a large number of the 06z/12z ensembles were also further NW than the op, something also to monitor going forth.

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Isaac looks to be trending east...I doubt that bodes well for those hoping for N/W solutions....good news for the worst drought stricken areas though

Thinking that might be just a wobble. Maybe Turtle can comment on the current movement. Forecast cone remains unchanged. Set to make landfall just west of the delta.

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Thinking that might be just a wobble. Maybe Turtle can comment on the current movement. Forecast cone remains unchanged. Set to make landfall just west of the delta.

i'm not getting too into our chances right now...potential is there but I still favor central Illinois and south.

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Skilling showed the latest GFS (I think) and the low moving to the southern tip of Lake Michigan before making a right turn eastward. Quoting Skilling, "All the models averaged together gives ORD 2.9" of rain from Issac's remnants."

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i'm not getting too into our chances right now...potential is there but I still favor central Illinois and south.

I would disagree, typically with these tropical systems the mid latitude troughs eject slower, which would tend to lead more credence to a further N and W solution. The GFS ensembles coming in more N and W is a bit of a tell.

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I would disagree, typically with these tropical systems the mid latitude troughs eject slower, which would tend to lead more credence to a further N and W solution. The GFS ensembles coming in more N and W is a bit of a tell.

I'll go dig it up but looks to me like they're going east.

ellipses.png

previous run was further north/west through chicago

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