ATL: ISAAC - Post-Tropical - Discussion

[northjaxpro]

Issac at 1004 mb. Wind 40 mph 5 a.m. advisory. However, he is beginning to slow down in forward speed considerably, now moving west at 12 mph.

[meriland23]

NHC advisory 5 am
AN AIR FORCE RECONNAISSANCE AIRCRAFT INVESTIGATING ISAAC THIS
MORNING HAS FOUND A POORLY DEFINED INNER CORE WITH A LARGE AREA OF
LIGHT WINDS AROUND A CENTER...WHICH IS SIMILAR TO WHAT AN EARLIER
NOAA RESEARCH MISSION INDICATED. RADAR DATA FROM GUADELOUPE AND SAN
JUAN ALSO INDICATE A POORLY DEFINED INNER CORE CONVECTIVE PATTERN.
RATHER THAN INITIALIZE THE CENTER OF ISAAC WELL TO THE SOUTH OF THE
PREVIOUS TRACK...I HAVE OPTED TO USE A BLEND OF THE RECON FIXES...
SATELLITE IMAGERY...DATA FROM NEARBY NOAA BUOY 42060...AND A 06Z
CONSENSUS FORECAST POSITION FROM THE GFS...ECMWF...AND UKMET
MODELS. THE INITIAL INTENSITY WAS ALSO DECREASED TO 35 KT BASED ON
DATA FROM THE RECON AIRCRAFT AND NOAA BUOY 42060.

THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 270/12 KT. THE 00Z
GFS...ECMWF...AND UKMET MODELS DID AN OUTSTANDING JOB PREDICTING
THE RECENT SOUTHWESTWARD JOG OR REFORMATION OF THE CENTER OF ISAAC.
THOSE SAME MODELS ARE ALSO FORECASTING ISAAC TO MAKE A SHARP JOG TO
THE NORTHWEST OVER THE NEXT 12-24 HOURS...AND THEN STEADY OFF ON A
GENERAL WEST-NORTHWESTWARD MOTION THROUGH 48 HOURS. AFTER THAT...
THE GLOBAL AND REGIONAL MODELS HAVE COME INTO BETTER AGREEMENT ON
ISAAC MOVING NORTHWESTWARD TOWARD A BREAK IN THE SUBTROPICAL RIDGE
THAT IS FORECAST TO DEVELOP AFTER 72 HOURS ACROSS FLORIDA AND THE
EASTERN GULF OF MEXICO. THE ECMWF MODEL HAS CONTINUED ITS EASTWARD
SHIFT OVER THE PAST 36 HOURS...AND EVEN THE LATEST NOGAPS AND
CANADIAN MODEL RUNS HAVE SHIFTED WELL TO THE WEST ACROSS THE
FLORIDA PENINSULA ARE NOW NO LONGER CONSIDERED TO BE OUTLIERS. DUE
TO LESS SPREAD IN THE LATEST NHC MODEL GUIDANCE...AND THE FACT THAT
ECMWF HAS SHIFTED CLOSER TO THE PREVIOUS FORECAST AT DAYS 4 AND
5...THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS
ADVISORY TRACK...AND IS CLOSE TO THE DYNAMICAL CONSENSUS MODELS
TVCA AND TV15.
[/b]

[USTropics]

No change in track, decrease in strength to 35kt though

[Shuriken]

(Bah! Got ninja'd.)

[meriland23]

decreased intensity and south, but like 8 mph slower..

[somethingfunny]

FOUND A POORLY DEFINED INNER CORE WITH A LARGE AREA OF
LIGHT WINDS AROUND A CENTER...WHICH IS SIMILAR TO WHAT AN EARLIER
NOAA RESEARCH MISSION INDICATED. RADAR DATA FROM GUADELOUPE AND SAN
JUAN ALSO INDICATE A POORLY DEFINED INNER CORE CONVECTIVE PATTERN.
RATHER THAN INITIALIZE THE CENTER OF ISAAC WELL TO THE SOUTH OF THE
PREVIOUS TRACK...I HAVE OPTED TO USE A BLEND OF THE RECON FIXES...
SATELLITE IMAGERY...DATA FROM NEARBY NOAA BUOY 42060...AND A 06Z
CONSENSUS FORECAST POSITION FROM THE GFS...ECMWF...AND UKMET
MODELS.

...... WHAT?

Visible imagery can't come soon enough this morning. I guess I say that every morning though....

[northjaxpro]

Yeah, the biggest changes is that Isaac is finally slowing down in forward speed, which is significant. This may be a sign which may allow Isaac to finally get vertically stacked and begin to intensify.

NHC track philosophy really remains the same basically for the time being, with a slight slowing with the timing. Projected NHC path has Isaac about 50 miles west of Tampa on 06Z Tuesday morning.

[meriland23]

Yeah, the biggest changes is that Isaac is finally slowing down in forward speed, which is significant. This may be a sign which may allow Isaac to finally get vertically stacked and begin to intensify.

NHC track philosophy really remains the same basically for the time being, with a slight slowing with the timing. Projected NHC path has Isaac about 50 miles west of Tampa on 06Z Tuesday morning.

Given all this new info on isaac.. the slow down, lower intensity, south shift.. does this favor more the east shirt through cuba and to FL or more into the gulf and west cuba? jw

[Shuriken]

FOUND A POORLY DEFINED INNER CORE WITH A LARGE AREA OF
LIGHT WINDS AROUND A CENTER...WHICH IS SIMILAR TO WHAT AN EARLIER
NOAA RESEARCH MISSION INDICATED. RADAR DATA FROM GUADELOUPE AND SAN
JUAN ALSO INDICATE A POORLY DEFINED INNER CORE CONVECTIVE PATTERN.
RATHER THAN INITIALIZE THE CENTER OF ISAAC WELL TO THE SOUTH OF THE
PREVIOUS TRACK...I HAVE OPTED TO USE A BLEND OF THE RECON FIXES...
SATELLITE IMAGERY...DATA FROM NEARBY NOAA BUOY 42060...AND A 06Z
CONSENSUS FORECAST POSITION FROM THE GFS...ECMWF...AND UKMET
MODELS.

...... WHAT?

Visible imagery can't come soon enough this morning. I guess I say that every morning though....

I think it's called "fudging".

[northjaxpro]

Yeah, the biggest changes is that Isaac is finally slowing down in forward speed, which is significant. This may be a sign which may allow Isaac to finally get vertically stacked and begin to intensify.

NHC track philosophy really remains the same basically for the time being, with a slight slowing with the timing. Projected NHC path has Isaac about 50 miles west of Tampa on 06Z Tuesday morning.

Given all this new info on isaac.. the slow down, lower intensity, south shift.. does this favor more the east shirt through cuba and to FL or more into the gulf and west cuba? jw

Apparently, NHC feels rather confident with the GFS and its consistency for days showing the significant weakness will be firmly in place over the weekend. The weakness would pinch off that western edge of the subtropical ridge and Isaac will be drawn poleward toward Florida eventually. It is simply a matter of how much interaction with the islands will Isaac be able to absorb and where the storm will re-emerge precisely after moving through the Greater Antilles.

[KWT]

wow looking at recon, this is such a mess at the low level, I've rarely seen such a poorly looking system at the low levels, there could be 3-4 different circulations of varying strengths going around a broad center.

Right now 'center' estimates aren't really worth anything because its not got a 'center' per say, but several rotating around a middle point.

[tgenius]

If its as big a mess as it appears than doesn't the forecast track open up the possibility that it won't go that way if the lower centers end up dominating? Not long before SFL is going to be in the 3 day cone.

[KWT]

Certainly, at the moment the NHC will struggle with this system and I think they are doing as good a job as they can with it. There is a center further north where the NHC have placed the center so who knows!

[Kingarabian]

I think we have 2 to 3 circulations folks.

[KWT]

Just reading the discussion, seems like the NHC think it'll rebound NW today based on the fact the models did spot a jog to the WSW and readjust back WNW/NW over the next 12hrs.

We'll have to see how that pans out, if it happens then the NHC track looks good, if it doersn't, it'll need shifting south.

[TreasureIslandFLGal]

The big slowdown will allow the storm more time over those warm waters and also time enough to get its center better organized. This morning it actually looks really good...better overall outflow and heavy convection over the center(s). This is a really huge storm too. The current track down teh middle of the cone is actually more disconcerting, as it allows the center to travers the extremely warm waters of the gulf, and could allow for much more strengthening before a final landfall further north. That would essentially rake the west coast of Florida with storm force winds, or worse. The directional heading would also pile huge amounts of water into Tampa Bay for a long time with a slow moving, very large storm. -the effect being larger with a larger system, aka Katrina's surge that seemed like it was from a stronger system. I'm not saying that this will be a Cat3/4, but the flooding could none the less be significant in Tampa as this goes by just offshore.

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[TreasureIslandFLGal]

relocations of the center to the further southern center would allow more time over water, less time over Haiti, and less disruption at that point. That would create a more intense system, which would likely be drawn more poleward as it was affected by the weakness more as a stronger storm. So the path would still be more northward. I remember seeing one of the models show that scenario better last night...it went initially more westward, then looked like it took a right angle to head towards Florida and bisected Cuba instead of went more lengthwise over it. hmmm

[KWT]

I think we have 2 to 3 circulations folks.

Without a doubt, its a total mess at the moment with regards to its centers and I can see multiple centers that keep strengthening and weakening looking at recon. Messy!!

[meriland23]

I wonder the chances of it jogging NW in 12 hrs vs staying its western south path

[jlauderdal]

I wonder the chances of it jogging NW in 12 hrs vs staying its western south path

25/75