Hurricane Isaac - Cat. 1

[wxman57]

I placed the disturbance closer to 13N this morning. That's the only rotation I could find. There's no convection near 9N/28W. There isn't much of a ridge to its north, so my initial thoughts is that this system, should it develop, will follow in the tracks of Gordon or more likely Helene. High probability it's another fish. It's very hard for CV systems to reach the Caribbean Sea without a VERY strong Bermuda High blocking it to the north, and that's not likely to happen.

GFS and ECMWF both indicate possible recurvatures at 45W-50W but carry the system westward to around 60-65W before there's a significant weakness in the ridge. That would make a track closer to Gordon's than Helene's. Both keep it well north of the Caribbean.

[hurricanetrack]

So there you have it. No need for any long nights this time around. At least this one will not keep us guessing for days on end- it looks like its fate has already been sealed and delivered. This is why it is nice to have pros on this board- they can keep us from suffering a lot of un-needed grief.

[Evil Jeremy]

its only an invest. this can change very easliy right now.

[weatherwindow]

IMHO..the most significant portion of the 530 TWO is "AS IT MOVE WESTNORWESTERLY AT 10-15 MPH....altho the disturbance is initialized at 8.5degN, which would normally be favorable for a more westerly long-term track, this very early north of west motion, may negate the advantage of such a southerly location...as wxman suggests it will gain latitude pretty quickly...even the bams, which initialize it with a due west heading, take it north of 15degN at 50degW...which tends to be a tipping point for an leeward island threat. with this year's synoptics, bermuda may have be the only location in the basin to have been dealt a bad hand.........rich

[Thunder44]

Don't be so confident of recurvative before 65W. The CMC develops a nice ridge over the Central Atlantic at 144hrs:

http://www.meteo.psu.edu/~gadomski/CMCT ... mc144.html

[storms in NC]

With all the fronts coming of the coast this time of year it would be hard for a CV storm to make it across. JIMO here. But the maps you showed it would turn before the 50 and head on out to sea.

[gatorcane]

Could possible future Isaac be the one to make it all the way across?

A TROPICAL WAVE ACCOMPANIED BY A BROAD SURFACE LOW PRESSURE SYSTEM
IS CENTERED ABOUT 450 MILES SOUTH-SOUTHWEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS. SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED
AND BECOME A LITTLE BETTER ORGANIZED THIS MORNING...AND ADDITIONAL
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS
AS IT MOVES WEST-NORTHWESTWARD AT 10 TO 15 MPH.

[StormTracker]

Per GFDL>>>2.5 hours to dissipation!!!

[gatorcane]

Per GFDL>>>2.5 hours to dissipation!!!

patehtic. Let me guess another ULL gets it?

[Thunder44]

Per GFDL>>>2.5 hours to dissipation!!!

patehtic. Let me guess another ULL gets it?

The GFDL typically doesn't do well with weak systems.

[wxman57]

Here's a satellite shot. Not very impressive. At least several days away from a TD, if ever.

[Windsurfer_NYC]

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT WED SEP 20 2006

[...]

A LARGE TROPICAL WAVE...ACCOMPANIED BY A BROAD AREA OF LOW PRESSURE
IS CENTERED SEVERAL HUNDRED MILES SOUTHWEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS. THIS SYSTEM HAS THE POTENTIAL FOR SOME
DEVELOPMENT DURING THE NEXT DAY OR TWO...AS IT MOVES TOWARD THE
WEST OR WEST-NORTHWEST AT 10 TO 15 MPH.

[hial2]

[quote="wxman57"]Here's a satellite shot. Not very impressive. At least several days away from a TD, if ever.

What happened to the circulation near 13n? The "X" is near 9n...

[wxman57]

Here's a satellite shot. Not very impressive. At least several days away from a TD, if ever.

What happened to the circulation near 13n? The "X" is near 9n...

I just identified where the NHC initialized the models. To tell the truth, I don't see any rotation in either convective complex. Just disorganized thunderstorms.

[hurricanetrack]

Ok- now we have something totally different. If it takes several days to develop, then is has a much better chance of sneaking under the traps that have been set for it. One thing to notice, the upward motion map, I don't know the true name of it, shows a lot of "brown" out in that region, meaning, I assume, that there is not much upward motion potential going on. So, one would think this wave/low will move west or slightly north of west for 3 or 4 days and develop very little. Once it gets past 50W or even 55W, then it could go. At that point, if it is at or below 15N then we could have a problem for our friends in the islands. We should take this one day and development stage at a time. I am not too concerned about the East Coast anymore, although it is possible to have something come west at a low latitude and then get yanked north like Hazel did in 1954. THAT would concern me. Otherwise, I think it will be interesting to watch this since it is NOT likely to pop anytime soon. That could make for a whole different scenario- we'll see.

[wxman57]

Ok- now we have something totally different. If it takes several days to develop, then is has a much better chance of sneaking under the traps that have been set for it. One thing to notice, the upward motion map, I don't know the true name of it, shows a lot of "brown" out in that region, meaning, I assume, that there is not much upward motion potential going on. So, one would think this wave/low will move west or slightly north of west for 3 or 4 days and develop very little. Once it gets past 50W or even 55W, then it could go. At that point, if it is at or below 15N then we could have a problem for our friends in the islands. We should take this one day and development stage at a time. I am not too concerned about the East Coast anymore, although it is possible to have something come west at a low latitude and then get yanked north like Hazel did in 1954. THAT would concern me. Otherwise, I think it will be interesting to watch this since it is NOT likely to pop anytime soon. That could make for a whole different scenario- we'll see.

Don't always assume that weak systems track more westward. In order for anything to track west, there needs to be a strong ridge to the north and low-level flow moving from east to west. The Bermuda High is shifted quite far east now, and there are several deep trofs in the path of this system. Even the BAMS (shallow layer movement) indicates a WNW-NW track. It won't necessarily track due west if it doesn't develop, it would track north of west. And from 28W, it only takes a heading of 285 degrees to miss the Caribbean. Any center reformation northward means even less of a movement north of due west would keep it north of the Caribbean.

It would be unusual for a system to reach the Caribbean Sea from so far out this late in September when strong cold fronts are pushing off the east U.S. Coast. And from its appearance on satellite, it may not develop at all.

[Sanibel]

Anticipating cold fronts to continue is tricky. They can continue all the way through to the end of the season or they can pause, causing a sudden change in synoptic steering patterns.

To me, this CV season has been spelled out. It is a recurve or oceanic track season. The only chance for any US landfall this year is from the Caribbean with that sudden lull in hostility. But seeing how utterly negative the West Atlantic has been, I would say we have seen the last of 2006.

It's kind of obvious this new invest will get sucked right behind Helene in the huge hole it has put in the Atlantic synoptic.

[rainstorm]

http://moe.met.fsu.edu/cgi-bin/gfstc2.c ... hour=144hr

yikes

[NoceoTotus]

http://moe.met.fsu.edu/cgi-bin/gfstc2.cgi?time=2006092006&field=Sea+Level+Pressure&hour=144hr

yikes

Heh, I was wondering if anyone else saw that model run. Seems there may be a couple to keep an eye on by the middle of next week if this proves out. If nothing else, the speculation should keep us busy for a while anyway.

[Sanibel]

Rainstorm:

If you read that map correctly it backs what I am saying. 96L will follow Helene into the gap shown on your model. Since the fronts coming from CONUS move west to east, by the time 96L confronts that synoptic shown in your model it will be well into recurve off the east coast.