Hurricane Isaac - Cat. 1

[Thunder44]

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Looking at this system this morning, it will probably develop over the next couple of days. But it will probably be another large, broad circulation that will be slow to develop like Helene and Florence.

First look at most of the global models I've seen this morning are creating enough ridging in the Central Atlantic that in whatever form it is, it's going to be making it to at least 60W before the next trough comes off the US East Coast about 7 days or so. They create enough ridging behind Hurricane Helene to keep either to move it WNW after a possible turn first to NNW near 50N.

The ECMWF doesn't show this, because it has Helene eventually come around the ridge and moving it south of the Azores, breaking the ridge in the East Atlantic, which is unlikely to me.

[SouthFloridawx]

An interesting bend to the west from the models today. Looks like your idea for this system is pretty good at this point. I'd say WNW or even NW until about 60-65 W and then a turn to the north as the next trough approaches.

[Evil Jeremy]

there north again.

[Thunder44]

there north again.

Those are mainly statisical models which are less reliable than the global models. I wonder how many of them turn it north before 50W or from where it is with so much low-level ridging to the north:

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm1.html

[Evil Jeremy]

is there a complete map plot with all of the global models?

[hcane27]

CMC - open wave @ 108 hrs
NOGAPS - open wave @ 48 hrs
UKMET - open wave @ 96 hrs
GFS - open wave @ 96 hrs
ECMWF - 27.9/52.1 @ 168 hrs

[HURAKAN]

Tropical Weather Outlook

Statement as of 11:30 am EDT on September 22, 2006

For the North Atlantic...Caribbean Sea and the Gulf of Mexico...

The National Hurricane Center is issuing advisories on Hurricane
Helene...located about 630 miles east-northeast of Bermuda.

A large tropical wave accompanied by a broad surface low pressure
area is located about 1000 miles west-southwest of the Cape Verde
Islands. This system has not become any better organized this
morning...but it still has some potential for slow development over
the next couple of days as it moves toward the west-northwest or
northwest at 10 to 15 mph.

Elsewhere...tropical storm formation is not expected through
Saturday.

Forecaster Rhome/Knabb

[wxman57]

is there a complete map plot with all of the global models?

Not many models being run. Only NOGAPS moves it WNW. All other models move it quickly NW-NNW for a while then turn it west to await the next trof before recurving.

[wxman57]

Here's a color shot of 96L. I can see a weak spin around 13N/39W, but very little organized convection:

[Nimbus]

The area of surface low pressure is broad so there should be only slow intensification. This is like bowling, the mark you set the ball down on can make the difference between a gutter ball and a spare. Most of the convection is still down between 11N and 12N so if the models initialize further south we may see some different tracks.

[wxman57]

The area of surface low pressure is broad so there should be only slow intensification. This is like bowling, the mark you set the ball down on can make the difference between a gutter ball and a spare. Most of the convection is still down between 11N and 12N so if the models initialize further south we may see some different tracks.

I don't see anything forming that far south. If anytihing the MLC is closer to 14N now. That's where an LLC would develop - or even north of there. This one, should it develop, will almost certainly track safely out to sea.

[Steve H.]

I actually think nimbus is correct. the focal point of rotation is off to the south and west. There really are two "centers." if the energy splits you could have the MLC going NW, and the LLC heading WNW. Both may develop or not. Interesting area is near 13N/54W. The LCC there is gaining some convection today with some shear coming from the north though. This is a long shot for development but something worth watching. Otherwise not alot to be concerned about.

[wxman57]

I actually think nimbus is correct. the focal point of rotation is off to the south and west. There really are two "centers." if the energy splits you could have the MLC going NW, and the LLC heading WNW. Both may develop or not. Interesting area is near 13N/54W. The LCC there is gaining some convection today with some shear coming from the north though. This is a long shot for development but something worth watching. Otherwise not alot to be concerned about.

I really don't see anything south of 13N. All cloud motions around 11N-12N are from east to west. Generally, the tendency would be for a system to develop beneath the MLC. If something breaks off farther south then it probably won't develop.

However, either way, I don't think this disturbance will be one that the Caribbean islands or the east U.S. Coast will need to be too concerned about.

Ok, time for lunch!

[Normandy]

I actually think nimbus is correct. the focal point of rotation is off to the south and west. There really are two "centers." if the energy splits you could have the MLC going NW, and the LLC heading WNW. Both may develop or not. Interesting area is near 13N/54W. The LCC there is gaining some convection today with some shear coming from the north though. This is a long shot for development but something worth watching. Otherwise not alot to be concerned about.

I really don't see anything south of 13N. All cloud motions around 11N-12N are from east to west. Generally, the tendency would be for a system to develop beneath the MLC. If something breaks off farther south then it probably won't develop.

However, either way, I don't think this disturbance will be one that the Caribbean islands or the east U.S. Coast will need to be too concerned about.

Ok, time for lunch!

U mean west to east at 11-12 N right? All I see is westward moving clouds right above 10N

[Weathermaster]

TROPICAL WAVE IS ALONG 39W S OF 19N WITH A 1010 MB LOW ALONG THE
WAVE NEAR 12N MOVING W 15 KT. BROAD MID LEVEL CYCLONIC ROTATION
COVERING A LARGE AREA WITH CLUSTERS OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION FROM 10N-19N BETWEEN 32W-41W.AND SOME GRADUAL
DEVELOPMENT IS POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES TOWARD
THE WEST-NORTHWEST OR NORTHWEST AT 10 TO 15 MPH.

[HUC]

weathermaster,i don't read that on the TWD of 2pm!!!!!!!!!!!!!!!!!!!!!Where this one come from???

[cycloneye]

weathermaster,i don't read that on the TWD of 2pm!!!!!!!!!!!!!!!!!!!!!Where this one come from???

http://www.storm2k.org/wx/modules.php?n ... ge&pid=109

Storm2k TWD page.

[SouthFloridawx]

weathermaster,i don't read that on the TWD of 2pm!!!!!!!!!!!!!!!!!!!!!Where this one come from???

485
AXNT20 KNHC 221801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 22 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.



...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 39W S OF 19N WITH A 1010 MB LOW ALONG THE
WAVE NEAR 12N MOVING W 15 KT. BROAD MID LEVEL CYCLONIC ROTATION
COVERING A LARGE AREA WITH CLUSTERS OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION FROM 10N-19N BETWEEN 32W-41W. THIS
SYSTEM HAS NOT BECOME ANY BETTER ORGANIZED THIS MORNING...BUT IT
STILL HAS SOME POTENTIAL FOR SLOW DEVELOPMENT OVER THE NEXT
COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST OR
NORTHWEST AT 10 TO 15 MPH.

TROPICAL WAVE IS ALONG 53W S OF 17N WITH A 1012 MB LOW ALONG
THE WAVE NEAR 13N MOVING W NEAR 10 KT. SOME CYCLONIC ROTATION IS
EVIDENT ON SATELLITE IMAGERY WITH SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 12N-13N BETWEEN 51W-53W. ACCORDING TO THE
GFS MODEL...THIS TROPICAL WAVE IS EXPECTED TO ENTER THE EASTERN
CARIBBEAN ON SUNDAY.

[MiamiensisWx]

TROPICAL WAVE IS ALONG 39W S OF 19N WITH A 1010 MB LOW ALONG THE
WAVE NEAR 12N MOVING W 15 KT. BROAD MID LEVEL CYCLONIC ROTATION
COVERING A LARGE AREA WITH CLUSTERS OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION FROM 10N-19N BETWEEN 32W-41W. THIS
SYSTEM IS SHOWING SIGNS OF ORGANIZATION...AND SOME GRADUAL
DEVELOPMENT IS POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES TOWARD
THE WEST-NORTHWEST OR NORTHWEST AT 10 TO 15 MPH.

I don't see that portion in bold in that section of the 2:05PM EST discussion, Weathermaster...

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 39W S OF 19N WITH A 1010 MB LOW ALONG THE
WAVE NEAR 12N MOVING W 15 KT. BROAD MID LEVEL CYCLONIC ROTATION
COVERING A LARGE AREA WITH CLUSTERS OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION FROM 10N-19N BETWEEN 32W-41W. THIS
SYSTEM HAS NOT BECOME ANY BETTER ORGANIZED THIS MORNING...BUT IT
STILL HAS SOME POTENTIAL FOR SLOW DEVELOPMENT OVER THE NEXT
COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST OR
NORTHWEST AT 10 TO 15 MPH.

[SouthFloridawx]

http://twister.sbs.ohio-state.edu/text/ ... XNT20.KNHC