Hurricane Isaac - Cat. 1

#241 Postby **hial2** » Sun Sep 24, 2006 4:31 pm

How can the TWO change so much in 6 hours?? NHC has all the computers and the know-how...How can they not foresee conditions in a 6 hour time span?

Weatherfreak000 · #242 Postby **Weatherfreak000** » Sun Sep 24, 2006 4:45 pm

It's pretty simple, there is just too much wind shear and too much dry air. Maybe if this were a threat to land it would get a pop classification but I think because of this kind of rather surprising blast of wind shear we can all but put the close on 96L.

Now, i'm not saying it WON'T develop, just saying the odds seem to have leveled off significantly since this morning due to the complete exposure of the circulation.

#243 Postby **Boricua** » Sun Sep 24, 2006 5:35 pm

I don’t know for sure but the center appears to be moving SW but the clouds clusters are moving NE so I will not expect it to develop for now.

Matt-hurricanewatcher · #244 Postby **Matt-hurricanewatcher** » Sun Sep 24, 2006 6:12 pm

This is kind of a shame, nice LLC but covnection getting sheared away from it. Should be a tropical cyclones if there was not shear.

WindRunner · #245 Postby **WindRunner** » Sun Sep 24, 2006 7:14 pm

Matt-hurricanewatcher wrote:This is kind of a shame, nice LLC but covnection getting sheared away from it. Should be a tropical cyclones if there was not shear.

Now, how many times have we said that this season, even with storms that WERE tropical cyclones?

Normandy · #246 Postby **Normandy** » Sun Sep 24, 2006 8:38 pm

Interesting to note that the LLC of 96L is moving SW, but has no convection

Sanibel · #247 Postby **Sanibel** » Sun Sep 24, 2006 10:13 pm

255* and west.

Shallow system should bloom later on.

We'll see if it yanks north in reaction to the huge CONUS front.

#248 Postby **Toadstool** » Mon Sep 25, 2006 12:01 am

Year of the Shear continues... either that or the GFDL computer crashed into a flatline...

Hyperstorm · #249 Postby **Hyperstorm** » Mon Sep 25, 2006 6:42 am

This system has not developed over the past 24 hours due to one major reason. Weak mid-upper level low located right to the W and NW of it.

Here's a simple image depicting the mid-upper level low in relation to this system:

Run a water vapor loop and you'll see the rotation.

This cold core low is doing two things. It's imparting SW shear all throughout the system. Also, it's pushing in the dry air to the circulation. Mid-upper level shear does that when there is mid-upper level subsidence nearby.

Other than that, the trough related to Helene has pushed NE and there is a strong flow of favorable easterly winds just to the north of this system. If the mid-upper low can somehow weaken even more or move SW, then this system will have favorable conditions to develop. However, it will continue to encounter problems through today at least.

Thunder44 · #250 Postby **Thunder44** » Mon Sep 25, 2006 6:56 am

Hyperstorm wrote:This system has not developed over the past 24 hours due to one major reason. Weak mid-upper level low located right to the W and NW of it.

Here's a simple image depicting the mid-upper level low in relation to this system:

Run a water vapor loop and you'll see the rotation.

This cold core low is doing two things. It's imparting SW shear all throughout the system. Also, it's pushing in the dry air to the circulation. Mid-upper level shear does that when there is mid-upper level subsidence nearby.

Other than that, the trough related to Helene has pushed NE and there is a strong flow of favorable easterly winds just to the north of this system. If the mid-upper low can somehow weaken even more or move SW, then this system will have favorable conditions to develop. However, it will continue to encounter problems through today at least.

Agreed. There are thunderstorms firing up NE of the center this morning, which are trying to move over the center. Although the shear today will probably prevent that from happening.

#251 Postby **cycloneye** » Mon Sep 25, 2006 7:35 am

25/1145 UTC 18.7N 45.2W T1.0/1.0 96L -- Atlantic Ocean

http://www.ssd.noaa.gov/PS/TROP/positions.html

Trying to make a comeback.

#252 Postby **HURAKAN** » Mon Sep 25, 2006 7:39 am

It's fighting but so far it seems shear and dry air are winning the battle. If it holds long enough, 96L may win the war at the end!!! :uarrow:

#253 Postby **cycloneye** » Mon Sep 25, 2006 8:16 am

DISTURBANCE INVEST (AL962006) ON 20060925 1200 UTC

...00 HRS... ...12 HRS... ...24 HRS... ...36 HRS...
060925 1200 060926 0000 060926 1200 060927 0000

LAT LON LAT LON LAT LON LAT LON
BAMD 19.7N 45.3W 20.9N 46.8W 22.3N 48.6W 23.9N 50.6W
BAMM 19.7N 45.3W 20.5N 47.2W 21.5N 49.4W 23.0N 51.6W
A98E 19.7N 45.3W 20.4N 46.3W 21.4N 47.6W 23.2N 49.0W
LBAR 19.7N 45.3W 20.6N 46.5W 21.9N 48.3W 23.3N 50.1W
SHIP 25KTS 26KTS 29KTS 34KTS
DSHP 25KTS 26KTS 29KTS 34KTS

...48 HRS... ...72 HRS... ...96 HRS... ..120 HRS...
060927 1200 060928 1200 060929 1200 060930 1200

LAT LON LAT LON LAT LON LAT LON
BAMD 25.7N 52.6W 29.4N 56.1W 33.0N 58.0W 37.1N 56.7W
BAMM 24.5N 53.6W 27.7N 56.9W 30.6N 58.3W 33.2N 58.3W
A98E 25.5N 50.8W 30.5N 54.7W 35.4N 55.3W 37.9N 50.4W
LBAR 24.8N 52.0W 27.4N 55.1W 29.7N 57.6W 32.0N 59.2W
SHIP 39KTS 50KTS 55KTS 57KTS
DSHP 39KTS 50KTS 55KTS 57KTS

...INITIAL CONDITIONS...
LATCUR = 19.7N LONCUR = 45.3W DIRCUR = 300DEG SPDCUR = 5KT
LATM12 = 18.9N LONM12 = 44.4W DIRM12 = 286DEG SPDM12 = 5KT
LATM24 = 18.8N LONM24 = 43.2W
WNDCUR = 25KT RMAXWD = 75NM WNDM12 = 25KT
CENPRS = 1009MB OUTPRS = 1012MB OUTRAD = 250NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

http://twister.sbs.ohio-state.edu/text/ ... s/?C=M;O=D

#254 Postby **curtadams** » Mon Sep 25, 2006 9:19 am

I don't see why it's not a TD or even a TS. Quickscats yesterday twice showed a closed circulation with an uncontaminated 35 kt vector. Convection and LLC today visibly associate into a sheared system. Seriously,what other evidence for a cyclone could you have at 45W 20N other than an eye?

#255 Postby **HURAKAN** » Mon Sep 25, 2006 9:29 am

NHC:
"Tropical Cyclone:
A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects)."

Maybe it's not considered well-organized enough to be a tropical cyclone or because the convection hasn't been persistent.

Sanibel · #256 Postby **Sanibel** » Mon Sep 25, 2006 9:34 am

The key here is 96L is headed towards warmer SST's and favorable waters where Florence blew up. Should develop further down the track.

Thunder44 · #257 Postby **Thunder44** » Mon Sep 25, 2006 9:57 am

curtadams wrote:I don't see why it's not a TD or even a TS. Quickscats yesterday twice showed a closed circulation with an uncontaminated 35 kt vector. Convection and LLC today visibly associate into a sheared system. Seriously,what other evidence for a cyclone could you have at 45W 20N other than an eye?

TPC is not going to classify a sheared and disorganzied storm out in the Atlantic. However, if it did already classify this system before and then it looked this way today, then they would probably keep writing advisories on it.

#258 Postby **curtadams** » Mon Sep 25, 2006 10:11 am

HURAKAN wrote:Maybe it's not considered well-organized enough to be a tropical cyclone or because the convection hasn't been persistent.

The convection has been persistent. What has not been persistent is the association between convection and LLC. It was clearly associated when it came out of eclipse night before last. Yesterday they got sheared apart. Last night the LLC reformed near the convection and now they're associated again. But I don't see a long lifetime or a long life expectancy in the definition of tropical cyclone.

#259 Postby **HURAKAN** » Mon Sep 25, 2006 10:14 am

Here is an image of TS Grace compared to 96L:

Tropical Weather Outlook

Statement as of 11:30 am EDT on September 25, 2006

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

Cloudiness and showers associated with a tropical wave and a broad
area of low pressure located about 1100 miles east of the northern
Leeward Islands remain poorly organized. Upper-level winds are not
conducive for significant development.

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

Forecaster Pasch/Landsea

#260 Postby **SouthFloridawx** » Mon Sep 25, 2006 10:28 am

Models heading a little farther west with this one.

Hurricane Isaac - Cat. 1

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