ATL HANNA: Extratropical - Discussion

[cpdaman]

can shear from gustav weaken a ULL, wv presentation shows high shear from gustav effecting and stretching SW part of ull.

[AJC3]

can shear from gustav weaken a ULL, wv presentation shows high shear from gustav effecting and stretching SW part of ull.

Yes, but it depends on its position. What has been happening over the past couple of days is that the some of the outflow from Gustav has actually been converging into the south side of the ULL (as sort of a mass sink) to help sustain it's vorticity. The forecasts for the ULL to weaken were obviously off the mark, probably (at least in part) as a result of this.

Edit: I think the ULL will weaken...but more as a function of what will be going on with Hanna itself, rather than Gustav...but we will see.

[cpdaman]

can shear from gustav weaken a ULL, wv presentation shows high shear from gustav effecting and stretching SW part of ull.

Yes, but it depends on its position. What has been happening over the past couple days is that the some of the outflow from Gustav has actually been converging into the south side of the ULL (as sort of a mass sink) to help sustain it's vorticity. The forecasts for the ULL to weaken were obviously off the mark, probably (at least in part) as a result of this.

yup i understand that part .......so are you saying that the ULL is still being enhanced by good ole gustav or at least certainly not in a position to weaken it yet

and another thing on the IR2 it looks like these features are almost stacked, that's not forecast to occur (or possible) is it? thank you very much

http://www.ssd.noaa.gov/goes/east/watl/loop-ir2.html

[Patrick99]

So really...why a SSW dive into Cuba yesterday, and now up to the Carolinas? I don't get it. Something doesn't seem right here. Why would you drastically shift from SSW to a turn to the north? What happened to this big high? Is there now going to be a big trough instead of the high? Odd....and really a pretty poor job if you ask me.

[AJC3]

can shear from gustav weaken a ULL, wv presentation shows high shear from gustav effecting and stretching SW part of ull.

Yes, but it depends on its position. What has been happening over the past couple days is that the some of the outflow from Gustav has actually been converging into the south side of the ULL (as sort of a mass sink) to help sustain it's vorticity. The forecasts for the ULL to weaken were obviously off the mark, probably (at least in part) as a result of this.

yup i understand that part .......so are you saying that the ULL is still being enhanced by good ole gustav or at least certainly not in a position to weaken it yet

and another thing on the IR2 it looks like these features are almost stacked, that's not forecast to occur (or possible) is it? thank you very much

http://www.ssd.noaa.gov/goes/east/watl/loop-ir2.html

An ULL over the top of a TC is not a good thing as far as the TC is concerned. I won't get into a schpiel about CISK (like I have in the past) but via convective processes that a TC goes through, it will build an upper high/anticyclone overhead. The two cannot coexist for true TC intensification to occur. Either the ULL will move away on it's own, the TC will produce enough convection and latent heat to build an anticyclone that will deform/shunt/bonecrush, etc. the ULL, or it won't and the ULL will hinder the whole TC intensifcation process.

[wxmann_91]

So really...why a SSW dive into Cuba yesterday, and now up to the Carolinas? I don't get it. Something doesn't seem right here. Why would you drastically shift from SSW to a turn to the north? What happened to this big high? Is there now going to be a big trough instead of the high? Odd....and really a pretty poor job if you ask me.

I think the models are stronger with a weakness that Gustav and a midlatitude trough leave behind, delaying the ridge to the east building westward and driving Hanna into FL. This looks attm a ride up the E Coast. Tentatively I will say that a recurve out to sea does not look very likely right now, but that may change if the ridge to the east continues to trend weaker.

[AJC3]

So really...why a SSW dive into Cuba yesterday, and now up to the Carolinas? I don't get it. Something doesn't seem right here. Why would you drastically shift from SSW to a turn to the north? What happened to this big high? Is there now going to be a big trough instead of the high? Odd....and really a pretty poor job if you ask me.

Well, some things model guidance handles well, others it doesn't. This has been all about how the global guidance has been handling the amplifcation of the large scale pattern over the eastern CONUS - i.e. the interaction between the large eastern CONUS high and the cutoff to it's east. Model guidance has been having trouble with just where the cutoff low digs - some runs have had it going SSE, others south, others toward the SSW. With this occuring to the north of a TC, even slight changes in the large scale mid/upper pattern have had a large effect on where Hanna eventually goes. This often happens during pattern changes in the northern stream while a TC is rather close the axis of the ST ridge (20-25N).

[ericinmia]

Accuweather has updated their graphic...

[Evil Jeremy]

HANNA IS MOVING TOWARD THE WEST-NORTHWEST NEAR 8 MPH...13 KM/HR.
A WEST TO WEST-NORTHWESTWARD MOTION IS EXPECTED WITH A GRADUAL
DECREASE IN FORWARD SPEED DURING THE NEXT COUPLE OF DAYS. ON THE
FORECAST TRACK...THE CENTER OF HANNA IS EXPECTED TO MOVE NEAR OR
JUST NORTHEAST OF THE TURKS AND CAICOS ISLANDS LATE TODAY OR
MONDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 55 MPH...95 KM/HR...WITH HIGHER
GUSTS. SOME GRADUAL STRENGTHENING IS FORECAST DURING THE NEXT
COUPLE OF DAYS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 200 MILES...325 KM
FROM THE CENTER.

[ericinmia]

I wonder what data they used for the increase in wind speed? Does anyone know...

[SouthFLTropics]

What time is the eclipse over? I need to go to bed but I wanted to see the new IR pic first...

SFT

[bahamaswx]

What time is the eclipse over? I need to go to bed but I wanted to see the new IR pic first...

SFT

Any moment now.

[ericinmia]

What time is the eclipse over? I need to go to bed but I wanted to see the new IR pic first...

SFT

Any moment now.

Click here to view your own...
http://www.ghcc.msfc.nasa.gov/GOES/goeseastconusir.html

[KWT]

It still looks far from textbook, a very messy TC indeed though that burst of convection is probably allowing for some slight strengtheing despite the ugly apperence.

[attallaman]

I'm focusing my attention on Gustav right now but down the road is Hanna forecasted to become a possible threat to the GOM or will that system more than likely pose a threat to the east coast of the USA?

[gatorcane]

talk about crazy cone shifts for this system. Started out maybe diving south to Eastern Cuba or Haiti and the latest takes it NW comfortably east of Florida. I'm thinking this track has to change again

http://www.nhc.noaa.gov/archive/2008/gr ... p_5W.shtml

[Blown Away]

I remember the models w/ Frances & Jeanne wanting to goto N Florida an/or Georgia as they got close to SFL. Just like the SW dive into Cuba would have been a first, hurricane landfalls on the N Florida and Georgia coasts are rare and if the models show that I'm not buying. So I'm still going w/ SFL landfall, Carolinas, or out to sea. I think we really need some recon to see how strong that ridge will be.

[jlauderdal]

I remember the models w/ Frances & Jeanne wanting to goto N Florida an/or Georgia as they got close to SFL. Just like the SW dive into Cuba would have been a first, hurricane landfalls on the N Florida and Georgia coasts are rare and if the models show that I'm not buying. So I'm still going w/ SFL landfall, Carolinas, or out to sea. I think we really need some recon to see how strong that ridge will be.

these slow movers/stallers are really tricky..nhc gives us something to look for

HOWEVER...BY 96 HOURS... NEARLY ALL OF
THE MODELS FORECAST THE STRONG UPPER-TROUGH TO LIFT OUT TO THE
NORTHEAST AND BE REPLACED BY A LARGE RIDGE TO THE NORTH AND EAST OF
HANNA. THE LATTER FEATURE IS EXPECTED TO GRADUALLY INDUCE A
NORTHWESTWARD COMPONENT OF MOTION BY DAYS 4 AND 5. THE KEY TO THE
FORECAST TRACK AT THOSE FORECAST TIMES WILL BE JUST HOW FAR SOUTH
AND WEST HANNA MOVES BEFORE IT BEGINS TO MOVE NORTHWESTWARD

[Blown Away]

I remember the models w/ Frances & Jeanne wanting to goto N Florida an/or Georgia as they got close to SFL. Just like the SW dive into Cuba would have been a first, hurricane landfalls on the N Florida and Georgia coasts are rare and if the models show that I'm not buying. So I'm still going w/ SFL landfall, Carolinas, or out to sea. I think we really need some recon to see how strong that ridge will be.

these slow movers/stallers are really tricky..nhc gives us something to look for as we forward

HOWEVER...BY 96 HOURS... NEARLY ALL OF
THE MODELS FORECAST THE STRONG UPPER-TROUGH TO LIFT OUT TO THE
NORTHEAST AND BE REPLACED BY A LARGE RIDGE TO THE NORTH AND EAST OF
HANNA. THE LATTER FEATURE IS EXPECTED TO GRADUALLY INDUCE A
NORTHWESTWARD COMPONENT OF MOTION BY DAYS 4 AND 5. THE KEY TO THE
FORECAST TRACK AT THOSE FORECAST TIMES WILL BE JUST HOW FAR SOUTH
AND WEST HANNA MOVES BEFORE IT BEGINS TO MOVE NORTHWESTWARD

If the NHC track continues movement into N Fl and/or Georgia I'm not buying. I think we will see that track go that way as long as the EURO keeps Hanna going into N Fl. If I read that correctly they are not talking a recurve situation at all, once that trough is gone the ridge builds in and Hanna goes NW and I can accept that as long as it is not between Melbourne Fl and Savannah.

[Trader Ron]

Latest GFDL has Hanna hitting the OBX in 120 hrs. Will this be a coast-hugger?

Yes, I know 5 day's out is subject to large errors.