ATL HANNA: Models Discussion

[AdamFirst]

Is there a reason why the models have it running into a brick wall at the end?

Or is that just some rouge models doing their own thing?

My part of Florida has its eyes on this one more than they ever did for Fay.

[Brent]

It's like Fay all over again.

[AJC3]

Is there a reason why the models have it running into a brick wall at the end?

Or is that just some rouge models doing their own thing?

My part of Florida has its eyes on this one more than they ever did for Fay.

Just about all the model guidance has a northerly component to the mid-upper level flow developing over the western ATLC n about 4-5 days. It all depends on the interplay between a large high pressure ridge, which will be over the eastern CONUS, and a cutoff low to it's east. This interaction will determine the steering flow near where Hanna is supposed to be at that time (the western Sargasso Sea area).

[fci]

WHXX01 KWBC 290030
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0030 UTC FRI AUG 29 2008

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

TROPICAL CYCLONE HANNA (AL082008) 20080829 0000 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080829 0000 080829 1200 080830 0000 080830 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 20.8N 60.2W 21.9N 62.2W 23.2N 64.1W 24.2N 65.8W
BAMD 20.8N 60.2W 21.8N 61.8W 23.0N 63.5W 24.0N 65.2W
BAMM 20.8N 60.2W 21.7N 62.0W 22.7N 63.8W 23.6N 65.5W
LBAR 20.8N 60.2W 21.9N 61.6W 23.0N 63.3W 24.1N 65.2W
SHIP 40KTS 45KTS 51KTS 58KTS
DSHP 40KTS 45KTS 51KTS 58KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080831 0000 080901 0000 080902 0000 080903 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 25.1N 67.3W 26.6N 69.8W 26.4N 71.4W 25.2N 73.7W
BAMD 24.9N 66.7W 26.2N 68.6W 26.2N 69.4W 25.7N 70.1W
BAMM 24.3N 67.0W 25.3N 69.1W 25.1N 70.3W 24.5N 71.5W
LBAR 24.8N 67.1W 25.0N 70.7W 23.0N 73.9W 20.2N 76.3W
SHIP 63KTS 73KTS 74KTS 70KTS
DSHP 63KTS 73KTS 74KTS 70KTS

...INITIAL CONDITIONS...
LATCUR = 20.8N LONCUR = 60.2W DIRCUR = 290DEG SPDCUR = 6KT
LATM12 = 20.2N LONM12 = 58.6W DIRM12 = 297DEG SPDM12 = 10KT
LATM24 = 19.5N LONM24 = 57.3W
WNDCUR = 40KT RMAXWD = 30NM WNDM12 = 35KT
CENPRS = 1001MB OUTPRS = 1009MB OUTRAD = 200NM SDEPTH = D
RD34NE = 45NM RD34SE = 45NM RD34SW = 10NM RD34NW = 20NM

$$
NNNN

Oh boy,look at that.

Golden question is what happens AFTER the southern component???

A completion of the loop and shooting off to the east?
Steadying of the track to the west and through the Florida straights?
West through Southern Florida?
Death by ULL and the whole discussion is moot???

[gtsmith]

Golden question is what happens AFTER the southern component???

A completion of the loop and shooting off to the east?
Steadying of the track to the west and through the Florida straights?
West through Southern Florida?
Death by ULL and the whole discussion is moot???

I'll take the fourth option please

[Bocadude85]

GFS should be running now correct?

[Tampa Bay Hurricane]

I think a building ridge would induce faster forward speed and bring
it closer to the Bahamas/SE Coast in 5 days than indicated by most models
currently.

[boca]

I think a building ridge would induce faster forward speed and bring
it closer to the Bahamas/SE Coast in 5 days than indicated by most models
currently.

I would normally agree with you but if theirs a trough directly north of Hanna it would disrupt the steering flow I would think.

[Bocadude85]

anyone paying attention what the GFS is doing with Hanna?

[AJC3]

I think a building ridge would induce faster forward speed and bring
it closer to the Bahamas/SE Coast in 5 days than indicated by most models
currently.

That would be true if the ridge was forecast to be directly to the north of Hanna, but it's not. It's forecast to be northwest of Hanna, hence the northerly flow between it and the cutoff low to it's east.. I think the models have a fairly decent handle on this general scenario...though there will still be differences in details.

[fci]

I think a building ridge would induce faster forward speed and bring
it closer to the Bahamas/SE Coast in 5 days than indicated by most models
currently.

That would be true if the ridge was forecast to be directly to the north of Hanna, but it's not. It's forecast to be northwest of Hanna, hence the northerly flow between it and the cutoff low to it's east.. I think the models have a fairly decent handle on this general scenario...though there will still be differences in details.

So again I ask the question that I do not think anyone has the answer for; yet

The models show a Southerly component.

WHAT HAPPENS AFTER THEN???

- A bend back to the W or WSW into South Florida or The Keys?
- A loop off to the NE?
- The loop completes and she heads NW?

I guess we have to wait for the models to go past 5 days to see what the answer is presumed to be.........

[Recurve]

To me looks like GFS is showing north winds behind a front swoop down on Hanna's forecast location north of the Bahamas. Front seems to come off the east coast with a strong cutoff low. Latest disco mentioned this, don't know if the other models are showing it.

I see the HWRF also showing a low/front or trough setup, with Hanna getting pulled northeast at the end.

Seems GFDL has a strong low develop to the north and a front with northerly winds driving Hanna southward a bit just at the end. Intensity jumps around some but remains above Cat 3 at the end.

MM5-fsu shows a southerly movement near the end, possibly with influence from a system developed in mid-Atlantic behind Hanna. It looks like the two are ready to dance at the end. Maybe binary storm, baby!

Like to hear what anyone sees in terms of trough/low being there to steer/shear Hanna at the end of the current track.

[AJC3]

So again I ask the question that I do not think anyone has the answer for; yet

The models show a Southerly component.

WHAT HAPPENS AFTER THEN???

- A bend back to the W or WSW into South Florida or The Keys?
- A loop off to the NE?
- The loop completes and she heads NW?

I guess we have to wait for the models to go past 5 days to see what the answer is presumed to be.........

Well, the GFS shows some brutal northerly shear...H25 winds of nearly 50 knots right over the top of where Hanna is supposed to be in 5 days, so that would suggest (potentially significant) weakening, and a turn to the SW or south with a reduction in forward speed. This is pretty much what the current NHC forecast shows.

[boca]

Would Gustav create a weakness also added to the messy track. Looks like a slow drift west at 150hrs,I should say crawl.

[Recurve]

Of course, this one would be my nightmare. Wish I could see the Betsy synoptics.

[Bocadude85]

Of course, this one would be my nightmare. Wish I could see the Betsy synoptics.

The GFS is showing something similar.. just a bit farther south...

[Scorpion]

Ummm... ok?

[Matt-hurricanewatcher]

Ummm... ok?

Not enough tchp for more then 915 millibars in that area.

[USTropics]

HWRF pressure is based on a ratio so is not very reliable. What you really want to pay attention to with the HWRF is the path and wind speed (compared to the GFDL/SHIPS). That seems a little high given the region.

[Vortex]

00Z Euro and yet another run and another hit for southern florida..This is becoming more than a trend at this point. Very consistent the last several runs with very small deviations between days 3-6.


http://www.ecmwf.int/products/forecasts ... 00!!!step/