ATL HANNA: Extratropical - Discussion

[mawolf3]

Do you think Hanna will survive? Anyone? She is not looking good this am and was downgraded to TS.

[sfwx]

The question that begs to be asked is why there haven't been ANY WARNINGS for Haiti's North Coast so far. If Hanna continues drifting south she won't be far away from landfalling.

Oh and the lovely Lady on the Weather Channel said that hanna has been moving west at 2mph over the past hours when the satellite view is showing quite clearly something else. .

Tropical Storm HANNA Public Advisory
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000
WTNT33 KNHC 021156
TCPAT3
BULLETIN
TROPICAL STORM HANNA INTERMEDIATE ADVISORY NUMBER 22A
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008
800 AM AST TUE SEP 02 2008

...HANNA WEAKENS TO A TROPICAL STORM...
...HEAVY RAINFALL AFFECTING THE SOUTHEASTERN BAHAMAS...TURKS AND
CAICOS ISLANDS...AND HAITI...

A HURRICANE WARNING REMAINS IN EFFECT FOR THE CENTRAL BAHAMAS...THE
SOUTHEASTERN BAHAMAS...AND THE TURKS AND CAICOS ISLANDS.

INTERESTS ALONG THE NORTH COAST OF HAITI...EASTERN CUBA...THE
NORTHWEST BAHAMAS...AND THE FLORIDA PENINSULA SHOULD MONITOR THE
PROGRESS OF HANNA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR LOCAL WEATHER OFFICE.

AT 800 AM AST...1200Z...THE CENTER OF TROPICAL STORM HANNA WAS
LOCATED NEAR LATITUDE 21.2 NORTH...LONGITUDE 73.1 WEST OR VERY NEAR
GREAT INAGUA ISLAND AND ABOUT 385 MILES...615 KM...SOUTHEAST OF
NASSAU.

HANNA IS DRIFTING TOWARD THE WEST NEAR 2 MPH...4 KM/HR. SLOW AND
ERRATIC MOTION IS EXPECTED TODAY. HOWEVER...HANNA IS EXPECTED TO
BEGIN MOVING NORTHWESTWARD TONIGHT AND WEDNESDAY. ON THE FORECAST
TRACK...HANNA WILL MOVE OVER THE SOUTHEASTERN BAHAMAS TODAY AND
INTO THE CENTRAL BAHAMAS TONIGHT AND WEDNESDAY.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 70 MPH...110 KM/HR...WITH
HIGHER GUSTS. ALTHOUGH LITTLE CHANGE IN STRENGTH IS EXPECTED
DURING THE NEXT 24 HOURS...HANNA COULD REGAIN HURRICANE STRENGTH
LATER TODAY OR TOMORROW.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 175 MILES...280 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB...29.15 INCHES.

HANNA IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 8 TO 12 INCHES...
WITH ISOLATED AMOUNTS OF 20 INCHES...OVER THE SOUTHEASTERN BAHAMAS
AND THE TURKS AND CAICOS ISLANDS. AMOUNTS OF 4 TO 8 INCHES...WITH
ISOLATED MAXIMUM AMOUNTS OF UP TO 12 INCHES...ARE EXPECTED IN THE
CENTRAL BAHAMAS. RAINFALL AMOUNTS OF 2 TO 4 INCHES WITH MAXIMUM
AMOUNTS OF UP TO 8 INCHES ARE EXPECTED OVER THE MOUNTAINOUS TERRAIN
OF EASTERN CUBA AND NORTHERN PORTIONS OF HISPANIOLA...WHERE THESE
RAINS COULD CAUSE LIFE-THREATENING MUDSLIDES AND FLASH FLOODING.

COASTAL STORM SURGE FLOODING OF 3 TO 5 FEET ABOVE NORMAL TIDE
LEVELS...ALONG WITH LARGE AND DANGEROUS BATTERING WAVES...CAN BE
EXPECTED IN AREAS OF ONSHORE FLOW WITHIN THE HURRICANE WARNING AREA.

SWELLS FROM HANNA ARE EXPECTED TO INCREASE THE RISK OF DANGEROUS RIP
CURRENTS ALONG PORTIONS OF THE SOUTHEASTERN UNITED STATES COAST
DURING THE NEXT COUPLE OF DAYS.

REPEATING THE 800 AM AST POSITION...21.2 N...73.1 W. MOVEMENT
TOWARD...WEST NEAR 2 MPH. MAXIMUM SUSTAINED WINDS...70 MPH.
MINIMUM CENTRAL PRESSURE...987 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 AM AST.

$$
FORECASTER RHOME/FRANKLIN

[KWT]

Looks like Hanna is becoming exposed, probably rapidly weakening now...almost looks like its pulling a Chris where it just threw off all of its convective in one go.

[apocalypt-flyer]

The quicker she gets moving the better for the system because otherwise the shear coming to her from the east might cause major problems.

[gatorcane]

Looks like Hanna is becoming exposed, probably rapidly weakening now...almost looks like its pulling a Chris where it just threw off all of its convective in one go.

it will be interesting to see how the models respond to this West movement and more shallow hanna.

[KWT]

What are the steering currnets for a weaker system right now Gatorcane by the way?

[gatorcane]

What are the steering currnets for a weaker system right now Gatorcane by the way?

For low-level systems that are shallow the steering currents are west as shown by CIMSS. But Hanna is not a true shallow system so probably wouldn't follow this flow exactly.

[jrod]

987mb is too low for Hanna to go poof imho. I do believe it will weaken further, but the storm has been surviving shear most of its life and when the conditions become favorable I expect it to recover quick.


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[CourierPR]

Do you think Hanna will survive? Anyone? She is not looking good this am and was downgraded to TS.

Hanna has survived before and she probably will this time, in my opinion.

[boca]

Is the shear due still to Gustav or is it between two high pressure cells?

[KWT]

Thanks gatrocane, the steering does suggest a westerly motion but probably not very fast at its latitude right now.

[boca]

Hanna might be moving west at 2mph but the convection is moving south right into Haiti which will tear apart Hanna even more.

http://www.ssd.noaa.gov/goes/flt/t2/loop-avn.html

[Frank2]

It's an unusual track for early September, but, one that everyone here is glad for, though this does mean more flooding rains for Haiti, however...

As for Ike, it seems to be moving more NW this morning (since it's already near 20N), so, that's some good news too...

Many down here were getting stressed over the sudden increase in activity, so, this morning's developments (and the outcome of Gustav in LA) are some good news items, though certainly we hope that the heavy rains in Haiti are short-lived...

[gatorcane]

Hi Frank, there is some good news no doubt. I don't see Ike moving NW though. Seems to be moving westerly or just slightly north of west at a good speed.

As for Hanna, she's on a temporary weakening trend but I think once that WNW or NW movement resumes, she can ramp up quickly again and will probably be a large system. Looking at the atest SAT loops, I see a huge moisture envelope for Hanna to work with and its the shear at the moment that is keeping from getting going.

[boca]

Since Hanna is temporarily weakening what does that do to the models,maybe further shift to the west.

[bahamaswx]

Convection is being rapidly sheared off to the south, but the center looks to be exposed now and appears to have been more of less stationary for the past few hours, still over Inagua.

[gtsmith]

yep...center is exposed and shear blew the top off of her...she'll need some really strong convection and shear will really have to abate for her to build back in size and strength...the latest loop in visible and IR I find truly amazing...

[KWT]

Yep looks like this one may be pulling a Chris and is getting totally exposed. I think the conditions will improve for Hanna after 24hrs time and the models have been very keen to strengthen it again which will probably occur.

[marciacubed]

Does anyone think that Hanna will go further west and then curve to the north and affect Fl?

[shortwave]

I do not see how in 48 hrs the northerly shear that is in place is just going to dissapear.
http://www.ssd.noaa.gov/goes/east/watl/loop-wv.html
If an exposed hanna keeps moving west and then northwest, even with the atlantic high building westwards, it looks like it will continue to encounter unfavorable winds aloft.
Currently it looks better for florida. If Hanna should persist and get close to the coast most of the convection would be off to the south and east of her.