ATL HANNA: Extratropical - Discussion

[NEXRAD]

Now that the GFDL is the right outlier showing Hanna within 110 miles of WPB and NOGAPS is the left outlier showing a direct WPB hit with HWRF annd GFS both within 50 miles of the coast I would fully expect the middle of the cone to be just off the WPB coast and a hurricane watch for this portion of S.Fla by 11:00PM tonight as tommorrow would be needed for preperations for a thursday hit. The Euro is the only model left to be heard from.

A question.

Why would they put up a hurricane watch at 11:00 PM, when a lot of people are in bed.

They would wake up to a hurricane watch. Doesn't make sense, but what do I know.

From what I've observed of NHC watch issuance patterns over the last decade, they tend to target watches for at least 36 hours lead time, but often for around 48 hours lead. Given that the time of arrival for the outermost TS-force winds (per the NHC forecast & forecast wind radii) is 2PM Thursday for Srn Palm Beach County, that puts 2PM today at 48 hour lead time, 2AM at 36 hour lead time.

I'd guess that the NHC issues watches with the 5PM advisory if they're confident with the forecast or if Hanna powers up a little; otherwise watches would likely be reserved for Wednesday AM.

- Jay

[Trader Ron]

I agree with NEXRAD. 5:00 AM Wednesday.

We'll see.

[KWT]

Well looks like Hanna is still taking its time to lift out, another decent convvective burst keeping Hanna going and if anything its probably strengthend a little again since 6hrs ago when it was downgraded though winds don't suggest that thus far.

I'm starting to think central Florida now based on the unwillingness to lift out to the NW.

[TreasureIslandFLGal]

Now that the GFDL is the right outlier showing Hanna within 110 miles of WPB and NOGAPS is the left outlier showing a direct WPB hit with HWRF annd GFS both within 50 miles of the coast I would fully expect the middle of the cone to be just off the WPB coast and a hurricane watch for this portion of S.Fla by 11:00PM tonight as tommorrow would be needed for preperations for a thursday hit. The Euro is the only model left to be heard from.

A question.

Why would they put up a hurricane watch at 11:00 PM, when a lot of people are in bed.

They would wake up to a hurricane watch. Doesn't make sense, but what do I know.

From what I've observed of NHC watch issuance patterns over the last decade, they tend to target watches for at least 36 hours lead time, but often for around 48 hours lead. Given that the time of arrival for the outermost TS-force winds (per the NHC forecast & forecast wind radii) is 2PM Thursday for Srn Palm Beach County, that puts 2PM today at 48 hour lead time, 2AM at 36 hour lead time.

I'd guess that the NHC issues watches with the 5PM advisory if they're confident with the forecast or if Hanna powers up a little; otherwise watches would likely be reserved for Wednesday AM.

- Jay

Watches are issued when those (tropical storm or hurricane as applicable) winds could be expected in the area within 36 hours.

Warnings are issues when the winds could be in the area within 24.

It is pretty cut and dry.

[bstruss]

Folks living along the NE Fl coast (myself included) need to take this thing very seriously. Many may not realize that the coastal setup is conducive to very strong storm surge. This is a pic not far from our beach home of the destruction we experienced during Dora. If I remember, this was about 80 mph winds on near low tide! The area was later declared a disaster area and homes were being towed in from the ocean via shrimp boats in the following days. Don't take chances!

http://www.amelia-island.net/images/dora.jpg

[NEXRAD]

Is that ridge gonna shear Hanna?

Bump!

Good question, I want to know that.

The primary cause for the shear is the tight upper level gradient between the Gulf UL ridge and the trough offshore the US/Canadian Eastern Seaboard. As the trough exits the gradient will relax, reducing the shear aloft. Should the Atlantic subtropical ridge have great enough depth to build-in throughout the upper levels, which many of the models suggest will occur, then a southerly flow will develop. Yes there will be shear, but mainly north of Hanna, and that might actually serve to simply enhance the storm's outflow.

- Jay

[Aristotle]

Me thinks Hanna is not out on a possible trip to the GOM if that ridge continues to move that quickly????

[tolakram]

Is drifting another word for south?

[Aristotle]

Wow, Thanks Jay. That really helped me get the overall picture. I appreciate your input!!!

[Brent]

Is drifting another word for south?

I'll believe this NW turn when I see it. Wouldn't shock me if the storm just crashed into Hispanola.

[El Nino]

I think Haïti doesn't have finished with flooding and deaths. Gosh, this storm is really unpredictable !

[NEXRAD]

Me thinks Hanna is not out on a possible trip to the GOM if that ridge continues to move that quickly????

This is a comment based on model outputs; this is not a forecast.

Based on what the 12Z NAM and GFS are doing with the mid-level picture, and knowing that Hanna is a bit weaker of a system as well as farther south at present, I'd keep watch for the Atlantic ridge to merge with the Ohio Valley/Central Appalachians ridging. If this develops, then the angle of ridging would be more SE to NW rather than S to N. The net result of such a set-up on Hanna could be to steer the storm towards Florida with the system possibly emerging in the extreme NE Gulf of Mexico.

Again, this is just a comment based on some model mid-level outputs. It does not take lower or upper levels into account and is not a forecast.

- Jay

[KWT]

I think Brent we are seeing a cyclonic loop, expecting the center to slowly swinground to th east then back round eventually to the NW over the next 12-18hrs.

Jay, thats a good point about the outflow, indeed the NHC has been mentioning the possible decent outflow channels that may set-up though its a wait and see game.

[cpdaman]

Is drifting another word for south?

I'll believe this NW turn when I see it. Wouldn't shock me if the storm just crashed into Hispanola.

yes me too brent


NEXRAD when do you anticipate hanna making any progress westward or northward for that matter..........another 24 hours and she looks like she will be over the DR

[artist]

Me thinks Hanna is not out on a possible trip to the GOM if that ridge continues to move that quickly????

This is a comment based on model outputs; this is not a forecast.

Based on what the 12Z NAM and GFS are doing with the mid-level picture, and knowing that Hanna is a bit weaker of a system as well as farther south at present, I'd keep watch for the Atlantic ridge to merge with the Ohio Valley/Central Appalachians ridging. If this develops, then the angle of ridging would be more SE to NW rather than S to N. The net result of such a set-up on Hanna could be to steer the storm towards Florida with the system possibly emerging in the extreme NE Gulf of Mexico.

Again, this is just a comment based on some model mid-level outputs. It does not take lower or upper levels into account and is not a forecast.

- Jay

thanks Jay. Guess you don't have time for a post in the Tropical Analysis forum? Thanks for the time you have given us.

[gatorcane]

Palm Beach Post in West Palm Beach area does not even mention Hanna on the front page...and are concentrating on storms that are thousands of miles away

Their focus will undoubtedly change in the next 24 hours if trends continue.

http://www.palmbeachpost.com/

[artist]

Palm Beach Post in West Palm Beach area does not even mention Hanna on the front page...and are concentrating on storms that are thousands of miles away

http://www.palmbeachpost.com/

why does that not surprise me?

[CalmBeforeStorm]

Palm Beach Post in West Palm Beach area does not even mention Hanna on the front page...and are concentrating on storms that are thousands of miles away

Their focus will undoubtedly change in the next 24 hours if trends continue.

http://www.palmbeachpost.com/

Amazing when I expect the center of the cone to be within 50 miles of extreme northern palm beach county at 5:00PM.

[NEXRAD]

Me thinks Hanna is not out on a possible trip to the GOM if that ridge continues to move that quickly????

This is a comment based on model outputs; this is not a forecast.

Based on what the 12Z NAM and GFS are doing with the mid-level picture, and knowing that Hanna is a bit weaker of a system as well as farther south at present, I'd keep watch for the Atlantic ridge to merge with the Ohio Valley/Central Appalachians ridging. If this develops, then the angle of ridging would be more SE to NW rather than S to N. The net result of such a set-up on Hanna could be to steer the storm towards Florida with the system possibly emerging in the extreme NE Gulf of Mexico.

Again, this is just a comment based on some model mid-level outputs. It does not take lower or upper levels into account and is not a forecast.

- Jay

thanks Jay. Guess you don't have time for a post in the Tropical Analysis forum? Thanks for the time you have given us.

I'd love to actually forecast Hanna (as I wanted to with Gustav, too), but with my classes and research all up and running, I'd really not have the time to keep updating the forecasts. Therein, I'll sit back a little and let the pros do the work while I enjoy the storms.

Jay

[Trader Ron]

Watches are issued when those (tropical storm or hurricane as applicable) winds could be expected in the area within 36 hours.

Warnings are issues when the winds could be in the area within 24.

It is pretty cut and dry.

I'm quite aware of that...