ATL HANNA: Extratropical - Discussion

[jlauderdal]

For all locations along the east coast:
No matter what, this storm is going to affect your weekend. No days off from work or school. Just a ruined rainy Saturday and Sunday. Everything will be fine just in time for your drive to work on Monday.

my daughter and her friends are the biggest people I disagree with fort lauderdale has ever seen, they dont want to lose power or be inconvenienced just a few days off school

[NEXRAD]

Some morning notes...

First, with the current convective disorganization, Hanna will not likely strengthen much over the next 12 hours. Second, notice the fast-moving upper level clouds near East Florida. That's the strong shearing that was previously impacting the tropical storm. Now that an upper low is in place over the Central Bahamas, that strong shear has been cut-off temporarily. Later today, the strong upper level winds will work around the base of that upper low, and Hanna could experience westerly shearing instead of northerly shearing. This type of air movement aloft will be a mixed blessing for the storm. While it will allow a good northeasterly outflow aloft and may work in-tandem with divergence south of Hanna to create a more dual channel-like outflow, the storm will still experience shearing across its NW quadrant. The upper low might also filter drier air into Hanna's western zones, which could infiltrate the storm and really affect strengthening (note what dry air did with Gustav).

- Jay

[KWT]

I've got tio admit I'm having a hard time finding a LLC as well, if ther eis one I think its between the two convective blobs, the circulation looks very poor but I think given the conditions should start to improve soon then we should see this restrengthen again.

Jay, i agree I can't see this doing much strengthening for a little while yet.

[tpr1967]

Looking at the visibles some more it seems recon might have been tracking a mesoscale vortex
spinning around the broad center of hanna. Thats why perhaps a south then east then north movement.

[Sanibel]

It's near 22N-72W Turks Caicos. Movement NW.


From the looks of the surface clouds there more spin there than the upper shows.

[tallywx]

tallywx, I think the key is its been drifting eastwards and so whilst the synoptic set-up hasn't changed a great deal from what was expected the NW turn comes further east and that shunts the landfall site further to the east, that plus we need to watch what Gustav does, if it lifts out quickly then I suspect Hanna will get a little further east yet further.

I couldn't have said it better myself. In fact...I did!

Couldn't a delay in her movement result in a west shift to her path, not an easterly shift, due to the progression of the ridge further west?

Not necessarily. First of all, most models didn't have this moving for another 15 hours or so anyway, so any repositioning now to the SE, as long as it starts moving then, would just shift the track to the east.

Tallywx, please see NEXRAD's comments about a building subtropical ridge. I've also taken note of your location with regard to your forecast.

CourierPr, would you like your crow fried or blackened?

[Sanibel]

So I suppose this means the void vacated by Hanna will be filled by a tongue of high pressure that guides Ike beneath it? NHC is pretty insistent on Ike going towards the Straits.

[NEXRAD]

I don't think that the more eastward shift in the guidance envelope is due to Hanna's more SE position today alone. Recall with yesterday's runs (esp. the 12Z, as I recall), many of the models initialized Hanna too far south and east, yet still kept the system in a fairly tight more west envelope. Today's shift might be more a factor of the upper low spinning-up.

- Jay

[tallywx]

I don't think that the more eastward shift in the guidance envelope is due to Hanna's more SE position today alone. Recall with yesterday's runs (esp. the 12Z, as I recall), many of the models initialized Hanna too far south and east, yet still kept the system in a fairly tight more west envelope. Today's shift might be more a factor of the upper low spinning-up.

- Jay

10-4.

[NEXRAD]

Also, the GFS and some of the other right-shifted guidance is a bit quicker with Hanna, which means it's assuming a lesser W-ward extent of the subtropical ridge.

- Jay

[boca]

How does the ULL developing affect Hanna's track?

[NEXRAD]

How does the ULL developing affect Hanna's track?

For a deeper system, it'd tend to steer the tropical cyclone around it, if the ULL was stuck. Yesterday's guidance took the upper low WSW pretty fast, but today's is slower. This doesn't mean the ULL will be stationary, however. Instead, it could be a reflection that the models are correctly working with a weaker initial TS Hanna, where the weaker storm would have less forcing on its environment. For Hanna's sake, the upper low should prohibit a due west motion unless forcing also moves the ULL west. If Hanna were to move due west, then the shearing impact from energy rotating around the Srn base of the ULL would conceivably shred the tropical storm. Note that this is my perspective, and not entirely fact. ULL's are tricky when it comes to tropical weather.

- Jay

[CourierPR]

Tallywx, I'll take it blackened. Seriously, if she comes your way, be safe.

[chris_fit]

I see a new LLC forming @ 21.8N 71.8W

[OuterBanker]

Listen I'm certainly no expert, but to me in the visible loop it appears that the the llc is expanding, as well as mid levels with a rather large long feeder band trying to wrap from the east and south of Hanna. I believe this may have a chance to get it's act together more than TPC (and most here) think. And if the Fl people I disagree with want her you are welcome to her.

[KWT]

I don't think that the more eastward shift in the guidance envelope is due to Hanna's more SE position today alone. Recall with yesterday's runs (esp. the 12Z, as I recall), many of the models initialized Hanna too far south and east, yet still kept the system in a fairly tight more west envelope. Today's shift might be more a factor of the upper low spinning-up.

- Jay

The thing is most models also showed the NW motion right away and that hasn't happened. I remember some models did show this heading NE breifly and I recall the UKMO did show this and had it eventually landfalling in the NC when most models were clusted furtther south-west of there. However I think the ULL is probably playing a part as well as well.

[tallywx]

Tallywx, I'll take it blackened. Seriously, if she comes your way, be safe.

Thanks, but at this point climatology and model shifting has me thinking the paradigmatic Wilmington to Cape Lookout skirter. That wouldn't bring much weather to the Raleigh/Durham area. On the other hand, I've been craving a shrimp burger from El's Drive In in Morehead City...

[NEXRAD]

The thing is most models also showed the NW motion right away and that hasn't happened. I remember some models did show this heading NE breifly and I recall the UKMO did show this and had it eventually landfalling in the NC when most models were clusted furtther south-west of there. However I think the ULL is probably playing a part as well as well.

I've noticed that with the guidance. Hanna's proving more troublesome to forecast than Fay; at least with TS Fay the storm was in range of Key West radar and there were the excellent Florida mesonets to use for analyzing the synoptic setup ahead of the storm. With Hanna, there's not as much to go on.

- Jay

[KWT]

There does appear to be a circulation to the SW of the northern deep convection, i wonder what level its at, its not a bad looking circulaton and wonder if the LLC has relocated further north?

[Sanibel]

http://www.ssd.noaa.gov/goes/east/nwatl/loop-wv.html



You can see the little nub of trough NEXRAD mentioned jutting down west of Hanna creating the more westerly shear he was talking about. It is almost like a little ULL forming off the bottom of the main ULL. The high pressure is harder to see on WV.

If I were to look at the WV loop I would say Hanna should go right up the trough edge and out to sea. The High that is preventing that doesn't really show on WV.

Your eye makes you want to say that since Hanna went more east that Ike should also pull up more north. Right now Ike's form is starting to distort in contact with the ULL synoptic. Makes me wonder about intensity issues because of it. I love it when you get hammered for saying close systems will weaken each other and then the systems end up weak.