ATL HANNA: Extratropical - Discussion

[Bocadude85]

upper lows can be poorly forecast by models because there is very little data over the oceans to initialize the models with in the upper levels

What do you think Hannas chances are of making it through this shear?

[cpdaman]

thanks derek for a serious reply

i was just pointing out what seems to be a weak link in forecasting accuracy and as they say your only as strong as your weakest link, trying to get feed back as to why are there such limitations on forecasting ull and how/what/if PRO forecasters can do to improve on these limitations- i didn't mean to sound like a jerk

[gatorcane]

upper lows can be poorly forecast by models because there is very little data over the oceans to initialize the models with in the upper levels

What do you think Hannas chances are of making it through this shear?

I posed this question in the Tropical Analysis forum just a few minutes ago...

Derek will reply when he gets a chance.

[storms in NC]

How many Storms have hit the US from where Hana is at now?

[Weatherboy1]

Hanna, we hardly knew ya! Just joking. But she sure is getting shredded to bits by this ULL. If that doesn't fill or move soon, I don't see how Hanna survives. Storms can only remain as "naked swirls" for so long before just falling apart.

[Bocadude85]

I guess this goes to show you how unpredictable weather can be... she looked great this morning and now look at her nothing but a naked LLC

[HURAKAN]

I guess this goes to show you how unpredictable weather can be... she looked great this morning and now look at her nothing but a naked LLC

There is nothing new about it. We have seen it countless times with storms experiencing shear. It's normal for them to look great during DMAX and completely exposed during DMIN. It's not that it's dying or anything close to it.

[Weatherboy1]

Of course wasn't there a system about 16 years ago in this general area that was getting shredded by shear ... but then the shear faded ... and then its general NW move was brought to a halt by a ridge ... and then the system was steered almost due W into South Florida? Hmmm.

No I'm not saying that Hanna is Andrew. Just that a lot could happen here. A complete dissipation, or depending on whether she survives, a strong storm heading toward FL or somewhere else in the SE U.S. Just interesting to note the somewhat similar setup.

[KWT]

Well the key thing is exactly where the ULL is going, they've really got to seperate but even then I think shear is here to stick for a little while yet.

[Bocadude85]

I guess this goes to show you how unpredictable weather can be... she looked great this morning and now look at her nothing but a naked LLC

There is nothing new about it. We have seen it countless times with storms experiencing shear. It's normal for them to look great during DMAX and completely exposed during DMIN. It's not that it's dying or anything close to it.

I agree with you we saw this with gus just last night.. im sure she will rebound assuming that ULL moves away or fills in.

[Category 5]

Of course wasn't there a system about 16 years ago in this general area that was getting shredded by shear ... but then the shear faded ... and then its general NW move was brought to a halt by a ridge ... and then the system was steered almost due W into South Florida? Hmmm.

No I'm not saying that Hanna is Andrew. Just that a lot could happen here. A complete dissipation, or depending on whether she survives, a strong storm heading toward FL or somewhere else in the SE U.S. Just interesting to note the somewhat similar setup.

I have to agree with you, she looks sick now but don't write it off until it dissipates when it has this much time.

[HURAKAN]

At least there is no discussion about if a LLC exists or not!!!

[Brent]

At least there is no discussion about if a LLC exists or not!!!

Refreshing change from Dolly and Fay.

[Weatherboy1]

For those interested in a little hurricane history (and to see why I even bring up the possible parallel/similar set up -- though I am certainly NOT saying Hanna will ever turn into an Andrew clone)

Between the 17th and 20th of August, the tropical storm passed south of the center of the high pressure area over the eastern Atlantic. Steering currents carried Andrew closer to a strong upper-level low pressure system centered about 500 n mi to the east-southeast of Bermuda and to a trough that extended southward from the low for a few hundred miles. These currents gradually changed and Andrew decelerated on a course which became northwesterly. This change in heading spared the Lesser Antilles from an encounter with Andrew. The change in track also brought the tropical storm into an environment of strong southwesterly vertical wind shear and quite high surface pressures to its north. Although the estimated maximum wind speed of Andrew varied little then, a rather remarkable evolution occurred.

Satellite images suggest that Andrew produced deep convection only sporadically for several days, mainly in several bursts of about 12 hours duration. Also, the deep convection did not persist. Instead, it was stripped away from the low-level circulation by the strong southwesterly flow at upper levels. Air Force Reserve unit reconnaissance aircraft investigated Andrew and, on the 20th, found that the cyclone had degenerated to the extent that only a diffuse low-level circulation center remained. Andrew's central pressure rose considerably (Fig. 2 [87K GIF]). Nevertheless, the flight-level data indicated that Andrew retained a vigorous circulation aloft. Wind speeds near 70 kt were measured at an altitude of 1500 ft near a convective band lying to the northeast of the low-level center. Hence, Andrew is estimated on 20 August to have been a tropical storm with 40 kt surface winds and an astonishingly high central pressure of 1015 mb (Figs. 2 and 3 [87K GIF]).

Significant changes in the large-scale environment near and downstream from Andrew began by 21 August. Satellite imagery in the water vapor channel indicated that the low aloft to the east-southeast of Bermuda weakened and split. The bulk of the low opened into a trough which retreated northward. That evolution decreased the vertical wind shear over Andrew. The remainder of the low dropped southward to a position just southwest of Andrew where its circulation enhanced the upper-level outflow over the tropical storm. At the same time, a strong and deep high pressure cell formed near the U.S. southeast coast. A ridge built eastward from the high into the southwestern Atlantic with its axis lying just north of Andrew. The associated steering flow over the tropical storm became easterly. Andrew turned toward the west, accelerated to near 16 kt, and quickly intensified.

[SouthFLTropics]

For those interested in a little hurricane history (and to see why I even bring up the possible parallel/similar set up -- though I am certainly NOT saying Hanna will ever turn into an Andrew clone)

Between the 17th and 20th of August, the tropical storm passed south of the center of the high pressure area over the eastern Atlantic. Steering currents carried Andrew closer to a strong upper-level low pressure system centered about 500 n mi to the east-southeast of Bermuda and to a trough that extended southward from the low for a few hundred miles. These currents gradually changed and Andrew decelerated on a course which became northwesterly. This change in heading spared the Lesser Antilles from an encounter with Andrew. The change in track also brought the tropical storm into an environment of strong southwesterly vertical wind shear and quite high surface pressures to its north. Although the estimated maximum wind speed of Andrew varied little then, a rather remarkable evolution occurred.

Satellite images suggest that Andrew produced deep convection only sporadically for several days, mainly in several bursts of about 12 hours duration. Also, the deep convection did not persist. Instead, it was stripped away from the low-level circulation by the strong southwesterly flow at upper levels. Air Force Reserve unit reconnaissance aircraft investigated Andrew and, on the 20th, found that the cyclone had degenerated to the extent that only a diffuse low-level circulation center remained. Andrew's central pressure rose considerably (Fig. 2 [87K GIF]). Nevertheless, the flight-level data indicated that Andrew retained a vigorous circulation aloft. Wind speeds near 70 kt were measured at an altitude of 1500 ft near a convective band lying to the northeast of the low-level center. Hence, Andrew is estimated on 20 August to have been a tropical storm with 40 kt surface winds and an astonishingly high central pressure of 1015 mb (Figs. 2 and 3 [87K GIF]).

Significant changes in the large-scale environment near and downstream from Andrew began by 21 August. Satellite imagery in the water vapor channel indicated that the low aloft to the east-southeast of Bermuda weakened and split. The bulk of the low opened into a trough which retreated northward. That evolution decreased the vertical wind shear over Andrew. The remainder of the low dropped southward to a position just southwest of Andrew where its circulation enhanced the upper-level outflow over the tropical storm. At the same time, a strong and deep high pressure cell formed near the U.S. southeast coast. A ridge built eastward from the high into the southwestern Atlantic with its axis lying just north of Andrew. The associated steering flow over the tropical storm became easterly. Andrew turned toward the west, accelerated to near 16 kt, and quickly intensified.

That synopsis is quite scary and eerily familar!!!

SFT

[gatorcane]

I hate to say it but this situation is very similar to Andrew with the synoptic setup that may happen

But I think in this case the steering patterns downstream are still a bit unknown, more so than Andrew.

Let's hope South Florida never has to deal with an Andrew storm from the east ever again.

[Bocadude85]

I hate to say it but this situation is very similar to Andrew with the synoptic setup that may happen

But I think in this case the steering patterns downstream are still a bit unknown, more so than Andrew.

Let's hope South Florida never has to deal with an Andrew storm from the east ever again.

Its only a matter of time until something like Andrew happens again... look at all the big storms that hit south florida from the east back in the 1940's

[lbvbl]

I hate to say it but this situation is very similar to Andrew with the synoptic setup that may happen

But I think in this case the steering patterns downstream are still a bit unknown, more so than Andrew.

Let's hope South Florida never has to deal with an Andrew storm from the east ever again.

The good thing about this so far is that the forecast models (GFS as an exception) agree on the track thus far. I would much rather have a storm with a certain track becuase surprises are less likely.

[HURAKAN]

18z Best Track:

AL, 08, 2008082818, , BEST, 0, 206N, 596W, 35, 1003, TS,

[Broward Mom]

I just know I'm going to be p.o.'ed beyond belief if both Gustav and Hanna are (let's say) Cat 3's and hit less than a week apart. Our people will have no national news coverage and MUCH worse, no sympathy or emotional support since Katrina...er, I mean Gustav...will have stolen the spotlight with his accompanying flood.

We will not exist, just like after Oct. 24, 2005, and every day thereafter. (Including today when the major outlet I am watching hasn't said "Hanna" in the past hour I've had it on.)

Sorry if I sound bitter. I just am. Spending a few hours in a tiny bathroom with your family and big dog under a mattress will do that to you (after you've seen 2 shutters peeling from your windows).

And for the people who didn't understand why you'd start preparing today? The "before people know about it" is the important part - gotta get my RT-600 (roof tile adhesive) and two-ton epoxy to firm up some of our anchors. Stores will be empty if another one is coming - we're South Floridians, trust us, we know.

Thanks to everyone as always on this forum - now I know it's not just me that hates the incompetence of TWC!