ATL HANNA: Extratropical - Discussion

[cpdaman]

Has anyone ever seen upper level divergence go from 50 plus to 10 in 3 hours well

good nite hanna (see you in a day or so) look at the 3 hour trends in divergence (jaw drops)

http://cimss.ssec.wisc.edu/tropic/real- ... dvg-1.html

[txwatcher91]

I think the biggest problem is Haiti/DR disrupting the southern inflow right now. The shear appears to be weak as the convective "thunderstorm" that popped near the LLC is not really being sheared in a direction right now. I think the problem is the inflow, and possibly cooler SST's from upwelling. Look at IR and you will see two "chunks" of convection that are south of Haiti and are not wrapping into the center because of the mountains. This is all IMO though.

[BigA]

Is it possible that the decrease in upper level divergence is a result of the decrease in convection, rather than visa versa? For instance that convection causes divergence, or am I utterly wrong, and the divergence allows convection to develop?

[cpdaman]

I think the biggest problem is Haiti/DR disrupting the southern inflow right now. The shear appears to be weak as the convective "thunderstorm" that popped near the LLC is not really being sheared in a direction right now. I think the problem is the inflow, and possibly cooler SST's from upwelling. Look at IR and you will see two "chunks" of convection that are south of Haiti and are not wrapping into the center because of the mountains. This is all IMO though.

land definitely not helping ....cooler water's maybe but should be enough to sustain a TS strength storm

do you have any idea how Upper level divergence goes from 50 plus at 6 pm to 10 at 9pm

my above post shows the link, i just can't believe it.

[txwatcher91]

Here is an image to help show what I am saying about the shear. Hanna is currently sitting in 15kts or less of shear with decreasing shear to the north.

[cpdaman]

Here is an image to help show what I am saying about the shear. Hanna is currently sitting in 15kts or less of shear with decreasing shear to the north.

umm shear looks like it increasing to the North west pretty good and north east, (with an area between the two (north) of no change, the shear is decreasing way up around 32 north or so....and the shear is also decreasing to her west and her east....but still i don't see the shear as the main reason she decided to stop producing convection......upper level divergence from 50 to 10 is all you need to really know, the question i have is what caused that (edit but you answered that so thank you!)

[txwatcher91]

I think the biggest problem is Haiti/DR disrupting the southern inflow right now. The shear appears to be weak as the convective "thunderstorm" that popped near the LLC is not really being sheared in a direction right now. I think the problem is the inflow, and possibly cooler SST's from upwelling. Look at IR and you will see two "chunks" of convection that are south of Haiti and are not wrapping into the center because of the mountains. This is all IMO though.

land definitely not helping ....cooler water's maybe but should be enough to sustain a TS strength storm

do you have any idea how Upper level divergence goes from 50 plus at 6 pm to 10 at 9pm

my above post shows the link, i just can't believe it.

Yes, two things have likely resulted in that.

1. The decrease in convection has resulted in a decrease in the divergence, not all that uncommon with a tropical storm. 10 is still pretty good though and when convection increases it should also.

2. The shear axis that was aiding in the strong divergence has now moved West of the center and is no longer helping Hanna, so she is on her own. Shear has actually decreased to 15kts per CIMSS. This is all IMO and based off of observations.

The shear to the NW of Hanna is moving W and the shear NE of Hanna is moving E and N as the trough is splitting and lifting out, as predicted by the models. The little area in the middle of less shear is diving south towards Hanna and should be there in time for DMAX...

[cpdaman]

thanks txwatcher that makes sense regarding divergence

[ConvergenceZone]

the good news in all of this is IF it does weaken further, then ithe NHC will in turn lower the landfall intensity up the east coast, and perhaps they may just show it as a strong tropical storm. The other good news is that it will be moving so fast once it gets going that it won't have the time to develop like it would if it were moving slow.

[txwatcher91]

thanks txwatcher that makes sense regarding divergence

No problem. I have learned alot about divergence from our local NWS office. If I understand correctly, a trough has a right entrance region of 50-100kt winds that can produce some very strong divergence. Given that Hanna was in that area yesterday and had divergence of her own, the right entrance region helped Hanna out significantly. This trough probably had about 50-60kt shear in the right entrance region.

[latemodel25]

eenie meenie miny moe http://weather.myfoxtampabay.com/maps/WTVT/custom/models/ecmwf_caribbean.html

[Sanibel]

If Ike runs into Hanna the Fujiwara relationship would be interesting. If Ike ran into Hanna on the same latitude Ike would go up and around Hanna counter clockwise to the north while Hanna went west.

[CajunMama]

Just a note to remember not everyone has a superduper computer or the highest speed interent access so please limit the quoting of large image loops please. Thank you!

[HurricaneRobert]

Hanna looks like garbage again.

[bahamaswx]

Yep. Her most recent attempt to flare-up over the center failed miserably. She'll come back though.

[Blown Away]

Hanna still near 20.5N she is supposed to be near 20.9 by 2am. It appears she is nearly 35 miles SSE of that first point rate now.

[storms in NC]

Well I will leave this to you all to figure out. Maybe my eyes can see better in the AM.

See if she is a TD or a open wave in the AM if she is a TS still then she 'll make it.
Maybe she wants a band-aid

Good Night All be long days ahead the next few days

Deb

[lbvbl]

based on current models, an eastern shift in the track should be expected, correct?

[cpdaman]

by 1 am when recon reaches center the reports will be interesting

i say her pressure is up to 994 and her winds are probably about 50 due to her vigorous LLC

[jaxfladude]

So Hanna is now on life support great for all, but Haiti which only a tropical wave with heavy rains can have nasty mudslides due to deforestation ?