ATL: TROPICAL DEPRESSION BONNIE - DISCUSSION

[Aric Dunn]

Looks to still be on a wnw movement. Elongated low pressure area gives the illusion of moving SW

[img][/img]

yeah wnw motion has continued all day...

[HURAKAN]

Let me bring back this analogy.

For the half empty side : Yes, it looks disorganized, weak, fighting against shear and dry air

For the half full side : Yes, it continues to improve, pressures are decreasing, convection increasing and many sheared storms have formed in the past

[artist]

Grace Bay in the Turks and Caicos has a pressure now down to 1007mb... the "center" is passing very close to the area..

any wind info?

low to mid 30s

http://www.wunderground.com/cgi-bin/fin ... 2.090&MR=1
scroll to the bottom

[shortwave]

http://egoscueportland.files.wordpress.com/2010/02/glass-half-full.jpg

Let me bring back this analogy.

For the half empty side : Yes, it looks disorganized, weak, fighting against shear and dry air

For the half full side : Yes, it continues to improve, pressures are decreasing, convection increasing and many sheared storms have formed in the past

if you could turn that glass to the left 90 degrees without the water moving that would be a good analogy for the system currently

...edited by wxman57 to remove the re-posting of the image. Please remove your "IMG" tags when you quote a post that has an embedded picture, people.

[MGC]

The ULL to 97L north has not weakened or moved out of the way. The ULL actually looks to be getting stronger. I can only see the shear increasing over 97L since the two are both moving to the west. I expect the chance of development of 97L to decrease in the short term. 97L should continue to move to the west to west-northwest at a fairly good clip. I doubt 97L developles before reaching 80W.......MGC

[wxman57]

I cannot see any evidence of an LLC on satellite loops - and in the actual observations across the islands. What I do see is some evidence that the westerly wind shear is beginning to relax a little as the upper low moves more rapidly westward than the disturbance is advancing. This is resulting in increasing convection east of the wave axis. If I was to point to a place to track for a possible LLC formation tomorrow, I'd point to 21.6N/72.3W, just south of the western tip of the convection. But I see no LLC there yet.

It remains to be seen if the upper low will continue moving out of the picture tonight/tomorrow. I think it will, and that should allow for gradual development on Thursday. Could be a TD in 24 hours if it's not hit by shear again tonight. Once it does gain that LLC in an environment of decreasing shear (assuming that happens), then it's a short jump to TS status east of Florida.

I don't buy the "hurricane models" (HWRF/GFDL) taking it toward the central peninsula. They assume it's already developed, and it hasn't. I prefer a continued WNW movement that would take the center near the Keys Friday afternoon/evening then on a heading of around 280 degrees into the Gulf for 24 hours until high pressure north of the system relaxes Saturday afternoon. Then, assuming it does develop, it could begin turning WNW-NW. This increases the threat farther west toward Louisiana. My track, in fact, now takes it inland SSW of New Orleans Sunday afternoon/evening. However, that's a VERY LOW CONFIDENCE forecast which is dependent on variables which we do not know (like if and when it will develop, and when the ridge will break down). I think that the FL Panhandle may be out of the woods now as far as a possible hurricane (or TS) landfall. I don't think it's coming to Texas as a TC, maybe if it doesn't develop at all we could get some rain out of it.

Remember, we never expected wind shear to drop off until tomorrow, anyway. So it's not behaving much differently than was originally forecast 3-4 days ago.

[wxman57]

The ULL to 97L north has not weakened or moved out of the way. The ULL actually looks to be getting stronger. I can only see the shear increasing over 97L since the two are both moving to the west. I expect the chance of development of 97L to decrease in the short term. 97L should continue to move to the west to west-northwest at a fairly good clip. I doubt 97L developes before reaching 80W.......MGC

MGC - I just opened GARP and plotted a 2145Z and an 0945Z WV image and calculated the movement in the past 12 hours to be toward 289 degrees at just over 15 kts (189.5nm in 12 hrs) for the upper low. It's definitely on the move westward and quite a bit faster than the disturbance.

[Nimbus]

The longer term forecast has too many 5 and 10 percent possible alternative scenarios to assimilate definitively. Especially if you tend to be a Briggs and Myers type J.

Today the TUTT has done such a good job of keeping the development to a minimum that a simple extension of the synoptic reasoning would be quite comforting. Tomorrow the NHC will have to call 97 based on the best evidence they have at the time. The TUTT could stall re amplify and dig in right? we've seen that happen many times before.

[HURAKAN]

Latest ... back in 3 hours (baseball practice)

[coreyl]

Wxman57, are you concerned about the possibility that the ULL could move far enough from Invest 97 L to allow it to strengthen more than the models are expecting?

[KWT]

I cannot see any evidence of an LLC on satellite loops - and in the actual observations across the islands. What I do see is some evidence that the westerly wind shear is beginning to relax a little as the upper low moves more rapidly westward than the disturbance is advancing. This is resulting in increasing convection east of the wave axis. If I was to point to a place to track for a possible LLC formation tomorrow, I'd point to 21.6N/72.3W, just south of the western tip of the convection. But I see no LLC there yet.

There was almost certainly a *weak* LLC a few hours ago but I think it has since probably opened up given the westerlies really were very weak indeed, it was pretty close to where you said, just WSW of the convection thats firing right now. Also it was VERY small indeed, thats probably why land obs doesn't reflect it at all, perhaps so small it may have just been an eddy I suppose...

ps, how fast do you have this system moving right now by the way?

[tailgater]

The ULL to 97L north has not weakened or moved out of the way. The ULL actually looks to be getting stronger. I can only see the shear increasing over 97L since the two are both moving to the west. I expect the chance of development of 97L to decrease in the short term. 97L should continue to move to the west to west-northwest at a fairly good clip. I doubt 97L developes before reaching 80W.......MGC

MGC - I just opened GARP and plotted a 2145Z and an 0945Z WV image and calculated the movement in the past 12 hours to be toward 289 degrees at just over 15 kts (189.5nm in 12 hrs) for the upper low. It's definitely on the move westward and quite a bit faster than the disturbance.

Just to piggyback a little, watch this loop. It also shows a decent jump to the west in the convection near 97at the end of the loop. Last nite I didn't give this a chance at developing for 36 hrs. I may have to eat a little crow.
http://mkwc.ifa.hawaii.edu/satellite/sa ... verlay=off

[frederic79]

Forgive me if my memory is not serving me correctly but wasn't Charley a sheared system back in 2004 as it moved north out of the Caribbean shortly before it exploded over boiling SST's before making landfall. Seems like we watched it struggle for quite awhile before it took off. I think that's what concerns me here is that conditions so far have not been good. If the ULL pulls away and the atmosphere destablizes, and the water temps only get warmer later, as Mike Watkins suggested, this one may surprise us.

[Florida1118]

Invest 98? Anyway, Bonnie better fine her self in there, or its a quiet July and there goes the predictions. it looks better than what it was this morning, but still, not as good as yesterday... Was or wasnt there a LLC?

[Aric Dunn]

the wave axis / llc is extremely sharp and we should see a more defined LLC in the next 12 hours... if not sooner

[ronjon]

the wave axis / llc is extremely sharp and we should see a more defined LLC in the next 12 hours... if not sooner

I agree Aric - latest VIS shows its really coming together now with convection being pulled into the forming center. Its on its way and looks as if shear has backed off.

http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

[Ivanhater]

You will notice some posts being removed from this forum. Stay on topic.

[alienstorm]

Possible LLC - located SW of the Caicos and Turks moving west to west northwest.

[smw1981]

Florida1118 - I think there is a small debate over whether there was an LLC or not at some point today. This morning they were saying there was one, then not one, then early afternoon some said there was one, now there's not one (according to our resident Pro Met and Moderater wxman).

My personal opinion from looking at satellite imagery, etc. is that there is no LLC AT THE PRESENT TIME, but it may not be far from developing one, especially since convection is/was firing around the MLC (which could work it's way down). We shall see in due time...

This is only my opinion, as I am not an expert...

[BigA]

Southern inflow seems to have picked up a good bit in the last hour. Will be interesting to see whether the inflow is strong enough to pull the land-based T-storms from hispaniola.