Area's of interest in Western Atlantic

[storms in NC]

Can someone please tell me about this ULL out by the Bahamas. it seem to be moving to Fl. If some one have time to tell me how the ULL forms and goes away or if the do?I know it is a upper level low and it has something to do with the jet stream at one time. But can they like go poof or do they just move around? Sorry for a dumb question
But just trying to put things together here with the wave and the Ull.

Deb

yeah they are a cut off low that was or is normally part of the larger scale jet stream patterns... but often the get cut off and retrograde back west as the jet stream move away.. they are also called TUTTS or tropical upper tropospheric trough..

and they can stay around a long time.. but they will eventually either weaken or get picked up by the next dip in the jet stream

Thanks a bunch

[Aric Dunn]

I cannot see a sign of justification for development. This upper low is non-tropical. Mid-level inversion is too strong. That factor is a negative sign. Convection can't consolidate. Where do you spy a low-level circulation? The sfc low is non-existant. Look here. Dry air continues its westward surge. SAL is encroaching upon the islands. If convection refired, I would give better chances. The trough will kill this system's chances. The favorable diffluence has vanished - cross-flow westerlies are strong. The entire basin is hostile.

wow buddy...

anyway.. current conditions are not the favorable.. agreed.. never said they were... as for the LLC its not quite there yet but in the process north of hispanola and east of the SE bahamas.. its not hard to see .. http://www.ssd.noaa.gov/goes/east/pr/loop-rgb.html .. agreed .. it still mostly just the wave axis.. there some signs that it may be taking shape.. and the sal is quite far away from where im talking about and it has a lot moisture to go thru(lol )

and convection takes time so dont just jump on it until at least some time has past..

oh and who said anything about an "upper being tropical "

[storms in NC]

I cannot see a sign of justification for development. This upper low is non-tropical. Mid-level inversion is too strong. That factor is a negative sign. Convection can't consolidate. Where do you spy a low-level circulation? The sfc low is non-existant. Look here. Dry air continues its westward surge. SAL is encroaching upon the islands. If convection refired, I would give better chances. The trough will kill this system's chances. The favorable diffluence has vanished - cross-flow westerlies are strong. The entire basin is hostile.

You saying the atlantic basin is hostile?

[Nimbus]

The ULL north of Hispaniola is starting to get pulled north by the front moving off the east coast. If the front does not dig and high pressure wedges itself in under the departing ULL this could get messy. The southern part of the wave is showing convection but does not have any low level circulation.

[MiamiensisWx]

Okay... I will clarify my position per the requests of others. I did not intend to inject a negative tone in my post.

I agree with Aric - it is difficult to judge conditions in advance... the main negatives for development include:

1) The lack of a persistent well-defined sfc low (i.e. pre-TD formation) - the deep layer steering will not help this system;

2) The upper-level thermodynamics are unfavorable for convective sustenance;

3) It is embedded in an upper-level trough - we have been searching for lower shear

The SAL has not arrived, although it could inhibit convection near the southern end of the wave axis. This could hurt the northern "branch" - the lack of inflow provides ample reasons to be concerned. I'm sure that the islands are glad - the southern portion was undercut by strong low-level shear; the convection was induced primarily via diffluence combined with the diurnal maximum and upper low's influence. The shower activity diminished; hopefully Vieques (knotimpaired) received some precipitation! Any way you slice it, most factors did not favor development. The outcome could have been much different if the upper low moved away from the system - the diffluence was ideal for fanning!

Currently I would hold back on our chances for development west of Bermuda. Most upper-air analyses indicate the presence of an East Coast trough. The system could make the transition to an ET low prior to a frontal merge - that setup would put a lid over its chances for structural organization; it would diminish its subtropical/hybrid characteristics. The current shear analyses suggests a likely option which would include this scenario. Nimbus noted the progression of the trough; it does not bode well for development. I doubt the validity of a ridge-bridge scenario; the trough's proximity is too close for a strengthening mid-level anticyclone.

The basin hardly defines a favorable regime at the moment - the quantity of upper lows speaks for itself. Nevertheless I think activity will increase over the next several weeks.

[gatorcane]

for real action with lots of moisture and low shear...

see the EPAC....as usual the Atlantic is ridden with ULLs and SAL...no different than 2006

[Aric Dunn]

look like the surface low offshore hispanola.. is becoming a little more defined .. this afternoon.. lets see what happens

http://www.ssd.noaa.gov/goes/east/pr/loop-rgb.html

[Aric Dunn]

298
ABNT20 KNHC 202115
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT FRI JUL 20 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

CLOUDINESS AND SHOWERS EXTENDING FROM THE CENTRAL CARIBBEAN SEA
NORTHEASTWARD INTO THE ATLANTIC FOR SEVERAL HUNDRED MILES ARE
ASSOCIATED WITH AN UPPER-LOW INTERACTING WITH WITH A WESTWARD
MOVING TROPICAL WAVE. UPPER-LEVEL WINDS ARE NOT CONDUCIVE FOR
DEVELOPMENT AT THIS TIME...BUT ENVIRONMENTAL CONDITIONS COULD
BECOME A LITTLE MORE FAVORABLE IN A DAY OR TWO.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER AVILA

[Aric Dunn]

the potential is there..( at least minimal ) for something to become if this system .. over the day ..

[Hybridstorm_November2001]

A very interesting, and unpredictable situation setting up for early next week that much is certain. I for one will have my eyes riveted on the area between Cape Hatteras and the Bahamas.

[storms in NC]

I need a new roof so come blow it off So DH will fix it. He think it will get fixed on it own.LOLOLOL

[HURAKAN]

Repeat? Possible but not intensity-wise I guess.

[wxman57]

A very interesting, and unpredictable situation setting up for early next week that much is certain. I for one will have my eyes riveted on the area between Cape Hatteras and the Bahamas.

Look closer to Bermuda, associated with the upper low - that's where there is a minimal chance of a subtropical storm forming. Anything that forms along the cold front off the Carolinas won't be tropical, probably a weak frontal low if anything. Pressures out there near the upper low are quite high now at the surface. No sign of anything yet. What has to happen is thunderstorms need to develop and persist near the upper low center. Could take days for something to get going, and by then the low will be moving off to the north up the trof/front that'll push off the east coast over the weekend. Any possible threat to land (besides Bermuda) would be from Maine northeastward across eastern Canada.

[Aric Dunn]

A very interesting, and unpredictable situation setting up for early next week that much is certain. I for one will have my eyes riveted on the area between Cape Hatteras and the Bahamas.

Look closer to Bermuda, associated with the upper low - that's where there is a minimal chance of a subtropical storm forming. Anything that forms along the cold front off the Carolinas won't be tropical, probably a weak frontal low if anything. Pressures out there near the upper low are quite high now at the surface. No sign of anything yet. What has to happen is thunderstorms need to develop and persist near the upper low center. Could take days for something to get going, and by then the low will be moving off to the north up the trof/front that'll push off the east coast over the weekend. Any possible threat to land (besides Bermuda) would be from Maine northeastward across eastern Canada.

i agreee and disagree.. the present area.. that may lead to sub trop or trop further north .. is still near hispanola.. that is where we have increasing cyclonic turning and evidence of a Low forming near there.. with that said.... it wil probably move north and begin to either take on sub tropical or tropical characteristics .. but there is nothing up that far north .. as you said pressure are high.. watch further south .. for something to move north.. by sunday..

and no sign that far north .. but near Dominican republic yeah... there is..

[Hybridstorm_November2001]

[quote="wxman57] Any possible threat to land (besides Bermuda) would be from Maine northeastward across eastern Canada.[/quote]

Indeed, that is exactly why I'm keeping an eye on it.

[wxman57]

i agreee and disagree.. the present area.. that may lead to sub trop or trop further north .. is still near hispanola.. that is where we have increasing cyclonic turning and evidence of a Low forming near there.. with that said.... it wil probably move north and begin to either take on sub tropical or tropical characteristics .. but there is nothing up that far north .. as you said pressure are high.. watch further south .. for something to move north.. by sunday..

and no sign that far north .. but near Dominican republic yeah... there is..

No, nothing down there by the DR, Aric. No low forming, and pressures at the surface are relatively high. I don't see any circulation - low, mid, or high-level north of the DR, just the upper low much farther north. If anything was to form, it would form near the area of greatest convergence. That would be near or just east of the upper low center. But pressures are not low up there, either - yet. That's why the NHC mentioned a possible recon way up near 33N/66W - where the upper low will be moving. It would take a day or two for thunderstorms to persist in one area before any LLC might begin to form. By then, the low should be tracking off to the north up or ahead of the front. Probably out to sea.

[Aric Dunn]

i agreee and disagree.. the present area.. that may lead to sub trop or trop further north .. is still near hispanola.. that is where we have increasing cyclonic turning and evidence of a Low forming near there.. with that said.... it wil probably move north and begin to either take on sub tropical or tropical characteristics .. but there is nothing up that far north .. as you said pressure are high.. watch further south .. for something to move north.. by sunday..

and no sign that far north .. but near Dominican republic yeah... there is..

No, nothing down there by the DR, Aric. No low forming, and pressures at the surface are relatively high. I don't see any circulation - low, mid, or high-level north of the DR, just the upper low much farther north. If anything was to form, it would form near the area of greatest convergence. That would be near or just east of the upper low center. But pressures are not low up there, either - yet. That's why the NHC mentioned a possible recon way up near 33N/66W - where the upper low will be moving. It would take a day or two for thunderstorms to persist in one area before any LLC might begin to form. By then, the low should be tracking off to the north up or ahead of the front. Probably out to sea.

ok will see..

[tailgater]

Plot of Caribbean
http://weather.unisys.com/surface/sfc_carib.gif
Wave axis on the Haitian coast might do something once it gets to Mona passage and should start moving NW then N with trough to the west, slight possilibilty of development IMHO.

[Sanibel]

Hey Aric. That swirl has been replaced by another coming up from the east above DR. Which tells you it is a synoptic vortex from all the systems and trade winds converging there. No surface feature. The wave is just a weak open tropical wave being badly sheared by a basin-wide hostile environment.

Nothing there. Wait til August.

[cpdaman]

i tried to see a chance near hispanola but i can't

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

nothing will develop moving westward or northward under a ULL with shear right in its face (the direction it is moing) IMO

the area to watch may be off NC outer banks starting tomorrow, since it is close to land and over the gulf stream water i would think somewhere further west near 35 n 72 w with possible subtropical formation (forecasts calling for winds 25 knots off the coast) but wxman has proved himself accurate many times and says the 33 66 is where ULL will be and the nhc is being cautious about it working it's way down to the surface in a couple days. also those recon planes may just be anxious to fly somewhere, anywhere