Atlantic Tropical Action 2014

[phil882]

92L is certainly intriguing. The circulation still appears to be closed, with a decent amount of westerly winds to the south of the convection over the Bahamas. Note the interesting wind shift that took place in Great Abaco Bahama earlier today. While 10-15 knot westerlies might not sound like much, that's more than what the global models are depicting currently. The easterly winds are likely stronger in the northern quadrant where the deep convection is ongoing. Pressure is still steady around 1014 hPa, but should typically be rising in a typical diurnal cycle. It will be interesting to watch these stations to see if there are any significant changes during the overnight hours. 

 

 

 

There is a really strong shear axis just to its north which is dropping south with time. So I agree 92L will probably have to keep dropping south if it wants to survive. However, I don't think the global models have an adequate depiction of the current organization of the circulation. Small systems like this often fly under the radar so to speak, and sometimes these relatively small llc's that form from upper-level TUTTs can be suprise developers (e.g. Michael 2012).

 

The key though is the convective organization. If it can build a symmetrical cirrus canopy, small systems like this can spin up quickly. If it doesn't do that before the shear hits though, its game over.  

[GaWx]

 Any opinions about this ASCAT pass from two hours ago?

 

 

[wxmx]

It shows nicely there's a closed circulation, and it doesn't look broad, although we can't see the western half. Convection is mostly confined to the NW quad, and it was probably temporarily naked an hour or two ago.

[Superstorm93]

[wxmx]

At a 12.5km resolution, it's clear it's a tight closed low, winds are unimpressive, although some of the convection to the west was not scanned. A 25kt TD case can be argued for 92L

 

[DopplerWx]

 

well then...

[wxmeddler]

well then...

 

Note that that is for 91L out in the eastern Atlantic not the system next to Florida (92L).

[Kory]

Looks like the shear is commencing from the ridge up north.  I don't expect much from it today.  Looks like it should start moving WSW as the ridge is pressing in from the north.  

 

[klw]

That looks like a lot of dry air for this to do much anytime soon.

[Kory]

There's clearly a surface low moving WSW according to this radar.  Looks very weak though.  Freeport International Airport is reporting a west wind at 4.  So the circulation must be just north of the island of Grand Bahama.  

 

[IsentropicLift]

Seems to be two camps this morning. One into the Houston area and the other more towards New Orleans.

 

[wxmx]

As the mid/upper ridge strengthened, so the shear has increased as well. Now we have a decoupled mid and low level vortices. The surface low is still north of the Abaco Islands, while the mid level vortex is moving WSW and is currently north of the Grand Bahama...unless there's a better stacked up low, I expect little development in the short term.

[IsentropicLift]

As the mid/upper ridge strengthened, so the shear has increased as well. Now we have a decoupled mid and low level vortices. The surface low is still north of the Abaco Islands, while the mid level vortex is moving WSW and is currently north of the Grand Bahama...unless there's a better stacked up low, I expect little development in the short term.

Would a stronger ridge to the north lend more confidence in a southern FL track rather than Central FL?

[Srain]

The robust cckw is nearing the Western Atlantic Basin. There is some potential of a 'sleeper' disturbance developing in the SW Caribbean to the Bay of Campeche during the next 7 to 10 days.

 

 

 

[Kory]

As the mid/upper ridge strengthened, so the shear has increased as well. Now we have a decoupled mid and low level vortices. The surface low is still north of the Abaco Islands, while the mid level vortex is moving WSW and is currently north of the Grand Bahama...unless there's a better stacked up low, I expect little development in the short term.

Now that I take a closer look at the radar, I do see two distinct circulations with the mid level one being more SW. It's probably compliments of shear since the main convection is moving SW along with the shear.

[Srain]

The NHC will initiate Advisories for TD 6 in the Central Atlantic at 11:00 AM EDT.

[bluewave]

The NHC will initiate Advisories for TD 6 in the Central Atlantic at 11:00 AM EDT.

 

Latest first TD of the season east of 40W in the Atlantic since 1997.

[GaWx]

I agree that the environment 92L is presently in is quite good. However, shear has been increasing steadily just 100-200 km to its north, and there's also some subsidence in the area. The fact that it's such a small system will make it more vulnerable to a deterioration of its environment. I'd say it's best chance is if it begins drifting southward overnight. A track along the lines of the NAM would probably be ideal.

It looks like the quite good conditions for development that we agreed were there yesterday have deteriorated due to the NE shear that you noted increasing just north of the system last night. It doesn't look as stacked to me now and it didn't take long for this to occur as it was still looking pretty good well into the evening. My prior thinking of 2/3 chance for TD+

while still E of FL is looking quite a bit too high to me now despite there apparently still being a pretty good LLC.

[Eskimo Joe]

TD No. 6 thread:  http://www.americanwx.com/bb/index.php/topic/44458-tropical-discussion-6/ 

[Superstorm93]

300mb winds are definitely starting to increase just to the north of 92L. Has to sink south if it wants to have any shot at developing. 

 

[phil882]

 

Even though the vertical wind shear is increasing over 92L, note that the the upper-levels will also be very diffluent over 92L as the upper-level low to 92L's northeast is causing some upper-level wind vectors to shift back westerly. This is one of the reasons the initial dry air over the region has moistened rapidly the last 12-18 hours. This should also allow convection to continue to pulse which will mitigate the strongest easterly vertical shear the next 24-48 hours. Center relocations south and west further into the deep convection are also entirely possible, and in fact might be trying to occur currently. 

[Superstorm93]

Recon scrubbed. 

 

LLC appears to be to the north of the convection for now. Might have some kind of shift to the south per radar and visible @ 1515 

 

[Kory]

Most wind reports are below tropical depression threshold and the lowest pressure I could find is 1015 mbars.  

[Superstorm93]

CMAN station reporting a pressure of 1017mb to the SW of the LLC...

 

(Also note the amount of lightning occurring...kind of interesting) 

 

[Kory]

We'll probably need that pressure to come down some more to tighten the gradient before we see any appreciable increase in winds. 

[wxmx]

 

 

Even though the vertical wind shear is increasing over 92L, note that the the upper-levels will also be very diffluent over 92L as the upper-level low to 92L's northeast is causing some upper-level wind vectors to shift back westerly. This is one of the reasons the initial dry air over the region has moistened rapidly the last 12-18 hours. This should also allow convection to continue to pulse which will mitigate the strongest easterly vertical shear the next 24-48 hours. Center relocations south and east further into the deep convection are also entirely possible, and in fact might be trying to occur currently. 

west?

 

It appears that the current burst of deep convection is doing the trick.

[IsentropicLift]

What about the system southeast of TD6? That looks pretty good right now as well

 

Edit: looks like that convection has collapsed.

 

[IsentropicLift]

West Palm Beach is reporting winds out of the N. Ft. Lauderdale is reporting winds out of the NW and Miami is reporting winds out of the W. It would appear that we have a broad cyclonic flow established on the western side of 91L.

[Superstorm93]

West Palm Beach is reporting winds out of the N. Ft. Lauderdale is reporting winds out of the NW and Miami is reporting winds out of the W. It would appear that we have a broad cyclonic flow established on the western side of 91L.

 

[phil882]

west?

 

It appears that the current burst of deep convection is doing the trick.

 

Haha yes... I mean west. In any event, I have yet to see a model that currently depicts the current large region of stratiform and embedded convective precipitation. The GFS has no convection over the region that currently has < -60 oC tops. Because the pressure minimum with the system is not that significant, its should be relatively easy for convection to result in a new center formation since there isn't much inertial stability in the circulation. If the convection collapses it could similarly destroy the vortex.