ATL: Tropical Depression Fay

[Scorpion]

Looks like convection might be trying to wrap around the center.

[Just Joshing You]

Usually a Depression is too disorganized to have anything "wrap" around anything, and this isn't even a TD.

[alan1961]

Think its feeling the effects of the ridge above it now..its looking a little flattened on its northern side due to the little jog that way..can only think this can go more WNW now..notice theres not much if any convection flying up off to the NNE/E and its pulling in some moisture on its southern side, is 92L ready to take off?

[MiamiensisWx]

The following post is NOT an official prognosis.

Convection in the vicinity of the low level circulation has increased over the past ~10 hours. Based on available data, the development of strong convection/thunderstorms was definitely related to decent ascent, which was adjacent to the upper level divergence provided by an upper low farther north. Low level convergence in the vicinity of the wave axis has also aided convection. Over the past ~24 hours, the proximity of the surface low (associated with 92L) to the upper low's divergence has been resulting in shear over the system, as evidenced by the sharp "boundary" on the southern semicircle. Note that additional convection has struggled to develop on the south side, as strong upper level winds "knocked down" the tops of the developing cumulonimbus cells. Outflow from these (southern) cells also sheared the convection juxtaposed over the region of ascent farther north, so we have not witnessed substantive development away from the best ascent. The concentration of convection is the sign of a curse, but it may also be the hint of a "blessing" for development: as convection is developing closer to the upper low, the strong divergence/shear may slowly start to provide ventilation and outflow. Conversely, a location farther south would have resulted in greater relative shear over the system. Another important trend is the changing upper air regime. Over the next ~24-30 hours, the upper low at 300 mb is anticipated to slowly fill and move NE, as the vorticity maximum and associated longwave trough over the Northeast enters the Atlantic. In other words, the synoptic environment will likely transition to a more conducive set-up for very slow development. I expect 92L to attain TS status prior to moving over the eastern Caribbean islands, though it will likely not intensify above marginal or moderate TS strength.

My original prospects on the general track/heading remain relatively unaltered. Based on the progged and documented H5-H85 steering, a general path through the southern Leewards toward Puerto Rico and the extreme eastern coastline of Hispaniola appears probable. Note that there will likely be large scale ascent over the system; with decent instability and local orographic lifting, thunderstorms could produce locally heavy precipitation over all of the Leewards and Puerto Rico, in addition to portions of Hispaniola. Residents should remain alert within these regions. Down the line, the track beyond the islands is extremely difficult to determine. The strength and location of the Midwest cutoff low (progged by the Euro, operational GFS/ensembles, and others) around day five is extremely crucial. The Euro and GFS ensembles have been consistent with a less amplified solution, which would lead to a path farther south. However, the operational GFS has been depicting a well defined cutoff low at 500 mb, which would partially contribute to a weaker H5 ridge over the western Atlantic because of longer wavelengths. The timing of 92L's arrival over the southern Bahamas will be very important as well; an earlier arrival would lead to better chances of a threat north of Florida (specifically the Carolinas), while a "delayed", slower solution would result in a track farther south toward the peninsula. The intensity/deepening of 92L and the strength of the ridging at all levels will be paramount, too.

One thing is increasingly plausible: 92L will likely track slightly farther east within the short/medium term, which will likely result in a "scrape" (as opposed to direct hit) with Hispaniola. This is very significant, as this trend would support a stronger system as any developing inner core remains off the eastern coast of the island. I also concur with the general solutions depicted by the GFDL and HWRF within the short term, though I personally anticipate a track slightly farther south over Puerto Rico and just east of Hispaniola.

[cheezyWXguy]

Think its feeling the effects of the ridge above it now..its looking a little flattened on its northern side due to the little jog that way..can only think this can go more WNW now..notice theres not much if any convection flying up off to the NNE/E and its pulling in some moisture on its southern side, is 92L ready to take off?

I dont know, but convection is beginning to warm again. Its more likely reform convection again tonight than last night. One thing Ive noticed is that when a storm is covered in popcorn convection then it likely means that there wont be much development over the next day. But when convection is more condensed then it means its more likely to strengthen.

[HURAKAN]

Looks pretty good. I would like to see it last until tomorrow before making any call on it. I still have Fay in it.

[OURAGAN]

I think the center is SW of the main convection.
The bouy 41NT0 - NTAS as a reading pressure of 1008 mb and the pressure is falling..

[Sanibel]

Dolly sputtered for a long time when it was in this phase.


I don't need to name a certain August storm that started weak and got taken under a strong ridge west into Florida.

[alan1961]

I know one thing..its about time they adjusted the floater on 92L..its almost going out of view

[HurricaneHunter914]

Looks pretty good. I would like to see it last until tomorrow before making any call on it. I still have Fay in it.

If it can maintain the organization it has, we could most likely see a TD tomorrow. It looks really good tonight with banding features on the north side and moderate to high convection. I hope the shear doesn't get to it.

[cycloneye]

[ConvergenceZone]

I would think that between both waves and all that moisture within the waves, something has to pop...

[Sanibel]

East coast WV Loop:

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

[alan1961]

its probably a good thing that its took a slight jog to the north instead of going due west, if it went due west think it would be goodnight josephine if that mess beyond the islands is still hanging about in 2/3 days time.

[curtadams]

Man, this is so reminiscent of Dolly! Convection keeps running away from the LLC (such as it is) and keeping it disorganized.

[Ed Mahmoud]

I hate that they ruined the IR2, for the floaters only.


Maybe I can see West to East motion in the low cloud elements suggesting a center at the Southern edge of the convection, but I'm not certain.

[cycloneye]

Its moving more slowly at 9kts per 00:00 utc guidance.If it continues to move in a relative slow pace,that will allow the ridge to build to its north causing the extreme Northern Leewards to be in the bulls eye.Lets see if it picks up foward speed and avoid the islands.

[Sanibel]

The curving convection on the very west side looks like it could be compressing as it pulls under a ridge.

[lonelymike]

Don't a lot of models have a history of overestimating the ridge strength and vice versa with troughs?

[alan1961]

oh well..off to bed ..been watching 92L all day and night spluttering and farting its way west..why oh why do you do this to us