Western Caribbean Area of Interest: (Is INVEST 90L)

[LarryWx]

I have yet to be in the likely to develop camp nor in the hurricane camp (both based on climo), but I did go into the "increasing threat of a TS to FL" camp yesterday when I noted the near unanimous ageement of the models for a tropical low to form in the NW Caribbean near day 7 (5/24). If anything, today that TS threat has fallen back some but there still is a low (more than minute) chance imo. I'm near 5% for a FL TS hit currently. Weak model progs along with climo and knowing that the Gulf has recently not been all that warm are keeping it down as there's a much greater chance that there will either be something weaker than TS, maybe even nothing organized, or maybe even a miss of FL.

Climo to keep in mind: There have been only 5 TS and no H on record to form in the W. Car. or GOM during 5/21-31 since 1851. So, that's only 5 in 167 years or 1 in 33 chance/3% of there even being a genesis. Only 1 of those 5 hit FL. So, only 1 in 167 years had a FL TS hit or well under 1%. So, even going with a 5% chance of a FL hit in 2018 in deference to the model consensus of a threat of something is WAY, WAY above the longterm climo based chance.

The 5 W Car/GOM 5/21-31 geneses on record since 1851:

- 5/30/2008
- 5/28/1959: hit LA at 40 knots
- 5/25/1953: hit FL at 40 knots
- 5/27/1890
- 5/29/1865

They're rare Larry no doubt but I think with this much model support - pretty much every major global model (GFS, FV-3 GFS, GEM, ECM, NAVGEM. and ICON) are on-board with low pressure development. So these globals are sniffing out an environment conducive for development. To me with this much model support in 5-7 days, something will develop and become either a TD or TS. i think Hurricane unlikely given the time of year. Track uncertain but somewhere in the SE GOM in 5-6 days and then from therefter too far away to know.

In deference to this model agreement, I'm currently near a respectable 1 in 3 chance for a TD to form next week either in the W Car. or in the GOM, which is quite high in that area for late May, but still only near a 5% chance for a subsequent FL TS hit. So, I'm saying that IF a TD forms next week, there's about a 1 in 6 chance for that TD to hit FL as a TS. That's how I get my 5% FL TS hit chance.

[Shell Mound]

Fun fact: if nothing forms, then 2018 will be the first season since 2014 to not feature at least one pre-season TS or stronger.

[LarryWx]

yeah still over a week away

That's the key. We're still talking about something that is about 8-9 days out even if it something, and moreover, this would be in late May, when only 1 in 167 years has had a FL TS hit from the NW Caribbean or Gulf. Assuming that one knows 167 years of late May climo, to go any higher than, say, a 10% chance for a FL TS hit as of now would be crazy imo. I'm sticking to a 5% chance, which itself is 8 times the longterm climo based chance of 0.6%.

If, say, there were already a TC in the W Caribbean and if, say, the models were unanimously showing a TS hit on FL in 3 days, I might then go with a FL TS hit being likely despite only 1 in 167 years having had that kind of hit. But right now with it being modeled ~8 days out and still nothing close to a TC yet, no way I'd go anywhere close to likely!

Early June has had plenty of Florida TS hits though. A few days will not make a huge difference. But I agree that it is still a bit out but it looks very likely that at least some sort of low will form.

But comparing late May to early June geneses actually has actually seen a big difference when looking at history: over 3 times the late May W Car/GOM genesis rate in early June. I think that's too large to ignore.

May 1-10: 2
May 11-20: 4
May 21-31: 5
June 1-10: 16
june 11-20: 26

[AtlanticWind]

EXTENDED FORECAST... The deep tropical moisture is forecast by the long range models to return to South Florida late next week from the south that is associated with a tropical disturbance in the western Caribbean sea moving northward into the Southern Gulf of Mexico. Therefore, showers and thunderstorms should increase in coverage again late next week with the possibility of heavy rainfall over South Florida.

From NWS Miami discussion

[cycloneye]

Edit: Changed title to Western Caribbean as the focus of some sort of development in the next few days will be there.

[cycloneye]

Main hazard regardless of any development will be the copious rains.

@weatherbell
Regardless of tropical development over the next 10 days, plenty of moisture will be in the Southeast and plenty of rain.

 https://twitter.com/weatherbell/status/997568266213253120

[gatorcane]

low-resolution JMA send this into the South-Central GOM. This marks the first run the model really has picked up on genesis:

[StruThiO]

didnt see this posted already

 https://twitter.com/ToddKimberlain/status/997531192953106434

[cycloneye]

The possible trigger.

[wxman57]

FYI - 12Z EC ensembles give this area a 42% chance of development (TD or greater) in the Gulf. GFS ensembles are at 86%. Big spread in EC ensembles now - from central Louisiana to south Florida. 2/3 of GFS 20 ensembles take it to SW Florida, 1/3 to SE LA.

GFS ensembles give this system a 10-20% chance of becoming a hurricane, EC ensembles less than 10%. GFS gives it a 50-60% chance of a TS, EC is 10-20% chance of TS or greater.

[chris_fit]

18Z GFS looks to be a little more east....

[northjaxpro]

18Z GFS run moves the potential sheared 1003 mb tropical cyclone over South Florida in 174 hours, then moves it off shore the Florida East Coast, making landfall as a 998 mb TS on the South Carolina coast in 210 hours.

[Tampa Bay Hurricane]

I’m not an expert at all- just an amateur- but I think this system could pose a dangerous flood threat and severe weather threat like Debby 2012 was if it tracks just west of Florida.

Regardless of development- excessive rainfall and flooding will impact Florida. I expect a foot of rain at least in addition to what has already fallen this week.

I think we will have a storm that comes up along the west coast or just west in the eastern gulf bringing massive amounts of rain and tropical storm conditions to much of the Florida peninsula. The biggest threat will be rain and flooding. Euro is pretty solid on a Florida peninsular soaker. Gfs and fv3 have been alternating between central gulf and east of Florida solutions- a mean path would be eastern gulf just west of the peninsula giving everyone from key west to Jacksonville heavy rain and some gusty winds. Rain will be the big story by far. With all the model consensus I’d say nearly 100% chance of development, 90% chance chance of heavy rain and wind for most of the Florida peninsula, 20% chance that it will make a run for hurricane status. Shear will drop rapidly over the gulf, and with the column moistening over the gulf due to the convective conveyor belt of this past week and all the moisture now established over Florida and westward to the central Gulf, dry air and shear will not be much of a problem, if any.

[northjaxpro]

Pretty much agree with all you said. I also favor the Eastern Gulf solution as well. We could be looking at dangerous potential of severe flooding over the Florida peninsula next week, especially if the Eastern Gulf potential track pans out. There will also be the threat of tornadoes as well over the region.

The Memorial holiday weekend does not look good for us here in Florida as it stands right now.

[cycloneye]

00z GFS tracks to the east of Florida after it moves thru Cuba.

[Tampa Bay Hurricane]

Gfs has an easterly bias due to its developing and intensifying a potent convective cluster to the northeast of the developing cyclone while it is in the Caribbean. This spurious convective cluster acts as a low itself and results in the gfs sending the storm much further east. For this reason I think a track along or just west of Florida is still the most reasonable, like what the 12z euro depicts. The euro is more reasonable because it does not create a spurious cluster to the northeast of the low. A track just west of the peninsula would bring heavy rain and some gusty winds for all of the peninsula, although heavy rain would be the most powerful impact.

[BobHarlem]

The ECMWF is very much west this morning and much weaker. I'm not sure how this system is going to be much more than a sloppy heavily sheared blob.

[northjaxpro]

I think this system overall likely will be a sheared, lopsided tropical cyclone, probably similar to T.S. Debby in 2012. I think like Debby turned out to be, this potential system could be a potential dangerous flooding disaster in the making over Florida next week during the Memorial holiday weekend.

Latest 06Z GFS is showing broad Low Pressure to slowly move north along the Florida East Coast with the lowest pressure shown to get down to about 1000 mb as the storm approaches Jacksonville by 210 hours.

I still am favoring the recent EURO solutions of a Eastern GOM potential track, which if this projected track were to materialize would be the worst case scenario for the peninsula, as the entire region would be on the right side of the storm center.

06Z GFS run did slightly shift left(west) this run as compared to the past couple of runs.

[Shell Mound]

The ECMWF is very much west this morning and much weaker. I'm not sure how this system is going to be much more than a sloppy heavily sheared blob.

Rather than Debby (2012), I'm thinking that any *potential* TS will end up like Colin (2016): a system so disorganised, lopsided, and sprawling that people will be wondering whether it was really a classifiable TC. As of now, however, I'm siding with LarryWx and his always-edifying historical statistics, and so I believe that "no development" is the most probable option at this point in time. The ECMWF is pushing actual closed-low genesis farther back in time and farther northwest with each passing run. The Gulf is unlikely to be more favourable for development than the Caribbean, so the model trends actually tend to mitigate rather than enhance the prospects of a system forming. Just my two cents...

[cycloneye]

Well,at least FV3 doesn't have a cat 1-2 hurricane in the past two runs.