Possible development in Western Caribbean - (Is INVEST 93L)

[cycloneye]

Up to 50%.

A complex area of low pressure is expected to form over the
northwestern Caribbean Sea and the Yucatan peninsula this
weekend. Conditions appear to be favorable for gradual development
of this system while it moves slowly northwestward toward the
southern Gulf of Mexico by early next week.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...50 percent.

[wxman57]

I think that the EC may be closest to what will happen next week. Large disorganized low forms Sunday. By Monday, it's near the northern Yucatan with TS winds through Yucatan Straits into south-central Gulf. Could be upgraded to Bret Monday PM as recon finds TS winds. Low tracks WNW toward NE Mexico, making landfall Thursday. Peak winds 45-50 kts north and east of the low center. These strong winds and heavy squalls move inland north of the low - across S. TX. This reminds me very much of Frances from 1998. Large, monsoonal gyre with a big open center and multiple low centers rotating around. Hard to consolidate into a strong TS or H before landfall.

I'd say we have a 60-70% chance this low will be upgraded to Bret by Monday evening. Higher chances beyond then. Now, when will the NHC begin their "Potential Tropical Cyclone" advisories? They begin once development is likely and TS winds are within 48 hrs of impacting land. That could occur Monday PM as TS wind brush western Cuba, which would mean that advisories might begin Saturday PM. However, I suspect the NHC may wait until Sunday. They said they're not going to try for 48 hrs in advance THIS season, maybe 24-36 hrs in advance of any land impact. And what about the impact to the 10s of thousands of workers across the NW Gulf of Mexico? Do they count as "impact"?

[AtlanticWind]

Could be a spin starting just off the eastern Honduras coast on the morning visible
If this were the case(probably not though)It could change the models.

[srainhoutx]

Thursday morning briefing from Jeff:

NHC has increased the potential for tropical cyclone formation around the Yucatan over the next 5 days to 50%.

Tropical system possible in the Gulf of Mexico late this weekend/early next week

A complicated pattern will evolve across the western Caribbean Sea and southern Gulf of Mexico this weekend which may give rise to the formation of a tropical storm in the Gulf of Mexico by late this weekend or early next week. A tropical wave currently moving through the Caribbean Sea will arrive into the western Caribbean Sea early this weekend while a northward lifting trough off the coast of Panama will interact with this wave. Convection has been increasing over much of the western Caribbean Sea over the last 24 hours and expect a continued increase in thunderstorm develop as these two features interact.

Model agreement from the ECWMF, GFS, CMC, UKMET, and many of the ensemble members show the formation of a very large surface low around the Yucatan over the weekend. While it is certainly possible for such a large surface low to develop into a tropical system, they tend to be very slow in doing so due to the massive size. What tends to be more common is that vorticity centers will rotate around the average low position and can sometimes become the dominate circulation center which can cause a plethora of forecast issues. Overall the organization of such a system takes longer than normal and can remain a disorganized mess. Several Gulf systems have developed this way and the main important feature from a system like this is to spread out the impacts over a wide area.

While the land interaction of the Yucatan will play some role in how this system develops and likely when, the overall model consensus and large size of the system should be able to overcome the interaction with the Yucatan. There is certainly enough support to have some confidence that a tropical depression or tropical storm will be forming in the south/south-central Gulf of Mexico by late this weekend.

The track of any developing tropical system will hinge on the ridge axis across the SW US and how far east that ridge axis may extend into TX. Additionally, the position of the mid and upper level ridge across the southern plains and where/how strong a weakness in this ridge over the W/NW Gulf by early next week. Models have been trending toward a ridge axis further to the north than previously expected along with the formation of an upper level weakness over the western Gulf of Mexico. This would likely help to bring any S/SC Gulf tropical system toward the WNW/NW into the western or northwestern Gulf of Mexico. It should be noted that some of the model guidance brings a stronger system more quickly northward toward the central and eastern US Gulf coast caught in the tail end of a trough over the Great Lakes. This solution appears less likely given the fact that the developing system will likely be disorganized and not as strong as those models are forecasting.

Most confident solution at this time is to bring a tropical depression/tropical storm away from the NW coast of the Yucatan Sun/Mon on a WNW motion and into the SC Gulf of MX Tues/Wed and then into the W Gulf of MX by the end of next week. A large mass of potential tropical storm force winds may cover much of the central Gulf of Mexico by the middle of next week.

Points of Interest:

o Actual formation of the surface center may be key to track…but may not be as important as with other systems…given the very large size
o Large size of the system will have far reaching impacts
o Land interaction will complicate development over the weekend
o Track is still uncertain

Possible TX Impacts:

It is too early to be certain of any impacts along the TX coast given the uncertainty in the track forecast and what shape the system gradually develops into. Following the WNW track coordinated by NHC and WPC overnight into the western Gulf of Mexico middle to late next week would bring some degree of impacts toward the TX coast.

o Seas will likely begin to respond as early as Tuesday especially if the large mass of TS force winds forms across the northern semi-circle of the system
o As seas increase so may tides as more water is brought toward the coast in larger swells. Additionally winds will back to a more ESE/E direction across the northern Gulf which is a favorable tidal increase direction for the TX coast
o At some point could see a significant increase in moisture into TX if the center reaches the western Gulf allowing deep ESE flow through the column to transport copious moisture toward the coast.

Impacts, if any, will continue to be defined and clarified over the coming days.

Residents along the Gulf coast should closely monitor the progress of this system. Now is the time to make sure hurricane preparation plans and kits are fully stocked and in place.

[Tireman4]

From HGX this morning...

TROPICAL...

There`s not much to be said at this point about the tropics that
astute watchers of the weather don`t already know (as the readers
of this AFD likely are). There is a pretty decent looking wave in
the eastern Atlantic and another about to exit Africa, but it`s
probably a little early for main development region activity.
Regardless, tons of time to monitor anything that far east.

Our Yucatan region has gotten a bump up to 40% for development in
the next 5 days from NHC. There`s certainly some potential here,
and we`ve given it the focus of this section in previous days. But
the expectation continues to be for any low pressure center to be
week, and stay confined to the southern Gulf with no direct
impact to our area. As yesterday`s 00Z Euro showed, there may be
avenues for that to change, but is also a caution against putting
much/any stock in individual runs of deterministic models at this
range. Something to watch, a good reminder to complete those
seasonal preparations, not something to stress over at this point.

[Steve]

I think that the EC may be closest to what will happen next week. Large disorganized low forms Sunday. By Monday, it's near the northern Yucatan with TS winds through Yucatan Straits into south-central Gulf. Could be upgraded to Bret Monday PM as recon finds TS winds. Low tracks WNW toward NE Mexico, making landfall Thursday. Peak winds 45-50 kts north and east of the low center. These strong winds and heavy squalls move inland north of the low - across S. TX. This reminds me very much of Frances from 1998. Large, monsoonal gyre with a big open center and multiple low centers rotating around. Hard to consolidate into a strong TS or H before landfall.

I'd say we have a 60-70% chance this low will be upgraded to Bret by Monday evening. Higher chances beyond then. Now, when will the NHC begin their "Potential Tropical Cyclone" advisories? They begin once development is likely and TS winds are within 48 hrs of impacting land. That could occur Monday PM as TS wind brush western Cuba, which would mean that advisories might begin Saturday PM. However, I suspect the NHC may wait until Sunday. They said they're not going to try for 48 hrs in advance THIS season, maybe 24-36 hrs in advance of any land impact. And what about the impact to the 10s of thousands of workers across the NW Gulf of Mexico? Do they count as "impact"?

Frances flooded the **** out of New Orleans. That was a wild afternoon where I got stuck trying to get out of downtown and had to camp it for a few hours on a neutral ground. It had that feeder moisture wrapping around. I've been scared of weaker tropical storms off of Brownsville ever since. It was also a large storm area-wise which Jeff Masters apparently says could happen again. I don't even know what this key code for rainfall is, but it rained and rained and rained until it flooded all over the city that afternoon. Edit to say 22+ inches in Terrytown which is just across the river about 3 miles from where I worked downtown. http://www.wpc.ncep.noaa.gov/tropical/r ... ainblk.gif

[gatorcane]

Yes can't discount ECM being on it's own....as it's correctly predicted the outcome in the past being the lone rider. Wait and see time...still 5-6 days out.

The UKMET is also BOC then Mexico-bound:

[Steve]

I think so too. Per Daily Update graphics, Joe B shows a ECMWF Product that is now showing over 60% chance of development. Rainfall swaths are mostly on the East Side in Central and Western LA and across the Gulf. EC has it come up into the central gulf and then hook westerly and then come up a little northerly toward the end.

The FL models, and particularly the CMC as discussed last night with the 00z run, don't have the system waiting around by the Yucatan or Central America. It just comes up quickly (6 day range) and hits. 00Z run of the CMC landfalls around Santa Rosa County (so a bit farther west again on that run) around 174 hours. That's 7.25 days from the run which would put landfall around next Wednesday at midnight or so as a pretty significant system. Looks like landfall is a relatively slow process with the system just offshore and impacting the Western Panhandle and points east of there for 30+ hours.

12Z GFS derived QPF shows the heaviest 7 day total of rain in the center of the Gulf due South of the FL/AL border and across the Peninsula. Looks like some more drought busting rains if that's the case (has 3.8" maximum coming up from like Naples to Ocala).
http://www.wpc.ncep.noaa.gov/qpf/p168i.gif?1497534723

Joe also said he think he's going to have to up his ACE and possibly Named Storms. In addition, and this would go in the indicators thread, but the JMA September Pressure Anomaly looks bad for the entire Western Atlantic Basin and Gulf of Mexico. If it's right or partially right, could be a rocky ride through what is usually the busiest month.

[Stormcenter]

Sounds like you are buying into the EURO run. I still say it's way too early to call anything. I'll stick with your Mexico to Florida earlier week prediction for now.

I think that the EC may be closest to what will happen next week. Large disorganized low forms Sunday. By Monday, it's near the northern Yucatan with TS winds through Yucatan Straits into south-central Gulf. Could be upgraded to Bret Monday PM as recon finds TS winds. Low tracks WNW toward NE Mexico, making landfall Thursday. Peak winds 45-50 kts north and east of the low center. These strong winds and heavy squalls move inland north of the low - across S. TX. This reminds me very much of Frances from 1998. Large, monsoonal gyre with a big open center and multiple low centers rotating around. Hard to consolidate into a strong TS or H before landfall.

I'd say we have a 60-70% chance this low will be upgraded to Bret by Monday evening. Higher chances beyond then. Now, when will the NHC begin their "Potential Tropical Cyclone" advisories? They begin once development is likely and TS winds are within 48 hrs of impacting land. That could occur Monday PM as TS wind brush western Cuba, which would mean that advisories might begin Saturday PM. However, I suspect the NHC may wait until Sunday. They said they're not going to try for 48 hrs in advance THIS season, maybe 24-36 hrs in advance of any land impact. And what about the impact to the 10s of thousands of workers across the NW Gulf of Mexico? Do they count as "impact"?

[lrak]

From Corpus Christi LT forecast

Remainder of extended forecast period is strongly contingent upon
how much the mid level ridge builds back into the region and what
effect the upper level pattern /particularly shear/ may have on a
potential tropical disturbance which may move into the southern Gulf
from the NW Carib. As of writing, NHC indicates a disturbance may
develop and slowly move into the southern Gulf next week with a
medium chance of organization occurring. Guidance suites then
provide a variety of solutions regarding handling of the disturbance
once it is in the Gulf. Most suites do, however, indicate that some
deeper moisture may begin to approach the W Gulf by next Wednesday
which could result in an increase in shower activity along the
coast. At this time it is way too early to speculate what impacts
/if any/ this potential disturbance may bring to the Gulf of
Mexico or Texas.

[PTrackerLA]

Local news station showed this graphic of rainfall potential from the 00z Euro. The Hi-res precip totals on weatherbell have hotspots of 15".

[wxman22]

Even though yesterdays 12z Euro and this mornings 0z Euro runs show the system making landfall in Mexico the majority of the moisture is well away from the center, showing very heavy rainfall across Southeast Texas and Louisiana. Which reminds me alot of Frances in 1998 which I lost my house due to flooding here in Houston i believe due to White Oak Bayou, i remember the water being so high that we had to be rescued by boat.

[Kingarabian]

00z Euro Paralell has this north of the Yucatan peninsula, moving NE. Then it quickly gets blocked at around hr 120 and moves WSW toward the WGOM. Bottoms out at 1001mb and then rapidly weakens in the BOC/WGOM before moving over the Mexico/TX border.

[wxman57]

Sounds like you are buying into the EURO run. I still say it's way too early to call anything. I'll stick with your Mexico to Florida earlier week prediction for now.

Yea, I think the Euro and most of its ensembles have the right idea in bringing a weaker system WNW toward NE Mexico. I agree completely with Jeff Lindner's discussion, above. It's like he was reading my thoughts.

I don't have the luxury of waiting until it develops to issue a track. Offshore clients (NW Gulf) need as much as 5-7 days to prepare for impact. Have to commit to a track today. We're initiating advisories after the 12Z model data come in. Could see TS winds affecting our clients off the mid-LA waters (deepwater areas) by noon Tuesday.

Note that although this low may turn out very similar to 1998's Frances, It may be a few hundred miles farther south, meaning less of a risk of heavy rain impacting south Louisiana and a greater risk to the lower to mid TX coast. I'm not ruling out the potential for some heavy rain as far north as south Louisiana yet, though.

[gatorcane]

12Z Parallel MU stronger in the Eastern Gulf:

[weathaguyry]

GFS has vorticity north again

[JtSmarts]

I'm getting flashbacks to Debby 2012 when the Euro was west and the GFS was east, and the GFS shockingly ended up being right. I'd bet this time that the Euro has the right idea though.

[cycloneye]

@EricBlake12
Starting to get that nascent shape in the western Caribbean with the primitive bands and broad turning- No doubt #hurricane season is here!

 https://twitter.com/EricBlake12/status/875386823266226176

[Stormcenter]

Well it will be interesting to see what the EURO shows this afternoon. I for one have not been sold on that westward Mexico track.
I guess we may have a battle of models if the EURO sticks to it's guns.

[gatorcane]

CMC simulated IR - a lot of rain for Florida if this verifies! CMC/GFS Para would follow climo here but skeptical of EGOM solution still, UKMET/ECMWF favor BOC/Mexico. By the way the CMC has shifted east: