Wed Aug 30 2017 03:17 PM
HUR Katia Lounge

An area of disturbed weather in the southwestern Gulf of Mexico is starting to become evident today. Models over the last few runs have suggested that this feature will become more prominent during the week, with several of the best Tropical Cyclone genesis models' runs indicating formation into a depression or storm by early next week, with a track generally north towards Texas or Louisiana.

This feature seems to be a combination of remnant trailing troffiness in the wake of Harvey + the monsoon trof being drawn northward + one or more African Easterly Waves. Such a combination can easily result in a very wet system, regardless of TC development, and we can only hope the best for locations already ravaged by Harvey.

As of the 200 PM EDT Wed Aug 30 2017 NHC TWO this still region has been highlighted for potential cyclogenesis within 5 days (20% per NHC) -

An area of low pressure could form over the southwestern Gulf of Mexico by the weekend. Development, if any, of this system is expected to be slow to occur as the low moves slowly northward. If this system does develop, it could bring additional rainfall to portions of the Texas and Louisiana coasts. However, any rainfall forecast is uncertain at this time range and it is too soon to determine any specific impacts. Interests in these areas should monitor the progress of this system for the next few days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

This disturbance is not yet Invest tagged, but likely will be this week if current trends continue, and the title will be updated as warranted.

As of Sat 2 September, surface troffiness remains in the SW Gulf, and is continuing to interact with passing waves. Organization has been limited at best since this thread was first started, and the disturbance is still not Invest tagged.

This is where to put mid to long range thoughts on this feature's potential for development, intensity, and forecast track. Longer range model output discussions are appropriate here.

As of 05 0z this low is now being tracked as Invest 95L

201709050000 21.7N 96.2W 25 KTS
201709051800 22.4N 96.8W 30 KTS

13L strengthened overnight and has been upgraded to a tropical storm, Katia. The title has been updated accordingly.

As of the 4PM Sep 6 Advisory, Katia has been upgraded to a hurricane.
4:00 PM CDT Wed Sep 6
Location: 21.7°N 95.1°W
Moving: SE at 3 mph
Min pressure: 992 mb
Max sustained: 75 mph

(Storm Tracker)
Fri Sep 01 2017 09:49 PM
Re: Possible New Development in Gulf

The rain bands coming into Pinellas County tonight, are these from whatever was discussed a few days ago about a possible system in the SW Gulf?

Or will I wake up to a new tropical system out of the blue?

Sat Sep 02 2017 02:58 AM
Re: Possible New Development in Gulf


The rain bands coming into Pinellas County tonight, are these from whatever was discussed a few days ago about a possible system in the SW Gulf?

Or will I wake up to a new tropical system out of the blue?

There is some residual trailing troffiness from Harvey, as well as a cold front, combined with an upper-level trof, that has helped fire convection over Florida tonight.

Tropical cyclone development in the southwestern Gulf from the surface trof out there, if any, will continue to be slow to occur in the near term, due to high wind shear and very dry air, and is not directly related to that rain over Pinellas Co.

(Weather Hobbyist)
Sat Sep 02 2017 10:28 AM
Re: Possible New Development in Gulf

Decent blow-up of convection this morning both in the SW gulf and east of the Yucatán, seemingly at the ends of the trough.

Will be interesting to see if it persists.

Sun Sep 03 2017 01:20 AM
Re: Trof in Bay of Campeche

Troffiness has been persistent in the Bay of Campeche for several days, and a few models' runs are once again sniffing out some development in the southwestern GOM during the coming week.

While not a strong development signal from most runs, we are now in the heart of not just any season, but what by all appearances is a serious one, so this thread will stay up and running until the threat, including that from development - if any - has completely passed.

0z September 3 Model Runs


Possible small, short-lived TD forms just offshore of Tampico, MX by 12z Thursday Sept 7 and gets shunted w/sw/s within 24 hours *in response to Mega Hurricane Irma* passing well to its ENE to NE. (Suffice it to say, if Irma has other plans, this track may not be valid). By Monday Sept 11, its remnants are sent scooting across the Isthmus of Tehuantepec and into the East Pac, dry air pouring down behind it. Possible redevelopment in the East Pac beyond 10 days, and may attempt to track back north through the isthmus around the 14th - 18th.

Rapid development of a TD-TS offshore of Tampico, MX by 12z Monday Sept 4. Shunted off to the E/SE/S in response to Mega Hurricane Irma. Makes landfall as a strong Tropical Storm in the southern Bay of Campeche midday Thursday Sept 7, and then crosses the Isthmus of Tehuantepec and into the East Pac over the next day or so, where its remnants split in two - The easternmost remnant residual vorticity is swept NW-NNW from up and out of the East Pac by Mega Hurricane Irma, and becomes a new TD just south of Cuba Tuesday Sept 12, tracking northwest. The westernmost remnant helps energize a preexisting tropical cyclone (TS) just south of the isthmus, and this TC then crosses back north across and back into the extreme southern Bay of Campeche by 0z Wednesday Sept 13. That all should be enough to make anyone's head spin. Even more so if it verifies!

Possible TD by 06z Wednesday Sept 6 off the coast of Tampico, MX. Tracks SW in response to Mega Hurricane Irma and makes landfall as a TS in the southern Bay of Campeche by 12z Saturday Sept 9. End of run.

Possible TD by 0z Wednesday Sept 4 off the coast of Tampico, MX. Over the next several days is shredded and sent flying SSW across the Isthmus of Tehuantepec and into the East Pac in response to Mega Hurricane Irma.

In summary, if recent Irma forecasts come close to verifying, these genesis models do cook something up in the region, but quickly send it south across Mexico and into the East Pac. We'll be watching.

Mon Sep 04 2017 07:39 PM
Re: Low in SW Gulf

The trof in the southwest GOM is trying to close off - at least near the surface - based on recent satellite trends (as we have not had a recent scatterometer pass to look down at the surface). This Low will likely be designated Invest 95L soon.

Wind shear could be just supportive enough to allow continued organization over the next few days as to allow some meaningful development to occur, and a named storm is possible. Modeling strongly suggests that the US Gulf states north southernmost Texas should be spared any impacts - that this is and will be more of a threat for Mexico - at least in the near to mid range. Beyond seven days there are some indications it could loop back around towards the US, but that remains almost a long shot.

Potential for downstream impacts on Irma track and intensity are TBD.

Maximum sustained winds based on available buoy and ship reports appear to be on the rise - now up to about 30 knots - and pressures are falling. If this low sufficiently closes off and becomes defined at the surface overnight tonight, it is conceivable it could be an officiated TD as soon as tomorrow morning.

Tue Sep 05 2017 01:32 AM
Re: 95L Lounge

Clean ASCAT pass from 0327z. Right where models progged development to begin (this is also a historically favored region for tropical cyclogenesis).

Fairly well defined surface circulation just offshore of Tampico, MX, but showers and thunderstorms remain sparse, fleeting, and insufficiently organized. There is a better chance later today, Tuesday, and tomorrow, Wednesday, of enough of a break in the moderately strong wind shear that has been plaguing this system for some development.

Regardless of development, potentially heavy rains will likely persist over eastern Mexico for much of this week.

Wed Sep 06 2017 06:18 AM
Re: TS Katia Lounge

THIRTEEN became Tropical Storm Katia last night and was upgraded operationally by NHC this morning.

Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1006 mb (29.71 inches).

Katia is forecast by nearly all models, save climos, to drift SE/S/SW into Mexico, where it may strike as a very moisture-laden hurricane later this week. Flooding rains are a probability, regardless whether TS orr HUR.

Sun Sep 10 2017 12:46 AM
Re: HUR Katia Lounge

The Final Advisory was written on Katia at 1000 AM CDT Sat Sep 09 2017. During its lifetime, together with Irma and Jose, helped set all-time records in the Atlantic basin: Daily ACE, number of Cat 2+ TCs simultaneously, etc.

By her own right, Katia attained solid Cat 2 status, with 105 MPH maximum sustained winds and 972mb minimum pressure. In the evening of September 8, Katia made landfall north of Tecolutla, MX.

Perhaps *perhaps* Katia's greatest impact will found to have been a steering influence (or, more aptly, a blocking influence) on Major Hurricane Irma's motion when the historic cyclone unexpectedly more or less came to a crawl just north of Cuba. (Will be looked into by researchers, to be sure). This would have been a byproduct of her outflow invigorating high pressure in the Gulf.

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