Tropical Depression Don

[David Reimer]

Looks like a WP-3D was flown down to Tampa this afternoon.

[phil882]

Shear in the NE Gulf will need to subside for any meaningful development...maybe RECON will find a TD…

I agree.

Shear has increased somewhat.

Not sure what you guys are referring to with respect to shear currently. There is a bit of westerly flow over the Yucatan, but most of the Gulf has deep layer easterlies. If this storm has shearing problems in the Gulf of Mexico, it will be from the east, and this should be mitigated somewhat due to the fact the storm will be moving towards the west.

[turtlehurricane]

Looks like a WP-3D was flown down to Tampa this afternoon.

They were returning from missions into Dora in the east pac. There is definitely discussion on flying into 90L though.

[Scott747]

0z package. Best guess at track and intensity if one was put out. Matagorda Bay, minimal hurricane if that -

[David Reimer]

Nothing that hasn't been said here, but for a general summary of the present state of Invest 90L and possible impacts to Texas.

http://txwx.co/q2by9m

[dan88]

Buoy 42056 has 21kt winds (27kt gusts) out of the Southwest now, showing signs that it is in the process of developing a surface circulation.

Location of the Buoy is very close to 20N 85W

IR image within 5 minutes of the observation

[phil882]

Microwave is still a bit inconclusive although the lower cloud motions suggest a broad circulation. Meanwhile radar is showing an interesting cluster of thunderstorms right around 21N 85W... seems like organization is continuing. My hunch is that they go 50% at 2am, although if it were me, I'd be at code red by this point.

[phil882]

From the buoy with the SW winds... nice pressure drop as well (down to 1009-1010mb)

[Superstorm93]

Very intense tops over the suspected circulation...

[dan88]

Got a cherry

1. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE OVER THE

NORTHWESTERN CARIBBEAN SEA JUST TO THE SOUTH OF THE WESTERN TIP OF

CUBA HAVE BECOME BETTER ORGANIZED OVER THE PAST FEW HOURS...AND

SURFACE OBSERVATIONS SUGGEST THAT A CIRCULATION COULD BE FORMING

ABOUT 125 MILES EAST OF CANCUN MEXICO. IF THESE TRENDS CONTINUE...

A TROPICAL DEPRESSION COULD DEVELOP LATER TODAY. INTERESTS IN THE

NORTHEASTERN YUCATAN PENINSULA SHOULD MONITOR THE PROGRESS OF THIS

SYSTEM AS IT MOVES WEST-NORTHWESTWARD NEAR 15 MPH. THIS SYSTEM HAS

A HIGH CHANCE...70 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING

THE NEXT 48 HOURS.

[HurricaneJosh]

Ch-ch-ch-cherry time!1!

[Superstorm93]

Fat cherry!

000

ABNT20 KNHC 270535

TWOAT

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

200 AM EDT WED JUL 27 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE OVER THE

NORTHWESTERN CARIBBEAN SEA JUST TO THE SOUTH OF THE WESTERN TIP OF

CUBA HAVE BECOME BETTER ORGANIZED OVER THE PAST FEW HOURS...AND

SURFACE OBSERVATIONS SUGGEST THAT A CIRCULATION COULD BE FORMING

ABOUT 125 MILES EAST OF CANCUN MEXICO. IF THESE TRENDS CONTINUE...

A TROPICAL DEPRESSION COULD DEVELOP LATER TODAY. INTERESTS IN THE

NORTHEASTERN YUCATAN PENINSULA SHOULD MONITOR THE PROGRESS OF THIS

SYSTEM AS IT MOVES WEST-NORTHWESTWARD NEAR 15 MPH. THIS SYSTEM HAS

A HIGH CHANCE...70 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING

THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS

[jrips27]

Cherry! RECON will be very interesting for sure!

[Brent]

I like the potential of this...

[peribonca]

looks like the presumptive COC is heading almost due west at this point looking at radar

[Floydbuster]

Looks like development may occur while still in the Caribbean Sea

[Scott747]

Looking good -

[HurricaneJosh]

Looking good -

Wait a second-- you feelin' OK?

[Superstorm93]

Impressive.

[Floydbuster]

Sea surface temperatures are boiling

[OHweather]

90L Forecast/discussion:

A current look at 90L reveals a relatively small area of intense and somewhat banded convection. Best estimate for a potential weak surface circulation is just north of 21N, 84.5 west based on earlier microwave/radar imagery and extrapolation based on 6-hour shortwave IR satellite loops.

The most recent and aforementioned microwave data shows a small area of intense convection with a potential circulation trying to develop with banding attempting to wrap around near 21.2N, 84.2W, at a little after 1z. This is certainly much improved organization since Monday afternoon.

Owing to a significant part of this organization is a small area of low shear, generally around 10 knots, that the invest has been traversing, which combined with good outflow especially to the north has created a favorable upper level environment for further organization over the past 24-36 hours. This looks to continue, as the invest moves WNW over the next day at about 15MPH.

The shear over the Gulf of Mexico is caused mainly by a TUTT over the Bay of Campeche that is continuing to retrograde and weaken, as it has moved from near the tip of the Yucatan to near the main Mexican coast over the past 48 hours. This is causing a gradual decrease in shear, which is evident on the 24 hour shear tendency map:

The global models continue to gradually weaken vertical shear over the northern/central Gulf over the next 24-48 hours, leading me to believe the invest will deal with a marginally favorable 10-20 knots of shear for most of its trek across the Gulf of Mexico.

The 0z GFS continues the trend that has shown up on the majority of global models for days now by weakening shear generally below 15 knots over much of the Gulf in time for the system to move through. Given the large upper level anti-cyclone camped over the southern US, this seems reasonable given the TUTT continues to retrograde into Mexico.

Given fairly low shear is expected over the Gulf of Mexico, the only other issues to worry about are large scale subsidence due to the MJO pulse over the western Pacific and some dry air.

Dry air is moving westward into the Bahamas and towards Florida currently.

The 12z ECM clearly shows this dry air moving into the Gulf of Mexico in the coming days, which seems reasonable given an easterly flow on the south side of a large high over the southern US. This will likely have some negative impact on 90L down the road, especially since the system has had a tendency—even Tuesday/this early morning—to not maintain consistent deep convection, with a clear up and down pulsing evident for much of the life of this system.

For the intensity forecast will go with gradual intensification, at about 15 knots per day through landfall. This is generally in line with most of the model guidance if not a little stronger than the consensus, but seems reasonable given a favorable upper level environment for intensification above very warm waters but with some dry air possibly limiting convection at times. This yields a strong TS/weak Cat 1 at landfall.

90L has been steered by a tight gradient on the southern side of a middle-Atlantic ridge of high pressure, which has resulted in a brisk WNW motion over the past few days. The invest has slowed in response to a weakness in ridging due to a trough along the US East Coast, and may also turn slightly right if it begins intensifying soon.

The general global model consensus has been for the ridge to re-intensify, as the trough along the US west coast weakens and flattens the ridge slightly over the Plains, forcing less troughing and more ridging farther east. The 12z ECM shows this well, with no evidence of a weakness in ridging and a rather brisk flow on the southern side of the ridging over the Gulf of Mexico:

This will likely result in about a 15kt/WNW heading through landfall, which takes it towards southern Texas. This is south of the ATCF consensus, but makes sense given building ridging to the north of the system.

Forecast track/intensity:

[phil882]

Good morning everyone... here are my latest thoughts with 90L. I think its well on its way to development, and I'm favoring a more southern solution since I think this will be a vertically deep system that will feel a greater influence of the mid and upper level flow (unlike what the GFS thinks). This is more in line with the current run of the ECWMF. At this point I'd hate to speculate on intensity until we have a developed system, but hurricane intensity is a distinct possibility.

http://philstropicalweatherblog.wordpress.com/2011/07/27/invest-90l-on-its-way-to-tropical-cyclone-status/

[phil882]

Looks like the radar in Cancun is up... and it shows a poorly organized llc.

[dan11295]

The truth is we really need this to land somewhere in S. Texas between Brownsville and Corpus where few people live ala Bret. Texas really needs the rain.

[David Reimer]

The truth is we really need this to land somewhere in S. Texas between Brownsville and Corpus where few people live ala Bret. Texas really needs the rain.

It won't make much difference where it makes landfall. There may be a localized area of hurricane force winds, but the small core should prevent a large area of significant winds and even then they won't likely be enough to produce much damage. I'm honestly hoping it makes landfall closer to Corpus because I really don't want to risk going as far south as Brownsville due to the crime issues going on. A vehicle with a few thousand dollars of electronic equipment isn't exactly what I want to have if I'm in Brownsville.

Here's a morning view at Future Don.

[blazess556]

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

800 AM EDT WED JUL 27 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE NEAR THE

YUCATAN CHANNEL CONTINUES TO BECOME BETTER ORGANIZED...AND RADAR

DATA FROM MEXICO SUGGESTS THAT A CIRCULATION COULD BE FORMING ABOUT

50 MILES NORTHEAST OF CANCUN. IF CURRENT TRENDS CONTINUE...A

TROPICAL DEPRESSION COULD DEVELOP LATER TODAY. INTERESTS IN THE

NORTHEASTERN YUCATAN PENINSULA...AS WELL AS THE CENTRAL AND WESTERN

GULF OF MEXICO...SHOULD MONITOR THE PROGRESS OF THIS SYSTEM AS IT

MOVES WEST-NORTHWESTWARD NEAR 15 MPH. THIS SYSTEM HAS A HIGH

CHANCE...80 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE

NEXT 48 HOURS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS

SCHEDULED TO INVESTIGATE THIS SYSTEM LATER TODAY.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER BEVEN

[metalicwx366]

Good morning everyone... here are my latest thoughts with 90L. I think its well on its way to development, and I'm favoring a more southern solution since I think this will be a vertically deep system that will feel a greater influence of the mid and upper level flow (unlike what the GFS thinks). This is more in line with the current run of the ECWMF. At this point I'd hate to speculate on intensity until we have a developed system, but hurricane intensity is a distinct possibility.

http://philstropicalweatherblog.wordpress.com/2011/07/27/invest-90l-on-its-way-to-tropical-cyclone-status/

Great tropical weather discussion phil!

[RaleighWx]

For those interested, my morning thoughts. Thanks for reading.

http://www.examiner.com/weather-in-raleigh/tropical-wave-nearing-tropical-depression-strength-caribbean

[RaleighWx]

Good morning everyone... here are my latest thoughts with 90L. I think its well on its way to development, and I'm favoring a more southern solution since I think this will be a vertically deep system that will feel a greater influence of the mid and upper level flow (unlike what the GFS thinks). This is more in line with the current run of the ECWMF. At this point I'd hate to speculate on intensity until we have a developed system, but hurricane intensity is a distinct possibility.

http://philstropical...cyclone-status/

The trend this year has been for upper anticylcones to get stronger in the models as we get closer. So your theory has validity.

[Srain]

Posted this in the TX/MX/NM/LA thread a bit earlier and will offer it here as well...e-mail from a local Met Jeff:

Potential tropical cyclone threat to the state of Texas later this week/weekend.

Significant forecast changes likely over the next 48 hours.

Discussion:

The strong tropical wave over the NW Caribbean Sea continues to become better organized with deep convection frequent near/over the wave axis. Radar out of Cancun and surface observations suggest that the strong mid level center may be working its way to the surface and developing a surface circulation, at this time it is weak and barely noted in the surface data and deep convection while persistent remains scattered.

Track:

Massive high pressure ridge holding over TX for months will be moving ENE toward the Carolinas over the next 48 hours allowing a weakness to develop over the NW Gulf of Mexico and the TX coast. The Caribbean system will track along the SW side of the ridge into this weakness or in the general direction of the TX coast. Global guidance is still not “seeing” what is happening in the Caribbean Sea and shows little development, so will toss it out as it is clear that a tropical system is forming. Will follow the expected ridge position and split the difference between the 2 hurricane forecasting models (GFDL and HWRF) and the multi model consensus package and indicate a potential threat from Galveston to Brownsville with highest threat right now from about Corpus Christi to Port O Connor. GFDL takes the system as a cat 1 hurricane into Galveston Bay while the HWRF takes the system as a strong cat 1 into the area near Corpus Christi. The multi model consensus is pegged just west of Port O Connor taking into account the GFS and GFDL upper coast and the HWRF and EURO southern coast.

Will get a better handle on the spreading track solutions by this evening as data from a USAF mission midday today is ingested into the models.

Intensity:

Overall size of the system is small which means it is vulnerable to surrounding atmospheric conditions moreso than a large system. The system is over very warm waters with temperatures in the mid to upper 80’s across much of the Gulf of Mexico and the NW Caribbean Sea. Upper level shear while strong over the northern Gulf of Mexico is light over the southern Gulf and forecast to gradually weekend as the southern plains high shifts eastward. The air mass over the southern Gulf does have a bit of dry air and this may be one reason as to why the convection has been fairly meager with this system and this could impact the system down the road as it moves across the Gulf. Overall conditions in the Gulf appear favorable for development and small system can spin up/down very quickly due to surrounding atmospheric changes (dry air intrusion, weak shear, ect). SHIPS guidance brings the system to a hurricane in the Gulf along with the GFDL and HWRF hurricane models, while the GFS, EURO, and CMC show very little development at all. Feel the big global models (GFS, EURO, and CMC) are missing this small system altogether and will not put much faith in their current forecast, while the hurricane models do seem high. For now will go with a blend of the two camps and lean toward the stronger solutions with a strong tropical storm or possibly a weak hurricane approaching the TX coast late Friday.

Impacts:

Feel it is best to await data from the aircraft this afternoon before going full force on coastal impacts. Forecast will no doubt need some significant changes with respect to seas, tides, rain changes, and rainfall amounts, along with wind forecast for Friday into Saturday. Will at least bump rain chances to 50% for Friday for areas south of I-10 and this could go much higher and hit those same areas with widespread 1-2 inches of rainfall. Coastal winds will begin to back from the SSW to ESE and then E Thursday night into Friday and increase. For now will hold winds below TS force over all areas awaiting NHC wind guidance if/once the system is declared. Based on current track guidance feel, TS force winds (40mph or greater) will be needed by Friday evening over parts of the middle and upper TX coast waters and coastal counties and spreading inland Friday night.

Preparations:

Residents along the TX coast should review hurricane preparation plans and be prepared to put these plans into effect over the next 48 hours. Closely monitor weather forecast for potential rapid changes and increasing impacts to the Texas coast.