Interesting low pressure development in the Gulf

[Sam Sagnella]

In a nearly unanimous consensus, most of the mainstream global forecast models are hinting at some rather low pressures in the central Gulf in the immediate wake of Stan in about the 60-72hr timeframe. In addition, the models are also significantly slowing down Stan's WSW motion towards the middle Mexican coast leaving us with a potentially very interesting scenario. Is this the start of a trend of pulling Stan back to the NE or is it showing the potential development of a separate entity? I'm very interested in seeing what the models will show in future runs, as I've never seen a scenario quite like this before -- let alone having such good model agreement to go along with it when it's still more than two days away.

 

[Michael Auker]

Yeah, I was watching this also. NAM sure has a huge area of low pressure in the Gulf in the 84 hr. timeframe. I thought NAM doesn't forecast tropical development, is this extra-tropical?

 

[Sam Sagnella]

I have never seen anything like this in my whole life.

Though only the CMC and the UKMET are out for their 03/0000z runs, I am noticing some INSANE similarities in the two. They are both developing an intense are of low pressure (probably tropical cyclone) that moves in a large cyclonic loop over the basically the entire periphery of the Gulf coast!! They both have the same exact scenario -- and a rather complex one at that -- beginning at around 24hrs. If this pans out...Tammy is going to be one MAJOR headache for millions of people.

EDIT: The 00z GFS is on board too - this really is quite remarkable.

03/0000z Runs:
--------CMC 48Hr ---------------UKMET 48Hr----------------GFS 48Hr-----------


--------CMC 60Hr ---------------UKMET 60Hr----------------GFS 60Hr-----------


--------CMC 72Hr ---------------UKMET 72Hr----------------GFS 72Hr-----------


--------CMC 96Hr ---------------UKMET 96Hr----------------GFS 96Hr-----------


--------CMC 120Hr --------------UKMET 120Hr----------------GFS 120Hr-----------

 

[Jeff Snyder]

The 250mb forecast guidance is interesting, since it shows an upper-level low associated with the surface low. Typically, as we all know, tropical cyclones are associated with upper-level highs (anticyclones). 500mb and 250mb temperature forecasts don't really show much of gradient across this system, so that doesn't argue for extratropical development. So, in many ways, it looks like the models are developing a tropical system, but I'm not sure the upper-level forecasts from most of the numerical models look like its a true tropical system. We shall see... If there's one thing I know, it's that we really can't forecast tropical cyclone genesis very well.

 

[Angie Norris]

Was just doing some model peeping, and I've noticed this too. NAM shows some rapid development south of Florida going into the southern Gulf in the 72-84 hour time frame. Not at all sure what to make of this, because I've never seen anything like it, either. No word from NHC, but Miami NWS is forecasting heavy rain, wind, etc later in the week.
Looks like Tammy may not be too far out in the future??
Angie

 

[rdale]

NHC does address it in the outlook:

A SURFACE TROUGH OF LOW PRESSURE IS ASSOCIATED WITH A LARGE AND
COMPLEX SYSTEM OF DISTURBED WEATHER THAT EXTENDS FROM HISPANIOLA
NORTHWARD FOR SEVERAL HUNDRED MILES. SATELLITE IMAGES AND SURFACE
REPORTS INDICATE THAT THE SURFACE TROUGH HAS BECOME BETTER DEFINED
THIS MORNING A SHORT DISTANCE EAST OF THE CENTRAL BAHAMAS. UPPER-
LEVEL CONDITIONS ARE EXPECTED TO GRADUALLY BECOME MORE FAVORABLE
FOR TROPICAL CYCLONE DEVELOPMENT OVER THE NEXT COUPLE OF DAYS...AND
A NOAA RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE THE
SYSTEM TOMORROW...IF NECESSARY. AS THIS SYSTEM MOVES WESTWARD
DURING THE NEXT 24 HOURS...HEAVY RAINS AND GUSTY WINDS ARE EXPECTED
TO SPREAD INTO THE CENTRAL AND NORTHWESTERN BAHAMAS...AND REACH THE
FLORIDA PENINSULA BY LATE TOMORROW OR WEDNESDAY.

 

[Tim Vasquez]

I'm not really paying attention to the weather, but those charts above seem to show a really good slug of polar air moving into the Gulf, and a potently baroclinic system. Maybe a strong frontal system or a mini- March 12, 1993 system might get going offshore.

Gonna have to go look at UCAR and see what kind of temperatures they're pushing down this way.

Tim

 

[Scott Olson]

There is a pretty good spread but I see several solutions being presented and supported by different models. Including the full loop through the Gulf into the Yucatan, A more N/NW direction and even cyclone formation pre-Florida and then going back into Florida. Two models (CMC and AF-MM5 develop this system and aim it into Georgia. (The AF-MM5 was the first model to start picking up on this several days ago.) There is also some models developing from near where Stan was near the Yucatan and taking aim on Florida or the NC Gulf (FSU MM5). Guess we will have to wait and see since this things do not always materialize but it looks at least promising for some MORE tropical activity.

 

[Mark Farnik]

I think this could be interesting. The area of disturbed weather in the Bahamas seems to be slowly getting better organized and will have to be watched carefully. Unfortunately this system is developing in the area where Katrina and Rita both originated from, and the SST's are still above average through much of the Gulf of Mexico, so let's hope "Tammy" (if it becomes a tropical system) does not become another "Bahama Buster" like the previous two ladies did. What's with these women hurricanes, they've been real b*****s this year, geez. :roll: If the model scenarios pan out, with the complete Gulf Coast loop they are prediciting... that would be insane. :shock: Especially if Tammy were to become a major hurricane like nearly every system that has a chance to move over the GoM this year has been doing.
This could be one of the more extraordinary weather events in our lifetime if it pans out... :shock:

 

[Sam Sagnella]

Wow...check out the eerie resemblence to the '93 storm's track in the 18z GFDL's track forecast for invest 92L (likely the catalyst for the development in the Gulf later in the week) -- pay particular attention the 72-96hr time frame.

HR LAT LON HEADING/SPEED(KT)
0 23.0 75.2 275./11.1
6 22.9 75.9 262./ 6.6
12 23.2 76.6 289./ 7.3
18 23.7 77.4 304./ 8.7
24 24.5 78.1 323./10.6
30 25.1 79.0 301./ 9.9
36 25.9 79.8 314./11.1
42 26.5 80.8 304./10.6
48 27.3 81.6 312./10.6
54 28.0 82.6 306./10.7
60 28.5 83.6 299./10.6
66 28.8 84.1 296./ 5.5
72 29.2 84.3 335./ 4.4
78 29.5 84.8 303./ 4.8
84 29.3 85.2 247./ 3.9
90 29.2 85.1 173./ .8
96 29.6 84.5 63./ 6.1
102 30.1 83.7 57./ 9.1
108 30.4 82.6 75./10.2
114 31.5 80.4 64./21.2
120 33.4 77.8 53./29.2
126 35.7 75.1 51./31.9


The 18z AF-MM5, which, as Scott noted, was the first to hint at future development (a few days ago) keeps this system on the eastern side of the FL peninsula before moving it to the north. The 12z UKMET still shows the cyclonic loop over the Gulf, except that it turns the system back to the NE far sooner, with a landfall N of Tampa along the FL Big Bend. The 12z NOGAPS doesnt show development until it's already exiting NErn FL near JAX.

The bottom line is that, as Jeff and TimV alluded to, this system may not be entirely tropical in nature and looks to take a very similar track to the 1993 "storm of the century." Regardless of whether it turns out to be a tropical, sub-tropical or some other type of hybrid storm, this appears to pose a significant threat to the NE Gulf coast/SE US by the end of the week.

 

[B Ozanne]

This thing really smells like an extra-tropical cyclone. Looking at the GFS it bombs out off North Carolina and takes the classic nor'easter track.

 

[Robert Dewey]

I agree with Bill - this thing has all the signs of being a classic nor'easter. It's a shame it isn't later in the Winter season, when the baroclinic zone would probably be even tighter...

 

[brody_clifton]

Looks to me to be a forecasted extratropical surface low also, I was surprised to see it showing up on the ETA, GFS, and NAM models this far in advance. If the models verify and the low track stays somewhat inland as the models are suggesting right now, it could make be some interesting action Friday PM along coastal SC/NC, with current suggestions of MLCAPE approaching 1000 J/Kg and 300+ 0-3km SRH.
I agree with you guys though, I'm believe this is the first time I've seem this type of thing forecast since I began in '96. If the system develops, I believe it will be the first nor'easter type warm sector I've ever had a chance to chase.

 

[rdale]

Eta is called the NAM now - they are not separate.

 

[B Ozanne]

Another interesting low pressure just popped up named Tammy.