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Atlantic Tropical Action 2011 - Part IV


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Pick your poison. HPC Model Diagnostics update for the 12Z suite:

...CENTRAL GULF OF MEXICO DISTURBANCE...

PREFERENCE: 12Z ECMWF/12Z GFS

THE NAM IS ON THE NORTHERN SIDE OF THE SPREAD WITH THIS SYSTEM.

THE UKMET AND THE NAM ARE BOTH STRONG WITH MID-LEVEL ENERGY MOVING

INTO THE GULF BUT THE 00Z UKMET KEEPS THE CENTER OF THE

DISTURBANCE SOUTH AND WEST OF THE 12Z NAM. BOTH THE 06Z GFS AND

00Z ECMWF ARE SLOW TO DEVELOP THIS DISTURBANCE AT THE UPPER

LEVELS...WITH THE FIRST DISCERNIBLE INDICATION OF THE DISTURBANCE

NOT POPPING UP UNTIL THE DAY 3 TIME PERIOD. AT THE SURFACE WEAK

LOW PRESSURE IS INDICATED BY THE GFS AND ECMWF...STAYING WELL TO

THE SOUTH AND MUCH WEAKER THAN THE NAM/UKMET. THE 12Z NAM SHOWS A

VERY DEEP AND STRONG SOLUTION ON DAY 3...MAKING ITS SOLUTION AN

OUTLIER AMONGST OTHER OPERATIONAL AND ENSEMBLE SOLUTIONS. THE 12Z

GFS HAS TRENDED NORTHWARD TOWARDS THE NORTHERN SOLUTIONS BUT IS

STILL FURTHER SOUTH THAN THE NAM AND MUCH WEAKER. THE 12Z UKMET

HAS WEAKENED THE SURFACE LOW AND HAS SHIFTED FURTHER SOUTH...MORE

IN LINE WITH THE 00Z ECMWF. IT IS STILL ONE OF THE WESTERN MOST

OPERATIONAL SOLUTIONS. THE 12Z ECMWF IS COMPARABLE TO ITS 00Z

RUN...PERHAPS SLIGHTLY WEAKER DEPTH WISE BUT THE LOW CENTER IS

STILL IN A SIMILAR LOCATION.

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Hour 192 of the 12Z Euro is pretty interesting... it looks like "future Maria" (the current NW Caribbean disturbance) teases the Gulf coast of Texas, dives south into the BoC as it is dying, and with the help of some baroclinic enhancement along the front... spits possible "Nate" out heading NE towards FL

The Euro seems to periodically try to intensify some low level vorticity, but never really organizes anything like earlier runs did. Having said that, many of the EC ensemble members must be pretty bullish given a mean low center of 1001 mb in the western Gulf at 144 hours. I am still thinking that the odds of a system that needs advisories in the Gulf in the next week is pretty high, but given the "monsoon" nature of the development and lack of really awesome conditions, the odds of a being a particularly robust system are relatively low for now.

BTW, the GFS EnKF and the FIM remain strongly on board for development over the next 5-6 days in the Gulf.

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Hour 192 of the 12Z Euro is pretty interesting... it looks like "future Maria" (the current NW Caribbean disturbance) teases the Gulf coast of Texas, dives south into the BoC as it is dying, and with the help of some baroclinic enhancement along the front... spits possible "Nate" out heading NE towards FL

You are predicting a 'Lee' developing somewhere first?

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The system in the NW Caribbean may be a fun one to track. Perhaps we won't see a significant landfall, but as others has mentioned, how often do we see monsoonal troughs sitting over a boiling hot Gulf of Mexico?

post-525-0-55249900-1314760565.jpg

The system is not really well organized at all yet and is nearing Yucatan Peninsula. The system is under 20-30 knots of northwesterly shear, which combined with proximity to land should significantly limit development potential over the next couple days. But, I do like that the system is near an upper level anti-cyclone (note how there is a clock-wise motion to the cirrus clouds rushing away from the system). As the system drifts north, the global models hint at it becoming situated directly under the upper level anti-cyclone, which should weaken shear to lighter amounts by the weekend:

post-525-0-31963500-1314760854.gif

This will occur above extremely warmSSTs (30-32C) and highTCHPs. This is an encouraging sign, and helps explain why vertually every useful global model shows development of this system over the weekend and into next week over the western Gulf of Mexico.

However, one factor to consider will be the systems large size. The system is currently associated with a broad and relativly weak area of lower to middle level vorticity stretching from over the southern B.O.C into the northern Caribbean:

post-525-0-45760900-1314761462.gif

This shows that the piece of vorticity the models try developing into Maria is part of a large monsoonal gire (I know, I probably spelled that wrong) and will likely take days to possibly consolidate into one, more intense area of low pressure.

Another possible detriment will be proximity to land and possible low level dry air getting ingested into any system that develops. As has been well documented, much of the Gulf coast, especially Texas, has been extremely dry for an extended period of time. This may cause another situation (like Don) in which a TC gets close to land and ingests this dry air, and has trouble maintaining deep convection. Also note how there is a very dry continental airmass in place over the northern Gulf that will need to retreat north in order to not have a negative affect on our system:

latest72hrs.gif

So right now, my guess would be for a moderate to high chance (50-70%) of some sort of tropical or subtropical cyclone forming at some point between Friday night and Sunday night. This is based on:

1. A tropical wave located within a larger monsoonal trough of low pressure that has a trackable and distint TPW increase associated with in and weak but trackable area of low-mid level vorticity moving northwest towards very warm waters, with relativly weak shear and good outflow potential expected.

2. Strong global model agreement on tropical or subtropical cyclonegenesis helps increase this confidence.

However, given the systems large nature and the fact that it might not have the space to develop into a stronger cyclone given possible land interaction and/or dry air issues, I have low confidence, about 15%, in this storm becoming anything more than a tropical/subtropical storm.

The track forecast for this system is interesting...due to ridging building to the north and west of the system, which results in a trough east of the system in the coming days.

post-525-0-35512000-1314762254.gif

The short term forecast is simple enough--NW movement into the western Gulf of Mexico.

However, the well modeled (so far) weakening of the +PNA will shift mid level ridging east into the western US and Plains, forcing a more northerly flow aloft over the system and forcing a trough to the northeast of the system next week:

post-525-0-58122900-1314762483.png

Given this, a track NW towards the north Texas coast over the next 2-3 days seems reasonable. Based on where models are parking the ridge to the NW of the system in a few days, a turn towards the southwest and a major slow down in a huge gap between two ridges appears likely. This would result either in a slowly drifting storm moving into eastern TX/MX or perhaps hugging the coastline late next week.

I know that wasn't Ph. D level stuff right there, but we'll see how this Gulf system goes.

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The system is not really well organized at all yet and is nearing Yucatan Peninsula. The system is under 20-30 knots of northwesterly shear, which combined with proximity to land should significantly limit development potential over the next couple days. But, I do like that the system is near an upper level anti-cyclone (note how there is a clock-wise motion to the cirrus clouds rushing away from the system). As the system drifts north, the global models hint at it becoming situated directly under the upper level anti-cyclone, which should weaken shear to lighter amounts by the weekend:

I actually don't agree with this statement at all. To me, the upper-air pattern during much of this system's lifetime is highly suggestive of shear, with strong upper-level southwesterlies going right through the TC core (centered just SE of the mouth of the MS River in the following image). This is further supported by the highly asymmetric and displaced vertical velocities, RH, and QPF distribution.

GFS_3_2011083100_F96_WSPD_200_MB.png

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I actually don't agree with this statement at all. To me, the upper-air pattern during much of this system's lifetime is highly suggestive of shear, with strong upper-level southwesterlies going right through the TC core (centered just SE of the mouth of the MS River in the following image). This is further supported by the highly asymmetric and displaced vertical velocities, RH, and QPF distribution.

Given this, I guess you don't see much of a future for this thing-- at least not if we want a 'cane out of it?

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I actually don't agree with this statement at all. To me, the upper-air pattern during much of this system's lifetime is highly suggestive of shear, with strong upper-level southwesterlies going right through the TC core (centered just SE of the mouth of the MS River in the following image). This is further supported by the highly asymmetric and displaced vertical velocities, RH, and QPF distribution.

The image you posted certainly would make it look like I'm wrong in my low shear assessment here.

The 12z Euro looked a little better based off the free images I looked at, though. By day 5, the model has a rather broad area of low pressure centered over the southwestern Gulf of Mexico (which is a good deal southwest of the 0z GFS). PSU e-wall's shear map off the 12z Euro valid at hour 120 shows relativly weak shear around the cyclone...

post-525-0-20107300-1314765728.gif

The 200mb wind maps off of the College of DuPage's website don't look horrible for shear either given where the model took the cyclone...with upper level winds generally at or under 20 knots at 120 hours...and with a clear indication of an upper level anti-cyclone over where the 12z Euro had the system at hour 144 (or at least some upper level diflucence and relativly weak shear):

post-525-0-98055700-1314765851.gif

post-525-0-62016000-1314765910.gif

I guess where the system ends up developing/tracking will have some bearing on how much it gets sheared (knock on wood). I'm not expecting anything spectacualar here although I still think there is a decent chance of eventual tropical cyclone development in the western Gulf in the coming days.

It may very well end up being a sheared cyclone, like the GFS shows, or perhaps a little more organized like the 12z Canadian suggested. I'm invisioning a broad low pressure similar to what the 12z Euro suggested that has trouble significantly intensifying, whether shear is unfavorable or perhaps marginal, just based on the current disorganization of the system and the large, broad nature of it.

I do appreciate you taking time to read and respond to my post though, even if you were correcting me :)

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Given this, I guess you don't see much of a future for this thing-- at least not if we want a 'cane out of it?

I don't see anything on the order of Cat 2+. If this hangs around for a very long time, long enough for that upper level low to erode away and have a large upper anticyclone replacing it, perhaps the storm has a shot at something more. I'm not holding my breath though.

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I don't see anything on the order of Cat 2+. If this hangs around for a very long time, long enough for that upper level low to erode away and have a large upper anticyclone replacing it, perhaps the storm has a shot at something more. I'm not holding my breath though.

OK, gotcha-- makes sense. So you think Cat 1 is attainable, perhaps?

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I don't see anything on the order of Cat 2+. If this hangs around for a very long time, long enough for that upper level low to erode away and have a large upper anticyclone replacing it, perhaps the storm has a shot at something more. I'm not holding my breath though.

The Canadian, while certainly no Cat 2+, does hold some promise if only it could be a bit more correct. The 00Z GFS is a bit too progressive, IMO

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The Canadian, while certainly no Cat 2+, does hold some promise if only it could be a bit more correct. The 00Z GFS is a bit too progressive, IMO

To add to that, the 0z Euro and UKMET give us some hope for this system to impact our area and Texas in general. Hell, even the 0z NOGAPS supports the Europeans. 0z Euro literally stalls the system in the NW Gulf for 3 days until moving onshore across the Upper Texas Coast just after day 7. The GFS seems to be on its lonesome with its progressive solution. Understandbly, models are all over and back again with this system since it doesn't yet exist. The GFS better have eaten some bad granola, as we could really use a system like this.

Though of note, but not really related to this tropical thread and moreso our local thread, it seems all global models are hinting at a significant fropa for this time of year just after day 7 (lows in the 50s)

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I don't know if I want to buy the ECWMF solution just yet, but it has our system stalling for the better part of 5 days in the same location as it slowly organizes and becomes smaller in size. While it's certainly a viable solution that seems awfully slow and the ECWMF is known for not being progressive enough.

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Seeing the operational EC "split off" a piece of energy from the monsoonal "slop" in the GOM and sending it northeast while maintaining a surface LLC in the GOM was a bit odd. Seems like central/east Gulf might ultimately be a bit more in play than TX in the end...unfortunately since that means any of that rain may work its way up the East Coast.

There are about 6-7 ensembles in the EC camp (maybe more, I'm looking at spag plots) that take the low and send it northeast, FWIW.

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All right. Here is what HGX is thinking and as mentioned yesterday, until we actually get something to begin to form, the forecast is a best guess at best:

ALL RIGHT...THE PART OF THE FORECAST EVERYONE WANTS TO KNOW

ABOUT. IS IT GOING TO RAIN THIS WEEKEND OR NOT? IF YOU LIVE

CLOSER TO THE COAST...YOU WILL HAVE BETTER CHANCES OF SEEING AT

LEAST A FEW DROPS. CONFIDENCE IN THIS FORECAST IS VERY LOW TO SAY

THE LEAST.

FIRST...TROPICAL WAVE IN THE NW CARIBBEAN IS NOT ALL THAT

ORGANIZED AND LOOKS TO POSSIBLY MOVE OVER THE YUCATAN PENINSULA.

HARD TO KNOW WHAT WILL REMAIN OF THE WAVE ONCE IT EMERGES INTO

THE GULF SOMETIME TOMORROW. THE WAVE IS NOT ALL THAT WELL DEFINED

BUT UPPER LEVEL WINDS MAY BE A LITTLE MORE FAVORABLE FOR

DEVELOPMENT EXCEPT FOR SOME WESTERLY SHEAR ACROSS THE NORTHERN

GULF WHERE THERE IS A WEAK UPPER LEVEL LOW. SAID ALL OF THIS TO

SAY THAT THE SYSTEM MAY BE SLOW TO DEVELOP AND LARGELY DEPEND ON

WHERE IT CAN DEVELOP A CORE OF CONVECTION.

SECOND...SINCE THE SYSTEM IS ILL-DEFINED...NONE OF THE MODELS

REALLY HAVE A GOOD GRIP ON HOW TO INITIALIZE IT OR HOW TO HANDLE

ITS EVOLUTION ONCE SOMETHING DOES FORM. THE NAM HAS BEEN THE MOST

CONSISTENT WITH DEVELOPING AT LEAST A TROPICAL CYCLONE OF SOME

SHAPE AND DEEPENING IT OFF THE LA COAST FRI. THINK IT WEAKENS THE

RIDGE TOO MUCH WHICH WILL STRETCH FROM THE S ROCKIES TO THE MISS

RIVER VALLEY. THE GFS AND ECMWF SOLUTIONS MINDS AS WELL BE POLAR

OPPOSITES WITH THEIR SOLUTIONS. GFS HAS A BROAD WEAK LOW ALONG

THE LA COAST AND MOVES IT EAST WITH TIME AND THEN UP THE EAST

COAST EARLY NEXT WEEK. THE ECMWF HAS A WEAK LOW FRI/SAT AND THEN

DEEPENS IT OFF THE LOWER TX COAST SUN. THE SYSTEM REMAINS IN THE

W GULF THROUGH MID OF NEXT WEEK BEFORE TURNING N INTO SE TX.

NEITHER OF THESE SOLUTIONS LOOK VERY REASONABLE AT THIS POINT.

THE SREF AND GFS ENSEMBLE MEAN PROBABLY OFFER AT LEAST SOME

GUIDANCE. THE SREF LIKE THE NAM DEVELOPS A LOW OFF THE LA COAST

BY FRI BUT IS MUCH WEAKER. SAME CAN BE SAID FOR THE GFS

ENSEMBLE. SREF DOES LOOK TO MOVE THE SYSTEM BACK TO THE WEST

SOME LIKE THE NAM AS WELL. THE MAIN TRICK WILL BE TO SEE IF A

STRONG SHORTWAVE TROUGH OVER THE NORTHERN TIER OF STATES WILL BE

ABLE TO PICK UP THE SYSTEM SUN/MON WITH THE UPPER RIDGE OVER THE

S ROCKIES AND WEAKENING OVER THE MISS RIVER VALLEY. THIS MAY OPEN

UP ENOUGH FOR THE SYSTEM TO PULL INLAND SUN/MON. ADD TOO THAT

THAT THE EXTENDED MODELS BRING A FRONT INTO THE REGION MON...THIS

TOO MAY GIVE REASON FOR THE SYSTEM TO PUSH INLAND IN THE SUN/MON

TIME FRAME.

SO UNTIL THE MODELS COME IN TO MORE AGREEMENT ON THE

DETAILS...BEST COURSE SEEMS TO BE TO GO WITH PARTS OF MODEL

SOLUTIONS THAT MAKE THE MOST PHYSICAL SENSE WHICH REALLY IS NOT

MUCH. ALIGNED POPS FOR THE REST OF THE WEEK AND WEEKEND KEEPING

IN MIND LOTS OF UNCERTAINTY BUT THAT THERE WILL BE SOME TROPICAL

DEVELOPMENT IN THE N GULF FRI. SYSTEM LINGERS IN THE N/NW GULF

THROUGH SUN WHEN STRONG SHORTWAVE ACROSS THE NORTH BEGINS TO PULL

IT INLAND SUN/MON. FRONTAL BOUNDARY THEN PUSHES INTO THE REGION

MON/TUE WHICH CLEARS EVERYTHING OUT AND MAY ACTUALLY BRING TEMPS

DOWN TO CLIMO NORMS WHICH WILL BE ABOUT 10-15 DEGREES COOLER THAN

TEMPS FROM THIS PAST WEEK. AGAIN...WILL REALLY HAVE TO WATCH THIS

SYSTEM BECAUSE QUITE POSSIBLE FOR THERE TO BE RAINBANDS TO AFFECT

THE AREA WHICH COULD BRING VERY HEAVY RAINFALL. STRONG EAST WINDS

THAT DEVELOP WOULD ALSO BUILD UP SEAS AND COASTAL FLOODING

THREAT. WHILE SE TX COULD USE THE RAINFALL...STILL LOTS OF OTHER

IMPACTS THAT WILL DEPEND ON THE DETAILS IN THE FORECAST WHICH

UNFORTUNATELY ARE SKETCHY AT BEST. GIVEN THE UNCERTAINTY AND THE

POSSIBILITY OF EXTREME IMPACTS TO THE AREA...BEST TO MONITOR

FORECAST TRENDS CLOSELY.

HPC thoughts:

A TROPICAL DISTURBANCE APPEARS DESTINED TO IMPACT AREAS

OF THE WESTERN AND CNTRL GULF OF MX DEPENDING ON THE MODEL CHOICE.

THE 00Z CMC IS MUCH MORE AGGRESSIVE CARRYING A POTENT H5 VORT MAX

INTO GALVESTON BAY BY 03/1200Z. SIMILARLY...THE 00Z UKMET ALSO

SHOWS A MODESTLY STRONG SYSTEM IMPACTING COASTAL LA BY SUN

MORNING. AS THESE SOLNS WERE RATHER EXTREME WITH SPREAD THAT WAS

ON THE HIGHER END...THESE MODELS WERE REMOVED AS OUTLIERS. FOR THE

EARLY PORTION OF THE PERIOD...A BLEND OF THE 00Z GFS/ECMWF WAS

UTILIZED BEFORE THE 00Z GFS BECAME A BIT MORE SUSPICIOUS. BY

SUN...THE 00Z GFS INDICATES A STRONG SFC CYCLONE SHOULD IMPACT THE

FL PANHANDLE WITH VERY FEW 12Z GEFS MEMBERS SUPPORTING A LOCATION

THAT FAR TO THE EAST. IT ALSO DID NOT AGREE WELL WITH ITS

PRECEDING THREE RUNS. IN ADDITION...THE GFS CONTINUES TO STRUGGLE

WITH A POTENT NE PAC SYSTEM ON MON WITH PRESSURES FCST TO BE MUCH

TOO DEEP. SO A BLEND OF THE 00Z ECMWF WITH THE GLOBAL MEANS WAS

UTILIZED FOR DAYS 4/5. THEREAFTER...TOO MUCH UNCERTAINTY IN THE

STRENGTH AND POSITION OF THE GULF OF MX DISTURBANCE LEAD TO MORE

OF AN ENS APPROACH TO CONCLUDE THE PERIOD OF INTEREST. IT DOES

APPEAR THE WESTERN GULF WILL BE FAVORED GIVEN THE MAJORITY OF THE

INDIVIDUAL ENS MEMBERS RESIDE IN THAT PORTION OF THE BASIN.

BUT...A MORE CONSERVATIVE APPROACH WAS UTILIZED GIVEN THE FCST

UNCERTAINTY IN PLACE.

Here are the Euro and SREF that HGX is mentioning...

post-32-0-30919700-1314788579.gif

post-32-0-10380600-1314788590.gif

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The Euro's 5 inches plus for all of SE Texas the next 10 days would make me as happy as a little girl getting a pony. AccuWx PPV scale only goes to 5.

BTW, I'm perfectly happy with minimal hurricanes or tropical storms as long as they water my lawn. Save the tight core major hurricanes for Florida, with good roads and people with camera phones and video cameras.

msl_uv850_z500!Wind%20850%20and%20mslp!216!North%20America!pop!od!oper!public_plots!2011083100!!chart.gif

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Here are the images of the FIM(GFS)/EnKF ensembles and another reason why the ensemble mean is being given some weight. This is experimental guidance that is used by forecasters and is rarely posted, so take it for what it is...

post-32-0-62378200-1314790232.gif

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Steve's ensembles- weaker and West would be better IMBY. Hurricane Rita came close enough for minor wind damage and power failure, but was only good for about an inch of rain. Only a little oer half those individual member solutions would make me happy.

.rb-l.jpg

I havvenn't checked the East Pac thread in a couple of days. Close to land, but someone must have written something about that on the Mexican coast

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