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Tropical Depression Ernesto - 35 mph - 1004 mb - W 14 mph


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TROPICAL STORM ERNESTO DISCUSSION NUMBER 15

NWS NATIONAL HURRICANE CENTER MIAMI FL AL052012

500 AM EDT SUN AUG 05 2012

DATA FROM THE LATEST HURRICANE HUNTER MISSION INTO ERNESTO

SHOWED THAT THE CIRCULATION CONTINUES TO BE RATHER DISORGANIZED.

THE CENTRAL PRESSURE ROSE TO 1009 MB ON THE LAST FIX AND THE

AIRCRAFT FOUND ONLY VERY WEAK WESTERLY WINDS OF LESS THAN 5 KT NEAR

THE CENTER. THE PEAK 850-MB FLIGHT LEVEL WIND WAS 52 KT AND THE

HIGHEST SFMR WINDS WERE 40 TO 45 KT. BASED ON THESE DATA...THE

INITIAL INTENSITY IS SET TO 45 KT. WHILE THE OUTFLOW REMAINS WELL

ESTABLISHED...THE CONVECTIVE STRUCTURE OF THE CYCLONE HAS DEGRADED

OVER THE PAST 6 TO 12 HOURS. RAOB DATA FROM CURACAO...MODEL

ANALYSES AND AIRCRAFT DATA SHOW A TONGUE OF DRY AIR IN THE LOWER TO

MID-TROPOSPHERE IMPINGING ON ERNESTO FROM THE SOUTH. THIS DRY AIR

IN COMBINATION WITH SOME MID-LEVEL SHEAR ANALYZED BY UW-CIMSS MAY

BE PARTLY RESPONSIBLE FOR THE LACK OF DEVELOPMENT IN THE LAST DAY

OR SO. DESPITE OTHERWISE SEEMINGLY FAVORABLE CONDITIONS...THE GFDL

AND HWRF NOW BOTH SHOW THE CYCLONE WEAKENING DURING THE NEXT 48

HOURS. THE SHIPS AND LGEM STILL SHOW INTENSIFICATION...BUT AT A

SLOWER RATE COMPARED TO THEIR PREVIOUS FORECASTS. GIVEN THESE

TRENDS...THE NEW NHC FORECAST HAS BEEN ADJUSTED DOWNWARD THROUGH 48

HOURS...BUT IS STILL ABOVE THE MULTI-MODEL CONSENSUS. AFTER THAT

TIME THERE IS STILL AN OPPORTUNITY FOR ERNESTO TO BECOME A

HURRICANE BEFORE REACHING LAND...WITH SOME RESTRENGTHENING POSSIBLE

AFTER THE CYCLONE MOVES INTO THE GULF OF MEXICO BY DAY 5.

THE LAST FEW AIRCRAFT PASSES THROUGH THE CENTER...SUCH AS IT IS...

SHOWED THAT ERNESTO HAS ACCELERATED BACK TOWARD THE WEST...WITH AN

INITIAL MOTION OF 275/19. THE INITIAL POSITION AND MOTION RESULTS

IN A SHIFT IN THE NHC TRACK OF ABOUT A HALF A DEGREE TO THE LEFT...

OR SOUTH...OF THE PREVIOUS FORECAST. APART FROM THIS ADJUSTMENT...

THERE IS NO CHANGE TO THE OVERALL FORECAST REASONING. ERNESTO IS

EXPECTED TO CONTINUE WESTWARD FOR THE NEXT DAY OR SO AND THEN SLOW

DOWN AND TURN WEST-NORTHWESTWARD BY 48 HOURS AS A WEAKNESS DEVELOPS

IN THE SUBTROPICAL RIDGE OVER THE EASTERN GULF OF MEXICO. THIS

WEST-NORTHWESTWARD MOTION SHOULD CONTINUE THROUGH THE END OF THE

PERIOD AS THE WEAKNESS PERSISTS OVER THE GULF. THE GFS...ECMWF...

AND THE GFS ENSEMBLE MEAN LIE ON THE SOUTHERN SIDE OF THE GUIDANCE

ENVELOPE...SHOWING LESS OF A NORTHWARD TURN AND A TRACK CLOSER TO

THE COAST OF CENTRAL AMERICA AND INTO THE CENTRAL YUCATAN

PENINSULA. THE GFDL...UKMET AND SOME OF THE HFIP MODELS...ARE

FARTHER NORTH AND TAKE THE CYCLONE OVER THE NORTHERN YUCATAN AND

INTO THE CENTRAL GULF. THROUGH 72 HOURS THE NHC FORECAST IS CLOSE

TO THE MIDDLE OF THE GUIDANCE ENVELOPE AND THE MULTI-MODEL

CONSENSUS. AT DAYS 4 AND 5 THE OFFICIAL FORECAST HEDGES TOWARD THE

USUALLY RELIABLE GFS AND ECMWF MODELS AND IS A LITTLE SOUTH OF THE

CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 05/0900Z 15.1N 74.8W 45 KT 50 MPH

12H 05/1800Z 15.3N 77.5W 45 KT 50 MPH

24H 06/0600Z 15.6N 80.1W 50 KT 60 MPH

36H 06/1800Z 16.0N 82.1W 55 KT 65 MPH

48H 07/0600Z 16.6N 83.9W 60 KT 70 MPH

72H 08/0600Z 18.5N 87.5W 75 KT 85 MPH

96H 09/0600Z 20.5N 91.0W 60 KT 70 MPH

120H 10/0600Z 21.6N 94.0W 65 KT 75 MPH

$$

FORECASTER BRENNAN

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Its rather ironic that in this weak state that Ernesto presents itself, the 00z ECMWF all of a sudden has become more bullish. For the first time since the development of Ernesto it does not completely dissipate the surface circulation, and has it returning with a vengeance in the Gulf of Mexico after a respectable first landfall in the Yucatan Peninsula. If Ernesto doesn't completely fall apart in the next 6-12 hours, as the low-level easterly flow relaxes we should see a return to form for the tropical cyclone.

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While the system is obviously still disorganized... it appears the surface circulation is largely intact. With some renewed support from the ECMWF, lets see what Ernesto decides to do today.

Extrapolating a 20 knot forward motion in the 2 hours since that M/I image was taken, the center of the latest convective blowup (centered around 15.5N 74W) is displaced about 1.5 degrees to the east.of Ernesto's center. That would put the LLC near the western edge of the CI canopy on IR.

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The 00Z ensembles (GFS/Euro) certainly show some interesting solutions and raise an eyebrow. While Ernesto has struggled and the low level circulation has 'out ran' the mid level vort and dry air at the lower levels have helped to keep Ernesto in check, there are strong suggestions that a slowing down is ahead in the NW Caribbean as a mid latitude trough dives SE into the Great Lakes and Tennessee Valley. After Ernesto make land fall in the Yucatan and emerges into the Bay of Campeche is where things take a turn that could allow for improved conditions and a strengthening system that becomes vertically stacked and ramp up rather quickly. The HPC mentions the morning a feature in the NW flow dropping SE that may tug Ernesto further N. This may well be what the ensembles are 'sniffing' and cannot be discounted. The HPC even mentions a situation ala TS Debby with that U/L and should it occur, a major fly in the ointment may well be in the offing for a further NW to NNW track in the Western Gulf. We here in Texas know some strange things can happen with systems crossing the Yucatan and into the Bay of Campeche and one can never discount a tropical system until it is inland and dead for good... ;)

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The 00Z ensembles (GFS/Euro) certainly show some interesting solutions and raise an eyebrow. While Ernesto has struggled and the low level circulation has 'out ran' the mid level vort and dry air at the lower levels have helped to keep Ernesto in check, there are strong suggestions that a slowing down is ahead in the NW Caribbean as a mid latitude trough dives SE into the Great Lakes and Tennessee Valley. After Ernesto make land fall in the Yucatan and emerges into the Bay of Campeche is where things take a turn that could allow for improved conditions and a strengthening system that becomes vertically stacked and ramp up rather quickly. The HPC mentions the morning a feature in the NW flow dropping SE that may tug Ernesto further N. This may well be what the ensembles are 'sniffing' and cannot be discounted. The HPC even mentions a situation ala TS Debby with that U/L and should it occur, a major fly in the ointment may well be in the offing for a further NW to NNW track in the Western Gulf. We here in Texas know some strange things can happen with systems crossing the Yucatan and into the Bay of Campeche and one can never discount a tropical system until it is inland and dead for good...;)

my concern would be will it get into the NW caribbean? if it keeps slamming west with a naked center it wont.

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First couple visible images showing Ernesto looking putrid this morning...I'm guessing the National Hurricane Center will downgrade Ernesto at 11 am...

With 40 knot winds and a decent chance it'll start to strengthen somewhat, I doubt they'll drop advisories just to re-start possibly in 12 hours, just because West winds aren't well established, First few vis frames show an mostly exposed LLC, which is closed, at least storm relative. May be popping a new cell on the East side of the mostly exposed swirl.

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PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1000 AM EDT SUN AUG 05 2012

VALID 12Z THU AUG 09 2012 - 12Z SUN AUG 12 2012

...ERNESTO EXPECTED TO MOVE THROUGH THE SOUTHERN AND WESTERN GULF

OF MEXICO THIS PERIOD...

LOCATED IN THE CENTRAL CARIBBEAN...ERNESTO IS STRUGGLING TO

ORGANIZE AS IT MOVES AT A RAPID CLIP TO THE WEST. CONDITIONS ARE

EXPECTED TO BECOME MORE FAVORABLE FOR INTENSIFICATION AS IT SLOWS

DOWN ACROSS THE NORTHWEST CARIBBEAN SEA IN 2-3 DAYS. THE NATIONAL

HURRICANE CENTER HAS ERNESTO WAVERING NEAR MINIMAL HURRICANE

STRENGTH FROM TUESDAY NIGHT THROUGH THURSDAY NIGHT...AND THE

PRESSURE MAPS BEYOND THEN MAINTAIN THAT IDEA UNTIL ITS FINAL

LANDFALL IN NORTHEAST MEXICO FRIDAY NIGHT. CURRENT 00Z GLOBAL

ENSEMBLE GUIDANCE HAD NARROWED SINCE FRIDAY...SHOWING A LANDFALL

ACROSS MEXICO NORTH OF VERA CRUZ STATE. CONFIDENCE IN THIS TRACK

IS NEAR AVERAGE OR ABOVE AVERAGE. IT IS WORTH

NOTING...HOWEVER...THAT A MINORITY OF ENSEMBLE

MEMBERS...PARTICULARLY FROM THE ECMWF ENSEMBLE...STEER ERNESTO

FARTHER NORTH. UNCERTAINTY DOES INCREASE BY EARLY NEXT

WEEKEND...AND A NORTHWARD SHIFT IN THE TRACK IS AT LEAST PLAUSIBLE

IF ERNESTO BECOMES INFLUENCED BY A MID LEVEL HEIGHT

WEAKNESS/TROUGH THAT TAKES SHAPE ALONG THE GULF COAST OF THE U.S.

THEREFORE... PEOPLE WITH INTERESTS ALONG THE GULF

COAST...PARTICULARLY IN SOUTH TEXAS...SHOULD CONTINUE TO MONITOR

THE OFFICIAL FORECASTS FROM THE NATIONAL HURRICANE CENTER.

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As I recently found out in teletraining for initializing TC guidance, very little of the dropsonde information ends up being used by the operational GFS/NAM/GFDL/HWRF, unless it is close to the first guess from their previous run. This applies moreso to the core upper air obs than the peripheral obs, as the NCEP guidance (including the GFDL) makes cold-core assumptions regarding various aspects of the TC, so they simply can't use the information. That is supposed to change in 2014.

This isn't entirely accurate (at least in terms of the GFS and GFDL models):

1. The GFDL uses a bogus vortexing scheme (which is not a cold core assumption)

2. The GFS/GDAS uses a hybrid ensemble-var scheme now, so the increments in the tropics are primarily driven by model derived ensemble perturbations (which in the tropics, are also not cold core).

Near storm observations cannot be (properly) used for a variety of reasons, notably issues of representativeness (for the GFS at least, which is currently on ~27km in horizontal resolution). I think if/when we have higher resolution, we can succussfully use such observations (even inner core observations) within the hybrid var/ens schemes (as is being explored for the 2014 HWRF implementation, and TBD for the GFS/GDAS).

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I have one thing more to say about this POS storm......next! The NHC forecasts have been way to aggressive and they are still likely overdoing the intensity, this is going to stay weak and plow into the Belize/southern Yucatan area. 12Z GFS has the right idea. Booooring!

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I have one thing more to say about this POS storm......next! The NHC forecasts have been way to aggressive and they are still likely overdoing the intensity, this is going to stay weak and plow into the Belize/southern Yucatan area. 12Z GFS has the right idea. Booooring!

i agree. its slamming west and most likely will never see the BOC.

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Epic collapse, looks like an upper level jet stream is slicing through where the anticyclone should be. It'll probably go due west into Central America since it has no vertical depth, but I'd wait a little bit before saying this is totally dead.

Yea I'm not quite ready to write this off yet. Bot the GFS and ECMWF show the storm reorganizing before landfall on the Yucatan Peninsula. Things are pretty dire though.

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