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


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This makes no sense. Outflow is allowed to... and usually does... curve. It does not usually go in straight lines. Yes the ULL is curving the outflow to the north, but as long as the outflow is moving away from the cyclone, this is okay, especially if the outflow is accelerated as ULLs that are in this sort of position with respect to a tropical cyclone usually do.

The ULL doesn't simply "curve" the outflow, huge amounts of energy are being lost as the outflow is forced to turn and slow down.

It's not ok as long as outflow is moving outwards, it's all about the relative rates of outward flow. If outflow is initially unimpeded and then slows down/forced to turn, that energy will be deducted from the optimal energy the hurricane could attain. In reality this translates to less upward motion and relative subsidence to before. The upper low to the east is a great example of an ULL that is actually helping since the outflow is tying right into the jet associated with the upper low, so it gains energy.

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Good thing recon was cancelled. The NHC forecast was a landfall at 75-80 mph. I'm sure there was not much enthusiasm for seeing what recon might find. Now they can bump the winds up a token 5mph to 85 and call it day based on a sat estimates.

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It's a shame recon can't get there. The eye on radar has contracted significantly over the past couple hours.

Yeah, looking at the latest loop, this thing might be taking off a bit. The good news for Josh (if he can get there, and bad news for that part of the coast) is that this thing will likely be at about peak intensity at landfall, especially with the acceleration. Given what might be the presence of a very early secondary eyewall formation, I don't know if another 3h over water would do it all that much good. Right now, though, the eyewall/eye structure on radar is frankly very impressive, and it would be of no surprise to me if this thing is at least cat-2 intensity at landfall.

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Good thing recon was cancelled. The NHC forecast was a landfall at 75-80 mph. I'm sure there was not much enthusiasm for seeing what recon might find. Now they can bump the winds up a token 5mph to 85 and call it day based on a sat estimates.

right on que...there's your token 5mph bump from NHC.

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Holy sh^t guys....all I was doing was pointing out what the NHC mentioned and you guys go all nuts on turtle!

There was dry air at the mid levels and some of that certainly could have been due to the descension of air between the outflows of the core and of the monstrous band that existed in the NW quadrant YESTERDAY. Also a possible origin of any "relatively" dry air YESTERDAY may have been entrained days earlier....it's not like this system had been super organized to efficiently spit out parcels in an expediant fashion.

Today looks much better wrt dry air.

Good post. I think we can admit we all saw the same satellite loops yesterday. And we don't need to respond to Turtle.

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right on que...there's your token 5mph bump from NHC.

Without recon and wanting to try to get things as accurate as possible this close to land, they are really in a tough situation. Raw T number is up to 4.3 at 2245Z, which would be about 85 mph.

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I think this southerly trend may be due to coastal interaction. Air north of the center is going from ocean to land so it's converging at the coast, air south of the center is going from land to ocean so it's diverging at the coast. So the more of its circulation that interacts with the coastline the more it's pushed south, since low pressure forms to the south and high pressure to the north. Or it could be something else :P

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Nice find... keeping an eye on the obs... pressure down to 996 hPa.. winds not yet TS force. This is certainly a tightly wound system.

This reminds me of hurricane Katrina when it hit Miami, we only got some 30-50 mph gusts until the actual eyewall hit, and then suddenly it was hurricane force. Had a similar radar presentation too, and was also a category 1 hurricane intensifying right at the coast.

It hasn't had enough time for its wind field to spread out I'm guessing.

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I think this southerly trend may be due to coastal interaction. Air north of the center is going from ocean to land so it's converging at the coast, air south of the center is going from land to ocean so it's diverging at the coast. So the more of its circulation that interacts with the coastline the more it's pushed south, since low pressure forms to the south and high pressure to the north. Or it could be something else :P

Turtle you might have it backwards. Surface convergence occurring to the north induces lift which can lower the pressure. Surface divergence occurring to the south will result in sinking air which higher pressure is produced. I don't think land is having a large impact on the motion of Ernesto since the terrain nearby is relatively flat. In cases where the steering flow is weak though, it would obviously have a larger impact (Isidore 2002). However, the steering flow has actually strengthened a bit today, so I don't think thats the culprit.

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Turtle you might have it backwards. Surface convergence occurring to the north induces lift which can lower the pressure. Surface divergence occurring to the south will result in sinking air which higher pressure is produced. I don't think land is having a large impact on the motion of Ernesto since the terrain nearby is relatively flat. In cases where the steering flow is weak though, it would obviously have a larger impact (Isidore 2002). However, the steering flow has actually strengthened a bit today, so I don't think thats the culprit.

Yeah you're right. I'm done doing dynamics for today :axe:

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NHC holds... Cat 1 at 11

summary of 1000 PM CDT...0300 UTC...information

-----------------------------------------------

location...18.7n 87.7w

about 40 mi...65 km ENE of Chetumal Mexico

about 200 mi...325 km ESE of Campeche Mexico

maximum sustained winds...85 mph...140 km/h

present movement...W or 270 degrees at 15 mph...24 km/h

minimum central pressure...980 mb...28.94 inches

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NHC holds... Cat 1 at 11

summary of 1000 PM CDT...0300 UTC...information

-----------------------------------------------

location...18.7n 87.7w

about 40 mi...65 km ENE of Chetumal Mexico

about 200 mi...325 km ESE of Campeche Mexico

maximum sustained winds...85 mph...140 km/h

present movement...W or 270 degrees at 15 mph...24 km/h

minimum central pressure...980 mb...28.94 inches

I could argue but wont say much, im happy with what i see.

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HURRICANE ERNESTO DISCUSSION NUMBER 27

NWS NATIONAL HURRICANE CENTER MIAMI FL AL052012

1000 PM CDT TUE AUG 07 2012

TECHNICAL ISSUES PREVENTED A RECON FLIGHT FROM INVESTIGATING ERNESTO

THIS EVENING. HOWEVER...IMAGERY FROM THE BELIZE RADAR INDICATE THE

HURRICANE HAD A WELL-DEFINED 15-NMI DIAMETER EYE EARLIER THIS

EVENING...BUT THE EYE HAS BECOME A LITTLE RAGGED OVER THE PAST

COUPLE OF HOURS. THE INITIAL INTENSITY HAS BEEN INCREASED TO 75 KT

BASED ON AN INTENSITY ESTIMATE OF 77 KT FROM BOTH TAFB AND SAB.

RADAR FIXES OVER THE PAST 6 HOURS INDICATE ERNESTO HAS BEEN MOVING

WESTWARD...OR 270/13 KT. THE EYE OF THE HURRICANE IS CURRENTLY

LOCATED OVER THE NORTHERN BANCO CHINCHORRO ISLANDS OF MEXICO...AND

WILL MOVING ONSHORE THE SOUTHERN COAST OF YUCATAN SHORTLY. THE NHC

MODEL GUIDANCE REMAINS IN VERY GOOD AGREEMENT ON ERNESTO MOVING

WESTWARD TO WEST-NORTHWESTWARD ACROSS SOUTHERN YUCATAN TONIGHT AND

WEDNESDAY...AND EMERGING OVER THE BAY OF CAMPECHE BY WEDNESDAY

AFTERNOON OR EVENING. LOW- TO MID-LEVEL RIDGING TO THE NORTH AND

NORTHWEST OF THE CYCLONE AS IT MOVES OVER THE BAY OF CAMPECHE IS

EXPECTED TO TURN ERNESTO TOWARD THE WEST-SOUTHWEST BY 48 HOURS AS

IT NEARS MAINLAND MEXICO. AFTER THE SECOND LANDFALL OCCURS...

ERNESTO IS EXPECTED TO RAPIDLY WEAKEN INTO A REMNANT LOW OVER THE

HIGH MOUNTAINS OF INTERIOR MEXICO BY 96 HOURS. THE OFFICIAL

FORECAST TRACK IS SIMILAR TO BUT SLIGHTLY SOUTH OF THE PREVIOUS

FORECAST TRACK...AND LIES CLOSE TO THE CONSENSUS MODELS.

LITTLE IF ANY ADDITIONAL STRENGTHENING IS EXPECTED BEFORE LANDFALL

OCCURS. ERNESTO SHOULD WEAKEN RAPIDLY AS IT PASSES OVER YUCATAN

TONIGHT AND TOMORROW...BUT THE INCREASE IN LOW-LEVEL FRICTIONAL

CONVERGENCE MAY ACTUALLY HELP TO TIGHTEN UP THE CIRCULATION BEFORE

IT EMERGES OVER THE BAY OF CAMPECHE IN 18-24 HOURS. THIS APPEARS TO

BE ONE OF THE DRIVING MECHANISMS IN THE HWRF AND GFDL MODELS...

WHICH MAKE ERNESTO A HURRICANE AGAIN BY 48 HOURS WHEN IT IS OVER

THE SOUTHERN BAY OF CAMPECHE. THIS SEEMS REASONABLE GIVEN THE

CURRENT AND EXPECTED FAVORABLE ANTICYCLONIC OUTFLOW OVER ERNESTO.

RAPID WEAKENING AND DISSIPATION SHOULD OCCUR AFTER THE SECOND

LANDFALL IN MAINLAND MEXICO DUE TO VERY HIGH TERRAIN. THE OFFICIAL

INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND

FOLLOWS A BLEND OF THE LGEM...GFDL...AND HWRF MODELS.

34-KT WIND RADII WERE EXPANDED IN THE EASTERN SEMICIRCLE BASED ON

WIND REPORTS FROM THE LAST RECON FLIGHT AND NOAA BUOY 42056.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 18.7N 87.7W 75 KT 85 MPH...OVER BANCO CHINCHORRO

12H 08/1200Z 19.1N 89.5W 40 KT 45 MPH...INLAND YUCATAN

24H 09/0000Z 19.4N 91.9W 45 KT 50 MPH...OVER WATER

36H 09/1200Z 19.4N 94.0W 55 KT 65 MPH

48H 10/0000Z 19.2N 95.8W 65 KT 75 MPH

72H 11/0000Z 18.7N 98.5W 25 KT 30 MPH...DISSIPATING INLAND

96H 12/0000Z...DISSIPATED

$$

FORECASTER STEWART

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