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


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I may be just a humble amateur, but I wasn't mistaking outflow for narrow little low cloud bands racing away from 05L.

Yes, what he highlighted there was not "outflow". One typically refers to outflow as the upper-level outflow at the anvil level associated with UL divergence. Those clouds in riptide's figure are arc clouds or outflow boundaries, which are associated with cold pools and surface divergence, and not generally referred to as outflow when dealing with tropical cyclones.

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"AFTER LOOKING VERY DISORGANIZED OVERNIGHT...SATELLITE IMAGERY THIS

MORNING SHOWS A MARGINALLY BETTER STRUCTURE WITH EVIDENCE OF

INCREASED CONVECTIVE BANDING."

Tropical cyclones do have a diurnal cycle signature in convection. Jasaon Dunion's most recent work shows that you will often see convection weaken beginning right at sunset and remain in a "suppressed" state through night. Sometimes you get this radially propagating ring of cold cloud tops away from the center of the storm, which has preferable distances from the storm depending on the UTC time. As the sun comes back up- the convection reorganizes near the center of the storm. I'm surprised no one talks about this...

The arc clouds + the center outrunning the convection makes me think this isn't TD 5's day.

I've read and seen quite a bit about this theory and you got it backwards I think. Convection begins to strengthen right after sunset, and this coincides with the development a ring of cold cloud tops that propagates outwards from the hurricane inner core. It can be tracked through the night and into the next day's afternoon. The best theory for it now (though I am not entirely convinced) is that the development of a cloud top inversion after sunset due to radiative imbalance leads to a favorable environment for an outwards propagating gravity wave, which wouldn't be possible during the day when there is no stable layer at cloud top. This gravity wave may significantly enhance divergence as it moves outwards, so the most rapid intensification would be when it's coupled with the inner core for that brief time and evacuating mass more rapidly. Fortunately they're doing a mission on this so we'll learn more. http://www.aoml.noaa..._TC_Dirunal.pdf

I agree with turtle, I think you had it backwards Mike. The cool rings develop during the daytime due to cooling away from the radius of maximum winds (RMW) and warming near the RMW, which weakens the secondary circulation. Overnight convection becomes concentrated near the center of circulation, strengthening the system.

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12z HWRF simulated MW imagery

(That's some cool stuff)

Certainly is cool... but will it be right? ;)

In current microwave imagery... Ernesto still has a ways to go, but the circulation envelope is rather large which might bode well for its future in the Caribbean even if the shear does increase.

acdjs6.jpg

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Do not fprget once it passed the leeward islands it hit the death zone. It will be a least four to five days before any real development can occur.

You mean the same death zone where Emily strengthened from a tropical storm to a category 4 hurricane? And the one where ivan went from cat 2 to cat 5?
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I agree with turtle, I think you had it backwards Mike. The cool rings develop during the daytime due to cooling away from the radius of maximum winds (RMW) and warming near the RMW, which weakens the secondary circulation. Overnight convection becomes concentrated near the center of circulation, strengthening the system.

That's how I always thought of it, but I'm no tropical expert. I was a little confused from his post.

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Do not fprget once it passed the leeward islands it hit the death zone. It will be a least four to five days before any real development can occur.

My worry is shear isn't supposed to let up for the next 3 days. If shear stregnthens in the death zone, it could eliminate Ernesto from the Gene Pool.

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^^

Which is exactly why we need a couple of RECON missions under our belt before making bold calls. I strongly suspect a G-IV mission or two will be tasked tomorrow for future flights. We will see...;)

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Not sure what the deal was with that.

LGEM is up to an unrealistic 101 knots.

101 kts is not unrealistic. If Ernesto does become an 80 mph hurricane and conditions are favorable in the upper level environment over those scaldingly hot sea surface temperatures in the Western Caribbean, what's another 30 mph?

Systems rarely strengthen gradually once they hit Category 1-2 strength. A hurricane in the Western Caribbean under favorable conditions in August is unlikely to go from 75 mph to only 80 mph the following day.

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1005mb is still nothing that 12 hrs of shear and dry air can't rip apart into an open wave

Ernesto is moving farther away from the primary source of shear from the TUTT in the central atlantic, here is the SHIPS intensity forecast.

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

120803 0000 120803 1200 120804 0000 120804 1200

LAT LON LAT LON LAT LON LAT LON

BAMS 13.3N 57.4W 13.8N 61.3W 14.2N 64.9W 14.6N 68.6W

BAMD 13.3N 57.4W 13.8N 59.7W 14.5N 62.1W 15.3N 64.6W

BAMM 13.3N 57.4W 13.7N 60.4W 14.5N 63.3W 15.2N 66.4W

LBAR 13.3N 57.4W 13.5N 60.5W 14.0N 63.6W 14.4N 66.6W

SHIP 45KTS 51KTS 57KTS 62KTS

DSHP 45KTS 51KTS 57KTS 62KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

120805 0000 120806 0000 120807 0000 120808 0000

LAT LON LAT LON LAT LON LAT LON

BAMS 15.3N 72.2W 16.0N 79.2W 15.4N 84.1W 14.4N 86.6W

BAMD 16.3N 67.3W 18.6N 72.6W 20.5N 76.4W 21.9N 79.0W

BAMM 16.1N 69.7W 17.9N 76.5W 19.0N 82.2W 20.0N 86.4W

LBAR 15.0N 69.7W 16.5N 75.3W 14.1N 80.9W 15.4N 83.7W

SHIP 65KTS 71KTS 78KTS 79KTS

DSHP 65KTS 71KTS 78KTS 79KTS

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People seem more pessimistic about Ernesto now looking much better than last night when it looked like it wasn't even a depression.

Ernesto has the possibility to turn into a significant storm IMO. The TCHP values are VERY high in the western Carribean, and with little to no shear forecast by the intensity models once it reaches the western Carribean, this thing should have no trouble intensifying by the time it progresses toward the W. Carribean.

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The problem with the ECarib is that the funneling of the low-level easterly flow between S. America and Hispaniola strengthens the LLJ to a point where issues with shear and the LLC running ahead of the convection/opening up become prevalent. This is less of an issue when storms are already well-organized (e.g. Emily or Ivan) or when the low-level easterly flow is already weak.

I expect that we could see situations where recon will find 50 kt winds without a well-defined circulation in the next couple of days.

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