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Beryl now TD; Landfall 70 mph Jax Bch 12:10 AM 5/28.; TS warnings lifted for S SC to NE FL


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94L could make for very interesting wx for part of the SE US coast this weekend. I found a halfway decent analog to which I'll compare and contrast:

Here's a late May STS from 1972, Alpha, that was moving NE but got blocked and backed westward into the SE coast:

http://weather.unisy...ALPHA/track.gif

Go here for the daily wx maps for the week of 5/22-28/1972:

http://docs.lib.noaa...ather_maps.html

1) Alpha was ST rather than tropical. The dewpoints were only in the 50's along the SE coast in advance of its arrival. In contrast, TD's are forecasted this weekend to be about 10 F warmer (near the mid 60's.). So, that would tend to favor more tropical for 94L than Alpha.

2) For Alpha, the lowest reported SLP then was pretty impressive, about 991 mb, which was near landfall. Highest winds were 60 knots. it landfalled at ~50 knots. 94L's lowest SLP is progged to be a good bit higher (1,000-1,009 mb).

3) For Alpha, the blocking 500 mb high was NNW of the storm, allowing for almost due west motion into the coast. The currently progged blocking 500 mb high is NW of the storm, favoring WSW motion into the coast.

4) Alpha had a chilly 1032 mb sfc high over the NE US., which allowed for pretty fast motion westward into the coast, a feed of cool, dry air just to its north, and a tight pressure gradient. The current setup has no big, chilly surface high. Instead, highest SLP's to the north are only in the 1020's and the high isn't cold at all. So, this means no big feed of cool, dry air (more tropical opportunities vs. 1972), a slower motion toward the coast, and a looser pressure gradient (not as high winds) unless tropical development is much stronger than progged.

post-882-0-39921000-1337875815_thumb.gif

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It is interesting how rapidly 94L has organized. 24 hours ago the system was a hot mess, yet today, you can clearly see the beginnings of a center of circulation on KAMX (Miami) radar. This may be a good example of how having slightly higher shear can accelerate TC genesis by acting to consolidate the convection and latent heating on one side of the initial broad low pressure center. Convection and upper-level divergence have also been enhanced by dynamical forcing courtesy of the upper-level trough over the Gulf, so even if this becomes a tropical cyclone, it will still have some extra-tropical origins while it was in the womb.

I think there's a high likelihood of genesis over the next day or two as the shear relaxes and the system looses that squall-line like appendage on the southeast side.

post-378-0-15282800-1337884343_thumb.gif

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Should be classified as a TD soon at least. Freeport obs show pressure dropping and winds nearing TS strength.

I think we have a bit more time to go before we see this system being classified. It hasn't yet merged with the amplifying upper level trough to its east, and the shear currently is too hostile to support tropical or subtropical genesis.

I've posted a preliminary outlook on 94L on my blog and have attempted to explain the basic environmental conditions that lead to subtropical cyclones.

http://philstropicalweatherblog.wordpress.com/2012/05/24/invest-94l-next-threat-in-the-atlantic-hurricane-bud-takes-aim-at-mexico/

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Well...

That was unexpected.

000

ABNT20 KNHC 250037

TWOAT

SPECIAL TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

840 PM EDT THU MAY 24 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN ASSOCIATED WITH THE

BROAD AREA OF LOW PRESSURE...LOCATED BETWEEN THE NORTHWESTERN

BAHAMAS AND SOUTHEASTERN FLORIDA...HAS GRADUALLY BECOME BETTER

ORGANIZED THIS AFTERNOON AND EVENING. ENVIRONMENTAL CONDITIONS ARE

EXPECTED TO BECOME MORE CONDUCIVE FOR THE FORMATION OF A

SUBTROPICAL OR TROPICAL CYCLONE BY SATURDAY OVER THE WESTERN

ATLANTIC OCEAN OFF OF THE SOUTHEASTERN UNITED STATES. THIS SYSTEM

HAS A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL OR

SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES

NORTHEASTWARD AT 10 TO 15 MPH.

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Well...

That was unexpected.

000

ABNT20 KNHC 250037

TWOAT

SPECIAL TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

840 PM EDT THU MAY 24 2012

. THIS SYSTEM

HAS A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL OR

SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES

NORTHEASTWARD AT 10 TO 15 MPH.

I'm not sure it is all that surprising, although I would surmise this is headed to subtropical, rather than tropical nascent stage.

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Here's my prediction...I think that it does form and tops out around 50 MPH then starts to weaken prior to landfall. Dry air will be an issue all weekend. Leaning towards a NE Florida landfall, but it could happen as far north as the Hilton Head Island area.

post-6373-0-91096700-1337949488_thumb.jp

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Here's my prediction...I think that it does form and tops out around 50 MPH and starts to weaken prior to landfall. Dry air will be an issue all weekend. Leaning towards a NE Florida landfall, but it could happen as far north as the Hilton Head Island area.

not a bad cone. My guess is just south of Savannah, but it all depends how the high going off the mid-Atlantic is oriented. We should know by tomorrow morning where she's headed. I don't believe we'll see as much dry air as we saw with Alberto, but will certainly be a factor in this storms growth potential.

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Never in a million years would I think something tropical, when I see the satellite presentation.

The overall size of the system is an anomaly in developing tropical cyclones, looks like something you'd see in the winter or in the pacific. It has a beautiful moisture feed from the carribean, quite an interesting system.

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While it's far from impressive, NESDIS sees a decent circulation.

I'm not a fan of the composite chart for weak systems, because they put in a bogussed irrotational vortex in the creation of those products. However, the AMSU and ASCAT images available below that image on the webpage are legit.

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It appears that 94L formulate itself in the general area discussed above; as a shallow warm core system. Some deep convection will be required for accelerated development. The future track is somewhat chaotic, it appears that the westward movement will not occur until late Saturday and 94L is already approaching 75W, nonetheless the forward speed appears to be decreasing.

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000

NOUS42 KNHC 251445

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1045 AM EDT FRI 25 MAY 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 26/1100Z TO 27/1100Z MAY 2012

TCPOD NUMBER.....12-007

I. ATLANTIC REQUIREMENTS

1. SUSPECT AREA

FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71

A. 26/1800Z A. 27/1200Z

B. AFXXX 01XXA INVEST B. AFXXX 0202A CYCLONE

C. 26/1515Z C. 27/0915Z

D. 33.0N 77.0W D. 30.8N 79.5W

E. 26/1730Z TO 26/2130Z E. 27/1130Z TO 27/1630Z

F. SFC TO 10,000 FT F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE 28/0000Z FIX

NEAR 30.8N 81.0W IF SYSTEM DEVELOPS.

II. PACIFIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. SUCCEEDING DAY OUTLOOK.....NEGATIV E.

JWP

HurricaneHunter.jpg

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