2:05 PM EDT TWD Special Feature

[cycloneye]

928
AXNT20 KNHC 081759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED 08 2005


...SPECIAL FEATURE...
NORTHWESTERN CARIBBEAN SEA 1006 MB SURFACE LOW PRESSURE CENTER
HAS FORMED AND NOW IS NEAR 17N85W...ABOUT 60 NM NORTH OF THE
HONDURAS COAST. THIS BROAD AREA OF LOW PRESSURE GRADUALLY IS
BECOMING BETTER ORGANIZED. IT APPEARS THAT A TROPICAL DEPRESSION
IS FORMING BETWEEN HONDURAS AND THE CAYMAN ISLANDS. THE UPPER
LEVEL WIND SCENARIO IS BECOMING MORE FAVORABLE. IT IS POSSIBLE
THAT THIS SYSTEM MAY BECOME A TROPICAL STORM DURING THE NEXT DAY
OR TWO AS IT MOVES SLOWLY NORTHWARD. AN AIR FORCE RESERVE UNIT
RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS SYSTEM
LATER TODAY. HEAVY RAINS AND GUSTY WINDS WILL BE AFFECTING THE
CAYMAN ISLANDS...JAMAICA...CUBA...AND THE YUCATAN PENINSULA
DURING THE NEXT COUPLE OF DAYS EVEN IF THE SYSTEM DOES NOT
DEVELOP. A MIDDLE TO UPPER LEVEL TROUGH IS DIGGING INTO THE
NORTHWESTERN CARIBBEAN SEA JUST EAST OF THE YUCATAN PENINSULA.
UPPER LEVEL ANTICYCLONIC FLOW WITH A RIDGE IS ON TOP OF THIS
FEATURE. SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS ARE FOUND FROM 11N TO 21N BETWEEN 76W AND
88W...FROM THE SOUTHWESTERN CORNER OF THE CARIBBEAN SEA TO
CUBA...AND INTO THE GULF OF HONDURAS. A TROPICAL WAVE ALSO IS
ALONG 82W SOUTH OF 16N.

[tallywx]

From visible satellite pics, it's clear that no closed and tight low-level circulation has formed yet. Recon. won't find anything. No distinct west wind, but a definite broad area of low pressure. Will probably take until at least overnight tonight for a cyclone to spin up.

[Brent]

<confused>

So a surface low pressure is different from a closed low pressure?

[Derek Ortt]

from visible, it does appear that there is a west wind, though the circulation is borderline as to whether or not it should be classified

[vbhoutex]

<confused>

So a surface low pressure is different from a closed low pressure?

Low pressure at the surface can be broad, as in spread out or it can have a tight gradient with a "closed" circulation around a small center area. Technically any low pressure system at the surface is closed(I think-correct me if I am wrong pros). When we are talking about an LLC or LLCC in the tropics we are talking about a low with a tight gradient around a definite center of circulation as opposed to a spread out center of circulation. Clear as mud??

[Brent]

<confused>

So a surface low pressure is different from a closed low pressure?

Low pressure at the surface can be broad, as in spread out or it can have a tight gradient with a "closed" circulation around a small center area. Technically any low pressure system at the surface is closed(I think-correct me if I am wrong pros). When we are talking about an LLC or LLCC in the tropics we are talking about a low with a tight gradient around a definite center of circulation as opposed to a spread out center of circulation. Clear as mud??

That's better. I was just thinking they were saying a broad low(like the normal ones you get with a front) weren't closed.

[Thunder44]

There seem to be two potential LLC's, one near 17.5N 85W and a more defined one near 17N 83.5W.

http://www.ssd.noaa.gov/PS/TROP/DATA/RT ... -loop.html

[Dave C]

I've seen from many systems that multiple LLCs can rotate in a larger broad low pressure. Steve Lyons is always good at pointing that out in early development stages. Definately a broad rotation is evident.