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Tracking #94L in the SW Carib likely to produce very heavy rains over C America this coming week and a Wave nearing NE coast of S America
Days since last H. Landfall - US: Any 4 (Michael) , Major: 4 (Michael) Florida - Any: 4 (Michael) Major: 4 (Michael)
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Archives 2000s >> 2008 Storm Forum

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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)

Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Area of Concern - Invest 92L
      #81351 - Thu Aug 14 2008 01:36 PM

Satellite imagery suggests that Invest 92L may be intensifying, near 18N 61.5W at 14/17Z (just northeast of Antigua), under a small but rapidly developing CDO. Movement of the system has slowed and is now westerly at about 6 knots. Recon is investigating the system and Tropical Depression (or Tropical Storm) formation is possible later today. Folks in the Virgin Islands, Puerto Rico and the Dominican Republic should monitor this system closely. Invest 92L could initialize as a small compact storm. Folks in the Bahamas and Florida should also keep a close eye on the movement of this system as it develops and heads to the west or west northwest over the next few days.

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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)

Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Area of Interest - Invest 92L [Re: Ed Dunham]
      #81405 - Thu Aug 14 2008 09:34 PM

Invest 92L is now more of an area of interest since intensification has not yet occured, however folks in the Virgin Islands, Puerto Rico, Hispaniola, The Turk & Caicos Islands and the southern Bahamas still need to closely monitor this system with the potential for heavy rainfall tonight over portions of the Virgin Islands and Puerto Rico. At 15/00Z, NHC places the system at 18.3N 64.6W with sustained winds of 30 knots and a central pressure of 1011MB. At 01Z the system was over St. Thomas but the winds at both St. Thomas and St. Croix were reported as calm - additional justification for no Tropical Depression yet. Invest 92L continues to move just to the north of due west at about 9 knots. With this movement, the system should skirt the north shore of Puerto Rico and the Dominican Republic tonight and early Friday and this proximity to land could impede any additional development for awhile - but eventual intensification is still anticipated by the NHC later on Friday. Until this system becomes a tropical cyclone, long range projections on its future track are a big unknown.

At 04Z winds at St. Thomas gusting to 30 knots out of the east southeast.

Edited by Ed Dunham (Fri Aug 15 2008 12:25 AM)

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Storm Tracker

Reged: Wed
Posts: 307
Loc: Palm City, Florida
Re: Area of Interest - Invest 92L [Re: Ed Dunham]
      #81410 - Thu Aug 14 2008 10:10 PM

Ed-- could you help us understand how a system with this type of satellite presentation is not a depression despite the calm winds at the surface. I have been tracking storms for a long time and do not remember a senario like this.

Why I'm here:
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Weather Watcher

Reged: Fri
Posts: 32
Loc: Palm Beach County, FLA
Re: Area of Interest - Invest 92L [Re: craigm]
      #81413 - Thu Aug 14 2008 10:31 PM

This is my question also. What is the science right now that would keep the NHC from pulling the trigger on this one to classify it in one form or the other. I look at it with an untrained eye, but with many years of following storms, and it looks to have the appearance of at least a strong depression. Please advise

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Weather Analyst

Reged: Thu
Posts: 859
Loc: Pinellas Park, FL
Re: Area of Interest - Invest 92L [Re: flanewscameraman]
      #81414 - Thu Aug 14 2008 11:05 PM

I'm seeing the same thing. It's a real head scratcher. Apparently, we are seeing excellent mid and upper level development while no low level/surface closed circulation exists (or it doesn't for very long). It seems that there have been some short lived LL vortices throughout the day, but nothing persistent. Surface wind observations are light. Tomorrow is another day and as the system clears PR, there is the chance of a LLC developing.

2018 Actual: 14/7/2

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Weather Hobbyist

Reged: Wed
Posts: 92
Loc: NC
Re: Area of Interest - Invest 92L [Re: MichaelA]
      #81416 - Thu Aug 14 2008 11:22 PM

With the excellent mid/upper level development but no closed low, could this is some way be compared to a funnel cloud that has not touched the ground?

I know kinda comparing apples to oranges but if the upper level structure is there and that is apparent, once lows closes off seems to me would be potential for almost instant development...instant problems.

Fran, Bertha, Dennis & Floyd (Tag Team)

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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)

Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: Area of Interest - Invest 92L [Re: craigm]
      #81417 - Thu Aug 14 2008 11:22 PM

This is probably one that is more appropriate to the Hurricane Ask/Tell Forum, but I'll start with a few definitions from the NHC Glossary:

A weather system for which a tropical cyclone forecast center (NHC, CPHC, or JTWC) is interested in collecting specialized data sets (e.g., microwave imagery) and/or running model guidance. Once a system has been designated as an invest, data collection and processing is initiated on a number of government and academic web sites, including the Naval Research Laboratory (NRL) and the University of Wisconsin Cooperative Institute for Meteorological Satellite Studies (UW-CIMSS). The designation of a system as an invest does not correspond to any particular likelihood of development of the system into a tropical cyclone; operational products such as the Tropical Weather Outlook or the JTWC/TCFA should be consulted for this purpose.

Tropical Disturbance:
A discrete tropical weather system of apparently organized convection -- generally 100 to 300 nmi in diameter -- originating in the tropics or subtropics, having a nonfrontal migratory character, and maintaining its identity for 24 hours or more. It may or may not be associated with a detectable perturbation of the wind field.

Tropical Cyclone:
A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects).

Tropical Depression:
A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 33 kt (38 mph or 62 km/hr) or less.

The recon flights earlier today were unable to confirm a 'closed circulation' at the surface, i.e., in the northern hemisphere this means the detection of a westerly surface wind on the south side of a westward moving tropical disturbance. The organized deep convection was located to the northeast of the low center this afternoon, rather than around the center. Tonight the convection is around the center (or at least close to it), but the westerly component to the surface wind is still not there - so no TD yet.

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