cieldumort
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Above: Invest 94L at 0445UTC Aug. 17, 2012
A large, potent tropical wave which has just exited Africa has been tagged as Invest 94L.
The center of Invest 94L's overall mass is located in the vicinity of 10N 21W, although its best vorticity at the moment may be slightly east-northeast of there. Movement is to the west at 15-20MPH.
NHC currently gives 94L a 10% chance of becoming a tropical cyclone within the next 48 hours.
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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At 17/12Z, the 1009mb low center of Invest 94L was located just off the west African coast at 11.6N 21.0W. Movement should be slow westerly at first, becoming more west northwesterly at an increased speed early next week. The Invest has the potential to become a long-track system. Wind shear should remain light and SSTs are favorable for eventual development. Dry air to the west is a negative factor that could keep development minimized for a few days.
ED
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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At 19/00Z, Invest 94L was located about 600 miles to the west of the Cape Verde Islands near 14.2N 32.6W moving to the west at 20 knots. Sustained winds are now at 30 knots and central pressure is 1008MB. The cloud presentation, outflow and evidence of gathering circulation already look far better than TS Helene ever did and I would expect that the system would be upgraded Sunday morning to at least Tropical Depression status. Wind shear ahead of the system should weaken over the next few days. Although SSTs will only be about 27C on Sunday into Monday morning, some slow development still seems likely as the system continues westward under the influence of an extensive Atlantic ridge and folks in the Leeward Islands should monitor this approaching system. The next name on the list this season is Isaac.
ED
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cieldumort
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As of 2:00 AM EDT Aug. 19, Invest 94L is looking better and better, and it appears increasingly likely that the ninth tropical cyclone of the 2012 Atlantic Hurricane Season will be declared within 48 hours, and probably considerably sooner rather than later.
There is beginning to be some serious question tonight as to whether or not the area of maximum vorticity in the lowest portions of the atmosphere associated with 94L hasn't shifted quite a bit west-northwest, getting nestled with the most consistent area of deep convection, and is now establishing itself around 14.8N 35W, and heading west from there.
Microwave and scatterometer data will be coming in later that will hopefully clear things up. Provided that an incipient LLC is now much better paired with deeper convection, it is possible that TD9, or Isaac, could be confirmed by later this morning.
As an aside, the 19/00Z model runs look as if they have a questionable handle on what is actually going on with 94L, and should probably all be taken with a grain of salt.
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doug
Weather Analyst
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There seems to be considerable organization necessary for the to declare that a cyclone has formed. I agree that the area in the NW portion of the envelope is becoming the dominant focal point, but it is not there yet at least based on visible evidence this am. I am also interested in the situation near the remnant of Helene. A burst of convection is occurring over the waters east of Mexico. While there is still evidence of a circulation over land the dynamic of the trough diving quickly SE'wrd over Texas may induce the circulation more to the east back over water...this still bears watching IMO.
9:35 update there seems to be a circulation at about 14.2/36.2. Two large convective areas are generally south and NW of that pointmso further organization will have to occur, but it seems to be underway.
The area of convection near the Mexico coast in the SW GOM is growing. The eastern edge of the former Helene's circulation seems to be just on the coast and may be over water, but most of it is on shore...still interesting.
Off to a conf. for a few days
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doug
Edited by doug (Sun Aug 19 2012 09:40 AM)
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Invest 94L was located at 14.4N 36.4W at 19/12Z. Although westward movement has slowed to 16 knots, dry air to the north and west of the system (something that I neglected to check last night) is substantial and has reduced convection and central pressure went up 3MB to 1011. Although the forward speed has slowed, convection still remains displaced to the north of the center.
Perhaps with consideration for the drier environment to the west, the last couple of runs on the model no longer develop 94L into a strong system. Although a weaker system now seems more likely, folks in the Islands should still closely monitor this Invest area.
ED
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danielw
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NHC is gearing up to fly 94L, if necessary.
NOUS42 KNHC 191517
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, National Hurricane Center, MIAMI, FL.
1115 AM EDT SUN 19 AUGUST 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 20/1100Z TO 21/1100Z AUGUST 2012
TCPOD NUMBER.....12-092
I. ATLANTIC REQUIREMENTS
SUSPECT AREA EAST OF ISLANDS.
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: LOW LEVEL INVEST FOR
21/1800Z NEAR 15.5N AND 53.0W IF SYSTEM DEVELOPS.
3. REMARKS: ADDITIONAL DAY OUTLOOK: BEGIN 6 HRLY FIXES
22/0600Z. A NOAA GIV FLIGHT FOR 22/0000Z.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
$$
[WVW]
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Invest 94L still looking very disorganized - so much so that to quote a favorite phrase of the , "80% chance for tropical cyclone development in the next day or so may be somewhat generous". The real problem with 94L and its development opportunity has been a combination of dry air to the north and west of the system - and the proximity of two circulation centers with the eastern center about 5 degrees (300 miles) east southeast of the westernmost center. Until one center predominates, consolidation and development is difficult and the entire system remains weak and travels westward at a good clip.
ED
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cieldumort
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As of 3:45 PM EDT Aug. 20, 94L is finally consolidating around a more dominant, and now well-defined LLC, centered at 15.6N 47W, with movement to the west at 20-25 MPH.
Most recently, a thunderstorm has begun firing right atop the LLC, and despite dry air in the region, this trend should continue, although perhaps in an on again-off again fashion.
It is now very possible that 94L becomes a tropical depression by midnight, and gives odds of 80% that 94L becomes a TD at least within the next 48 hours.
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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At 21/00Z, Invest 94L was located at 15.3N 48.8W with sustained winds estimated at 30 knots and pressure at 1009mb. The system has moved 8.2 degrees to the west in 24 hours - that equals to an average speed of 20.5 kts. When a system chugs along at that rate for an extended period of time, consolidation is difficult at best - especially for a system with a large overall area of circulation, and 94L is rather large. Although 94L should start to slow down, it will pass through the Lesser Antilles on Wednesday - and if it slows down enough, it could be a tropical cyclone at that time so folks in the Islands should continue to closely monitor this developing system.
This evening some new convection is firing near the center and in the band to the west but it still has a way to go. On Wednesday as the system approaches the Greater Antilles, it will slow down quite a bit which would allow a better opportunity for development/intensification - but it will also encounter increasing westerly shear at that time. It is worth noting that the and the have not been quick to ramp up this system for the past few days and the 21/00Z run maintains a weaker cyclone for a few more days until it gets west of Hispaniola and near Jamaica/eastern Cuba early Saturday.
ED
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cieldumort
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Invest 94L has been upgraded to Tropical Depression Nine as of 5:00 AM EDT 21 August.
TD 9 is presently centered near 15.2N 51.2W, and movement is to the west at around 20 MPH.
Nine's minimum central pressure is estimated to be down to 1007mb, and maximum sustained winds are about 35 MPH. These estimates could be a little conservative, and Nine may be upgraded to Tropical Storm Isaac at any time.
The following watches and warnings have just been issued:
THE METEOROLOGICAL SERVICE OF BARBADOS HAS ISSUED A TROPICAL STORM WARNING FOR DOMINICA.
THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WARNING FOR GUADELOUPE...DESIRADE...LES SAINTES...MARIE GALANTE...AND ST. MARTIN.
THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WARNING FOR ST. KITTS...NEVIS...ANTIGUA...MONTSERRAT...AND BARBUDA.
THE GOVERNMENT OF CURACAO HAS ISSUED A TROPICAL STORM WATCH FOR SABA...ST. EUSTATIUS...AND ST. MAARTEN.
THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WATCH FOR THE BRITISH VIRGIN ISLANDS.
A TROPICAL STORM WATCH HAS BEEN ISSUED FOR PUERTO RICO...VIEQUES... CULEBRA...AND THE U.S. VIRGIN ISLANDS.
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cieldumort
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Recon is now inside the center of Nine and finding that despite the mostly exposed center, winds are as strong as sustained at and above 40 MPH. Ironically, these strongest winds so far are being found in the drier northeast quadrant, suggesting that should convection increase back over this region, even stronger winds will likely be transported to the surface.
Minimum surface pressure looks to be running at or below 1006mb.
Nine will probably be upgraded to Isaac very soon.
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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I'll make an attempt at analyzing Isaac from what we do know - but right now thats a limited analysis. At 24/03Z TS Isaac was south of the Dominican Republic and probably centered at a latitude lower than 16N. Multiple vortices rotating within a broad area of low pressure have limited the ability of the storm to organize, however, there are signs once again that enhanced convective development is underway. Outflow has improved considerably in the southwest quadrant, and Isaac has slowed down considerably in the last couple of hours. Usually when a storm slows down it means that its going to turn or intensify, or both. As Mike stated elsewhere, we should have some better insight into what Isaac really is and where it is heading by daybreak. For now, its wait and see mode - a time for patience.
ED
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Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
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Isaac is still a tropical storm as of 28/03Z located about 260 miles south southeast of Gulfport, Mississippi, and moving to the northwest at 9 knots with sustained winds of 60 knots and a central pressure of 979MB. The core has again been disrupted by dry air entrainment and an eyewall which formed earlier this evening is now open in places according to earlier Recon reports, but as it has in the past, Isaac will like strengthen again later tonight.
NHC projects landfall as a strong Cat I which seems reasonable if the cyclone can shunt off the entrainment. The strong ridge influence of 24 hours ago is probably not as significant a player tonight. Earlier this evening pressure falls along the Florida and Georgia east coast suggested that the Atlantic ridge was not able to build further west - perhaps because of the vorticity maxima that was associated with the breakaway feeder band that moved across the Florida east coast on Monday (and I think directly linked to one of the rotating vortexes that we watched for a couple of days). This should all translate to a more north northwesterly and eventually northerly movement in the next 24 hours with landfall Tuesday evening along the Mississippi coast. BUT given the nature of tropical cyclones in general - especially those in the Gulf of Mexico - and Isaac's history in particular, you indeed do not want to focus on the centerpoint of the projected path but instead, the entire hurricane warning area. Isaac will be a slow moving system as it approaches the coast so those folks in the warning areas can expect high winds, heavy rains and storm surge for a considerably long duration. If you live near the coastline and are ordered to evacuate, please use common sense and do so.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...As of 28/03Z:
A HURRICANE WARNING IS IN EFFECT FOR...
* EAST OF MORGAN CITY LOUISIANA TO THE ALABAMA-FLORIDA BORDER...
INCLUDING METROPOLITAN NEW ORLEANS...LAKE PONTCHARTRAIN...AND LAKE MAUREPAS
A HURRICANE WATCH IS IN EFFECT FOR...
* INTRACOASTAL CITY TO MORGAN CITY LOUISIANA
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* FROM THE ALABAMA-FLORIDA BORDER TO THE AUCILLA RIVER
* INTRACOASTAL CITY TO MORGAN CITY LOUISIANA
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* EAST OF SABINE PASS TO WEST OF INTRACOASTAL CITY LOUISIANA
ED
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berrywr
Weather Analyst
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Loc: Opelika, AL
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Given a choice, I rather have a hurricane hit me than a tropical storm; flooding being it's most potent weapon. The greatest height falls were along the north central coast of FL where there is a weakness...a COL between the upper ridge (finally) building in the Inter-mountain west and the Bermuda ridge; heights between the two ridges have been mostly neutral with a ridge axis continuing from west to east along a line from the border of MO, AR, KS & OK extending ESE to near Charleston SC; inverted trough associated with Issac from about Columbia, SC extending SW through central GA to Tallahassee to Issac. At 200/300 millibars there is an upper ridge right along the Big Bend part of FL. Wind Shear analysis has a somewhat sharp gradient from the 200/300 millibar high westward...Issac is centered under 10 knots from the SE but no more than 150 miles to the west is 20 knots from the SE, 300 miles to the west..30 knots from the SE and a few miles beyond it...40 knots from the SE. New vortex message as of 28/0515Z has Issac's pressure at 979 mbs...winds 52 knots and a 40 mile wide "eye"...open to the SW. Look forward to reading about this storm later...it might be no more than a tropical storm for most of its life...rather rare given the distance it travelled to date.
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Sincerely,
Bill Berry
"Survived Trigonometry and Calculus I"
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