Disturbance 90L close to tropical depression strength; TD 2 may rise again
A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.
Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.
Figure 1. The remnants of Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).
Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.
I'll have an update Saturday morning, or earlier, if significant developments occur.
Jeff Masters
Reader Comments
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well basically all folks have to do at this time, is make sure you have a plan or its up to date. 90L may miss us but what about storms later in the hurricane season, we still have September to go. So its better to be safe and not hit you than to dont prepare and somethings hit you.
Hurricane shelters are schools, health centers, etc. I know example set, exmaple follow, but I'm not going to a shelter unless if its cat 3 or less. lol
Thats currently the interpolated run, the actual run should be up soon.
ABNT20 KNHC 142325
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT FRI AUG 14 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
SATELLITE IMAGES AND DROPSONDE DATA FROM A NOAA HIGH ALTITUDE JET
INDICATE THAT FORMER TROPICAL DEPRESSION TWO LOCATED ABOUT 1000
MILES EAST OF THE LESSER ANTILLES IS REGENERATING AND COULD BECOME
ONCE AGAIN A TROPICAL CYCLONE TONIGHT OR EARLY SATURDAY. UPPER-
LEVEL WINDS ARE MARGINALLY FAVORABLE FOR ADDITIONAL DEVELOPMENT AS
THE SYSTEM MOVES WESTWARD AT 12 TO 15 MPH. THERE IS A HIGH
CHANCE ...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
THE BROAD AREA OF LOW PRESSURE CENTERED ABOUT 400 MILES SOUTHWEST OF
THE WESTERNMOST CAPE VERDE ISLANDS IS ACCOMPANIED BY A LARGE AREA
OF CLOUDINESS AND THUNDERSTORMS. THIS SYSTEM IS GRADUALLY BECOMING
BETTER ORGANIZED AND A TROPICAL DEPRESSION COULD ALSO FORM TONIGHT
OR SATURDAY. THE LOW IS EXPECTED TO MOVE WESTWARD AT 15 MPH. THERE
IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING
DISORGANIZED CLOUDINESS AND SHOWERS OVER THE WESTERN CARIBBEAN
NORTHWARD ACROSS CUBA AND THE BAHAMAS. THE ACTIVITY IS MORE
CONCENTRATED JUST NORTH OF THE COAST OF CENTRAL CUBA AND IS
EXPECTED TO SPREAD WEST-NORTHWESTWARD OVER SOUTH FLORIDA AND THE
SOUTHEASTERN GULF OF MEXICO DURING THE NEXT COUPLE OF DAYS. THERE
IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
DISORGANIZED SHOWERS AND THUNDERSTORMS OVER THE NORTHEASTERN GULF OF
MEXICO ARE ASSOCIATED WITH A WEAK TROUGH OF LOW PRESSURE. SURFACE
PRESSURES ARE RELATIVELY HIGH IN THIS AREA. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER AVILA
Hey hows it going,
Are you from the Dominican Republic or PR?
Bears watching, as anything can Happen with the SSt's and things can and do usually change fast in these situ's.Monitor the NHC and your Local NWS for anything that changes
I get those images from the EUMETSAT page. The most impressive images are usually in the RGB Composite section. That satellite gets a good angle to show the height of cloudtops in the visible spectrum.
As for the high pressure ridge, my thought is this: While there is a spread in the model runs, it appears the ridge will be in place long enough to threaten somewhere on the North American continent. Whether that's Mexico, the Gulf Coast, Florida, or the East Coast is uncertain at this point. The biggest variable I see is TD2. If it can strengthen into a tropical storm, it may create enough weakness in the ridge to start turning 90L WNW while it is east of the Lesser Antilles. If this occurs, then I think 90L will be an East Coast event. If TD2 dissipates, then I don't think enough of a weakness will remain and 90L will continue west.
TD2 is the key to 90L's track beyond 5 days.
I thought what 456 posted was the 18Z. I'm in need of a good nights sleep.
a define circulation can really help tell where 90L is going
Herbert boxes are also good
and speed of motion
So exciting.
Very excellently thought out and written on all counts.
TWO REDS
Very true,Our Odpm says our home is our first shelter.
You are addicted to this blog...just like the rest of us...lol.
whats see what storm make land fall 1st
this kinding
Entertainment and education all in one place!
18Z HWRF
HOUR: 126.0 LONG: -63.10 LAT: 16.90 MIN PRESS (hPa): 929.00 MAX SURF WIND (KNOTS): 102.00
18Z GFDL
HOUR:126.0 LONG: -64.24 LAT: 16.98 MIN PRESS (hPa): 960.93 MAX SURF WIND (KNOTS): 99.34
I think im addicted to my computer in general. Got one window open with all my tropical weather stuff and one with my facebook window open lol
just like it got very un-impressive at an extremely high rate... lol
wish storm???
Sorry, 90L
Grothar here! You have been of assistance to me before. Do either of you know what the projection is on the building high pressure which should be over both systems? Would this not have a great effect on the path of the systems? The models which I have seen on this site, would indicate a very westerly motion. Unless I have missed it, there is not much mention of it. I would appreciate your assistance.
fail
dont do that >:|
90L is moving at 15 mph now. With a movement of 15 mph, you can throw out the 12Z ECMWF run. It shows it just beyond 40W on Monday at 12z...way too slow.
It'll be near 50W by Monday afternoon.
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