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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Yes, its either Ana or her reminants.
15/1145 UTC 11.4N 33.5W T2.5/2.5 90L
ecmwf 00z
Large wave on the African coast is getting ready to exit. This is another one to be watched over the next few days.
Reflector site for those at work, which includes Weather456, daily update.
ANA
TD3
AOI
AOI
Oh! That's been happening at work to a lot of people - and they're using PC's. It's a pop up that wants you to "update" your Microsoft virus scan....it even looks like it links to a Microsoft site - but it doesn't. It downloads a nasty little trojan that ultimately causes your computer to crash every time you turn it on. We've been using Malwarebytes to remove it. Malwarebytes has their own website - you can google it or download it from Cnet.
IT LOOKS LIKE SOMETHING TO KEEP AN EYE ONThat is what my thoughts are. It lookslike it is starting to show some rotation. Quickscat didn't go over that area this morning. Also Key West doesn't have anything mentioned about this except thunder storms.
Good moring, looks like we are going to get tropical appetizers with the wave in the gulf this weekend and no fishing.
CMC and GFS pick it up as a smaller disturbance headed toward the panhandle.
I respect Kman's opinion, he's been right on a lot of storms, but Andrew was written off as dead and going out to sea, and Katrina was "just a tropical storm" before it came ashore. The very warm waters off the Bahamas and South Florida can cause unexpected intensifying, and needs to be watched.
whadya guys think, TD or TS
This morning's Key West AFD. Interesting discussion on radar presentation of convection associated with the wave entering the GOM.
Isn't it already a Tropical Depression?
If not, it should be.
Ana still exposed... (yet again)
Actually both came out as 2.5
T2.5/2.5
Ana came out as 2.0 from the TAFB.
I concur.
You need to read my post again. The NHC will decide at 11 whether it warrants maintaining the TS classification or whether a downgrade to TD may be on the cards then or later today.
That was the point I was making.
Is Ana what used to be TD2?
Thank you for your analysis. I've been watching wave for hours with regard to its effect on south Florida which now just appears to be rain. (Just was in it) This wave appears to be organizing and drifting into the Gulf, and that's not good for quite a few folks.
Now, we have Ana, and Bill could possibly be here at 11 a.m. (if not, definitely TD3).
So, anyone here have any crow recipes for breakfast
You are 100% correct.
No?
DVTS, CI, , 1170N, 3290W, , 3, 30, 2, TAFB,
Ana was 2.5 from both.
Yea, and has alot of hot water to traverse. Hot enough that in the past things have morphed out there.
NATIONAL WEATHER SERVICE KEY WEST FL
948 AM EDT SAT AUG 15 2009
.DISCUSSION...
.CURRENTLY...
THE NORTHERN PORTION OF A TROPICAL WAVE EXTENDING FROM THE FLORIDA
STRAITS INTO THE CARIBBEAN IS CURRENTLY MOVING WESTWARD THROUGH THE
FLORIDA STRAITS AND IS BEGINNING TO IMPACT THE MIDDLE AND UPPER
KEYS...AND WILL IMPACT THE LOWER KEYS WITHING THE NEXT FEW HOURS. A
CONVECTIVE MASS IN THE STRAITS EAST OF THE KEYS IS EVIDENT ON KBYX
RADAR...WITH A BROAD MID LEVEL CIRCULATION DETECTABLE FROM AROUND
10KFT THROUGH 25KFT. THE APPROXIMATE MAXIMUM OF THE CIRCULATION IS
AROUND 700MB...AND THERE IS ALSO A WEAK CIRCULATION DETECTED FROM
AROUND 5KFT TO THE SURFACE. SURFACE WINDS AT ISLAND STATIONS ALONG
THE KEYS HAVE BEEN MORE OF LESS SOUTHEAST FROM 5 TO 10 KNOTS OVER THE
PAST FEW HOURS...WITH CMAN STATIONS ALONG THE REEF A COUPLE OF KNOTS
BELOW 10 KNOTS WITH GUSTS NEAR 15 KNOTS. MOLASSES REEF...WHICH IS
NEAREST THE CONVECTION...HAS REGISTERED THE HIGHEST WINDS THUS FAR
WITH SUSTAINED WINDS OF 16 KNOTS AND GUSTS OF 18 KNOTS.
Link
WORD
With the track pointing towards the US, they'll be reluctant to downgrade it right after it's named.
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