Disturbance 90L close to tropical depression strength; TD 2 may rise again

By: Dr. Jeff Masters , 2:02 PM GMT en Agosto 14, 2009

Share this Blog
5
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 234 - 184

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114Blog Index

90L looks like a classic cape verde wave that could be well on its way to tropical storm status by sunday.
Member Since: Agosto 31, 2008 Posts: 0 Comments: 833
Quoting CaneAddict17:



Link
It says: "access forbidden."
Member Since: Posts: Comments:
if it doesn't work try this address:

http://euler.atmos.colostate.edu/~vigh/guidance/northatlantic/track_late2.png
Member Since: Posts: Comments:
South Florida, what about Central or north Florida? I can see a Frances track where it hits north of South Florida :P

I'm still thinking a Carolinas to New England threat (Gloria 1985)
Member Since: Posts: Comments:
Quoting Stormchaser2007:


I think thats worse. lol


Thats what Katrina did!
Member Since: Posts: Comments:
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
957 AM CDT FRI AUG 14 2009


LONGER RANGE MODELS DEPICT THE BERMUDA HIGH RIDGING OVER THE
REGION AS A MID TO UPPER LEVEL HIGH DEVELOPS OVER THE SERN
STATES.
HAVE TAPERED POPS FROM CHC CATEGORY TUESDAY TO SLT CHC
THURSDAY AS UPPER RIDGE BUILDS OVER THE REGION WITH TEMPS EXPECTED
TO GRADUALLY INCREASE.

Ok. This from the western GOM. What models show this?? And if thats true then is the high supposed to retreat back east before 90l could get in the gulf? Just curious because as far west as i have seen the models was N.O.

Member Since: Posts: Comments:
Quoting MrSea:


I disagree. The convection was offcentered, and there were no SW winds on the south side. (they were all west, feeding into what became 90L)

I agree with your disagreement it look better now than it did before
Member Since: Posts: Comments:
226. jipmg
TD 2 looking good with each satellite image..
90l looks like half moon on the rainbow loop.
Member Since: Posts: Comments:
Quoting canesrule1:
really, can i have the link?



Link
Member Since: Posts: Comments:
90L could be a TD:

14/1145 UTC 12.1N 27.9W T1.5/1.5 90L
Member Since: Posts: Comments:
Quoting caneluver:


Nobody said it was a "Monster trough"


Nobody said it was going out to sea either, it was mainly an east coast possible event. If it does go out to sea, it will do so AFTER it passes Bermuda which brings it close enough to the USA to watch it.
Member Since: Posts: Comments:
Quoting CaneAddict17:
I'm no expert, but I noticed that there was an OFCL track for 90L on the late cycle 06z models. Should we start to see advisories at 5?
really, can i have the link?
Member Since: Posts: Comments:
Now looking at 02L's models they are also suggesting a Florida hit, it's going to be a tough one this year for FL.
Member Since: Posts: Comments:
I'm no expert, but I noticed that there was an OFCL track for 90L on the late cycle 06z models. Should we start to see advisories at 5?
Member Since: Posts: Comments:
Quoting Drakoen:
nvm the GFS ensemble mean takes it into extreme southern Florida before getting into the GOM


I think thats worse. lol
Member Since: Posts: Comments:
Quoting Drakoen:
nvm the GFS ensemble mean takes it into extreme southern Florida before getting into the GOM
WOW! SFLA is inn big danger right now, because models have been consistant with a SFLA hit for over 80 hours, ughhh!
Member Since: Posts: Comments:
former td2 much smaller but looking more organized than 90l imo
Member Since: Posts: Comments:
Quoting TheCaneWhisperer:



The convection is to the W & NW of the LLC. Shear and dry air are messing with it temporarily.



LLC 12N 28.1W
Member Since: Posts: Comments:
Quoting IKE:


I checked the discussions in Amarillo,TX...St.Louis...Chicago...saw very little mention of any significant trough heading east over the next 7 days.


KC is mentioning the trough, but also saying it will get hung up

Meanwhile the middle level low will continue to move east across the
Pacific northwest across the northern plains toward the Hudson Bay
region through the first half of next week. Trailing low pressure
trough is expected to become somewhat anchored over the southwest
US...as middle level ridging stays in place over the southeast
two-thirds of the country.


Of course just yesterday there was saying the opposite.
Member Since: Posts: Comments:
Looks like this time around 90L and old TD2 have completely separate circulations...

Member Since: Posts: Comments:
Quoting RitaEvac:


Isn't Accuweather headquarters located somewhere on the East coast?


Penn State
Member Since: Posts: Comments:
Thanks for the update, Doc.
Member Since: Agosto 9, 2009 Posts: 10 Comments: 5077
Quoting ackee:
thanks


The convection is to the W & NW of the LLC. Shear and dry air are messing with it temporarily.
Member Since: Posts: Comments:
206. MrSea
Quoting centex:
Thanks, but it seems to be in some special ex category. I guess they don't want to go back to 99L or up to 91L. Kind of like when TD has former name.


yea its name is still 02L.Two
nvm the GFS ensemble mean takes it into extreme southern Florida before getting into the GOM
Member Since: Posts: Comments:
Quoting Drakoen:
Accuweather thinking an east coast threat


gut says David "esque" track, the weakness is right over the FL peninsula
Member Since: Posts: Comments:
Quoting StormW:


Morning!
Big fan of you. I look forward everymorning for your synopsis.
Member Since: Posts: Comments:
12Z NAM has now TD#2 Remnants moving through the Northern Leeward Islands...still keeping a good 500MB VORT and looking to be consolidating better towards the latter part.
Member Since: Posts: Comments:
200. MrSea
Quoting extreme236:


Well when it was close to TS status it looked better than this.


I disagree. The convection was offcentered, and there were no SW winds on the south side. (they were all west, feeding into what became 90L)
Quoting DaytonaBeachWatcher:


he is always thinking east coast threat when its not straight for nola

Very true. Everything gets hyped up with them. And I can already tell when something *does* hit anywhere near NYC, they will be shouting "I told you so" from the mountaintop.
Member Since: Posts: Comments:
198. ackee
Quoting TheCaneWhisperer:


Looks to be right at 11.8 to 12N where the models were initialized. Shear may be deceiving you?
thanks
Member Since: Julio 15, 2008 Posts: 0 Comments: 1376
Quoting ackee:
does any notice 9oL appers to be further north than the models has it or that just where the convection are ?


Looks to be right at 11.8 to 12N where the models were initialized. Shear may be deceiving you?
Member Since: Posts: Comments:
Quoting MrSea:


It still has a floater satellite and it still is being plugged into the models, so its still an invest
Thanks, but it seems to be in some special ex category. I guess they don't want to go back to 99L or up to 91L. Kind of like when TD has former name.
Member Since: Posts: Comments:
Quoting IKE:


Prognostic discussion....8-14 day outlook...from yesterday...TODAYS GFS-BASED ENSEMBLE MEANS ARE IN GOOD AGREEMENT IN DEPICTING A DEEP
TROUGH NEAR THE EASTERN CONUS
AND A RIDGE NEAR THE WESTERN CONUS.

Be back soon.


The GFS ensemble mean now recurves it just before hitting South Florida. We really gotta keep our eye on this thing.
Member Since: Posts: Comments:
Quoting Drakoen:
Accuweather thinking an east coast threat


Isn't Accuweather headquarters located somewhere on the East coast?
Member Since: Posts: Comments:
First off people.. 90L hasnt formed yet, and when it does (like Dr Masters has said) the models will have a better handle on this.

Second,since this does have a general consenses of close model tracks, we can go out to 5 days in advance of what area within 200 miles of where this may be...(probably around 15-17N and 60-62W) so this is still far far off to be talking about Florida or even Puerto Rico right now.

Third... dont look @ model runs more than 5 days out...patterns change...best reliable models are the GFDL,GFS and Euro...the rest I wouldnt give a dime to.

Finally.... keep more of a close eye on old TD2... this for 1 is closer and more of a chance to be in the SE Bahamas in 4-5 days.. dont overlook something closer because of what the models show behind... this does have a 60% chance of coming back.
Member Since: Posts: Comments:
189. ackee
does any notice 9oL appers to be further north than the models has it or that just where the convection are ?
Member Since: Julio 15, 2008 Posts: 0 Comments: 1376
Little spin at 22n 76w.
Member Since: Posts: Comments:
187. IKE
Quoting caneluver:


Nobody said it was a "Monster trough"


Prognostic discussion....8-14 day outlook...from yesterday...TODAYS GFS-BASED ENSEMBLE MEANS ARE IN GOOD AGREEMENT IN DEPICTING A DEEP
TROUGH NEAR THE EASTERN CONUS
AND A RIDGE NEAR THE WESTERN CONUS.

Be back soon.
Member Since: Junio 9, 2005 Posts: 23 Comments: 37860
Quoting caneluver:


Nobody said it was a "Monster trough"


nobody did but for August that was one heck of a trough forecasted
Member Since: Posts: Comments:
"Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now."

Is that 26.6 to 28.4, 27.4 to 27.6, or somewhere in-between? Big difference. 27 to 28 is meaningless if you're rounding to the nearest degree.
Member Since: Posts: Comments:
Looking at the floater of X-TD2 ...
To these untrained eyes, it looks like as dry air from the south of the storm wraps to the east, then 90L passes off some moisture, helping with the deficit of moisture.
It is a passing game! LOL
Member Since: Posts: Comments:

Viewing: 234 - 184

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
41 ° F
Nublado