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

By: Dr. Jeff Masters , 2:02 PM GMT on August 14, 2009

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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

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Quoting tikikopamsxm:
thanks Stormwatcher!
Sorry for the misundertood, i m just a bit worried about that two invest that will perhaps landfall on my home here in st martin.Our weather forecast here is not very relevant they used to tell us things very late.
Thanks all of you(sorry for my english)
Your english is okay and understandable. I am worried about both of them too. I live in Grand Cayman.
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Quoting jipmg:
big blow up of convection right over the center of 90L, and TD 2 getting another eruption over its center as well, TD 2/ TD 3 likely by 11
agreed.
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Oh boy... am I the only one seeing something ELSE behind 90L now via the GFS?
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Quoting Vortex95:


thats outside 02L though they said they weren't going in.
yes they are, the lat/lon provided at the observations in very close to that of the COC.
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2130. jipmg
big blow up of convection right over the center of 90L, and TD 2 getting another eruption over its center as well, TD 2/ TD 3 likely by 11
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<
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting Joshfsu123:



That is not the case... a very good circulation, which has been there for a while. Much tighter than 90L and in my opinion, not elongated.

The environment is also improving.

If DMAX helps tonight, I would expect it to be a Tropical Depression probably later tonight or at 5am tomorrow morning.


I think if you look at it again you will see that the circulation is not circular but oval from NW to SE, hence elongated but you are entitled to your opinion.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
2125. jipmg

Quoting Joshfsu123:



That is not the case... a very good circulation, which has been there for a while. Much tighter than 90L and in my opinion, not elongated.

The environment is also improving.

If DMAX helps tonight, I would expect it to be a Tropical Depression probably later tonight or at 5am tomorrow morning.


I think maybe even a tropical storm by 5am
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so far the recon found 25 knots at 925 mb.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
blockquote class='blogquote'>Quoting KerryInNOLA:
Agree with you Reed! I also agree. Of course can't be overly concerned yet. Could still do a lot of things. It wouldn't surprise me to see southern NC get hit this year. It has been 13 years since Fran, and 10 since Floyd. I also think because in the past four or five years the Gulf has had so much activity that some people here may be a little complacent. Needless to say it has been a wet summer here in Wilmington.
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Quoting kmanislander:


Elongated to the SE



That is not the case... a very good circulation, which has been there for a while. Much tighter than 90L and in my opinion, not elongated.

The environment is also improving.

If DMAX helps tonight, I would expect it to be a Tropical Depression probably later tonight or at 5am tomorrow morning.
Member Since: July 6, 2005 Posts: 5 Comments: 580
Thank you all who visited the XtremeHurricanes.com chat room this evening.

It was a pleasure answering your questions.

Please feel free to e-mail me if you have anymore.

I'll be leaving the chat room shortly now...

Have a great weekend everyone! :)
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recon has found 41 knot winds (TS) at 957MB which is rather close to the surface.
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Hi all:



Take a look at TD2's remains. I was wrong earlier. The wind shear looks like its diing down. Anybody have an atlantic wind shear chart I can use? Oh and look at the new discussion in Western Florida, pretty unlikely, but still amazing due to El Nino
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Quoting canesrule1:
I'm following Recon's observations, and they have found 26 knot winds at the surface which is indicative of a TD.


They can't tell from 41,000 feet, it could be just straight line winds.
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thanks Stormwatcher!
Sorry for the misundertood, i m just a bit worried about that two invest that will perhaps landfall on my home here in st martin.Our weather forecast here is not very relevant they used to tell us things very late.
Thanks all of you(sorry for my english)
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I'm following Recon's observations, and they have found 26 knot winds at the surface which is indicative of a TD.
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Quoting chevycanes:

looks much better on the zoomed in image.


Elongated to the SE
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting kmanislander:
This evening's quikscat of Ex TD 2. Not overly impressive

looks much better on the zoomed in image.
Member Since: August 6, 2007 Posts: 0 Comments: 693
Quoting Chiggy007:
San someone PLEASE let me know where the LLC of 90L is?? I am seeing it at 11.5N - 30 W


Member Since: July 24, 2005 Posts: 407 Comments: 19076
2111. jipmg
Quoting canesrule1:
I'm looking at Recon's observation and we are very close to having a TD.


can you post it
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18Z trended south than 00Z

Member Since: July 24, 2005 Posts: 407 Comments: 19076
I'm looking at Recon's observation and we are very close to having a TD.
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2108. tbrett
Quoting Weather456:


Saint Kitts, first time talking to someone in Montserrat on the blogs
Hey neighbor...I guess if it hits you I get it too.
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Quoting palmasdelrio:
It happened in 1979, Sept.4, Frederick, and hurricane DAvidLink
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Quoting reedzone:
Here's a map I just made concerning the possibility of the track. Yellow is slight chance, orange is medium chance.. there is no high chance because it's too far away to make assumptions. I still think this will be an East Coast event.

Photobucket



Possibly too east for some or all of these projected tracks...

But it's still too far out to know, so this is a valid "cone" you've created for today's date.
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San someone PLEASE let me know where the LLC of 90L is?? I am seeing it at 11.5N - 30 W
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Quoting reedzone:
Here's a map I just made concerning the possibility of the track. Yellow is slight chance, orange is medium chance.. there is no high chance because it's too far away to make assumptions. I still think this will be an East Coast event.

Photobucket


Man your orange zone is huge...You are basically saying there is a med chance for the east coast and a med chance for the Gulf and a med chance to hit FL haha.
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Looks like they tried to hit TD2 with a dropsonde, pretty hard from 41,000 feet.

Release Location: 15.09N 45.61W (View map)
Release Time: 22:09:54Z

Splash Location: 15.04N 45.67W (View map)
Splash Time: 22:24:15Z
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Quoting tikikopamsxm:
Hi!

I'm wondering how NHC can say that ex td2 can become a tropical hurricane in one night but did not put it back TD 2 yet?
Perhaps it's a stupid question but i usually only read you and rarely comment only if needed (tracking St Martin)
thks
It doesn't say Tropical Hurricane it says Tropical Cyclone which is TD, TS or Hurricane.
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This evening's quikscat of Ex TD 2. Not overly impressive
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting tbrett:
Where are you at? I am in Montserrat


Saint Kitts, first time talking to someone in Montserrat on the blogs
Member Since: July 24, 2005 Posts: 407 Comments: 19076
NRT: re last year, yep.

Last year older daughter was having a baby, I was in Maine.

This year I am chaparoning a school trip for youngest daughter for five days. Could be interesting.

Went through our hurricane prep plans with office staff today, tomorrow will be with rest of family.

If we are all prepared it will go somewhere else, happens every time!
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Here's a map I just made concerning the possibility of the track. Yellow is slight chance, orange is medium chance.. there is no high chance because it's too far away to make assumptions. I still think this will be an East Coast event.

Photobucket

Member Since: July 1, 2008 Posts: 13 Comments: 7396
Quoting WPBHurricane05:
Fellow South Floridians and our friends in the Bahamas should still keep a close eye on (ex)TD 2:

yup.
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Smaller systems can change very quickly...either way..ramping UP or DOWN.
Member Since: September 25, 2007 Posts: 53 Comments: 8533
Quoting wunderkidcayman:
GUYS SOON WE WILL HEAR THIS Link


BUT...for those of you who do still tune into them, I am a stringer for them and there's a chance some of my HD footage will wind up being broadcast by them.
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Check it out...if we dont get a named storm tomorrow (which probably wont happen but could have 2 TDs) that means we did fall in the 29% arena for a year when a named storm forms in the first half of August. Def a interesing year. The second wave is the one that has me concerned. 12Z GFS had a bullseye on southern MS. still too early though.
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what is that spin that I see just to the right of the 25 mark on that map? Is that another area of interest? That is too close to be 02L isn't it?
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Hey everyone,

I've been using this site for years...love it.

I'm going to bring this site up on the radio tomorrow during my "sports" show. I'm also going to have on from CBS4 in Miami, David Bernard to talk about the tropics and specifically 90L.

I am not trying to "advertise", but I thought it would be nice to mention this site and also field all of your telephone calls on the weather, as well...

I'd love to have Jeff Masters be a guest, too.

The show is on tomorrow, Saturday at 11:00am Eastern on 640AM in S. Florida.
We'll be talking about the tropics after 12:00pm...

You can listen live online via the site on Facebook at www.facebook.com/theslatershow (listen live link will be posted in the morning)

Once again, not trying to break a rule here on the board, I post often, but thought it'd be great for this site and it's viewers.

Thanks guys.

Slater
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2090. tbrett
Quoting Weather456:
Lord Have mercy, I live right at the center

Where are you at? I am in Montserrat
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TD 2 and 90L define the steering and if any of those make it to land, it will confirm this:



Remember the blog I posted back in July

Recurving Vs Landfalling Cape Verde Hurricanes

Last fall the NAO was in negative phase, which is probably what we might see this season, since the pattern over the last several weeks, and the forecasts issued by the Climate Forecast System (CFS) indicate we may be entering a negative phase of the NAO. Now we can look at all the troughs leaving the Eastern United States now, but that the CVS starts next month and peaks September. This really implies a greater risk for the Western Hemisphere this year regardless of storm numbers. Another problem 2009 poses is that tropical waves may not start to develop until about 50-60W, closer to home.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Winds are certainly increasing here in Palm Beach county to around 15-25mph and thin rain bands can be seen on the radar. Man 4 circles!
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quikscat actually caught former td2 but all i can manage to click is the a partial of each, could be upgraded to named storm later tonight imo
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good evening WS
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guys what the hell is going on with reconnaissance decoder
Decoded recon data in the last 30 minutes:

No decoded data could be found.
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Quoting Relix:
Worst Case Scenario: PR gets hit by both Ana and Bill. Unlikely and has never happened before but entirely possible. Would be a disaster though.


In 1979 Hurricane David passed 79 nm southwest of PR. Five days later Frederick passed right over the island as a tropical storm. But you're right. It would be a disaster
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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