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

By: Dr. Jeff Masters , 2:02 PM GMT on August 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: 3434 - 3384

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

3434. Patrap
Quoting Funkadelic:
Cycloneoz, My cousin is still going out if 90L, and x td 2 pose a threat to land. As of right now what is the best place to set up shop in the Conus?




.."WS's front yard Im sure is available"..
Member Since: Posts: Comments:
I am going to bed, night all.

Hope I do not see tomorrow am, what I expect now to see.

Nighty, night.
Member Since: Posts: Comments:
Wonder how far west that wave will have gone by tomorrow night.

I'm not looking forward to flying through that weather.... :o(
Member Since: Posts: Comments:
patrap...that's what i'm watching...once it gets in the gom...watch out for the boom....
Member Since: Posts: Comments:
Quoting bajelayman2:
Canesrule, no I did not type it, when I replied, the posting process did that, I do not know why?

Sorry again.
no need to say sorry, it was a computerized mistake, happens all the time, chill out, lol.
3428. lennit
whats funny EPAC has a spanish Bill and Atl may have an english Bill
Member Since: Posts: Comments:
Cautious, yes, but worried is a bit strong.
Member Since: Posts: Comments:
3425. Patrap
Member Since: Posts: Comments:
StormW,

So you do not think we should get worried now, here in the islands?
Member Since: Posts: Comments:
Possible paths

Photobucket
Member Since: July 1, 2008 Posts: 13 Comments: 7437
From the time those 2 hit 50W, well see:

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Canesrule, no I did not type it, when I replied, the posting process did that, I do not know why?

Sorry again.
Member Since: Posts: Comments:
Quoting bajelayman2:
Canesrule,

Sorry, it printed like I was quoting what you said, but I did not set it up like that.

Apologies.
im sorry too, i was kinda rough, been a loooooong day, lol, and now with the 11 o'clock advisory dilemma, lol.
3419. jipmg
Quoting canesrule1:
maybe, i think TD 2 at 2am and TD 3 at 5?


I think TS ana already and TD 3 (TS bill at 5) based on the satellite estimations =O
Quoting Weather456:


nice shot, can i have a link? I assumed Fox News?


Here..yeah it's fox news.
Member Since: October 5, 2007 Posts: 3 Comments: 2151
3417. Patrap
TD 2 AL022009 - Tropical Depression TWO

2km Storm Relative IR Imagery with BD Enhancement Curve


Time of Latest Image: 20090814 2115


Member Since: Posts: Comments:
StormW: Those monkeys are probably going to be wrong again!
Member Since: Posts: Comments:
We could wake up tomorrow to both Ana and Bill.
Member Since: Posts: Comments:
Quoting cirrocumulus:
Weather456:

Just got on. That's just what I was thinking after reviewing the loops. 90L may increase in intensity rapidly. Also, note the dive to the southwest away from Saharan air by 02L. It amazes me the hurricane center was writing it off at all. Usually when these storms ring out their storms but have good circulation, they come back strong from the warm waters and instability present from previous storms in their path. They actually do better at times without the mass of precipitation and clouds to start with.


yea...I'm watching TD 2 more closly than b4.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting TampaSpin:
I say we have ANA and TD3
maybe, i think TD 2 at 2am and TD 3 at 5?
i think we have two tropical stoms to deal with
Member Since: Posts: Comments:
Canesrule,

Sorry, it printed like I was quoting what you said, but I did not set it up like that.

Apologies.
Member Since: Posts: Comments:
Quoting TampaSpin:
I don't recall NHC ever being this late with an update....anyone
when fay was over cuba we went through this but not as many posts or fun as this time.
Member Since: Posts: Comments:
Quoting gaweatherboi:
Quick question if Ex TD 2 was to regenerate would it still be TD 2 or TD3?


td 2, same name when the original system remains intact.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting gaweatherboi:
Quick question if Ex TD 2 was to regenerate would it still be TD 2 or TD3?
Td 2
I don't think we will see a new advisory before 2 a.m. Both of the systems are looking good, but I think NHC is justified in a) wanting to see a little continuity and b)waiting on additional model support.

Good night ya'll. Hopefully the blog will run a wee bit slower in the a.m. I doubt it though.....
Member Since: Posts: Comments:
Weather456:

Just got on. That's just what I was thinking after reviewing the loops. 90L may increase in intensity rapidly. Also, note the dive to the southwest away from Saharan air by 02L. It amazes me the hurricane center was writing it off at all. Usually when these storms ring out their storms but have good circulation, they come back strong from the warm waters and instability present from previous storms in their path. They actually do better at times without the mass of precipitation and clouds to start with.
Member Since: Posts: Comments:
Quoting CaneAddict:


Definitely unless our eyes are all playing tricks ;)


Yeah since the season was inactive I got to watching stocks too...not like I need another excuse to be on the computer more lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
I say we have ANA and TD3
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting bajelayman2:


Do what, I just posted normally, I do not know why it went into capitals, I did nothing different to usual?
U posted something mine, that u typed, look at post #3367
3400. Droab92
I see a lot of people think a possible s fla hit, I'm in Jupiter, and have a feeling about 90L. Went thru Andrew, and 90l would be close to the 17th anniversary of this storm.
Member Since: Posts: Comments:
3399. Relix
Could it be possible that the NHC is calling the government of the islands before going ahead with the new advisory?
Member Since: Posts: Comments:
Hey Stormdude, yes.

And I am telling you that I am getting very nervous.

This is not good.
Member Since: Posts: Comments:
Bouy 14.4N 46W


Member Since: Posts: Comments:
3396. Patrap
90L 2km Storm Relative IR Imagery with BD Enhancement Curve

Time of Latest Image: 20090815 0245 UTC



2km Storm Relative IR Imagery with BD Enhancement Curve

The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively.
Member Since: Posts: Comments:
Quick question if Ex TD 2 was to regenerate would it still be TD 2 or TD3?
Member Since: Posts: Comments:
Quoting mikatnight:


nice shot, can i have a link? I assumed Fox News?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting TampaSpin:
I don't recall NHC ever being this late with an update....anyone


Maybe there isn't anything to update.
Member Since: Posts: Comments:
Ex TD-2's best track fix for 00 UTC:

AL, 02, 2009081500, , BEST, 0, 145N, 448W, 25, 1007, TD, 34, NEQ, 0, 0, 0, 0

No Isotachs...yet. But is no longer a "LO".
Member Since: Posts: Comments:
Quoting extreme236:


lol had a nice little bounce back in the last hour though

Definitely unless our eyes are all playing tricks ;)
Member Since: October 5, 2007 Posts: 3 Comments: 2151
I don't recall NHC ever being this late with an update....anyone
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting canesrule1:
WHY DID U DO THAT!?!?!?


Do what, I just posted normally, I do not know why it went into capitals, I did nothing different to usual?
Member Since: Posts: Comments:
WOW! WOW!

WOW!
What do we have coming off the coast now? Anyone else notice the systems behind 90L in the GFS runs?
Member Since: Posts: Comments:
Hey bajelayman...interesting times ahead, huh?
Member Since: Posts: Comments:
Quoting Weather456:
Thats how Dean and Georges evolved, lopsided convection became more symmetric. This is so similar to those 2 storms, that its hard to ignore the models



I know exactly what you mean...I don't like the model consensus for either of the two systems at all. The problem with TD2 is it originally would of went well north but since it died out and is making a comeback further west it changed the whole scenario from pretty much definite fish to a land bound system.
Member Since: October 5, 2007 Posts: 3 Comments: 2151
Quoting TampaSpin:


Its going south again watch....



lol had a nice little bounce back in the last hour though
Member Since: August 2, 2007 Posts: 19 Comments: 19234

Viewing: 3434 - 3384

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
27 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron