Danny weakens further; 94L worth watching

By: Dr. Jeff Masters , 1:54 PM GMT on August 28, 2009

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Tropical Storm Danny continues to weaken, and may merely be a tropical depression. Data from the Hurricane Hunters early this morning showed top winds of just 40 mph at the surface, and satellite intensity estimates of Danny's strength are now rating the storm a tropical depression. Danny looks very disorganized on satellite imagery (Figure 1), with the low-level circulation center exposed to view. There is no heavy thunderstorm activity near Danny's center, and only a small area of heavy thunderstorms lying several hundred miles east of the center.


Figure 1. Morning satellite image of Danny, showing the exposed swirl of clouds where Danny's center is, well displaced from the heaviest thunderstorm activity to the east.

The forecast for Danny
With wind shear at 15 knots this morning, and forecast to increase to 20 knots tonight and 30 knots Saturday morning, is is unlikely Danny will be able to strengthen to more than a 50 mph tropical storm. Dry air from the upper-level low that has been keeping Danny disorganized continues to be a problem for the storm, as well. The GFDL and HWRF models continue to insist Danny will strengthen to a strong tropical storm or weak Category 1 hurricane, but this seems very unrealistic given Danny's current struggles. With Danny's heavy thunderstorms all on the east side of the storm, it is unlikely that New England will feel tropical storm force winds from Danny when it scoots past on Saturday. Large swells from Danny creating high surf along the beaches of New England will be the primary hazard from the storm.

Massachusetts hurricane history
Two tropical storms have affected Massachusetts in the past decade, though neither of these storms brought sustained winds of tropical storm force (39 mph) to the state. Tropical Storm Beryl of 2006 just missed Cape Cod as a weak tropical storm with 45 mph winds. Beryl brought wind gusts to tropical storm force to Nantucket Island, and a 1 foot storm surge. Tropical Storm Hermine hit southeast Massachusetts on August 31, 2004, as a minimum-strength tropical storm with 40 mph winds. No land stations in Massachusetts reported tropical storm force winds during Beryl. The last time Massachusetts measured tropical storm force winds was in 1991 during Hurricane Bob, which hit Rhode Island as a Category 2 hurricane. Provincetown, Massachusetts measured sustained winds of 98 mph, gusting to 115 mph, and Buzzard's Bay received a 15 foot storm surge.


Figure 2. Tropical wave 94L, a few hundred miles west of the Cape Verdes Islands.

Invest 94L
A well-organized tropical wave (94L) lies a few hundred miles west-southwest of the Cape Verdes Islands. This disturbance has shown little change this morning. This morning's QuikSCAT pass shows a complete circulation, elongated in the east-west direction, with top winds of 30 mph. Satellite imagery shows only a small amount of heavy thunderstorm activity near the circulation center, but considerable thunderstorm activity south of the center. Shear is low, about 10 knots, and is expected to remain low to moderate, 5 - 15 knots, over the next five days. The waters are warm enough to support development, 28°C, and are expected to remain in the 27 - 28°C range over the next five days. The dry Saharan Air Layer (SAL) lies about 200 miles to the north and west of 94L, and it appears from water vapor satellite imagery that a modest amount of dry air from the SAL is now being ingested into the storm, slowing development. Dry air will continue to slow development until 94L's heavy thunderstorm activity can moisten the atmosphere enough to shield the storm from the Saharan Air Layer. NHC is giving 94L a medium (30 - 50% chance) of developing into a tropical depression by Sunday. The GFDL and SHIPS models both predict 94L will be a Category 1 hurricane five days from now. However, the HWRF model does not develop 94L. Most of the models predict 94L will take a significant northward jog 3 - 5 days from now, in response to a strong trough of low pressure passing to the north (this is the same trough of low pressure that will be recurving Danny out to sea). It is then probable that 94L will be forced to the west again as the high pressure ridge steering the storm builds back in, and 94L will likely be a few hundred miles northeast of the Northern Lesser Antilles Islands seven days from now.

I'll have an update this afternoon.

Jeff Masters

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574. ncstorm
11:38 PM GMT on August 28, 2009
hey everyone

very stormy here in wilmington..would this be because of the ull or Danny outerbands?
Member Since: August 19, 2006 Posts: 13 Comments: 15649
573. PcolaDan
11:10 PM GMT on August 28, 2009
Quoting flsky:
Just for my info - why do people keep posting "New Blog?" Is this for their own blog, or something related to WU?


It means Dr. Masters has a new blog.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
572. Cavin Rawlins
10:51 PM GMT on August 28, 2009
Earliet today

Member Since: July 24, 2005 Posts: 407 Comments: 19076
571. flsky
10:11 PM GMT on August 28, 2009
Just for my info - why do people keep posting "New Blog?" Is this for their own blog, or something related to WU?
Member Since: October 24, 2006 Posts: 0 Comments: 2005
570. hurricanejunky
8:07 PM GMT on August 28, 2009
Quoting Drakoen:
94L is slowly becoming better organized. The system has a broad low level circulation within the ITCZ. The 200mb observations indicate an upper level anticyclone over head which should aid in development. The system's environment is steadily becoming more moist.


Hey Drak!What are your thoughts on the track for this one?
Member Since: August 28, 2006 Posts: 6 Comments: 2899
569. OSUWXGUY
7:51 PM GMT on August 28, 2009
Haven't really thrown my 2 cents in on 94L much today...so here it goes:

I expect only slow development - possibly a storm by Sunday or Monday.

Reasons for slow development:

1. Still in the ITCZ - most of the convergence is associated with this and is linear
Surface Convergence

2. Vorticity also linear - rotation not around a singular point but more along a line with strong southerlies south of the ITCZ and strong easterlies to the north of the ITCZ.
850 Vorticity

3. Super strong 700/850 easterly flow will make it tough for a circulation to wrap up. The GFS show only slow westward progression with its low. The discrepancy in how fast the flow is and expected motion of the low is weird. This would either suggest the area will be sheared heavily in the low to mid-levels or it will race west and the models are way wrong.

568. stormsurge39
7:46 PM GMT on August 28, 2009
The models at 2pm on 94L do not have it gaining a lot of Latitude
567. hurricanehanna
7:43 PM GMT on August 28, 2009
Quoting atmoaggie:
We just have a couple of models so far on our 94L friend, but I am not sure you guys that are worrying about it need to be. This is a lot of latitude gained that far out. If that happens, no one on terra firma will be seeing this one in person.


(longer Pink-looking one is XTRP)

I sooooo hope you are right!
Member Since: September 5, 2007 Posts: 0 Comments: 3488
566. stormsurge39
7:42 PM GMT on August 28, 2009
Kman can you tell what kind of steering 94L will have if it enters the Carribean? The concern is the GOM!
565. Stormchaser2007
7:41 PM GMT on August 28, 2009
NEW BLOG
Member Since: June 9, 2007 Posts: 4 Comments: 15920
564. sporteguy03
7:40 PM GMT on August 28, 2009
old blog :(
Member Since: July 7, 2005 Posts: 0 Comments: 5342
563. gtownTX
7:40 PM GMT on August 28, 2009
Would it be possible for those of you knowlegeable folks who post grapics to include a title or brief explanation of the graphic for us newbies? I know it would help me continue learn.
Member Since: July 14, 2009 Posts: 0 Comments: 29
561. atmoaggie
7:38 PM GMT on August 28, 2009
New blog
Member Since: August 16, 2007 Posts: 6 Comments: 12461
560. kmanislander
7:38 PM GMT on August 28, 2009
Good afternoon all

I have not been on much lately but have started to pay close attention to 94L.

There are several important factors at work in respect of this feature but they are not all conducive to rapid development. On the plus side you have warm water, an anticyclone overhead and little in the way of shear ahead. On the negative side you have the fast forward speed of 23 mph, dry air close by and the inhibition caused by being tied into the ITCZ.

The net effect of all this IMO is that 94L will not likely become a TD before reacing 50W assuming it does develop. If that happens, the trough that is supposed to lift it out will probably pass it by.

There is, IMO , a greater than 50% chance of 94L entering the Caribbean, probably around 16 or 17N depending on when it develops as a cyclone and how quickly the intensity ramps up. The low center is already closing in on 40W very quickly and the models have already abandoned the abrupt right turn to the N.

I am expecting each successive model run to trend further and further W over the next 24 hours so we will see how all of this plays out.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
559. atmoaggie
7:36 PM GMT on August 28, 2009
We just have a couple of models so far on our 94L friend, but I am not sure you guys that are worrying about it need to be. This is a lot of latitude gained that far out. If that happens, no one on terra firma will be seeing this one in person.


(longer Pink-looking one is XTRP)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
558. largeeyes
7:36 PM GMT on August 28, 2009
Link

Watch this loop with radar on. One layer of clouds goes one way, one goes another, and I think the rain is coming from both. Strangest stuff I've seen.
Member Since: August 22, 2006 Posts: 0 Comments: 1455
557. stormsurge39
7:36 PM GMT on August 28, 2009
When is 94L going to be pulled N? How long is this suppossed to last until it levels off and starts going west again? It looks like its going faster West than the models are forcasting.
556. Patrap
7:34 PM GMT on August 28, 2009
Member Since: July 3, 2005 Posts: 426 Comments: 128617
555. popartpete
7:34 PM GMT on August 28, 2009
Every weather system within 1000 miles of Danny seems to be entrained in its vast quasi-tropical circulation. This is a crazy one-in-a-lifetime scenario possibly.
Member Since: July 10, 2007 Posts: 0 Comments: 429
554. hurricanehanna
7:33 PM GMT on August 28, 2009
Quoting P451:

Looks like a very wet weekend for some on the East Coast
Member Since: September 5, 2007 Posts: 0 Comments: 3488
553. bwat
7:33 PM GMT on August 28, 2009
Anyone with me on thinking Danny might not go north but rather start moving NNE then NE? If is does go north I think it will be for a very short period of time.
Member Since: August 18, 2009 Posts: 0 Comments: 353
552. Orcasystems
7:32 PM GMT on August 28, 2009


AOI

AOI

AOI

AOI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
551. Patrap
7:32 PM GMT on August 28, 2009
Member Since: July 3, 2005 Posts: 426 Comments: 128617
550. Floodman
7:31 PM GMT on August 28, 2009
Quoting tropicofcancer:
It looks to me you are looking through one red lense and one green lense, no?


LOL...you would be correct!
Member Since: August 2, 2006 Posts: 10 Comments: 9922
548. largeeyes
7:30 PM GMT on August 28, 2009
Danny starting to move N-NE?
Member Since: August 22, 2006 Posts: 0 Comments: 1455
547. hurricanehanna
7:30 PM GMT on August 28, 2009
CMC is showing something off Florida's East Side - before 94L? or is that 94L?
Member Since: September 5, 2007 Posts: 0 Comments: 3488
546. TStormSC
7:28 PM GMT on August 28, 2009
Press: WU mail
Member Since: July 15, 2007 Posts: 6 Comments: 205
545. OSUWXGUY
7:28 PM GMT on August 28, 2009
Quoting Patrap:


I like it...


LOL. Okie Dokie.

544. tropicofcancer
7:28 PM GMT on August 28, 2009
It looks to me you are looking through one red lense and one green lense, no?
Quoting Floodman:


With a couple of notable exceptions, but yes, this is more like it once was...or am I looking at the past through rose-cloured glasses?
Member Since: September 19, 2006 Posts: 0 Comments: 143
543. ttweathergirl
7:27 PM GMT on August 28, 2009
Hi everyone, I usually lurk but seeing that there is a system that might come our way, I thought I'd just sign in to see if my username is still working in case I have to use it to comment on 94L. Trinidad is a bit rainy, it has been for the past 2 weeks or so. Anyway I hope 94L really does get pull up north before reaching us.
Member Since: June 11, 2008 Posts: 0 Comments: 0
542. katroy
7:26 PM GMT on August 28, 2009
Quoting fmbill:


They will wait until 5pm. But, sometimes the 5pm comes out earlier than 5pm.

Watch this blog...I subscribe to a program for getting the updates quickly, and I can't beat these guys when it comes to posting it here.


Thank you! (AllStar17, too!).

I subsribe to the NHC advisory emails, but will have to sign up for these, too. I've used this site as a supplemental reference tool for the last year - it's awesome! The NHC is "just the facts and only the facts," but there's some very nice interpretation of those facts here that have really helped me make some decisions for our company.
Member Since: August 28, 2009 Posts: 0 Comments: 10
541. hurricane23
7:25 PM GMT on August 28, 2009
We'll if this run is correct nothing should get past 60-65 west during the next 8-10 days.

Member Since: May 14, 2006 Posts: 8 Comments: 13804
540. Patrap
7:25 PM GMT on August 28, 2009
Quoting OSUWXGUY:


You really like this graphic, Patrap.

Any reason you feel compelled to post it now?


I like it...
Member Since: July 3, 2005 Posts: 426 Comments: 128617
539. fmbill
7:24 PM GMT on August 28, 2009
Man! Check out that western side of Danny's swirl. Danny will be on the fast train out of town soon.

Link
Member Since: May 27, 2008 Posts: 0 Comments: 457
538. Patrap
7:24 PM GMT on August 28, 2009
NexSat Viz Loop,Danny
Member Since: July 3, 2005 Posts: 426 Comments: 128617
537. yonzabam
7:24 PM GMT on August 28, 2009
I'm getting an ominous feeling about 94L. It's very far south, so has a good chance of escaping the trough and making it all the way across. It's on the same latitude as Trinidad. Can't remember the last time Trinidad took a hit, it's at the lower extremity of the hurricane zone.

It's pretty disorganised, but clearly rotating and it's BIG. So, what's gonna stop it? SSTs are high, don't know about shear or dry air. If those two variables are favourable, it could turn into a very dangerous storm.
Member Since: July 20, 2008 Posts: 0 Comments: 2926
536. antonio28
7:23 PM GMT on August 28, 2009
Quoting Drakoen:
94L is slowly becoming better organized. The system has a broad low level circulation within the ITCZ. The 200mb observations indicate an upper level anticyclone over head which should aid in development. The system's environment is steadily becoming more moist.


94L NE caribbean with the watch flag raised once again, seems that we likely will see a storm or maybe more than one this year. NAO neagative all over the month of September has been forerscast no fish storm in the peak of 2009 season. Heads Up!!
Member Since: July 15, 2008 Posts: 0 Comments: 799
535. hurricanehanna
7:23 PM GMT on August 28, 2009
Quoting Patrap:
Atlantic, 2 Sept 2008



*shudder* Gustav...oy.
Member Since: September 5, 2007 Posts: 0 Comments: 3488
534. OSUWXGUY
7:22 PM GMT on August 28, 2009
Quoting Patrap:


You really like this graphic, Patrap.

Any reason you feel compelled to post it now?
533. Floodman
7:22 PM GMT on August 28, 2009
Quoting btwntx08:

i edit read again


okay, now it makes more sense...lol
Member Since: August 2, 2006 Posts: 10 Comments: 9922
532. futuremet
7:22 PM GMT on August 28, 2009
12Z ECMWF retards the eastward propagation of the ridge that is expected to establish over the east coast. The exact time frame when this ridging pattern will establish is uncertain, but should be established by September 10th.

Image: Notice that longwave trough approaching the west coast. This will bring anomalously cold temperatures to the western U.S. and warm temps to the east.

Member Since: July 19, 2008 Posts: 43 Comments: 4051
531. adjusterx
7:22 PM GMT on August 28, 2009
Quoting lennit:
man this season so far is something else..Florida seems to have a purchased a deflector shield program.. everytime a system looks like it may or could develop. A east coast trof shows up. or if it lifts .it splits and leaves an upper low..same with 94L as it starts to develop an upper low looks to develop in the face of the ridge lifting more it N.. even if this does't happen another STRONG east coast trof tries to show up in 10 days or so..


We got Rosie O Donnell living in SEFL, thats enough to scare most anything away!
530. reedzone
7:24 PM GMT on August 28, 2009
Danny remains a Tropical Storm, weak one though. This will probably start moving north then north-northeast by tomorrow. The Carolinas up to Canada still needs to watch Danny just in case something unexpected happens which has been happening alot lately these years. Probably will get up to 50 mph. at the highest.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
529. atmoaggie
7:22 PM GMT on August 28, 2009
Quoting nrtiwlnvragn:


You can select just the BAMS here

Yeah, forgot about that one, too.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
528. atmoaggie
7:21 PM GMT on August 28, 2009
Quoting reedzone:
Guys we really don't know what the actual pattern will be in September. People need to stop being overly confident. I understand you want no storms, I don't either, but we can't just call the season a 2006 season just yet. Who knows, maybe a Hurricane will come knocking on your door.

Yep. And MJO forecast has been exceptionally useless, even less than a week out.

GFS steadily losing the battle of wits to the ensemble mean:
Member Since: August 16, 2007 Posts: 6 Comments: 12461
527. Floodman
7:21 PM GMT on August 28, 2009
Quoting btwntx08:

what western shear that model is overreacting,its outlier throw this model away for now
Quoting justalurker:
oh no its 3:00 schools out and that means comedy hour is about to start!!


Cover yo ears, darlin'
Member Since: August 2, 2006 Posts: 10 Comments: 9922
526. Patrap
7:20 PM GMT on August 28, 2009
Atlantic, 2 Sept 2008


Member Since: July 3, 2005 Posts: 426 Comments: 128617
525. midgulfmom
7:22 PM GMT on August 28, 2009
Hi to all the LA girls. Now I've got to go pick up the kids. Good to see Ya'll on the blog. Nishinigami, I remember during Gustav hearing WWL radio call for volunteers to help build/repair the levee from a break. How scary was that! Good luck to ya. BBL :)
Member Since: July 9, 2005 Posts: 2 Comments: 1163
524. nrtiwlnvragn
7:20 PM GMT on August 28, 2009
Quoting StSimonsIslandGAGuy:
Does anyone have a link showing the low level BAM track for Danny?


You can select just the BAMS here
Member Since: September 23, 2005 Posts: 14 Comments: 11209

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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.