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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"Apologies for newbiness, but can someone post a link to the computer models? I remember last year there was a site (off of WU) that had a ton of models you could turn on/off, but I've lost the link :("

If you type "www.google.com" into your address bar, a site will come up that is called a searh engine. In the box in the center of the page type "hurricane tracking models" and then click on the search button. The next page will bring you to a list of sites containing the search criteria. I am sure that you will find the models on one of these sites. In the future, you can use search engines like google to look for any information on the internet. Give it a try it's really easy.


SNOOPY?
Member Since: August 22, 2006 Posts: 0 Comments: 1455
Quoting CaribbeanWave:


Where do you get these images?


Here you go.
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www.stormpulse.com
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History Channel is running a doc about the Great Hurricane of 1938...very interesting...
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Quoting Acorna:
Apologies for newbiness, but can someone post a link to the computer models? I remember last year there was a site (off of WU) that had a ton of models you could turn on/off, but I've lost the link :(


here is one
Link
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Also...the 18Z BAM suite models trendeda lot more West than previous...
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417. bwat
Quoting Acorna:
Apologies for newbiness, but can someone post a link to the computer models? I remember last year there was a site (off of WU) that had a ton of models you could turn on/off, but I've lost the link :(
Link
Member Since: August 18, 2009 Posts: 0 Comments: 353
I agree..at least to my visible eye I DO NOT see any rotation at 11N - 36W..

I def see something of interest at 10N - 38W..

Anyone agree on here...!?
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Quoting Stormchaser2007:
SAL



Mid level WV.



Is that African dust I see in the western Caribbean?
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Quoting Stormchaser2007:
SAL



Mid level WV.



Where do you get these images?
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Apologies for newbiness, but can someone post a link to the computer models? I remember last year there was a site (off of WU) that had a ton of models you could turn on/off, but I've lost the link :(
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stormpulse is showing 94l at 9.4N 39.6W
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I see no rotation at 11N 36W
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Watching to visible floater, It looks like Danny is reacting with the low pressure above the GOM. This could be causing it to slow down. It also looks like it is starting to pull some of the convections clouds out of the west and turning them toward the south east. Any thoughts?
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Quoting btwntx08:

no look again at 12z it was at 34w now at 18z its 36w u mixed it up


Look at the 12Z SHIPS for 94L. What is the initial position?
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Quoting cajunmoma:


I for one hope you are right. But I got a feeling that things have just been way too quiet here in the GOM this year, and honestly its creepy...Worried that when something gives, its going to be BIG.

Hello, LA Mom here too. It does seem rather quiet in the GOM. I'm grateful and anxious now with 94L and the next possible invest behind it with all of the talk of a high building and heading some of these storms westward.:p
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ORCA, inland you are looking at Wilmington, New Bern, Greenville, Morehead City. Lots of pine trees.....other than trees down, shouldn't impact the area much.
Member Since: August 22, 2006 Posts: 0 Comments: 1455
The 5:00 pm update on Danny could be quite interesting if he doesnt get a move on
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SAL



Mid level WV.

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AL94 18Z position. Looks like they changed the 12Z position, origionally it was 36W, they now have 34W at 12Z.


AL 94 2009082812 BEST 0 107N 340W 25 1010
AL 94 2009082818 BEST 0 110N 360W 25 1010
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Quoting jasoniscoolman10:
maybe 95L SOON.


48hours at the very least.
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Quoting fmbill:
94L, the wave behind 94L, and the cluster behind that over Africa, all look very similar when they each reach the prior system's position.

Click on the link, and slowly advance each frame. You'll see what I mean.


I see excactly what you mean.
Member Since: August 19, 2009 Posts: 0 Comments: 248
Quoting serialteg:


Hi good afternoon, do you know of a total precipitable water link (like this one) that shows the TPW over the african continent?


I dont know of any. I believe that those are restricted to water only.
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94L, the wave behind 94L, and the cluster behind that over Africa, all look very similar when they each reach the prior system's position.

Click on the link, and slowly advance each frame. You'll see what I mean.
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Quoting Stormchaser2007:


I haven't put much time into looking at the future conditions, but I would imagine that SAL wouldnt increase all that much between now and the period when it exits. Looking at some loops of the wave broad cyclonic turning is already noticeable. I havent seen a wave this good since last year. I imagine if it can keep its presentation it should become an invest once it hits the water.


Hi good afternoon, do you know of a total precipitable water link (like this one) that shows the TPW over the african continent?
Member Since: August 22, 2006 Posts: 2 Comments: 1983
393. 789
Quoting NEwxguy:


Just too many troughs coming off the east coast,sweeping the storms out to sea,its our own invisible shield.
high will set in the us midwest next week and sit there troughs for 94l 95l may be hard to come buy but this is some tim e to wait and see
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I hope this year is the best season in years where no storms cause any damage. The Feds need all the money they can hold on to. LOL
Member Since: August 19, 2009 Posts: 0 Comments: 248
94L is racing
Quoting nrtiwlnvragn:
TPC/TAFB 72 hour surface forecast




So where is the northward motion lol
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Is it me, or is Danny now south a smidge from his initialized spot? He better get a move on if he's supposed to hit that 8pm spot.
Member Since: August 22, 2006 Posts: 0 Comments: 1455
TPC/TAFB 72 hour surface forecast


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Quoting cajunmoma:


I for one hope you are right. But I got a feeling that things have just been way too quiet here in the GOM this year, and honestly its creepy...Worried that when something gives, its going to be BIG.


dont forget the GOM has had quiet years before when something big didnt get em
it doesnt happen every year thank goodness
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94L is racing
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EUMETSAT
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Quoting jaxbeachbum:
You are correct, I meant the gulf stream. Whew, I'm glad it's Friday! Thank you for straightening me out on that one. I'm finally getting the hang of viewing the different level of clouds on radar. Guess that's where my head is today, in the clouds. lol Thanks again to all!



No Problem jax we are all learning in here
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Hey Orca, for whatever reason, my link to Eumet is not working...can you post it for me?

Thanks!

How you been, by the way?
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Nevermind Image did not work. Sorry
Member Since: August 19, 2009 Posts: 0 Comments: 248
EUMETSAT, Real time

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You are correct, I meant the gulf stream. Whew, I'm glad it's Friday! Thank you for straightening me out on that one. I'm finally getting the hang of viewing the different level of clouds on radar. Guess that's where my head is today, in the clouds. lol Thanks again to all!

Quoting will40:
Quoting jaxbeachbum:
Should have worded that question different. At what point will Danny get into the jet stream? I think you may be a lil confused the jet stream is upper level wind. The gulf stream is water
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378. bwat
Quoting fire16:
ref-357) The outerbanks and residence can weather 50 knots ir the tourists can be evacuated. Depending upon the tides there may be some overwash but that is a hardy group on that sand.
I like the way you think!
Member Since: August 18, 2009 Posts: 0 Comments: 353
Quoting K8eCane:
I "got a feelin" 94L is gonna be an east coast surfer too


I for one hope you are right. But I got a feeling that things have just been way too quiet here in the GOM this year, and honestly its creepy...Worried that when something gives, its going to be BIG.
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Quoting K8eCane:
I "got a feelin" 94L is gonna be an east coast surfer too


Just too many troughs coming off the east coast,sweeping the storms out to sea,its our own invisible shield.
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Quoting Stormchaser2007:


I haven't put much time into looking at the future conditions, but I would imagine that SAL wouldnt increase all that much between now and the period when it exits. Looking at some loops of the wave broad cyclonic turning is already noticeable. I havent seen a wave this good since last year. I imagine if it can keep its presentation it should become an invest once it hits the water.


I have a gut feeling this is the one we'll be taking very seriously shortly. Interesting to get NHC's take on it when it exits the coast.
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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.