Danielle a hurricane; TD 7 forming off coast of Africa

By: Dr. Jeff Masters , 2:18 PM GMT on August 24, 2010

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Hurricane Danielle has stopped intensifying and is now looking a bit ragged this morning, but remains a respectable Category 1 hurricane with 80 mph winds. The intensity of Danielle's heavy thunderstorms has waned in the past few hours, and the organization of the storm is less impressive. This is probably due do strong upper-level winds out of the west that are creating a moderate 10 - 20 knots of wind shear, and injecting some of the dry air from the Saharan Air Layer (SAL) that surrounds Danielle. Danielle is over warm 28°C water, but is far from any land areas.


Figure 1. Morning satellite image of Tropical Storm Danielle (left side of image) and the forming Tropical Depression Seven (right side of image.)

Forecast for Danielle
A powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Danielle more to the northwest by Wednesday, keeping Danielle well to the east of Bermuda. Most of the models predict that this trough will be strong enough to fully recurve Danielle out to sea. It is possible that Danielle could eventually threaten Newfoundland, Canada, but it currently does not appear that any other land areas will be at risk from this storm. History suggests that a storm in Danielle's current location has only a 20% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. As far as intensity goes, it is looking unlikely that Danielle will attain major hurricane status (115+ mph winds.) There is enough dry air and wind shear affecting the storm today that it will take several days for the storm to recover its strength, making it less likely the storm can hit Category 3.

The formation of Danielle is remarkable in this it was successfully forecast by the GFS model nearly two weeks in advance. The ECMWF and NOGAPS models also did a good job of predicting Danielle's formation a week in advance. The models are getting better and better each year at forecasting genesis of tropical cyclones, though a successful 1-week forecast of genesis is still a rarity. For example, none of the models foresaw the development of 96L until just 3 - 4 days ago.


Figure 2. Plot showing historically the percent chance of a tropical cyclone in a given location impacting the U.S. East Coast. For storms in Danielle's current position (orange hurricane symbol), about 20% of them go on to hit the U.S. East Coast. For storms in 96L's current location (red circle with a "?" in it), the odds are also 20%. Image credit: Bob Hart, Florida State University.

96L (soon to be Tropical Depression Seven)
Satellite images suggests that a tropical wave (96L) that emerged off the coast of Africa yesterday morning has developed a closed circulation, low-level spiral bands, and an increasing amount of heavy thunderstorms. While this morning's ASCAT pass does not show a clear closed circulation, satellite estimates of 96L's strength support calling this a 30 mph tropical depression. It is likely that this storm will be designated Tropical Depression Seven later today. 96L is already bringing heavy rain and strong, gusty winds to the southern Cape Verde Islands. Winds were sustained at 26 mph at Mindelo in the northwest Cape Verde Islands this morning, and 24 mph at Praia, the station closest to the center of 96L. Both stations were reporting widespread dust, due to strong winds blowing Saharan dust from the coast of Africa. However, water vapor satellite images show that only a modest amount of dry air is accompanying this dust, and dry air is currently not a major detriment to 96L. Wind shear is about 10 - 20 knots, and sea surface temperatures are warm, 28°C.

Forecast for 96L/Tropical Depression Seven
Wind shear is predicted to remain low, 5 - 10 knots, for the next four days. SSTs will cool a bit to 27°C by Thursday, but this is still above the 26.5°C threshold for hurricane development. Dry air will probably be the main inhibiting factor for 96L. Most of the intensity forecast models bring 96L to hurricane strength by four days from now, and this is a reasonable forecast. 96L should become Tropical Storm Earl later today or on Wednesday, and will probably bring sustained winds of 40 mph to the southernmost Cape Verdes Islands tonight and Wednesday.

The long range fate of 96L remains unclear. The storm is being steering by the same ridge of high pressure steering Danielle, and will initially follow a track similar to Danielle. 96L may encounter the cold waters stirred up by Danielle at times this week, inhibiting development. As 96L approaches the central Atlantic five days from now, the storm will encounter the same mid-Atlantic trough that will be steering Danielle, and 96L should turn more to the northwest. It is unclear at this point whether this trough will be strong enough to fully recurve 96L out to sea, east of Bermuda. This will, in part, depend upon how strong Danielle gets. A stronger Danielle is likely to create more of a break in the ridge of high pressure steering 96L, encouraging the storm to turn north and recurve out to sea. A weaker Danielle will make 96L more likely to miss recurvature, and follow a track to the west or west-northwest towards the U.S. East Coast early next week. History suggests that a storm in 96L's current location has only a 20% chance of making landfall on the U.S. East Coast.

When will the Caribbean and Gulf of Mexico get active?
The large scale atmospheric circulation over the Caribbean and Gulf of Mexico currently features relatively dry, stable, sinking air. This is due, in part, to the Madden-Julian oscillation (MJO). The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The latest MJO forecast from the GFS model calls for the wet phase of the MJO to move into the Caribbean during the first week of September. However, keep in mind that forecasts of MJO activity 1 - 2 weeks in advance are not very skillful. The GFS model forecast of MJO activity made two weeks ago did fairly well for the first week, but poorly for the second week of the forecast.

Tropical Storm Frank spares Mexico
Over in the Eastern Pacific, Tropical Storm Frank has moved away the coast far enough from the Mexican coast to no longer pose a heavy rainfall threat, and all tropical storm warnings have been dropped.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. I'll focus on Danielle, Earl, and Frank, and discuss the possibilities of a hyperactive Atlantic hurricane period coming during the first week of September.

Today's show will be 30 - 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

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Anyone else notice the spread in the intensity models to the end of the forecast period for Invest 96? Some hinting at major hurricane, others low end TS. Interesting to have such divergence.
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Quoting mbjjm:


All the long range models recurve Earl to sea, but it there is too much uncertainy, anyones guess right now.


Computer models


Aren't those statistical models? They always seem to be vastly inaccurate in comparison to the dynamical models, which aren't foreseeing recurvature (save, of course, the poleward biased GFS).

I'm not wishcasting at all. I just forecast. And right now, I don't see 96L/Earl recurving. But you're right. It's uncertain.
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2597. smuldy
Quoting traumaboyy:


Going well thanks....been very busy tonight.so far...just stick my head in from time to time to make sure it is not headed for Panama City then Run on down the way. This season seems to be making everyone look like amateurs.
lol ya it is, very odd setup so far
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Quoting smuldy:
ya, been to bermuda (st georges never made it to hamilton too much to do just on that one side), it is a beautiful place with amazing people and a lot of hills. But IF it is going to get hit, and right now it looks likely that it will feel some effects of this, hoping for the storm to be a CAT1 is the most realistic and hopeful scenario right now. If they do feel the effect there will be damage there, but hopefully no loss of life, which is the key thing, so long as they prepare well and it stays below major status.


Not really.
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2594. mbjjm
Quoting KoritheMan:


We can. Earl's not going out to sea, because it isn't going to deepen that quickly. Even if it does, most other models favor an equatorial track. GFS has been biased in a poleward direction for the last several days.

All the long range models recurve Earl to sea, but it there is too much uncertainy, anyones guess right now.


Computer models
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2593. smuldy
Quoting mbjjm:


much of Bermuda is hilly moderate cat 1, would bring weak cat 2 winds to some areas
ya, been to bermuda (st georges never made it to hamilton too much to do just on that one side), it is a beautiful place with amazing people and a lot of hills. But IF it is going to get hit, and right now it looks likely that it will feel some effects of this, hoping for the storm to be a CAT1 is the most realistic and hopeful scenario right now. If they do feel the effect there will be damage there, but hopefully no loss of life, which is the key thing, so long as they prepare well and it stays below major status.
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Quoting smuldy:
sorry for delayed response getting caught up on tv, just finished no reservations from monday; i'll be cracking one open in about an hour still early evening given my schedule lol; did you catch the 36 hour more or less stall on the 0z? high comedy. Bermuda better watch out, 96L is still at 90% and ragged and just doesn't seem to be gaining much considering 48 hours ago (the time period for the forecast) they were also 90% certain it would be a TD by now. Hope your night is going well


Going well thanks....been very busy tonight.so far...just stick my head in from time to time to make sure it is not headed for Panama City then Run on down the way. This season seems to be making everyone look like amateurs.
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2591. mbjjm
Quoting smuldy:
or as is; as long as it stays a weak to moderate cat1 not likely to cause any loss of life just wind damage, unless there are an unusual amount of tornadoes occurring within the storm, just need to hope that Danielle doesn't blow up to a vastly stronger system as the models suggest at this point.


much of Bermuda is hilly moderate cat 1, would bring weak cat 2 winds to the mountains.
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Quoting Kowaliga:

A "FISHY" SEASON?


Can we talk about this?



We can. Earl's not going out to sea, because it isn't going to deepen that quickly. Even if it does, most other models favor an equatorial track. GFS has been biased in a poleward direction for the last several days.
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2589. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2588. smuldy
Quoting mbjjm:


Bermuda "I hope she looks worst in a couple of days.
or as is; as long as it stays a weak to moderate cat1 not likely to cause any loss of life just wind damage, unless there are an unusual amount of tornadoes occurring within the storm, just need to hope that Danielle doesn't blow up to a vastly stronger system as the models suggest at this point.
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Quoting bigwes6844:
I HEARD ON OUR LOCAL WEATHER THAT IT SHOWS WELL DEVELOPMENT AND HEAD TO TEXAS.


Where are you Wes?
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2586. xcool
she wnw
Member Since: September 26, 2009 Posts: 2 Comments: 15684
SmileyCentral.com

Dang it! Hi everyone! If my post shows this time.
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2584. mbjjm
Quoting robert88:
Looks like a ragged Cat 1 cane. Hopefully she will look better in a couple of days when conditions improve.

""


Bermuda :Hopefully she looks worst in a couple of days.
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Looks like a ragged Cat 1 cane. Hopefully she will look better in a couple of days when conditions improve.

""
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2581. leo305
Wow so the Official track has it moving NW almost NNW during the next 48-72 hours?

It's moving W/WNW now though

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2580. xcool
txsweetpea .not really
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2579. mbjjm
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2577. smuldy
Quoting traumaboyy:


Agreed.....and how is smuldy this morning??

Drinking one for me??
sorry for delayed response getting caught up on tv, just finished no reservations from monday; i'll be cracking one open in about an hour still early evening given my schedule lol; did you catch the 36 hour more or less stall on the 0z? high comedy. Bermuda better watch out, 96L is still at 90% and ragged and just doesn't seem to be gaining much considering 48 hours ago (the time period for the forecast) they were also 90% certain it would be a TD by now. Hope your night is going well
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Quoting xcool:
hmm

xcool-do you think the models are taking this too far north or what?
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I HEARD ON OUR LOCAL WEATHER THAT IT SHOWS WELL DEVELOPMENT AND HEAD TO TEXAS.
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2574. Grenada
Quoting TXEER:
Come on out...I'll be the only house in Oakhurst with lights. ;~)


Try 6 months with no electricity, Amanda would not be so keen on seeing a storm after that!!
(Sorry guys for butting in, I'm a reader trying to stay on top of anything that may come our way) :)
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2573. xcool
hmm
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting TORMENTOSO83:

saludos desde Vega Baja!!!


woo! cool bro, watchin the storms
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Quoting JLPR2:


Hiya!
Saludos desde el área norte! XD

saludos desde Vega Baja!!!
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2570. mbjjm
Agreed, development off the SE Us Coast as being hintede by some models not looking promising either.
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2569. mbjjm
Danielle at 7pm, making a come back, eastern eyewall reforming.










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Quoting mbjjm:


Anything which develops in the Gulf along the front, wont have much time to strengthen before moving on the Texas Coast


And will have to deal with shear and dry air
over north part of GOM...
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2567. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting serialteg:


haha. i haven't seen them this preseason! sadly, GB's defense looks again to be a letdown.

be advised, the vikings are still favorites in the division... with green bay, no doubt. your bears and lions can fight for the other spots. ;)
LOL. Time will tell. Couldn't help it.
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2564. xcool
mbjjm .yeah
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Kowaliga:

A "FISHY" SEASON?


Can we talk about this?



not very much interested in bantering 162h model projections. :)
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Why does NOGAPS keep spinning up systems in the caribbean?
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Quoting serialteg:


listening to that. I definetly come from that grunge-style, simplistic hard rock genre. but i also have that strong Rush, progressive influence on me... plus The Police, Duran Duran, and all that jive lol


Bless you. Black Flag may have become hard rock, grunge later on, but they sure didn't start out that way! LOL!!!
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2559. mbjjm
Quoting xcool:


Nogaps has been the western most outliner
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A "FISHY" SEASON?


Can we talk about this?

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2556. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting hulazigzag:
BTW. GO BEARS!!


haha. i haven't seen them this preseason! sadly, GB's defense looks again to be a letdown.

be advised, the vikings are still favorites in the division... with green bay, no doubt. your bears and lions can fight for the other spots. ;)
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2554. jonelu
Quoting ChrisDcat5Storm:
yea its WNW mabey NW

agreed
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Quoting serialteg:


interesting
BTW. GO BEARS!!
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2551. EtexJC
Quoting sflawavedude:


all of you had to be anxious seeing what would happen. sounds like a not so bad time except for the generator running inside and also cant be good when too much family hang around enclosed for too long. people could get irritated with one another! hehe


I remember that hurricane too, the worst part was the downstairs flooding in our condo off of 1960 and 45. The sound of our back gate hitting our ford tempo(maybe it was the datsun 210), and the weird sound the wind was making, still gives me chills today when i think about it.....
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Quoting alfabob:


Probably not turning north anytime soon.



interesting
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Quoting weatherman566:


There might be a low that forms from a stationary front in the Gulf, but nothing significant will develop from it.

Houston looks fine for the next 10 days.

The blobs the forecasters look at are tropical waves. These waves sometimes produce an area of low pressure. If these waves look promising....in other words, they have potential to develop, the National Hurricane Center will designate the wave as an invest. They number it 90-99 for invests, and label it L for Atlantic.

And, really, you shouldn't hope for storms hitting your area. They hurt the economy. Mmmkay?


If you go to StormW blog, he got alot of the terms that would help you follow the terms used here and other weather blogs
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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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