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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1499. JLPR2
96L is having some convection problems.

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1498. breald
Quoting NHCstevehayward:
Here's the GFS model Run
Link


Thanks Steve & Cribboy.
Member Since: May 28, 2008 Posts: 38 Comments: 5303
1485. NHCstevehayward 10:57 PM GMT on August 24, 2010

GFS did nail this upswing in the CV season 2 weeks ago, so it could be right about the 6 storms

6 storms in 2 weeks at the peak of the hurricane season of an above-average season should be expected
Member Since: March 10, 2010 Posts: 1 Comments: 7813
Danielle likely to regain hurricane status tonight if the current organizational trend continues.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting NHCstevehayward:
I don't see 6 storms on the run. remember after 96 hours the GFS is not accurate, I do see Danielle , Earl and Possibly Fiona on the lastest runs


Put on ur glasses
Member Since: Posts: Comments:
Something about that GFS run is suspicious... yet another side of my mind tells me this could happen so idk.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
1477 reported


just because we dont like him does not mean you should wish for his life to be ended.
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1491. breald
Quoting NJ2S:


im in hoboken nj we r barely 10 ft above sealevel that being generous we flood in every noreaster


ok, I just don't see what all the hype is about then. Thanks Taz
Member Since: May 28, 2008 Posts: 38 Comments: 5303
Quoting NJ2S:


what would that mean for me in nnj/nyc?


Keep abreast of updates from the NHC and your local emergency management.
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See you later folks
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Quoting NHCstevehayward:
I don't see 6 storms on the run. remember after 96 hours the GFS is not accurate, I do see Danielle , Earl and Possibly Fiona on the lastest runs



you have too look deeper in to the run
Member Since: May 21, 2006 Posts: 5091 Comments: 115247


Next feature coming off the Atlantic. Might be a depression in 4 or 5 days.
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1483. will45
Quoting breald:
Can someone please post the gfs model? I mam curious to see what you are all talking about. Thanks.



Link

breald heres the shot of it hitting the east coast
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Quoting sebastianflorida:
yea but the shift the cone along with the way the storm is going
Yes, of course. They have to move the cone forward 1 day every day. My point was that at the 5 day(120 hr) point...the storm has been well within the cone AT DAY 5.
.
.
There's enough goverment agencies that don't work quite as well as we'd like. The one that concerns this blog however, the NHC, has a record second to none. They're not perfect, but in this science, that's impossible.
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Quoting NJ2S:


what would that mean for me in nnj/nyc?
It don't mean nothing yet. Just a model run. What it does mean is that everyone should have a degree of preparedness wherever you live. Clammily comes in many guises.
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Quoting CaribBoy:
Oh not five but six systems. Yes definatly hyperactivity!



and olny the 1st week of sep
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
Caribbean trekker?

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Quoting RJT185:


Links Please!


Watch the entire run : Link
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Quoting breald:
Can someone please post the gfs model? I mam curious to see what you are all talking about. Thanks.



this watch the blog has we are posting the photos of the GFS runs
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
1474. HarryMc
I live on the coast in New Hampshire. If I believed the models after about 72 hours out, I'd be packing right now... BUT... at 200 hours out, the skill of even GFS is way less than 20%. So, maybe I'll start thinking about packing but not leave yet. Next 3 days, models will change a lot.
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1473. NJ2S
Quoting breald:


No it wouldn't. I live 15 miles from the Atlantic ocean....LOL


im in hoboken nj we r barely 10 ft above sealevel that being generous we flood in every noreaster
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Oh not five but six systems. Yes definatly hyperactivity!
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1471. smuldy
Quoting muddertracker:
Man, the GFS has gone storm crazy! If the latest run pans out it will be very interesting to see how fast FEMA gets checks out...just sayin'
it wont dont worry-the models have not faired well with this complex unseasonal synoptic setup
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Quoting muddertracker:
Man, the GFS has gone storm crazy! If the latest run pans out it will be very interesting to see how fast FEMA gets checks out...just sayin'


But Obama already had his Katrina.....
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1469. Skyepony (Mod)
Quoting nrtiwlnvragn:


You can look at the dropsonde data from the DC-8 on this PREDICT webpage


Thanks! I've had little time to look for it..
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1467. xcool
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Man, the GFS has gone storm crazy! If the latest run on Daniel pans out it will be very interesting to see how fast FEMA gets checks out...just sayin'
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As we are getting closer to the pic of the hurricane season, I think the GFS is responding to this.
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1464. smuldy
Quoting sporteguy03:
That GFS run is hyperactive
A Carib system, A central Atlantic One and one coming off Africa. 6 storms in one run lol.
ya 6 ts+ at once wonder why some of us doubt these models lol
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1463. NJ2S
Quoting nrtiwlnvragn:





what would that mean for me in nnj/nyc?
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1462. breald
Quoting jason2010xxxx:
that will be so funny if the northeast get hit by three hurricanes in two weeks..


No it wouldn't. I live 15 miles from the Atlantic ocean....LOL
Member Since: May 28, 2008 Posts: 38 Comments: 5303
Quoting Skyepony:


That was scheduled for today..

3. REMARKS: THE NASA DC-8 WILL FLY AN 8-HR RESEARCH
MISSION IN THE GULF OF MEXICO TODAY AT 38,000 FT.
TAKEOFF TIME IS 24/1400Z.

near wrapping up I suppose.. I haven't found the data but AF301 went out chucked a dropsonde at that area of interest (1011mb) from 400mb then went to 1300' & flew through it once with the SFMR on found up to 38kt surface winds.. a little less at flight level. Good change of wind direction.. E to NE, NNE to NW noted.


You can look at the dropsonde data from the DC-8 on this PREDICT webpage
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1460. KEEPEROFTHEGATE (Mod)
Quoting jason2010xxxx:
i did not see that high before,
there is a lot of things that you have never seen before but you are going to see them at least once
Member Since: July 15, 2006 Posts: 173 Comments: 54266
Quoting ROBTX09:
carboy looks like the second is a fish cause it gets to close to danielle that it flick it to the east


This is quite possible, however E moves fairly close to bermuda (again). As regards the Caribbean islands, the F storm seems the most threatening.

Also, it's interesting to notice that the GFS shows 5 systems in this run.
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1456. breald
Can someone please post the gfs model? I mam curious to see what you are all talking about. Thanks.
Member Since: May 28, 2008 Posts: 38 Comments: 5303
That GFS run is hyperactive
A Carib system, A central Atlantic One and one coming off Africa. 6 storms in one run lol.
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I think Danielle is starting to get its act together mabye eye wall starting to reform?!
P.S. at 5:00 AM Danielle has a very nice eye!
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1453. RJT185
Quoting CaribBoy:
Per 18Z GFS, D, E and F may not be fishes


Links Please!
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1450. xkcd
Where do y'all look at the 18z run? The one on http://www.wunderground.com/modelmaps/maps.asp?model=GFS&domain=TA is still labeled the 0z run. Is that actually the 0z/12z run, making the 18z the one after that?
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1449. jonelu
Quoting breald:


Why?

Because its showing a New England hit...so people are going to go nuts..even though it too far out to know for sure.
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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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