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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748. xcool
SOUTHEAST/EAST COAST...
A VARIETY OF SOLUTIONS REMAIN IN REGARDS TO THE EVOLUTION OF A
POSSIBLE UPPER LOW ROUNDING THE SOUTHEAST SIDE OF THE EASTERN
RIDGE BY NEXT TUESDAY... WITH THE GFS STRONGEST JUST OFF THE
SOUTHEAST COAST AND ECMWF RUNS STRONGEST OVER/NEAR THE LOWER
MISSISSIPPI VALLEY. THE GEFS MEAN REPRESENTS BOTH AREAS TO SOME
DEGREE WHILE THE 12Z ECMWF MEAN IS NOT ENTHUSIASTIC ABOUT EITHER
AREA... SUPPORTING A COMPROMISE APPROACH FOR NOW. A SMALL
PERCENTAGE OF THE 00Z MULTI-MODEL ENSEMBLE MEMBERS USE THIS UPPER
LOW TO SWING HURRICANE DANIELLE TOWARDS THE
CAROLINAS/MID-ATLANTIC/NEW ENGLAND COASTS IN 7-10 DAYS. EVERY
COUPLE YEARS THE ENSEMBLE GUIDANCE /OR THE DETERMINISTIC CANADIAN
GLOBAL MODEL/ TRIES TO ANOMALOUSLY TURN/STAIR-STEP A RECURVING
SYSTEM WESTWARD TOWARDS THE NORTHEASTERN UNITED STATES. BELIEVE
DANIELLE IS TOO FAR GONE INTO THE RECURVATURE PROCESS AROUND THE
SUBTROPICAL RIDGE TO ITS EAST AND THAT THE UPPER LOW WHICH FORMS
NEAR THE SOUTHEAST SHOULD BE TOO FAR AWAY FROM DANIELLE TO TURN
THE STORM BACK TOWARDS THE EAST COAST. DANIELLE...AMONG OTHER
SYSTEMS...WILL BE COORDINATED WITH NHC AT 16Z TODAY

HPC
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Quoting xcool:


What is that showing on SE TX?
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Quoting KanKunKid:


I, for one, agree. This carp isn't necessary.
fishcaster
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Quoting jason2010xxxx:
WOW


Such a beautiful picture of Danielle, wow... Thanks for sharing that Jason.
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743. xcool
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jason2010xxxx 1:52 PM EST on August 24, 2010

What happened to F12# stirn?
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Quoting Cotillion:
Assuming that's all correct considering PhD's are all made clear...

Link

Well, what d'ya know... not all NHC staff have PhDs. Including the forecasters.


don't think anyone said a Ph.D is required. The point was that, seeing as how we're all commenting on a blog written by a Ph.D, maybe we shouldn't make it sound like a worthless piece of paper either. Just my two cents.
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pilotguy1 6:53 PM GMT on August 24, 2010

Its why I have no respect for scottsvb, he comes off as very brash and as you can see he loves throwing peoples' predictions in their face

I could care less what credentials he has, that is why he is on my ignore list and has been for months.
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736. DVG
Levi32....Yup that's it. The two highs have been reaching towards each other. Storm said he watches how the movement is proceeding, so I was looking at this. The last three frames or so of motion show them stretching out.

Now thx to you, I can also watch the progress of the trough and how it impacts things.
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Quoting jason2010xxxx:
ITS THE HURRICANE GOING TO HIT Bermuda
thgought it was 200% fish
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734. srada
Quoting Levi32:


Indeed, they are the gray lines on this map:

I think some of the models are seeing the ridge take over for a short while, turning Danielle perhaps back NW for a while and gain some more longitude before being fully recurved. This puts Bermuda squarely in the danger zone, which they really have been all along but the models weren't showing it.



Ignore User


Hey Everyone!

Wet day here in eastern NC..is this the trough split and something home brewing off the coast per the previous model runs..I ask Storm W about a potential storm developing off the coast and maybe steering Danielle..are the models taking in all the variables if this happens, in other words, If we get a development off the coast here and they dont pick up the development in their runs, wouldnt this throw a monkey wrench in the whole scheme of things as far as Danielle track?
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thx levi!

Quoting Levi32:


You guys speaking of this?



The way it looks right now, the weakness currently directly north of Danielle is allowing her to gain latitude and she should gradually curve more northwest over the next day or two, but once that first trough lifts out, the ridge will probably be strong enough to curve her back to the left just a tad, before being fully recurved to the north by trough #2, coming in from the west, which you can see currently digging into Wisconsin.


Apprieciated Levi!
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Quoting Sting13:


I never doubted you Storm. :)

"If I ever lose my faith in you...there'll be nothing left for me to do.." Sing it, Sting!
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What am I missing here? I don't see anything epic or unforecast happening here. So far, Danielle has pretty much followed the cone of doom from advisory #1. And Bermuda was never completely out of the question, as far as the NHC was concerned.
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Assuming that's all correct considering PhD's are all made clear...

Link

Well, what d'ya know... not all NHC staff have PhDs. Including the forecasters.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting WindynEYW:
Linksat pic refreshes every minute nice pics of danielle

Thanks for that post, abosolutely beautiful. As long as she stays out over open water anyway lol... great pic!
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Thought this was interesting,even if its not likely to happen,as indicated at the end of the paragragh from the long range forecast.

A SMALL
PERCENTAGE OF THE 00Z MULTI-MODEL ENSEMBLE MEMBERS USE THIS UPPER
LOW TO SWING HURRICANE DANIELLE TOWARDS THE
CAROLINAS/MID-ATLANTIC/NEW ENGLAND COASTS IN 7-10 DAYS. EVERY
COUPLE YEARS THE ENSEMBLE GUIDANCE /OR THE DETERMINISTIC CANADIAN
GLOBAL MODEL/ TRIES TO ANOMALOUSLY TURN/STAIR-STEP A RECURVING
SYSTEM WESTWARD TOWARDS THE NORTHEASTERN UNITED STATES. NHC
AGREES THAT DANIELLE IS TOO FAR ALONG IN THE RECURVATURE PROCESS
AROUND THE SUBTROPICAL RIDGE TO ITS EAST AND THAT THE UPPER LOW
WHICH FORMS NEAR THE SOUTHEAST SHOULD BE TOO FAR AWAY FROM
DANIELLE TO TURN THE STORM BACK TOWARDS THE EAST COAST.
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Quoting Levi32:


You guys speaking of this?



The way it looks right now, the weakness currently directly north of Danielle is allowing her to gain latitude and she should gradually curve more northwest over the next day or two, but once that first trough lifts out, the ridge will probably be strong enough to curve her back to the left just a tad, before being fully recurved to the north by trough #2, coming in from the west, which you can see currently digging into Wisconsin.
Ok thank you very much
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682. sebastianflorida 1:38 PM CDT on August 24, 010



I never doubted you Storm. :)

Puking as I am reading

Sounds like a serious case of forecast envy
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Quoting KanKunKid:


Too bad it is hours old


doesnt change how awesome the image looks :p
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Quoting Engine2:
Levi/Storm can you help us with this one?


You guys speaking of this?



The way it looks right now, the weakness currently directly north of Danielle is allowing her to gain latitude and she should gradually curve more northwest over the next day or two, but once that first trough lifts out, the ridge will probably be strong enough to curve her back to the left just a tad, before being fully recurved to the north by trough #2, coming in from the west, which you can see currently digging into Wisconsin.
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Quoting Skyepony:
AF301 went out in the gulf today too & flew through that in the gulf, 1 pass with the SFMR on. Wind shift there Maybe some 30kt winds..


Interesting..any other comments about this?
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Quoting reedzone:


An epic model shift StormW, it all puts Bermuda at a much higher risk.
.......lol,epics a little extreme,slight model shift,nbc has never said bermuda was safe!!!!,interesting pattern developing,imo things in the gom should get interesting in about 10-14days,as energy advects northly from the west carib,a little early,but it'd put the chances of a cane in the first half of sept at better than 50%,stay tuned....
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Quoting WindynEYW:
Linksat pic refreshes every minute nice pics of danielle
is goes 15 the newest satellite. i know one was launched last year and put into storage.maybe it is goes 15?
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Quoting KanKunKid:


I take it you didn't see the movie?


I've seen it.. I'm just telling you that he's lying. I never predicted Danielle to threaten anyone. I was actually repeating myself as DestinJeff would say a few days ago that it was just too early.
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Quoting xcool:


A substantial WEST shift in models....
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Quoting StormW:


Well, I've always had a theory...Hurricanes do not go to school, and do not care about Calculus, and Differential Equations, and don't read computer model guidance outputs.


Storm, No doubt. Otherwise, we would only need meteorologists to do the computer programming. And look where that has gotten us. It is the analysis from observations and personal experience that differentiate the forecasters.
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A major shift WEST in (18Z) models of 96L!!
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Quoting DVG:


I asked about that a bit ago. The CIMSS looks like the two highs are reach out towards each other. Still hoping someone would comment on it.
Levi/Storm can you help us with this one?
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You all need to not listen to scottsvb, he's lying. I never predicted Danielle to hit the USA, I said it was possible due to the NAO becoming positive, but never had a forecast set in stone! It was too early to tell at that time where Danielle would go.
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Quoting WindynEYW:
Linksat pic refreshes every minute nice pics of danielle


Thats amazing!
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Quoting Hurricanes101:


In the early stages with invests, the center position tends to get jumped around by the atcf

does not necessarily mean it is moving in that direction, just that they are relocating the center


Thanks. I learn something new every day on the blog.
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702. DVG
Quoting CJ5:


Wow, that is a huge change since I checked around 10am. Concerning.


I asked about that a bit ago. The CIMSS looks like the two highs are reach out towards each other. Still hoping someone would comment on it.
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Linksat pic refreshes every minute nice pics of danielle
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Quoting KanKunKid:


Don't be so hard on Reed, he is the "Happy Gilmore" of tropical forecasters.


I never said it would hit Miami, I never said it would hit anywhere because I was very uncertain because the storm didnt even form!
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Try this again, NHC did a forecast on 96L

18Z Interpolated


AL 96 2010082418 03 OFCI 0 130N 253W 30 0 LO
AL 96 2010082418 03 OFCI 12 138N 283W 35 0 DB
AL 96 2010082418 03 OFCI 24 146N 313W 40 0 DB
AL 96 2010082418 03 OFCI 36 156N 343W 47 0 DB
AL 96 2010082418 03 OFCI 48 166N 370W 54 0 DB
AL 96 2010082418 03 OFCI 48 166N 370W 54 0 DB
AL 96 2010082418 03 OFCI 60 176N 396W 59 0
AL 96 2010082418 03 OFCI 60 176N 396W 59 0
AL 96 2010082418 03 OFCI 72 184N 422W 64 0 DB
AL 96 2010082418 03 OFCI 72 184N 422W 64 0 DB
AL 96 2010082418 03 OFCI 84 192N 449W 69 0
AL 96 2010082418 03 OFCI 96 201N 473W 72 0 DB
AL 96 2010082418 03 OFCI 108 211N 493W 72 0
AL 96 2010082418 03 OFCI 120 223N 510W 70 0 DB
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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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