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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Quoting popartpete:
HOLY COW! I just saw the GFS, with what looks like a bullseye for Danielle towards the Jersey Coast. If it does make and NJ landfall at Cat 1 or 2 strength, it would be a 1 in 100 year event. (Last 1903) If it was a 3 or higher, it would be a 1 in 200 year event. (Last 1821) If Danielle takes the current GFS course, it would be a track eerily similiar to the 1903 "Vagabond" hurricane. See wikipedia link. My builing is right on the oceanfront at sea level. Think I should brave it out if it does come to pass? I really don't think so!
Link


Watch Witness Katrina on Nat Geo, after watching that you'd have to be stupid to ride out a hurricane especially on beach front property. Anyways don't freak out yet, could just be a classic 18z anomaly.
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I'm starting to have my doubts about a fish storm. Be interesting to see what the percentage of east coast strike probabilities are with tomorrow morning's location update.
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Quoting popartpete:
HOLY COW! I just saw the GFS, with what looks like a bullseye for Danielle towards the Jersey Coast. If it does make and NJ landfall at Cat 1 or 2 strength, it would be a 1 in 100 year event. (Last 1903) If it was a 3 or higher, it would be a 1 in 200 year event. (Last 1821) If Danielle takes the current GFS course, it would be a track eerily similiar to the 1903 "Vagabond" hurricane. See wikipedia link. My builing is right on the oceanfront at sea level. Think I should brave it out if it does come to pass? I really don't think so!
Link


Definitely not brave it out... and saturday if it still is a possibility I would book a hotel room reservation... if the storm hits you will have a place to go if not then just cancel the reservation
Member Since: August 1, 2006 Posts: 28 Comments: 3716
Just checking in from Bermuda and am very tired, so to read all the posts would make me crossed eyed. At the risk of making a fool out myself. We run a water tour operation. Haul the boat out of the water or not?
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Quoting pilotguy1:


That's good cause it doesn't make any sense.


no it dont not yet anyway
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HOLY COW! I just saw the GFS, with what looks like a bullseye for Danielle towards the Jersey Coast. If it does make and NJ landfall at Cat 1 or 2 strength, it would be a 1 in 100 year event. (Last 1903) If it was a 3 or higher, it would be a 1 in 200 year event. (Last 1821) If Danielle takes the current GFS course, it would be a track eerily similiar to the 1903 "Vagabond" hurricane. See wikipedia link. My builing is right on the oceanfront at sea level. Think I should brave it out if it does come to pass? I really don't think so!
Link
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2042. will45
Quoting Nateball:
Hello All, just wondering what time EDT does the FSU model page update with the 00z run.


GFS begins at 11:30 finish about 2:30 NOGaps begin 1:00pm UKMET begins about 2:00 AM
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2040. o22sail
Quoting hunkerdown:
i want to know who typed that


It's not the TAZ I know either...and I've been around here for almost 5 years.
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I just saw the latest models and... wow.. Maybe I should up my percentage of the Northeast impact to 10%-15% from -10%
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Thanks for the info
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Quoting TampaSpin:
Before i start lurking the BAMS just did a big hook and back south and NOW the BAMM just went West....


That could really bad!
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im in attleboro
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Quoting Tazmanian:




i like you better when you where being a fishcaster
i want to know who typed that
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2034. angiest
Quoting Levi32:


That's what I think.....slow, if anything. I don't see anything too serious coming out of it, but given our history of TDs in the gulf this season associated with old fronts, it should be watched, and will probably bring a rain event of some kind into Texas regardless.


If its far enough south and/or west to escape the dry air, there is plenty of energy out there for it. Will it have enough time to draw on that, however.
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These things are like a woman. TRying to figure out what they are going to do is a work of art!!!

Joke
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Quoting jason2010xxxx:
the nhc will have a new update at 11pm the path of tropical storm Danielle will be more back to the west mean next to the east coast.




i like you better when you where being a fishcaster
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting TampaSpin:
Before i start lurking the BAMS just did a big hook and back south and NOW the BAMM just went West....



had a gut feeling it might pull something like that i didnt want to say anything though
my mind said no way
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Quoting Nateball:
Hello All, just wondering what time EDT does the FSU model page update with the 00z run.


Next GFS will be at 11:30EDT at the NCEP Model guidance site.
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2028. Levi32
Quoting unf97:
Levi I am just getting caught up on things since I have been out all day. I saw NHC put a yellow circle 10% probability on a surface trough devloping in the GOM. What are your thoughts on that? I did some checking and to me it looks that if anything develops it will be very slow. Plus lots of dry air surrounding the Northern Gulf Coast area also.


That's what I think.....slow, if anything. I don't see anything too serious coming out of it, but given our history of TDs in the gulf this season associated with old fronts, it should be watched, and will probably bring a rain event of some kind into Texas regardless.
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2025. angiest
Quoting MiamiHurricanes09:
Ouch?



Gustav, Camille, Carla... anyone else care to name big storms that have fed off that part of the Caribbean?
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Hello All, just wondering what time EDT does the FSU model page update with the 00z run.
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Before i start lurking the BAMS just did a big hook and back south and NOW the BAMM just went West....

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Storm... has dissipated!
lol
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2021. unf97
Levi I am just getting caught up on things since I have been out all day. I saw NHC put a yellow circle 10% probability on a surface trough devloping in the GOM. What are your thoughts on that? I did some checking and to me it looks that if anything develops it will be very slow. Plus lots of dry air surrounding the Northern Gulf Coast area also.
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night StormW
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Quoting StormW:


I think what is happening is, if you back to your loop, the way it appears to be setting up, if you look on the east coast at the trof, and the ridge directly to its east, then look a little NE of there, which appears to be another ridge center, and the ridge near Danielle, you can pretty much see it setting up to "split" in the middle of that. That is supposed to be her "out". Just isn't happening very quick.

Thanks for that loop and your input BTW!


LOL......honestly i thought we was talking about weather.....LOL....guess i will just post my pic....and just lurk. Nite all!
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2018. bappit
Quoting aspectre:
TropicalStormDanielle's heading has turned westward to 2.5degrees north of WestNorthWest
from the previous heading of 8.4degrees north of WestNorthWest

24Aug - 12amGMT - 15.5n42.3w - - 75knots . . . . 982mb - NHC-ATCF
24Aug - 03amGMT - 15.6n43.2w - - 85mph . . . . . 982mb - NHC.Adv.10
HurricaneDanielle becomes Cat.2
24Aug - 06amGMT - 15.7n44.0w - - 85knots . . . . 973mb - NHC-ATCF
24Aug - 09amGMT - 15.9n44.6w - - 100mph . _ . 973mb - NHC.Adv.11
24Aug - 12pmGMT - 16.1n45.8w - - 75knots . . . . 983mb - NHC-ATCF
24Aug - 03pmGMT - 16.6n46.5w - - 80mph . . . . . 985mb - NHC.Adv.12
24Aug - 06pmGMT - 17.1n47.5w - - 65knots . . . . 990mb - NHC-ATCF
H.Danielle becomes TS.Danielle
24Aug - 09pmGMT - 17.5n48.2w - - 70mph . . . . . 993mb - NHC.Adv.13
25Aug - 12amGMT - 17.9n49.1w - - 65knots . . . . 990mb - NHC-ATCF

65knots=~74.8mph _ _ _ ~60.9knots=70mph _ _ _ 65knots=~74.8mph
NHC rounds windspeeds to the nearest 5mph or to the nearest 5knots

Copy&paste 16.1n45.8w-16.6n46.5w, 16.6n46.5w-17.1n47.5w, 17.1n47.5w-17.5n48.2w, 17.5n48.2w-17.9n49.1w, bda, mia into the GreatCircleMapper for a look at the last 12hours.

Thanks!
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Well seeing the latest computer models, Storm you were onto something the whole time!! Good call.
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Quoting StormW:
Good night all...I'm out.


Night Storm! Have a good one!
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Peace Storm!
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2013. unf97
Have a good evening Storm
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Good evening BAHA

I always breath easier when storms out there to the East get above 20N
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Quoting StormW:
Good night all...I'm out.
Good night Storm!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting extreme236:


Most likely. Just a wait and see I guess. Nothing imminent there.
Thankfully.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2009. Levi32
Quoting StormW:
Good night all...I'm out.


Night Storm.
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Quoting MiamiHurricanes09:
And when it does, it's going to be ugly.


Please dont say that lol.
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2007. caneman
I hope there's more dry air to intrude into these meddlesome tropical blobs.
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2005. Levi32
I think the simple answer to the "logic" of the thing is yes, there is a big deep-layer high to the south of Bermuda, so how can Danielle go northwest? Simple....the high is going to move lol. The trough will be pushing it to the east, north of Danielle, which will open the door for her recurvature, and this is also the same thing that will allow her to make a run at major hurricane status. She will finally be out of the confluent zone at that point and be in a more ventilated environment aloft.
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Quoting StormW:


That was a serious thank you.


oh sorry
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting weathercrazy40:
ok what happened i left the comp for a litle only to come back and see big change in comp models so im taking it sitting here in south eastern mass just north of cape cod we now have to keep and eye on danielle


Weathercrazy40 where you at? I grew up in Bridgewater. Sounds like you're in the vacinity. My entire family is still up there. Watching Danielle carefully for them.
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Quoting MiamiHurricanes09:
And when it does, it's going to be ugly.


Most likely. Just a wait and see I guess. Nothing imminent there.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2000. Levi32
One can pick out the eyewall structure attempting to reform, but still highly disorganized and under attack by dry air from the west.

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Quoting extreme236:


Somethings bound to tap into that at some point.
And when it does, it's going to be ugly.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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