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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I still think Danielle hitting the East Coast is a bit far fetched, but storms coming in from behind it have a better chance. Different ridging conditions, and a "guiding" high pressure could cause closer calls.
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i remember in 54and 55carol and diane hit north carolina and up to new england the storms went south of burmuda and toward the ncand up to n e thanks
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Quoting Tazmanian:



reported


reported
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Quoting mojofearless:


No. It won't be. They are NOT prepared.


WHy are the models calling for that to happen?
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Quoting MrstormX:
I suspect the latest GFS run is "spurious anomalous data", anybody else remember when Kimberblain from the NHC used something like that in his TWD for 92L way early in the season. Very fancy term for an anomaly lol.
Yea, sort of like the guy who brought a lawnmower into the machine shop where I worked. He told the guy at the desk that "the integrity of one of the joints was severely compromised." When we got it in the shop we discovered one side of the push handle had almost broken off.
Member Since: September 9, 2007 Posts: 36 Comments: 4687
1543. wjdow
Quoting Hurricanes101:


why should it be considered far fetched that we get 6 named storms in a 2-week span during the heart of the season?

That does happen in active seasons all the time.


i don't remember six named storms developing in two weeks, do you? help me remember
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Quoting SevereWeatherAddict:
So is the possibility of an east coast strike by Danielle now out of the question? Thanks in advance I live in NY. (Back to Lurking)


just watch this...
not at all outta the woods
Link
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1539. JLPR2
Danielle looks bigger.
Member Since: September 4, 2007 Posts: 7 Comments: 8752
Is this the "big one" NYC has been long over due for?
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1537. will45
Quoting MrstormX:


Thats not what im commenting on, im talking about the sudden jerk Danielle takes toward NYC... notice it happens right about the time the GFS is switching to its long-term solution.


yea thats what i understood you were saying
Member Since: July 18, 2009 Posts: 1 Comments: 995
1535. Gearsts
Quoting jason2010xxxx:
I do not like that huge ridge of high pressure over the Northeast that will make lots of hurricane hit the east coast.
LOL what happen to the 100% fish you were screaming?
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1534. xcool
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1522. Clearwater1 11:08 PM GMT on August 24, 2010

Its more the idea that the models continue to trend west and have for about a day now.

Also it does work the other way; why is it when a run takes it out to sea you think it is believable and yet when it takes it further west you think its crazy and should not be trusted?
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1532. HarryMc
Quoting SevereWeatherAddict:
So is the possibility of an east coast strike by Danielle now out of the question? Thanks in advance I live in NY. (Back to Lurking)

East coast is in "stay tuned mode". No alarm YET.
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Quoting mojofearless:


No. It won't be. They are NOT prepared.


I think that depends where in the NE you are exactly. Where I grew up on Long Island, our High School football team was named the hurricanes....and it was historically relevant as there have been 4 or 5 to come through the area in the last century. We grew up with hurricane shutters in the basement.
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Quoting Hurricanes101:


why should it be considered far fetched that we get 6 named storms in a 2-week span during the heart of the season?

That does happen in active seasons all the time.


Thats not what im commenting on, im talking about the sudden jerk Danielle takes toward NYC... notice it happens right about the time the GFS is switching to its long-term solution.
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I would not be surprised at all if the GFS verifies with the 6 named storms in a 2 week span. I mean, it's that time of year, we're in a bad pattern, it's about time that things pop, and the GFS is definitely showing us. We might be up to Fiona by Sunday.
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Quoting KEEPEROFTHEGATE:
may not mean much VA but if there is any likly hood of this panning out you will know i will make it a point of it all of eastern seaboard will know you will get at least a minimum 72 hr notice


If the 0Z and 12Z tomorrow continue the trend im gonna call them
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So is the possibility of an east coast strike by Danielle now out of the question? Thanks in advance I live in NY. (Back to Lurking)
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The GFS trending west on the model will it continue trending west....... We will soon know
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1523. KEEPEROFTHEGATE (Mod)
Quoting VAbeachhurricanes:


not funny at all.... idk experts this has been trending west! im in college should i be calling my family about this?
may not mean much VA but if there is any likly hood of this panning out you will know i will make it a point of it all of eastern seaboard will know you will get at least a minimum 72 hr notice
Member Since: July 15, 2006 Posts: 189 Comments: 59031
I love it. When a model has it hitting the east coast or other notable land mass, many buy it. . . But if it has it going out to sea, it must be wrong. Just an observation, but true.
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africa is going to be just spitting out storms. The person who said the gfs is inaccurate after 96 hours is incorrect.

the GFS is good out to 5 days with track and with cyclogenesis is great out to about 192 hours when convective feedback starts occurring
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Quoting MrstormX:
I suspect the latest GFS run is "spurious anomalous data", anybody else remember when Kimberblain from the NHC used something like that in his TWD for 92L way early in the season. Very fancy term for an anomaly lol.


why should it be considered far fetched that we get 6 named storms in a 2-week span during the heart of the season?

That does happen in active seasons all the time.
Member Since: Posts: Comments:
1519. will45
Quoting MrstormX:
I suspect the latest GFS run is "spurious anomalous data", anybody else remember when Kimberblain from the NHC used something like that in his TWD for 92L way early in the season. Very fancy term for an anomaly lol.


yea the next run may take it east of Bermuda.
Member Since: July 18, 2009 Posts: 1 Comments: 995
Quoting NHCstevehayward:
I agree, i really enjoyed your blog as well, i heard you are young, but you have a lot of experience at such a young age!! Keep up the great work!!
Thank you!
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1517. txjac
Quoting WeatherNerdPR:
Good evening!
Good evening back at ya
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1516. breald
Quoting VAbeachhurricanes:


not funny at all.... idk experts this has been trending west! im in college should i be calling my family about this?


Well, I am not going to worry about these darn models. They flip flop so much.
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Quoting VAbeachhurricanes:


not funny at all.... idk experts this has been trending west! im in college should i be calling my family about this?

That is just freaky! The start of the storm parade maybe??!!
Member Since: Posts: Comments:
I suspect the latest GFS run is "spurious anomalous data", anybody else remember when Kimberblain from the NHC used something like that in his TWD for 92L way early in the season. Very fancy term for an anomaly lol.
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Good evening!
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Quoting CaribBoy:
As we are getting closer to the pic of the hurricane season, I think the GFS is responding to this.
I agree.....as I recall we see this most years at this time of year. The peak.
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1510. breald
Quoting NJ2S:


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


I live in a very hilly city. The lower part of the city on the river always floods but I am up top of a steep hill and will get minor flooding but nothing too bad.

I have gone thru 2 hurricanes here and both were nasty.
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not funny at all.... idk experts this has been trending west! im in college should i be calling my family about this?
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1507. JLPR2
Quoting Tazmanian:



give it time


it has time XD
D-max should help it out, it probably detached from the ITCZ therefore it lost convection.
Member Since: September 4, 2007 Posts: 7 Comments: 8752
Quoting JLPR2:
96L is having some convection problems.




give it time
Member Since: May 21, 2006 Posts: 5093 Comments: 115936
Quoting jason2010xxxx:
that will be so funny if the northeast get hit by three hurricanes in two weeks..


No. It won't be. They are NOT prepared.
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Quoting ShenValleyFlyFish:
Clammily comes in many guises.
True Dat!
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1499. JLPR2
96L is having some convection problems.

Member Since: September 4, 2007 Posts: 7 Comments: 8752

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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