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 angiest:
Danielle looks like she will make it to the next forecast point, but not at the forecast time.


huh?
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Quoting MiamiHurricanes09:


Vertical instability plummeting, and I mean plummeting in the tropical Atlantic.


The vertical instability chart is for the GOM.
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Quoting wial:
Another 1 minute loop of Danielle


great image thanks!
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2146. LemieT
I've been offline for a few hours now, a lot can change in that time. Apparently my girl Danielle is looking to be upgraded to a hurricane again, and beginning to look robust again on satellite.
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Quoting Weatherdad27:

Quoting Krycek1984:

It's so sad to take down trees...if they are healthy, and are varieties that are not prone to breakage, I sure wouldn't take them down.

Agreed - there are three huge white pines (small root system, subject to breakage or uprooting) and several oaks that are starting to get unhealthy. We're being careful on what we take down - I want to keep shade but not have a family member get hurt from an unhealthy tree crash through the roof as happened to a neighbor over the winter.


White pines are the worst! We have quite a few of them and when Ike blew through Ohio we lost several huge branches...one of them busted a plum tree in half and another broke a huge branch off of an apple tree.

After being through the Ike windstorm is when I became more interested in tropical weather. It was scary. I've never seen sustained winds like that.
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Quoting StSimonsIslandGAGuy:
Danielle looks a little better to me in satellite pictures. I think a decent chance upgrade to hurricane status again at 11---what do y'all think.


Just happened lol
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2143. xcool
traumaboyy .lol .way too much hype
Member Since: September 26, 2009 Posts: 2 Comments: 15675


Vertical instability decreasing in the tropical Atlantic.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Danielle is a hurricane again
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ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE DANIELLE DISCUSSION NUMBER 14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062010
1100 PM AST TUE AUG 24 2010

A SERIES OF MICROWAVE PASSES DURING THE PAST SEVERAL HOURS SHOW THAT
DANIELLE IS BECOMING BETTER-ORGANIZED...WITH HINTS OF AN EYE
FEATURE ON THE 37-GHZ CHANNELS. THIS IS ALSO SUGGESTED BY AN
INCREASE IN DEEP CONVECTION NEAR THE CENTER...ALTHOUGH THE SYSTEM
APPEARS TO STILL BE EXPERIENCING NORTHWESTERLY SHEAR. SATELLITE
CLASSIFICATIONS ARE A LITTLE HIGHER THAN SIX HOURS AGO...AND THE
INITIAL WIND SPEED IS RAISED TO 65 KT.

THE INTENSITY FORECAST IS A CHALLENGING ONE THIS EVENING. FOR THE
NEXT DAY OR SO...THE HURRICANE WILL BE INTERACTING WITH THE
MID-OCEANIC TROUGH TO ITS NORTHWEST AND EXPERIENCING MODERATE
SOUTHWESTERLY SHEAR. DESPITE WARM SSTS...THESE UPPER-LEVEL
CONDITIONS USUALLY DO NOT FAVOR MUCH INTENSIFICATION.
HOWEVER...MOST OF THE GLOBAL MODELS FRACTURE THE TROUGH IN 36-48
HR...WHICH CAUSES A DECREASE IN SHEAR AS HIGH PRESSURE BUILDS
CLOSER TO DANIELLE AND AN OPPORTUNITY FOR A MORE SIGNIFICANT
RESTRENGTHENING. THIS IS THE SCENARIO FOLLOWED IN THE NHC
INTENSITY FORECAST...AND IS IN GOOD AGREEMENT WITH A BLEND OF THE
GFDL/LGEM/SHIPS MODELS.

THE INITIAL MOTION OF THE CYCLONE CONTINUES TO THE WEST-NORTHWEST AT
ABOUT 16 KT. A RIDGE OVER THE CENTRAL ATLANTIC SHOULD PROVIDE THE
STEERING FLOW FOR DANIELLE DURING MOST OF THE FORECAST PERIOD. AS
THE RIDGE WEAKENS...A TURN TOWARD THE NORTHWEST IS EXPECTED
TOMORROW...WITH THAT GENERAL MOTION AT A SLOWER SPEED CONTINUING
FOR A FEW DAYS AFTERWARD. THE BIGGEST QUESTION IN THE LONG-TERM IS
HOW MUCH A MID-LATITUDE TROUGH THAT IS FORECAST TO MOVE OFFSHORE OF
THE NORTHEAST UNITED STATES OVER THE WEEKEND WILL AFFECT DANIELLE.
THE OVERALL TREND IN THE MODELS IS FOR A WEAKER TROUGH...WHICH
CAUSES A DELAYED NORTHWARD TURN OF THE CYCLONE. THE OFFICIAL
FORECAST IS WEST OF THE PREVIOUS ONE INITIALLY...BUT ENDS UP SLOWER
THAN THE PREVIOUS FORECAST AT 120 HOURS. IT IS IMPORTANT TO NOTE
THAT THE MODEL SPREAD IS INCREASING AT THE LONG-RANGE...SO THE
FORECAST CONFIDENCE AT THAT TIME IS LOWER THAN AVERAGE.



FORECAST POSITIONS AND MAX WINDS

INITIAL 25/0300Z 18.2N 49.8W 65 KT
12HR VT 25/1200Z 19.4N 51.5W 70 KT
24HR VT 26/0000Z 21.3N 53.5W 70 KT
36HR VT 26/1200Z 23.0N 55.3W 75 KT
48HR VT 27/0000Z 24.4N 57.0W 80 KT
72HR VT 28/0000Z 27.0N 60.0W 90 KT
96HR VT 29/0000Z 30.0N 61.5W 90 KT
120HR VT 30/0000Z 33.0N 61.5W 85 KT

$$
FORECASTER BLAKE

NNNN
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Quoting HurricaneLovr75:


Thats why I think Mass would not be able to handle even a Cat 1 very well. No palm trees here. Major of wind damage, and flooding rains. Got a big rain storm in May I believe and the rivers were cresting everywhere. Imagine 9 or 10 inches with Hurricanre force winds.


9 or 10" is unlikely because hurricanes move quite a bit faster that high in the latitudes but I suppose it could happen.

When do leaves start falling in MA? The less leaves on the trees the better the outcome. They aren't usually off here until past Halloween in Cleveland.
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2137. Levi32
I'm out for now, later all.
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Quoting RichlandStrangler:
Hurricane



once again

Why hello Danielle...
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Quoting xcool:
here go hype about hit ny


You know Cantore wants to cover it from the Empire State Building..lol
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Quoting angiest:


Yes, this is not the first time GFS has showed Danielle hitting or skirting the NE US.


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The eyewall of Danielle was rather impressive before it collapsed. It now appears to be trying to redevelop one on the northern side of the circulation. I also noted that it has begun a more WNW motion lately.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
2131. angiest
Quoting Chicklit:


hello


Party like its 1995.
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Quoting Chicklit:


hello

choo choo!
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hello
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2128. angiest
Quoting CATMAN5:
If anyone has a link to the GFS archives please post it and check the runs back on Aug. 17 which show a weak system striking near NYC on Aug. 29, 2PM or +288hrs.


Yes, this is not the first time GFS has showed Danielle hitting or skirting the NE US.
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2126. Gearsts
Quoting Tazmanian:




i like you better when you where being a fishcaster
lol
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Quoting Krycek1984:

It's so sad to take down trees...if they are healthy, and are varieties that are not prone to breakage, I sure wouldn't take them down.

Agreed - there are three huge white pines (small root system, subject to breakage or uprooting) and several oaks that are starting to get unhealthy. We're being careful on what we take down - I want to keep shade but not have a family member get hurt from an unhealthy tree crash through the roof as happened to a neighbor over the winter.
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2124. wial
Another 1 minute loop of Danielle
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2123. gator23
Quoting pilotguy1:


Oh good grief. Get a grip,

+1
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2122. Patrap
00z Early Cycle NHC model tracks
Danielle
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)



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Quoting CaicosRetiredSailor:
BAHA....Danielle looks to get past 50 before hitting the big two - oh....

I hear ya... I'm thinking positive thoughts, and trusting in some folks who know more than I do about these storms.

It's been quiet up this way.
I'm not ruling out the foolishness potential with this Danielle storm, mind u.... we both know strange things can happen... lol But I feel a fair amount of ease with this right now.

Somebody else just posted that it looks like the centre is at 50W already, and still under 20N. That to me puts Bermuda more squarely on the hot seat. But, as always, we'll keep watching...

I'm beat - long frustrating day. Think I'll turn in early tonight.

Good night to all....
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Quoting CaicosRetiredSailor:
Tonight's show:

Danielle's eye Deja vu


Looks like they are playing re-runs of last nights episode. :)
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She's a hurricane again

Information About Hurricane Danielle


Storm information valid as of: Wednesday, August 25, 2010 0:00 Z
Coordinates: 17.9N 49.1W (View Map or View Storm Centered Satellite Image)

Location: 775 miles (1247 km) to the ENE (65°) from Bridgetown, Barbados

Distance Calculator: How far away is this storm from me?

Pressure (MSLP): 990 mb (29.24 inHg | 990 hPa)

Sustained wind speed (1 min. avg.): 65 knots (75 mph | 33 m/s)


Link
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Has anybody posted this graphic of the 18Z GFS. Wow! Bowling with storms!
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2117. CATMAN5
If anyone has a link to the GFS archives please post it and check the runs back on Aug. 17 which show a weak system striking near NYC on Aug. 29, 2PM or +288hrs.
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Member Since: September 2, 2009 Posts: 130 Comments: 21193
Looks like a small west wobble is taking place. This will pass over or go south of the first forecast point.
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Tonight's show:

Danielle's eye Deja vu
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Quoting Skyepony:

Click pic for the long loop. A blow up there in the Big Bend area maybe beginning.

Getting some nice stratiform precip (gentle rain) here in East Central FL.

The blowup near the big bend area looks like an outflow boundary hitting some moisture, and going off. Lets see if it persists.
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Quoting Weatherdad27:


I'm a bit further away from the coast in Boxford with a lot of trees within striking distance of my house. We were gonna start taking them down perhaps this coming weekend. Hopefully a big wind doesn't complete the task for us. Looking like a wild half month or more in the tropics.


Thats why I think Mass would not be able to handle even a Cat 1 very well. No palm trees here. Major of wind damage, and flooding rains. Got a big rain storm in May I believe and the rivers were cresting everywhere. Imagine 9 or 10 inches with Hurricanre force winds.
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You gotta say anytime you get this kind of dry air in August here in S. La. you better enjoy it..and if that next front moves through, you gotta believe it has enough pull on its N. end
to handle Danielle....
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Quoting Levi32:


Yeah....will be interesting next year to see if this is one of those La Ninas that comes back up to neutral during the hurricane season like 2008, or goes back down again into one of those super multi-year La Ninas that you can get during cold PDOs, like 1955-57, 1973-76, and 1998-2001.
Should be very interesting.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting Enigma713:
It is possible if it misses the connection with the trough, and then connects up with another one, or the high weakens. With the way things are lining up, I doubt it will go west, then north. I think a more WNW with some NW track is possible, with an eventual recurvature out to the NE.


Well i will pray for east coast and ber.
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2107. Skyepony (Mod)

Click pic for the long loop. A blow up there in the Big Bend area maybe beginning.

Getting some nice stratiform precip (gentle rain) here in East Central FL.
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2106. Levi32
Quoting MiamiHurricanes09:
Great! Did you see the ECMWF August Nino3.4 forecast? Consensus keeps it near 1.5C-1.7C through February, then it starts to warm.



Yeah....will be interesting next year to see if this is one of those La Ninas that comes back up to neutral during the hurricane season like 2008, or goes back down again into one of those super multi-year La Ninas that you can get during cold PDOs, like 1955-57, 1973-76, and 1998-2001.
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2105. angiest
Danielle looks like she will make it to the next forecast point, but not at the forecast time.
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Quoting nolacane2009:
Just a learners question but any way Danielle could move back more west then north to affect either East Coast or Ber.?
It is possible if it misses the connection with the trough, and then connects up with another one, or the high weakens. With the way things are lining up, I doubt it will go west, then north. I think a more WNW with some NW track is possible, with an eventual recurvature out to the NE.
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Quoting Weatherdad27:


I'm a bit further away from the coast in Boxford with a lot of trees within striking distance of my house. We were gonna start taking them down perhaps this coming weekend. Hopefully a big wind doesn't complete the task for us. Looking like a wild half month or more in the tropics.


It's so sad to take down trees...if they are healthy, and are varieties that are not prone to breakage, I sure wouldn't take them down.
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2102. xcool
here go hype about hit ny
Member Since: September 26, 2009 Posts: 2 Comments: 15675
Just a learners question but any way Danielle could move back more west then north to affect either East Coast or Ber.?
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Quoting Levi32:


For a bit more yeah.
Great! Did you see the ECMWF August Nino3.4 forecast? Consensus keeps it near 1.5C-1.7C through February, then it starts to warm.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting HurricaneLovr75:


Funny thing..I work at a college in Boston and we had a meeting with safety to go over our Hurricane prepare plan this morning. Then come home to see that 18z GFS run. Got the chills!


I get that. When you've got tens of thousands of kids on campus you are responsible for, better have a plan! Even though it's a rare event up there, it can and does happen. Always be prepared if you live anywhere on the East and Gulf coasts. Of course, the islands as well.
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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.