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 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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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)

according to this, she's a hurricane again...

Link
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2097. angiest
Quoting Enigma713:

Unpossible!


Tomorrow will just be a little above normal, not way above normal with worse than normal humidity!
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Quoting angiest:


No more heat advisories for Houston!

Unpossible!
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2095. Levi32
Quoting MiamiHurricanes09:
Levi,
You around?


For a bit more yeah.
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Danielle back to a hurricane at this next advisory, im pretty dang sure. Look a IR, she's regaining her shape.
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2093. wial
In case no one's posted this yet.

Awesome 1 minute loop of Danielle.
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Quoting CapeObserver:


Have some relatives up there on Cherry St. Looks like this year is going to be one of those special years for NE. Last time I went through a storm up there was Bob. Now I'm in FL where is a regular occurance. My Mom is up there for the summer. Keeping a close eye on things.


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!
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2091. angiest
Quoting KoritheMan:


That's actually a pretty large difference.


No more heat advisories for Houston!
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Quoting KoritheMan:


That's actually a pretty large difference.

Yea that is good, means it is a strong trough and should hold together.
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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.
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GFS Ensembles
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Levi,
You around?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Hurricanes101:
Danielle is now at 50 west tonight

last nights 11pm had her north of 20N by the time she got to 50W

Danielle continues to be on the southern side of the cone


I agree
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Quoting TropicalAnalystwx13:


I know, I'm in Fort Worth, and is was only 88 degrees today!!! Its was 107 yesterday!!!!!


That's actually a pretty large difference.
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I just hope everyone on the East Coast is watching and prepared, should Danielle not make that recurve. These types of storms don't always go out willingly, without any tricks up their wind.jmo
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Quoting HurricaneLovr75:


I'm watching too here in Plymouth MA


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.
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Blog Update

Danielle starting to intensify, again; Tropical Depression #7 imminent from 96L
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Only system I am concerned about is 96L...got a weird feeling it could slip under the trough and we will then see a big shift in the models. Danielle might hint at hitting the east coast but not buying it yet. Plus it if just grazes the coast with the west side of the storm it wont be bad. I lived in va beach for 18 years and had quit a few hit use with just the west side and it was never too bad, just a lot of rain and a weak surge.
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Quoting nolacane2009:
Link


Last look looks weird can see a little eye and a little drift to west
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i know i remember bob and gloria we have had many years of tree growth and buildings going up so now we get anything there will be a lot more damage then people will ever expect.you know like why arent my lights back on next day hmmm u try to rewire a city
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Quoting KoritheMan:
Gonna be a chilly 69F tonight in Prairieville, Louisiana! Bring out the jackets! :P

No but seriously, that is a little unusual for this time of year. We usually don't expect to see that until mid September.

"Doin the happy dance!!"
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Thanks, the boat is 70'. We are booked at the boatyard just in case. No other tour operator has called, so the yard was surprised. however they all called for Collin so go figure. Guess they don't know about this blog. We have good moorings, but it is always better to be safe than sorry.
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The Magicseaweed Wave model has Danielle making the "right" turn at a point between Cape Cod and NS on Tuesday.
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2075. angiest
Quoting HaboobsRsweet:

Gustav and Camille not sure about Carla came from the Atlantic and did not form in the Gulf if I remember correctly. They did not peal off a front like the yellow area we have now. That yellow area is a rain maker. That is about it.


We were looking at a TCHP chart showing the area off the S/SW coast of Cuba. I believe all three of those storms passed through that particular area.

If you are looking at trough splits in the northern Gulf, Alicia came from the same general area.
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Link
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2073. Buhdog
@Tampaspin LOL!!!!


Something has to give, you cant have 3 days of non stop rain in SWFL and not get a Low develop. I say one pops up on surface map by 9 am.
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Danielle is now at 50 west tonight

last nights 11pm had her north of 20N by the time she got to 50W

Danielle continues to be on the southern side of the cone
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Quoting HaboobsRsweet:

Gustav and Camille not sure about Carla came from the Atlantic and did not form in the Gulf if I remember correctly. They did not peal off a front like the yellow area we have now. That yellow area is a rain maker. That is about it.


Wilma
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2070. angiest
Is Danielle trying to spread out?
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Kinda strange.... the gfdl take pre-Earl to a Cat 4 hurricane @ 126 hours.
117kts=134mph= cat 4.

The season has amplified. Bustcasters? anywhere?

http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2010082418-invest96l&field=Sea+Level+Pressure&hour= Animation
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Quoting angiest:


Gustav, Camille, Carla... anyone else care to name big storms that have fed off that part of the Caribbean?

Gustav and Camille not sure about Carla came from the Atlantic and did not form in the Gulf if I remember correctly. They did not peal off a front like the yellow area we have now. That yellow area is a rain maker. That is about it.
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Hey Patrap whats a frontal inversion?
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Quoting KoritheMan:
Gonna be a chilly 69F tonight in Prairieville, Louisiana! Bring out the jackets! :P

No but seriously, that is a little unusual for this time of year. We usually don't expect to see that until mid September.


I know, I'm in Fort Worth, and is was only 88 degrees today!!! Its was 107 yesterday!!!!!
Member Since: July 6, 2010 Posts: 113 Comments: 32811
2065. unf97
Quoting Goaskalice:
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?


I would definitely begin making preparations to take action for sure. I think Danielle is going to get close to Bermuda. Just have to keep watching, but I think watches will possibly be issued within the next 24 -36 hours there.
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Quoting CaicosRetiredSailor:
Good evening BAHA

I always breath easier when storms out there to the East get above 20N
Hey, CRS.... I was just thinking that Danielle looks to get past 50 before hitting the big two - oh.... not good.... I dunno with these systems this season.... they get going, and then they get stumped.

BTW, we have been having some spectacular lightening off to our W and NW this evening... pity I don't have the use of my camera tonight...
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2061. Patrap
730
fxus64 klix 250131
afdlix


Area forecast discussion
National Weather Service New Orleans la
831 PM CDT Tuesday Aug 24 2010


Short term...
sounding discussion...
a very dry sounding this evening due to a frontal boundary that
moved through the area yesterday...precipitable water value is
down to 1.25 inches. A frontal inversion is present near 800 mb
along with northerly winds up to 7k feet then shifting to westerly
winds aloft.


&&


Previous discussion... /issued 344 PM CDT Tuesday Aug 24 2010/


Short term...


A hint of Fall like weather has overspread the area today and
should remain in place through tomorrow...as a dry and stable area
of high pressure remains over the Gulf south. With mainly clear
skies and lower dewpoints in place...temperatures are expected to
fall into the middle to upper 60s tonight across the northern half
of the forecast area. South of Lake Pontchartrain...temperatures
will be closer to normal with lows dipping into the lower to
middle 70s. These same conditions are expected for tomorrow night.
During the day...the drier airmass combined with some increased
subsidence aloft and ample sunshine will allow temperatures to
climb into the middle 90s. Fortunately...the lower humidity values
will keep heat indices below 100 degrees.


The pattern will begin to transition back to a more normal late
August regime of heat and humidity on Thursday. In the upper
levels...a weak trough of low pressure will develop over the
western Gulf of Mexico. In addition...southerly flow off the Gulf
of Mexico will begin to take hold of the region. Moisture will
slowly stream into the area...as the low level ridge begins to
shift more toward the eastern Seaboard. This increasing moisture
combined with the weakness aloft should be enough to induce some
isolated convection over coastal Louis Ana on Thursday.


Long term...


Conditions
will become more unsettled across the entire forecast area for
the weekend as southeast flow off the Gulf increases in the low
levels...and strong moisture advection takes place in the middle-
levels. Aloft...a weakness in the broad upper level ridge
dominating the eastern two thirds of the nation will remain in
place. This upper level support...combined with increased moisture
and resultant instability...will allow for scattered convective
activity Friday through Sunday. Overall temperatures will be near
normal during this period...with overnight lows in the middle to
upper 70s and daytime highs of around 90 degrees.


Heading into early next week...there is some difference between
the GFS and ecwmf on the strength of another back door front
sliding into the Gulf south. The GFS is much stronger...with front
clearing the County Warning Area and pushing into western Louisiana by Tuesday
morning. However...the Euro has the front progressing much more
slowly...with continued moisture and higher probability of precipitation across the area
through Wednesday. Given the uncertainty...have opted to keep
chance probability of precipitation in across the area on Monday. Temperatures will remain
seasonable over the period. 32
Member Since: July 3, 2005 Posts: 428 Comments: 129827
Gonna be a chilly 69F tonight in Prairieville, Louisiana! Bring out the jackets! :P

No but seriously, that is a little unusual for this time of year. We usually don't expect to see that until mid September.
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And don't forget to consult with the BWS...
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Quoting HurricaneLovr75:


I'm watching too here in Plymouth MA


Have some relatives up there on Cherry St. Looks like this year is going to be one of those special years for NE. Last time I went through a storm up there was Bob. Now I'm in FL where is a regular occurance. My Mom is up there for the summer. Keeping a close eye on things.
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if it were to get us here in the ne when would be the thinking
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Quoting Goaskalice:
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?


Wait till tomorrow, if the models continue to point towards you or watches and warnings are issues consider getting it somewhere safe. If the hurricane isn't looking like its going to hit you consider suspending operations, as sometimes the outflow thunderstorms can spawn waterspouts.
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Quoting Goaskalice:
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?

I would. Waves are going to be nasty, and with the models starting to shift west, closer to you... yeah, haul the boat out Friday-ish, maybe Saturday morning. Wait until the models and the NHC have more time to make projections.
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2054. Patrap


Member Since: July 3, 2005 Posts: 428 Comments: 129827
More models are beginning to bend towards the Mid-Atlantic and Northeast.

Member Since: June 29, 2006 Posts: 65 Comments: 3197
2052. angiest
Quoting Goaskalice:
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?


No watches or warnings up yet. How long does it take you to get the boat out of the water?
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Quoting CapeObserver:


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.


I'm watching too here in Plymouth MA
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The 18z GFS at 384 hours clearly shows we have active days ahead in the long range into September. The active period we've all been talking about has just started...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
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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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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