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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1699. Engine2
Quoting StormW:


No...I haven't..yet.
Prepare yourself, it seems a little extreme
Member Since: Posts: Comments:
96L has that feeling that it could slip under the trough and impact FL or some part of the east coast. Models keep shifting but still curving it northward at the end of the run. Going to be interesting to watch the speed of the trough to see how quick it picks up Danielle and either pick up 96L or miss it all together.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
1695. angiest
Quoting AtHomeInTX:


Hi Everyone. If you didn't get a wu-mail I was Homelesswanderer. Long story new name. :)

Anyway, SE TX locals said possible tropical development. Ch 12 said it would move into South Tx. And the water was 93 degrees per channel 6.


Beaumont?
Member Since: Posts: Comments:
1693. wxhatt
Quoting StormW:
Good evening!
Good Evening, I think, looks like your prediction of ramp up are coming true!
Member Since: October 5, 2005 Posts: 2 Comments: 885
Have the models shifted west due to Danielle's weakning,and if so is the U.S in danger.
Member Since: August 14, 2010 Posts: 10 Comments: 16369
buenas noches stormw :)
Member Since: July 10, 2006 Posts: 1 Comments: 833
Quoting XStormX:
de que hablan, eso no viene para ka


just talking about a 96l model run
Member Since: July 10, 2006 Posts: 1 Comments: 833
Quoting jason2010xxxx:
wow 10% in the GOM NOT GOOD AT ALL the water is over 90F


Hi Everyone. If you didn't get a wu-mail I was Homelesswanderer. Long story new name. :)

Anyway, SE TX locals said possible tropical development. Ch 12 said it would move into South Tx. And the water was 93 degrees per channel 6.
Member Since: August 24, 2010 Posts: 0 Comments: 676
Quoting StormW:
Good evening!


Evening stormw.. How you doing sir.. Gotta lot of Potential Development in the next 48hrs.. Do u concur with that.. Or the GOM feature will probably bring a lot of rain for someone.. ?
Member Since: August 15, 2008 Posts: 0 Comments: 2133
1686. Walnut
Good evening Storm! What do you make of the GOMEX disturbance? Anything to it?
Member Since: August 21, 2007 Posts: 0 Comments: 185
1685. Engine2
Storm - I take it you have seen the GFS?
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1684. BDAwx
Quoting BDAwx:
Apparently the power grid in Bermuda is still fragile from the severe winter storms from January to March.


Our newspaper reports that a fault caused 5000 people to lose power today.
Member Since: Posts: Comments:
Quoting Hurricanes101:
1648. barotropic 11:46 PM GMT on August 24, 2010

those same models that have been fantastic are taking a big shift to the west
Quoting Hurricanes101:
1648. barotropic 11:46 PM GMT on August 24, 2010

those same models that have been fantastic are taking a big shift to the west


Yeah, out nearly 150 hours.....I and U should expect those kinds of shifts in time......thats why they run them. But overall model performance has been excellent. I have even heard anyone here even begin to discuss why it shifted. I heard a couple regulars exclaim"oh man I that big high in the east is going to drive all three storms in". Well if they bothered to look, its the "complete" and total breakdown of that eastern high which allows a westward jog. The high "completely disappears in a 12 hr period off the map. Which no other model is remotely showing at this time....so until another run I would consider it suspect, take a look for yourself.......
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting centex:
My point is weather can't be predicted that far, much less the tropics which is even harder. I know they are fun to talk about and watch but lets put them in there place.

I disagree...I do a lot of work for all times. We do forecasts a month out. I nailed a massive snow storm 3 weeks in advance and was within 12 hours of first snowfall. Weather can be predicted in advance...just hard to do sometimes but def can be done. Need to know how to balance climo with current conditions and forecast models.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
1680. wxhatt
Quoting jason2010xxxx:
tropicals are going crazy tonight,
you betcha!
Member Since: October 5, 2005 Posts: 2 Comments: 885
1679. centex
Quoting xcool:





850mb Vorticity

GOM

not toobad
what is date stamp on that 850mb Vorticity?
Member Since: August 10, 2007 Posts: 0 Comments: 3223
Quoting JLPR2:
Dry air is getting stronger in Danielle's path, hm... makes you wonder about the future of this storm.
It seems 96L has a little patch of dry air to deal with too.



I saw that.. I wonder if she can hold on.. I have to check out other maps to see whats up..
Member Since: August 15, 2008 Posts: 0 Comments: 2133
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE AUG 24 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM DANIELLE...LOCATED ABOUT 895 MILES EAST OF THE LESSER
ANTILLES.


1. A BROAD AREA OF LOW PRESSURE LOCATED ABOUT 125 MILES SOUTHWEST OF
THE CAPE VERDE ISLANDS IS ACCOMPANIED BY A LARGE AREA OF CLOUDINESS
AND SHOWERS. ALTHOUGH SHOWER ACTIVITY HAS RECENTLY BECOME A LITTLE
LESS ORGANIZED...ENVIRONMENTAL CONDITIONS AND COMPUTER MODELS FAVOR
THE FORMATION OF A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF
DAYS. THERE IS A HIGH CHANCE...90 PERCENT...OF THIS SYSTEM BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WEST-NORTHWESTWARD NEAR 15 MPH.

2. A LARGE AREA OF SHOWERS AND THUNDERSTORMS OVER THE CENTRAL GULF OF
MEXICO EXTENDING EASTWARD FOR SEVERAL HUNDRED MILES IS ASSOCIATED
WITH A SURFACE TROUGH. DEVELOPMENT...IF ANY...OF THIS SYSTEM IS
EXPECTED TO BE SLOW TO OCCUR AS IT DRIFTS WESTWARD. THERE IS A LOW
CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BLAKE
NNNN

Member Since: August 15, 2008 Posts: 0 Comments: 2133
1675. JLPR2
Dry air is getting stronger in Danielle's path, hm... makes you wonder about the future of this storm.
It seems 96L has a little patch of dry air to deal with too.

Member Since: September 4, 2007 Posts: 7 Comments: 8493
Quoting Clearwater1:
They really can't evacuate, can they? Could be disastrous. I saw one of those, "what if show" once. The sub city was underwater from a direct hit.


Of course they can evacuate, given enough time...literally millions of people move into the city every morning in the span of 2 or 3 hours, no reason the 2 million or so people in Manhattan can't move out in 6 hours if given proper direction from authorities.
Member Since: Posts: Comments:
1672. XStormX
Quoting FLPandhandleJG:


Possibly a storm could develop in the GOM.. if showers keep developing and if the L develops.. But right now its a low risk that i would say at this moment.. But tampa has been getting soak the last 3 days or so.. Just saying!
hey, pandhandle, i'm sorry about the comment earlier, it was joke, i got carried away :-(
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Member Since: August 15, 2008 Posts: 0 Comments: 2133
1669. xcool





850mb Vorticity

GOM

not toobad
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1668. centex
Quoting barotropic:


From Dr Masters blog today....

"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............




You must be a genius.....you could have predicted it so far in advance....that I am amazed about......LOL
My point is weather can't be predicted that far, much less the tropics which is even harder. I know they are fun to talk about and watch but lets put them in there place.
Member Since: August 10, 2007 Posts: 0 Comments: 3223
1667. XStormX
Quoting JLPR2:


It's going west for the moment.



LOL! Susan Soltero said that it was not going to affect us, so start boarding up. XD
de que hablan, eso no viene para ka
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1666. XStormX
Invest 96 is the same location where hurricane hugo hit 21 years ago


Member Since: Posts: Comments:


Member Since: August 15, 2008 Posts: 0 Comments: 2133
1664. xcool
god i'm going need 55 eyes to watch tropical .
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1663. JLPR2
Quoting traumaboyy:


Yes it is...I was expecting a CAT 5 when I got back to work....wow....this thing just trying to hold on....oh and I see it is still going wnw right?


It's going west for the moment.

Quoting mrpuertorico:

wow yeah and for the worse
oye pero que vaina!rofl


LOL! Susan Soltero said that it was not going to affect us, so start boarding up. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8493
Member Since: Posts: Comments:
Quoting XStormX:


Possibly a storm could develop in the GOM.. if showers keep developing and if the L develops.. But right now its a low risk that i would say at this moment.. But tampa has been getting soak the last 3 days or so.. Just saying!
Member Since: August 15, 2008 Posts: 0 Comments: 2133
1660. BDAwx
Apparently the power grid in Bermuda is still fragile from the severe winter storms from January to March.
Member Since: Posts: Comments:
Quoting Snowlover123:

Good Evening.

LongbeachNY,

The 18Z GFS is particularly disturbing. Look at the animation. The Storm is so powerful, according to the GFS, that it plows right through the ridge building along the Eastern Seaboard.



Triple Tropical Trouble.

:o WoW!
Member Since: July 7, 2010 Posts: 0 Comments: 5625
Quoting centex:
I've been waiting for that.


From Dr Masters blog today....

"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............




You must be a genius.....you could have predicted it so far in advance....that I am amazed about......LOL
Member Since: August 22, 2010 Posts: 0 Comments: 652
This blog is likely to implode with all this tropical activity. Going to b a crazy season here on out I feel. Might as well get my posts on here while I can cause come next week I doubt ill be able to get a word in..
Member Since: Posts: Comments:
Quoting JLPR2:
Hm... the blog ate one of my posts.

As I was saying in the one that got eaten.
I'm amazed at how much the models have changed since yesterday for 96L.



Yes it is...I was expecting a CAT 5 when I got back to work....wow....this thing just trying to hold on....oh and I see it is still going wnw right?
Member Since: August 18, 2008 Posts: 0 Comments: 2265
1655. angiest
Quoting VAbeachhurricanes:




Does anyone actually respect NGFDL? I don't recall ever seeing anyone use its forecast, which is often quite far off all the rest.
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Bermuda is going to get hammered if these models are correct.



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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1648. barotropic 11:46 PM GMT on August 24, 2010

those same models that have been fantastic are taking a big shift to the west
Member Since: Posts: Comments:
Quoting JLPR2:
Hm... the blog ate one of my posts.

As I was saying in the one that got eaten.
I'm amazed at how much the models have changed since yesterday for 96L.


wow yeah and for the worse
oye pero que vaina!rofl
Member Since: July 10, 2006 Posts: 1 Comments: 833
Quoting FLPandhandleJG:

Danielle is lookin' better...I think she's obviously a hurricane again.
Member Since: July 7, 2010 Posts: 0 Comments: 5625
1649. XStormX
Member Since: Posts: Comments:

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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.