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 XStormX:
lol, i still see it moving west northwest, you know what's sad and funny, everyone on this blog has no lifes........


Everyone meaning yo?
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1748. centex
Quoting barotropic:


You a preaching to the wrong guy. I had a similar post about this last night.....its the human factor that makes the difference.
Sorry. They are a good tool but not the best tool.
Member Since: August 10, 2007 Posts: 0 Comments: 3293


Member Since: August 15, 2008 Posts: 0 Comments: 2133
Quoting KerryInNOLA:
He drinks a lot because he worries about his health. You see, he is on the waiting list for a new liver. He says he was born with a bad liver, then Katrina, the oil spill, his old lady left him for a Liberian, and now this


LOL.....and NOLA is not a typical non drinking invironment...lol....sorry about your brother's liver!
Member Since: August 18, 2008 Posts: 0 Comments: 2265
Quoting TampaSpin:
Evening all...Kinda shocked what happened to Danielle.....just shows we don't know much beyond just hours out.
The system over the gom won't amount to much but a heavy rain maker.Nothing serious.The storms off of africa are a different story though.
Member Since: August 14, 2010 Posts: 10 Comments: 17651
1744. Levi32
Quoting naplesdreamer28:
Can someone post 96L's track? I read they did not like the shift. To what?


Well as we knew, the models were too far north yesterday with 96L, and have shifted farther south today, that's all.

Member Since: November 24, 2005 Posts: 635 Comments: 26698
Quoting JLPR2:


Maybe the slight shift of Danielle's track to the west is allowing 96L to move further west.

Since 96L was supposed to follow Danielle, the farther west Danielle recurves, the farther west 96L can reach, no?

It is possible...I think 96L has a better shot to move west if the trough picks up speed and collects danielle with it. Danielle is a little farther north at the moment and before 96L drifts a little to the north the trough needs to push through.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
1742. hercj
Quoting StormW:


I have to tend to agree. I did a forecast for Orca, our blogger, for a trip he did to Cancun...gave him a 14 day forecast...only had one bad day in the forecast.

Senior just for info the NASA DC-8 flew today out of Ft Lauderdale. I think they were trying to lay a base line for their cyclo genesis experiments.
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Quoting centex:
Don't want to slam models too much but what would happen if we just had data feed to humans, wouldn't the tracks adjust similar? I just don't believe the programming is better than experts looking at the same data. I've been watching NWS and NHC forecast for years and they mention the models but also says how they discount them, change forecast inspite of them or pick one they seem to like. Where is the science, not in the models.


You a preaching to the wrong guy. I had a similar post about this last night.....its the human factor that makes the difference.
Member Since: August 22, 2010 Posts: 0 Comments: 652
1739. xcool


more strong wave..
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Can someone post 96L's track? I read they did not like the shift. To what?
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1737. Levi32
Quoting Walnut:
Is that ridge forecast to stay there for awhile or move out in a week or so?


The GFS shows fairly solid ridging over the southeast US for the next week at least.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
Quoting Dakster:
Wow... I don't like 96L's track shift... That is for sure.


yea that has me uneasy...I can just see the standard event that the models were trying to locate the center of the storm and figured the trough would pick it up but as the trough picks up speed it has a shot to slip under it...go through some shear to weaken it for a day or two but then gather itself and continue on. Who knows at this point but that is one thing that could happen.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
Interesting, both the GFDL and the HWRF 18z runs have trended slightly eastward, more so the GFDL - by near 1.5 degrees and shows a sharp eastward turn north of Bermuda to recurve. Neither show anything remotely like the gfs where the western ridge completely dissolves, which is why the GFS shows a potential NE seaboard brush.
Member Since: August 22, 2010 Posts: 0 Comments: 652
1734. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1733. Levi32
Quoting FLPandhandleJG:


Hey Levi.. Let me ask ya a question.. Might be stupid one but O well lol.. Um so that dry air that is heading southwest in front of Danielle.. right? Will it lead Danielle into another weaking stage or the wind shear has to be in part of it? I know Hurricanes take on some dry air.. Just want to hear some of ur thoughts.. Im thinking Bermuda needs to watch it as well and maybe near New England.. So whats ur take?


Well she suffered quite a setback last night but I think she should resume gradual strengthening tonight and tomorrow. The dry air and confluent environment in front will keep her in check for now, but once she starts recurving in the vicinity of Bermuda she will have a chance to become a major hurricane as the high breaks down, which is why you see the models jumping all over her intensity by that time.

As far as track....18z GFS is interesting and illustrates the concerns from earlier last week, but Bermuda is still the most threatened and I think ultimately Danielle will recurve before being able to hit the US.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
1732. JavPR
Quoting alpha992000:


She already said so?! O_o OK, time to run to the nearest store and get as much canned food and batteries as possible then. Poor Susan, I like her but I still remember her saying early on that Georges wasn't a threat. Yeah, sure.

lol i remember that....and the late Ponce Mayor Churumba Cordero who also said George wasn't a threat....
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1730. Walnut
Quoting Levi32:


Yeah when you have the trough and the front down there everything will be moving along the front SW to NE, but remember that trough is leaving to go get Danielle, and the ridge building in behind it is going to set up to the north of the GOM and start steering everything westward towards Texas. The stuff that gets trapped at the tail of the front will get stuck south of the high and get directed westward.
Is that ridge forecast to stay there for awhile or move out in a week or so?
Member Since: August 21, 2007 Posts: 0 Comments: 185
1729. Dakster
Wow... I don't like 96L's track shift... That is for sure.

Member Since: Posts: Comments:
Quoting StormW:


I have to tend to agree. I did a forecast for Orca, our blogger, for a trip he did to Cancun...gave him a 14 day forecast...only had one bad day in the forecast.
Storm have the models shifted west due to the weakning of Danielle?.And if so is the U.S in danger.
Member Since: August 14, 2010 Posts: 10 Comments: 17651
Quoting Levi32:
Danielle's back, probably getting back up to Cat 1 now. New CDO should be able to survive now and although the west side needs filling in, she should be able to gradually make a comeback. Scattered showers firing northwest of the center is a good sign, but dry air in that direction is still very much a problem.


That's pretty much the situation with Danielle this evening.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
The stalled frontal system across Florida and into the GOM is gonna create a problem as i have been saying. I believe Levi32 has been allover that as well and has done a great job for over a week of telling us as well that something would happen as well.
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Member Since: August 15, 2008 Posts: 0 Comments: 2133
Quoting DestinJeff:
GFS, You so crazy!


jeff and gfs babies!!!!!!!! WOW
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1723. JLPR2
Quoting alpha992000:


She already said so?! O_o OK, time to run to the nearest store and get as much canned food and batteries as possible then. Poor Susan, I like her but I still remember her saying early on that Georges wasn't a threat. Yeah, sure.


She said that? :O
Ok, time to check the flashlights!
Ah, poor Susan LOL!
Member Since: September 4, 2007 Posts: 7 Comments: 8747
1722. Levi32
Quoting clwstmchasr:
Hey Storm, help me understand this. We have had storms coming in from the GOM for two days. Everything is moving from SW to NE. Now the NHC has put a circle out there and says that it will move west.

I don't get that at all.


Yeah when you have the trough and the front down there everything will be moving along the front SW to NE, but remember that trough is leaving to go get Danielle, and the ridge building in behind it is going to set up to the north of the GOM and start steering everything westward towards Texas. The stuff that gets trapped at the tail of the front will get stuck south of the high and get directed westward.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
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


She already said so?! O_o OK, time to run to the nearest store and get as much canned food and batteries as possible then. Poor Susan, I like her but I still remember her saying early on that Georges wasn't a threat. Yeah, sure.
Member Since: Posts: Comments:
Quoting Levi32:
Danielle's back, probably getting back up to Cat 1 now. New CDO should be able to survive now and although the west side needs filling in, she should gradually be able to make a comeback. Scattered showers firing northwest of the center is a good sign, but dry air in that direction is still very much a problem.



Hey Levi.. Let me ask ya a question.. Might be stupid one but O well lol.. Um so that dry air that is heading southwest in front of Danielle.. right? Will it lead Danielle into another weaking stage or the wind shear has to be in part of it? I know Hurricanes take on some dry air.. Just want to hear some of ur thoughts.. Im thinking Bermuda needs to watch it as well and maybe near New England.. So whats ur take?
Member Since: August 15, 2008 Posts: 0 Comments: 2133
pop a satellite photo up, what are you talking about?
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Quoting XStormX:
de que hablan, eso no viene para ka
Hablan de 96L, Danielle keeps wobbling to the west at this hour, is supposed to turn right soon, hopefully!
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Evening all...Kinda shocked what happened to Danielle.....just shows we don't know much beyond just hours out.
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Quoting Hurricanes101:


having you say that, makes it an eye opener lol

haha I can throw a curveball from time to time. Hey I told my coworkers a week ago that we would have a Cat 3 storm in the atlantic this week...danielle was on its way and still could get there. Hope it does (out to sea of course) so I can save face.
Member Since: May 20, 2009 Posts: 0 Comments: 1640
1713. centex
Quoting barotropic:


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.......
Don't want to slam models too much but what would happen if we just had data feed to humans, wouldn't the tracks adjust similar? I just don't believe the programming is better than experts looking at the same data. I've been watching NWS and NHC forecast for years and they mention the models but also says how they discount them, change forecast inspite of them or pick one they seem to like. Where is the science, not in the models.
Member Since: August 10, 2007 Posts: 0 Comments: 3293
1712. wxhatt
Quoting StormW:


No...I haven't..yet.
Maybe a bit overdone!
Member Since: October 5, 2005 Posts: 2 Comments: 930
1709. JLPR2
Quoting HaboobsRsweet:
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.


Maybe the slight shift of Danielle's track to the west is allowing 96L to move further west.

Since 96L was supposed to follow Danielle, the farther west Danielle recurves, the farther west 96L can reach, no?
Member Since: September 4, 2007 Posts: 7 Comments: 8747
I go to work and come back to some scary models...Hold on to your bloomers Gertrude, the last frame of GFS aint good...
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Quoting StormW:


No...I haven't..yet.

ok everyone get ready with some excedrin and some pillows so he can lie down
Member Since: July 10, 2006 Posts: 1 Comments: 833
Quoting angiest:


Beaumont?


Yeah sorry. :) East of Houston area.
Member Since: August 24, 2010 Posts: 0 Comments: 253
Quoting StormW:


GOMEX area is going to be pretty slow to develop...if it does. I haven't looked at any updated stuff yet.


Yea i believe so if it does.. But most models have going towards South Texas or up to south west Louisania.. Thats if it develops.. But Tampa has been getting a lot of rain the past few days or so..
Member Since: August 15, 2008 Posts: 0 Comments: 2133
1702. xcool
centex.justing update .why
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1701. Levi32
12:05 AM GMT on August 25, 2010
Danielle's back, probably getting back up to Cat 1 now. New CDO should be able to survive now and although the west side needs filling in, she should be able to gradually make a comeback. Scattered showers firing northwest of the center is a good sign, but dry air in that direction is still very much a problem.

Member Since: November 24, 2005 Posts: 635 Comments: 26698
1700. Hurricanes101
12:04 AM GMT on August 25, 2010
Quoting HaboobsRsweet:
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.


having you say that, makes it an eye opener lol
Member Since: March 10, 2010 Posts: 1 Comments: 7874
1699. Engine2
12:04 AM GMT on August 25, 2010
Quoting StormW:


No...I haven't..yet.
Prepare yourself, it seems a little extreme
Member Since: February 27, 2006 Posts: 0 Comments: 482

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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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