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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The season tally will be up to 5-2-0 later today...but with things proceeding as they are with Danielle, the nascent Earl, and perhaps that whatever-it-is in the GoM, I wouldn't be surprised at all to see it up to 6-3-1 by, say, tomorrow evening...

Here's a nice WV image of Danielle, soon-to-be-Earl, possibly-to-be-Fiona, and even a just-might-end-up-being Gaston (that small, dark swirl in northern Nigeria has already caught the attention of the pouch trackers, who may christen it PGI37L later today).

Click for larger image:
Member Since: Posts: Comments:
Can we stop with the New Orleans/Florida loops unless there's a disturbance there? Really clog up the blog where 2 actual storms are forming
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3197. Skyepony (Mod)


The blow up over the big bend area lastnight has persisted..still dragging off to the ENE. It's trying to stay over water. Fl is a real inhibiter here. Enjoy the rain.
Member Since: August 10, 2005 Posts: 175 Comments: 38213
3196. wxhatt
Quoting catastropheadjuster:
didn't StormW say after this trough there was another one coming down and much stronger? And it would lift D more northward. I may have it wrong.
sheri


I think so, unless the Azores Bermuda High stregnthens more.
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Quoting catastropheadjuster:
didn't StormW say after this trough there was another one coming down and much stronger? And it would lift D more northward. I may have it wrong.
sheri


I am not sure if Storm said it but yes there is another trof coming down... look at US water vapor imagery and you will be able to see the trof easily (Link) it will be moving into western NY today and tonight.
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didn't StormW say after this trough there was another one coming down and much stronger? And it would lift D more northward. I may have it wrong.
sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3678
3191. wxhatt
Yes I understand that there is supposed to be a 500 mb height anomoly over the Northeast, but I think that it may also allow for a weakness in the AB High over the Mid-Atlantic region thus recurving a lot of CV storms.
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Quoting SFlKatCane5:


Poll:

We are all _________!

1) okay
2) hunkered down
3) ready for some action
4) DOOM

You forgot "end times." ;)

Good morning. So, the wave behind Danielle is 100% chance of developing? I don't think I've ever seen that before. Shouldn't it just be TD7?
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Quoting wayfaringstranger:


Wow, very good views. Id love to have that link...thanks for that info.


all of the images are short lived pages so here is the link to the home page... you just click the storm on the left side and click the box on the image you want to see... try and look at ones that are in green

Link
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3188. Bonedog
LOL surfmom. That would be awsome if PR does go off.

Im thinking some of the bermuda reefs might get epic too, especially with wrap around.

With a constant onshore flow lately it will be closeout but hopefully one of these digging troughs sends them offshore and then it will glass up and get nice here. New break formed down the beach by me and I think it will go off in a nice 12 to 16 sec period swell just need to wait for one. I am hoping Danielle delivers it. Found the bar while diving one day. Havent seen it break though.
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Quoting surfmom:
Quoting RitaEvac:
If you are TX and LA residents, you shall know that there is a possibility of a tropical system in our backyard. Nothing at the moment but be aware that there is some potential for development close to home.
Corpus Christi here so I am paying attention.
SRQ w/ a kid moving to Galveston here so I am paying attention


Houston here - could use some showers for sure.
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Quoting Thundercloud01221991:
More pictures of a developing eyewall... on the visible you can see the entire northern half of the the eyewall is a new hot tower blowing way up above the cirrus deck





Wow, very good views. Id love to have that link...thanks for that info.
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See the hot towers on here
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3179. Skyepony (Mod)
Recon plan of the day was out early..

2. SUCCEEDING DAY OUTLOOK: BEGIN 12-HRLY FIXES
ON HURRICANE DANIELLE NEAR 25.5N 59.7W
AT 27/1800Z.

Member Since: August 10, 2005 Posts: 175 Comments: 38213
Quoting DestinJeff:
D looks to be getting another westerly shove along 20N

Link


DJ~~ Danielle looks like she's going due west, but I don't have a trained eye either, so i could very well be wrong.

sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3678
it is beginning to appear that there could be double trouble down the road. the trough that was suppose to take Danielle off to sea is weakening. the ridge now seems to be rebuilding and going a little more west. at the moment DAnielle and what i pesume to be TD7 are both moving west in response to the strenghening ridge. the whole scenario will change if ther eare no unforseen changes in the upper level environment
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Quoting wxhatt:
I think we will be pretty safe from any major impacts on the east coast this year. There are a lot of troughs digging down already, and one of the strong analog years (1995) shows that all off the CV storms had stayed out to sea as well.






WIth the way things may be setting up in the next 10 -12 days, I would be careful about taking that idea for granted.
Member Since: August 22, 2010 Posts: 0 Comments: 652
Quoting WxLogic:
New 12Z Steering:

Weakness not as strong as before and based on the last 3HRs it does appear to be attempting to close out some.

According to this steering map Daniel has missed the trough and should now take aim for the next trough so it is possible it could again take a more westerly path
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3174. surfmom
MLC - I'm just not understanding what's happening in my backyard right now - gomex - thanks for the floater link
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More pictures of a developing eyewall... on the visible you can see the entire northern half of the the eyewall is a new hot tower blowing way up above the cirrus deck



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Quoting StormW:


Lookin at things now...I'll have it in my synopsis.
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3171. bethie
Good Morning....

Leaving in 10 days for my 50th birthday celebration cruise to the "Saints" (eastern caribbean)... Wondering if TD7 will be a issue?

Thanks to all, especially Dr.M & StormW. I learn so much reading this blog. Formerly from MI, hurricanes didn't mean much until I moved to Tallahassee in 2001. I really enjoy tracking hurricanes. Smiles... -bethie-
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Quoting StormW:


Good morning!

Storm W: greetings. Do you see a real threat to Caribbean with TD7?
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3168. surfmom
Quoting RitaEvac:
If you are TX and LA residents, you shall know that there is a possibility of a tropical system in our backyard. Nothing at the moment but be aware that there is some potential for development close to home.
Corpus Christi here so I am paying attention.
SRQ w/ a kid moving to Galveston here so I am paying attention
Member Since: Posts: Comments:
Quoting wxhatt:
I think we will be pretty safe from any major impacts on the east coast this year. There are a lot of troughs digging down already, and one of the strong analog years (1995) shows that all off the CV storms had stayed out to sea as well.






?????
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3166. surfmom
Quoting Bonedog:
hey surfmom. sounds like you got some nice days ahead of you down there =)

Waitin on Danielle up here. Big wind driven chop right now from the low hanging around. Nothing ridable. Danielle should gives us some nice groundswell soon (weekend maybe sooner)

If you read back, Aurasurf thinks the winds may keep this messy for a while.... but I'm sure the clean up will be real fine. Aura thinks PR may go "Indo".....
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Quoting RitaEvac:
If you are TX and LA residents, you shall know that there is a possibility of a tropical system in our backyard. Nothing at the moment but be aware that there is some potential for development close to home.


Corpus Christi here so I am paying attention.
Member Since: Posts: Comments:
3164. wxhatt
I think we will be pretty safe from any major impacts on the east coast this year. There are a lot of troughs digging down already, and one of the strong analog years (1995) shows that all off the CV storms had stayed out to sea as well.



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3163. Bonedog
hey sheri. Been around all season just havent posted. Been too busy lately. I check up between calls.

have time down today so instead of watching the rain I decided to pop my head in =)
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3161. surfmom
Taz -- if you are still about - eye wall ID on Danielle would be most appreciated...( when she's finished)
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3160. Bonedog
hey surfmom. sounds like you got some nice days ahead of you down there =)

Waitin on Danielle up here. Big wind driven chop right now from the low hanging around. Nothing ridable. Danielle should gives us some nice groundswell soon (weekend maybe sooner)
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Quoting Bonedog:
am I on ignore?

wierd...


No I can see ya, haven't seen ya around lately. Good to see you.
sheri

Morning StormW.
Member Since: August 24, 2006 Posts: 21 Comments: 3678
3157. WxLogic
New 12Z Steering:

Weakness not as strong as before and based on the last 3HRs it does appear to be attempting to close out some.

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Great...now I've got Airplane on my mind. I can see handing Storm a chart:

"Storm, what can you make of this?"

"Well, I can make a hat, a brooch, a pteradactyl..."

Hoping to see some rain today in PBC so I can get out of coaching soccer practice!!
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AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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3153. surfmom
Quoting Bonedog:
am I on ignore?
wierd...
Morning! would never iggy you man of waves
SWFL/Gomex - this is the yellow circle illustrated

and the Surfer's View SWFL/Gomex Gulfster:
We still have a wave in the water this morning in the waist to occ. chest high range with an incoming tide peaking @ 12:12pm.(low @ 6:52pm) Surf looks a bit smaller than yesterday, but there is a few worthy peaks rollin' through. Wind today not as much as a factor, but there are some patches of rain out in the Gulf that will push onshore during the day. Tropics alive and kicking with hurricane Danielle churning towards Florida's wave window and another one, soon to be Earl right on her heels. EC looking at building surf starting on Saturday and lasting well into next week, but the quality will depend on how strong those E/NE winds crank!
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Quoting jason2010xxxx:
SHE IS STILL MOVING WNW ON HERE
How about the last few frames
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Quoting DestinJeff:


Yes. And Leroy got larrrrrrrger.


Leon... giggle
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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.