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 CaicosRetiredSailor:

now thats just too funny (one post up)...
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This ain't too shabby.
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2197. help4u
Where is jason2010xxxx when we need hurricane advice,he nails the forcast.
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Quoting Chicklit:


Yeah, nice evening out there 2night, a little cooler. Just drove up from Melbourne in it. Could even open windows for a change; humidity quite high. Nother long work day with many more to come. (Why I get to slack in June/July tho.)

Must say, 96L is looking good and lower than Danielle was at her longitude.
96L: 13N 25 W 8 p.m. Tues.

Danielle: 12.1N 33.4W 8 a.m. Sun.
14.2N 35.9W 11 p.m. Sun.
14.8N 37.1W 5 a.m. Mon.
ahhh, that would be HIGHER than Danielle
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96L starting to fire off more convection.
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Quoting Chicklit:


Yeah, nice evening out there 2night, a little cooler. Just drove up from Melbourne in it. Could even open windows for a change; humidity quite high.
open the windows in this humidity, the entire house would sweat
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2191. angiest
Quoting Orcasystems:


50/50


Yes, they will or they won't.
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Thanks Zoo. I learned early on if you're going to hang on this blog you have to learn to ignore a lot of things. Kind of like a life skill, lol.
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Quoting Hurricanes101:


I dont think we have an invest in the GOM, unless I missed something

rofl
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Quoting Huracaneer:


Well at least a yellow circle (more like oval). Ten percent chance! (got to start somewhere).


from NHC:

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.

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Quoting RMM34667:


It's been pouring in West Central FL for four day. I just want it to move on!

just tell it to go up to I-10, drive about 1000 miles west, and hang out over SE Texas for a bit. It is welcome to stay for a few days.
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Quoting Hurricanes101:


I dont think we have an invest in the GOM, unless I missed something


We don't.
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Quoting want2lrn:
Good Evening, would someone please tell me where to find Levi's blog. I follow this one and Storm's, but i hear his is really good too! Thank you

look for Levi32.
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Quoting Alockwr21:
What are the chances of the models shifting west even again?


50/50
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Quoting Hurricanes101:


I dont think we have an invest in the GOM, unless I missed something


Well at least a yellow circle (more like oval). Ten percent chance! (got to start somewhere).
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Quoting xcool:
traumaboyy .lol .way too much hype


DON'T MISS THE MOON.....I am sure it is a lot nicer from where you live.....but it is rocking tonight.....sorry central/south florida....rain mucking up a beautiful night!
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2181. angiest
Quoting Hurricanes101:


I dont think we have an invest in the GOM, unless I missed something


Just an AOI, so far/
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>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.

All of the sudden we're in a new ball game. The storm weakens and as a result stays left, a weaker trough is trending, and Bermuda has to prepare. That is a quick change from twelve hours ago!

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Quoting Huracaneer:
I knew it! Predicted an invest in the Gulf by the end of the week last weekend due to the continuing drop in pressures and continuous storms (hasn't stop raining at my house for days). My first successful prognostication.


I dont think we have an invest in the GOM, unless I missed something
Member Since: March 10, 2010 Posts: 1 Comments: 7505
2178. KEEPEROFTHEGATE (Mod)
06L/H/D/C1
MARK
18.79N/50.01W

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Quoting CapeObserver:


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.


Sorry for those being rude - of course they have to have a plan, and you are correct about keeping an eye out.

The same ones being rude would be the first ones to yell if something happened and they didn't have a plan.
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I knew it! Predicted an invest in the Gulf by the end of the week last weekend due to the continuing drop in pressures and continuous storms (hasn't stop raining at my house for days). My first successful prognostication.
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Quoting Enigma713:

Pretty much anything with "pine" in it is bad for windstorms. We have mostly lobolly pines down here in Houston, and Ike didn't uproot many of them... but quite a few of them were missing branches, or broke 15-20 feet up.


I know they aren't around down there but I don't usually see *too* many problems with norway or blue spruces, but I guess they aren't "technically" pine trees, either.
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What are the chances of the models shifting west even again?
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All the computer models fails to forecast Danielle's track since yesterday morning.Thanks God that happens in the far central Atlantic and not close to the lesser antillies.
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Thank you
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Quoting Skyepony:
BR>Getting some nice stratiform precip (gentle rain) here in East Central FL.


Yeah, nice evening out there 2night, a little cooler. Just drove up from Melbourne in it. Could even open windows for a change; humidity quite high. Nother long work day with many more to come. (Why I get to slack in June/July tho.)

Must say, 96L is looking good and lower than Danielle was at her longitude.
96L: 13N 25 W 8 p.m. Tues.

Danielle: 12.1N 33.4W 8 a.m. Sun.
14.2N 35.9W 11 p.m. Sun.
14.8N 37.1W 5 a.m. Mon.
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Quoting Krycek1984:


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.

Pretty much anything with "pine" in it is bad for windstorms. We have mostly lobolly pines down here in Houston, and Ike didn't uproot many of them... but quite a few of them were missing branches, or broke 15-20 feet up.
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Quoting MiamiHurricanes09:
G'night everyone!


Night Miami! Study hard in school tomorrow :)
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2168. Patrap
Katrina felled Pines ,Bucktown Aug 30th,,west of 17th St. Canal.



photo by Patrap
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Quoting StSimonsIslandGAGuy:
Ah....MrStormX my predictions are always better when looking back! :)


lol, good times
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2165. Relix


Next one off Africa looking good as well.
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Quoting reedzone:
NHC not buying the new models right now.


Not buying any models in the long term... after Bermuda there is a big Question Mark.
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2162. xcool
reedzone i'm not too
Member Since: September 26, 2009 Posts: 2 Comments: 15648
G'night everyone!
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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.


I know that the majority of my family and friends in MA do NOT take hurricanes seriously. Most have never experienced anything much stronger than a Cat 1 in their lifetime. Should a hurricane even bordering on a major strike that area the complacency will take many lives I fear.
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Quoting want2lrn:
Good Evening, would someone please tell me where to find Levi's blog. I follow this one and Storm's, but i hear his is really good too! Thank you


Levi
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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.
Already updated. Back to hurricane at 75 mph. 18.2N 49.8W.
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Quoting Enigma713:

The vertical instability chart is for the GOM.
Oops! Fixed it.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
NHC not buying the new models right now.
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AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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uh oh here goes the drama!!!!!! SHES NOT GONNA TURN WOOT WOOT
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Good Evening, would someone please tell me where to find Levi's blog. I follow this one and Storm's, but i hear his is really good too! Thank you
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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.


It's been pouring in West Central FL for four day. I just want it to move on!
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2151. angiest
Quoting Chicklit:


huh?


On track but slower.
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Note the ending of the discussion which says, "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."
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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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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.