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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Has anyone heard of who? If its somebody from the nhc its possible they are in a supporting role not a lead forecaster. Just saying...
Member Since: May 27, 2009 Posts: 0 Comments: 4436
StormW and all Look at this loop and look at the Low on the East Coast and tell me what you see.....I DON'T LIKE IT!
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1947. Levi32
96L doesn't have a well-defined surface circulation yet, but it's getting there slowly.

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FDL - GFS - NOGAPS... all trending west (again)... "feeling" the High.
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1944. Vero1
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1943. unf97
Good evening everyone!
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1942. bappit
Quoting KEEPEROFTHEGATE:
06L/H/D/C1
MARK
18.13N/49.36W


Some more bursting by Danielle it seems in those pics Keeper. The one you posted a couple days ago was really impressive. Showed it from an oblique view (I think that's the term).
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Quoting extreme236:


An overnight convective burst would bring it up to TD status.
Basically yea. The circulation appears well-defined and closed so all it needs is some convection before being designated.

SAL is to blame, after it passes to around 35W or so is when it will really ramp up.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting jason2010xxxx:
three models jump to the west.


Some might ought to tell our TS which way it needs to go looks a littel lost there
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Quoting StormW:


Very interesting! No, not tonight...we do have our dress rehearsal tomorrow night, though.


You guys will do great.....and please let me know when you have another conference....We want YOU to be as educated as you can be....so you can shine the light for dummies like me!
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Quoting Levi32:


I could totally set him up to do it :)


Well between yours and his it would save me a lot of time here! Get 'er done Storm!
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1935. Levi32
Quoting breald:
Do you think NHC will shift to the west @11pm update?


Probably because of the model consensus slightly farther west, but they likely won't go towards the new GFS solution.
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Quoting Hurricanes101:
Am I missing something with 96L?

I look at it and to me it does not look to be on the verge of being a tropical depression


An overnight convective burst would bring it up to TD status.
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1933. breald
Do you think NHC will shift to the west @11pm update?
Member Since: May 28, 2008 Posts: 38 Comments: 5303
Quoting KEEPEROFTHEGATE:
well its like this if he is real cool if he is fake well thats fraud and a illegal act so it will not last long if the latter


I love that attitude. live and let live. Thanks, Keeper
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1929. KEEPEROFTHEGATE (Mod)
06L/H/D/C1
MARK
18.13N/49.36W

Member Since: July 15, 2006 Posts: 169 Comments: 53296
1927. Levi32
Quoting blsealevel:


StormW ever concidered doing a forcast video?


I could totally set him up to do it :)
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Looks like Dry Air and the ULL to Danielle's North will keep her from becoming a huge storm that i first thought.....given that...i don't believe she will now go much further West than models are showing....Just my Opinion.
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StormW ever concidered doing a forcast video?
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Quoting StormW:


Hey Chief...Interesting hurricane season we got cooking here.....not beating the drums tonight??
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Look closely at the HWRF model..it doesnt look like it has it going immediately out to sea either
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Am I missing something with 96L?

I look at it and to me it does not look to be on the verge of being a tropical depression
Member Since: March 10, 2010 Posts: 1 Comments: 7361
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Quoting StormW:
Storm, I am trying to learn. Can you please explain how Danielle is supposed to go through that high to her nw. tia
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Quoting MiamiHurricanes09:
Agreed, the LGEM appears to have the best handle on it with the steady intensification IMO.


I think the reason why they may be a little on the conservative is because they might taking into account that of Danielle's outflow having an influence on the storm
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Quoting StormW:


Not much of a big turn there StormW....HUM...i know that will change but, but, but,!!!
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Quoting KEEPEROFTHEGATE:
well its like this if he is real cool if he is fake well thats fraud and a illegal act so it will not last long if the latter


I have asked him a couple times if he knew Dr Bob case and a couple of others I knew from the NHC and he never responded and just went away. Dont know if that means anything or not - he just didnt respond.
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Quoting Stormchaser2007:
The official intensity seems a bit conservative for 96L.

Agreed, the LGEM appears to have the best handle on it with the steady intensification IMO.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
TropicalStormDanielle's heading has turned westward to 2.5degrees north of WestNorthWest
from the previous heading of 8.4degrees north of WestNorthWest

24Aug - 12amGMT - 15.5n42.3w - - 75knots . . . . 982mb - NHC-ATCF
24Aug - 03amGMT - 15.6n43.2w - - 85mph . . . . . 982mb - NHC.Adv.10
HurricaneDanielle becomes Cat.2
24Aug - 06amGMT - 15.7n44.0w - - 85knots . . . . 973mb - NHC-ATCF
24Aug - 09amGMT - 15.9n44.6w - - 100mph . _ . 973mb - NHC.Adv.11
24Aug - 12pmGMT - 16.1n45.8w - - 75knots . . . . 983mb - NHC-ATCF
24Aug - 03pmGMT - 16.6n46.5w - - 80mph . . . . . 985mb - NHC.Adv.12
24Aug - 06pmGMT - 17.1n47.5w - - 65knots . . . . 990mb - NHC-ATCF
H.Danielle becomes TS.Danielle
24Aug - 09pmGMT - 17.5n48.2w - - 70mph . . . . . 993mb - NHC.Adv.13
25Aug - 12amGMT - 17.9n49.1w - - 65knots . . . . 990mb - NHC-ATCF

65knots=~74.8mph _ _ _ ~60.9knots=70mph _ _ _ 65knots=~74.8mph
NHC rounds windspeeds to the nearest 5mph or to the nearest 5knots

Copy&paste 16.1n45.8w-16.6n46.5w, 16.6n46.5w-17.1n47.5w, 17.1n47.5w-17.5n48.2w, 17.5n48.2w-17.9n49.1w, bda, mia into the GreatCircleMapper for a look at the last 12hours.
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Quoting K8eCane:
wake me up when september ends


I tried that already. Something keeps waking me up! :(
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1907. gtownTX
Quoting tropicfreak:


And didn't TD 2 make landfall in TX or in MX?


One can quibble over where it made landfall but please acknowledge the subsequent destruction of the flooding which went on for weeks after the storm. People in the RGV on both sides of the border are still in recovery.
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Quoting StormW:



POOF!
Hear, hear. Tv and print Mets. may be looking for rating's, but if you are on this blog, you should know better than to paint with such a broad brush. Thank you Senior Chief.
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Quoting K8eCane:
wake me up when september ends



september is overe lol
Member Since: May 21, 2006 Posts: 5091 Comments: 114710
Quoting KerryInNOLA:
Seriously, I think I'm going to make me a tall Mint Julep while I ponder this frenzy of tropical activity.


that is evil....Sorry I can't join....at work....but it is nice to have the BIG DOGS here to explain what's going on.
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1903. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #23
TROPICAL DEPRESSION, FORMER MINDULLE (T1005)
9:00 AM JST August 25 2010
===============================

SUBJECT: Tropical Depression Overland Vietnam

At 0:00 AM UTC, Tropical Depression, Former Mindulle (1000 hPa) located at 19.0N 104.0E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The cyclone is reported as moving west slowly.

Dvorak Intensity: T1.5


THIS IS THE FINAL TROPICAL CYCLONE ADVISORY FROM THE JAPAN METEOROLOGICAL AGENCY
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1902. KEEPEROFTHEGATE (Mod)
Quoting XStormX:
i don't mean any disrespect about him, i'm just curious, has anyone heard from him before?
well its like this if he is real cool if he is fake well thats fraud and a illegal act so it will not last long if the latter
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting Stormchaser2007:
The official intensity seems a bit conservative for 96L.




thats makeing it in too a vary strong storm
Member Since: May 21, 2006 Posts: 5091 Comments: 114710
And I'll turn myself in. Goodnight. :) Got a busy day tomorrow.
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1899. K8eCane
wake me up when september ends
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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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