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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2299. jonelu
looks lik the air in front of Danielle is moistening a little as she slowly strengthens. But I wonder how that pesky ULL to her north will effect her.
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2298. scott39
Danielle is definitely going more West on the Sat Loop. I hope the forecast on the High to weaken is correct. Why is it going to weaken?
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2297. Seastep
Quoting CosmicEvents:
I'll say this.....if the 00z and 06z GFS runs show the same trend, then the NHC is going to have to widen that cone like a light bulb and sound the klaxon in the main ne metro areas. It'll be big news come mid-morning....out of respect for continuity.


continuity... lol.
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Quoting F4PHANTOM:
DRUNK. Did the same thing 10 days ago; developed EVERY wave. had 4 at a time. if that would have played out then we would be up to 15 or more storms by now. It SHOULD calm down on the next run.


Difference is, 10 days ago we were stuck in an unfavorable circulation pattern which is not the case now. It is not out of the realm of possibility to see what the GFS is projecting with the conditions about.
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2295. will45
Quoting angiest:


I'm not sure. I don't see an appreciable change, yet. And steering doesn't seem to show much reason to turn at this point...


look at 30hrs
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2294. Seastep
GFS not so drunk when it comes to Danielle.

I've been looking at the CIMSS steering maps constantly with this one. All along I've thought it would miss the first trough... with greater confidence as time went on.

Since the beginning I have thought she would go under the ridge, now split to the NE by the weakness. Not skilled enough to really say how that would play out.

GFS is now showing just that.

CIMSS 5-day steering java loop
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2293. angiest
Quoting will45:
started making the turn at 24 hrs tho


I'm not sure. I don't see an appreciable change, yet. And steering doesn't seem to show much reason to turn at this point...
Member Since: August 26, 2006 Posts: 16 Comments: 4766
2292. raggpr
Quoting will45:


refresh if you on the loop page


Thanks!
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2291. Hhunter
Quoting all4hurricanes:

Half the models now don't recurve Danielle she may end up being a threat to the US


Bastardi discussed this tonight as a real risk
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the link stops loading half way through
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Look at IR rainbow loop and you can see eye.
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2288. will45
Quoting raggpr:
does the link from the gfs updates new image automatically or do i have to press refresh?


refresh if you on the loop page
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been a very common theme hasnt it? south of models?
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2286. will45
started making the turn at 24 hrs tho
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2285. raggpr
does the link from the gfs updates new image automatically or do i have to press refresh?
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2284. angiest
Quoting CosmicEvents:
I'll say this.....if the 18z and 00z GFS runs show the same trend, then the NHC is going to have to widen that cone like a light bulb and sound the klaxon in the main ne metro areas. It'll be big news come mid-morning....out of respect for continuity.


This far away you won't see that big a change. However, the local mets will show a largely uneducated populace spaghetti plots, and the population won't pay attention to what they actually mean.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
I'll say this.....if the 00z and 06z GFS runs show the same trend, then the NHC is going to have to widen that cone like a light bulb and sound the klaxon in the main ne metro areas. It'll be big news come mid-morning....out of respect for continuity.
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Very slightly farther west through 18.
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2281. will45
Quoting CapeObserver:


Link?


Link

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Link

OMG
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watch the 0z gfs here

Link
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Through 9 hours, a noticeable difference over the 18z GFS is that the storm is faster.
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Quoting LongIslandXpress38:
Holy Moly, whats up with the 18Z GFS at 192 hrs?
DRUNK. Did the same thing 10 days ago; developed EVERY wave. had 4 at a time. if that would have played out then we would be up to 15 or more storms by now. It SHOULD calm down on the next run.
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Quoting philliesrock:
0z GFS is out to 6! :)


Link?
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2275. angiest
Hmm, TD in the Gulf?

Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting KEEPEROFTHEGATE:


remember models are meant to be used for guidance purposes only and donot depict final outcome in any single event


Whatever man, I'm packing up the car and heading to Cleveland...
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Here we go, 0z GFS stay away from my house!!!!
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0z GFS is out to 6! :)
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2271. KEEPEROFTHEGATE (Mod)
Quoting LongIslandXpress38:
Holy Moly, whats up with the 18Z GFS at 192 hrs?


remember models are meant to be used for guidance purposes only and donot depict final outcome in any single event
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2270. Seastep
Quoting Relix:


Someone needs a better internet! =P


Or, maybe the server side is having issues because it is being cached for everyone, when a link would suffice for such a large file and lighten the load.

Large stuff should really be linked.
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2269. smuldy
Quoting Skyepony:
The AEMN which is a gfs ensamble has out preformed the rest, though not impressively. Models over all are doing poor with Danielle.

Average Position Error (nm) for core models
model Error Trend 24hr Error 48hr Error 72hr Error Day 4 Error Day 5 Error
AEMN INCREASING 73.2 71.3 76.2 74.7 -1
OFCL INCREASING 92.1 120.2 74.6 -1 -1
LBAR DECREASING 100.7 160.9 244.8 225.6 -1
MM5E INCREASING 101.8 157.5 211.6 -1 -1
MM5B INCREASING 106.9 157.3 143.3 208.8 -1
BAMD DECREASING 117.3 140.6 185 129.4 -1
GFDL INCREASING 127.5 95.4 110.6 183.2 -1
HWRF INCREASING 138.6 130.2 143.9 208.1 -1
KHRM DECREASING 158.7 324.2 293.5 -1 -1
NGPS INCREASING 193.9 267.6 336.5 357.1 -1
sorry i should know this but im being lazy atm as only half here:are these charts on huffman's site or noaa or where are you grabbing the data from. thanks very much in advance, not doubting the data at all just want to know where to run to read it in the future. thanks again
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2268. scott39
If the ridge is weakening, why is Danielle going more W?
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Quoting KEEPEROFTHEGATE:


ALERT ATCF MIL 96X XXX 100824180000
2010082418
13.0 334.6
14.7 328.2
100
13.0 334.7
250100
1008250100
1
WTNT21 KNGU 250100
MSGID/GENADMIN/NAVMARFCSTCEN NORFOLK VA//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A TROPICAL CYCLONE IS POSSIBLE WITHIN 100NM
EITHER SIDE OF A LINE FROM 13.0N 25.4W TO 14.7N 31.8W OVER THE
NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF A NUMBERED
TROPICAL CYCLONE WARNING AT THIS TIME.
2. A 1050 ZULU ASCAT PASS SOUTH OF THE CAPE VERDE ISLANDS
SHOWS AN ELONGATED AREA OF CYCLONIC CIRCULATION. CURRENT REGIONAL
MODELS ARE SHOWING INTENSIFICATION OF THIS LOW OVER THE
NEXT 24HRS. THIS, IN CONJUNCTION WITH WARM SEA SURFACE TEMPERATURES
OF 86 TO 88 DEGREES FAHRENHEIT SHOULD HELP TO ENHANCE THE DEVELOPMENT
OF THIS TROPICAL FEATURE.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO A WARNING OR ALLOWED TO
EXPIRE BY 260100Z AUG 2010.//
Quoting KEEPEROFTHEGATE:


ALERT ATCF MIL 96X XXX 100824180000
2010082418
13.0 334.6
14.7 328.2
100
13.0 334.7
250100
1008250100
1
WTNT21 KNGU 250100
MSGID/GENADMIN/NAVMARFCSTCEN NORFOLK VA//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A TROPICAL CYCLONE IS POSSIBLE WITHIN 100NM
EITHER SIDE OF A LINE FROM 13.0N 25.4W TO 14.7N 31.8W OVER THE
NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF A NUMBERED
TROPICAL CYCLONE WARNING AT THIS TIME.
2. A 1050 ZULU ASCAT PASS SOUTH OF THE CAPE VERDE ISLANDS
SHOWS AN ELONGATED AREA OF CYCLONIC CIRCULATION. CURRENT REGIONAL
MODELS ARE SHOWING INTENSIFICATION OF THIS LOW OVER THE
NEXT 24HRS. THIS, IN CONJUNCTION WITH WARM SEA SURFACE TEMPERATURES
OF 86 TO 88 DEGREES FAHRENHEIT SHOULD HELP TO ENHANCE THE DEVELOPMENT
OF THIS TROPICAL FEATURE.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO A WARNING OR ALLOWED TO
EXPIRE BY 260100Z AUG 2010.//


Can you give me the link?
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2266. KEEPEROFTHEGATE (Mod)
lol
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Holy Moly, whats up with the 18Z GFS at 192 hrs?
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Quoting Relix:


Someone needs a better internet! =P

Meh. It's not dial-up, and that's all I care about.
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Quoting ChrisDcat5Storm:
guys the NHC updates there pics every how many minutes?


In most cases, every thirty minutes, at 15 minutes and 45 minutes pas the hour. It usually takes them an hour to post them, however. For instance, the next image update is due at 11:45 EDT, but the newest image at that time will be the 10:45 snapshot.
Member Since: November 8, 2009 Posts: 4 Comments: 13726
I will say this - it's diff being on the opposite coast and watching all of this. We have the quakes which most of the time you might confuse with your wash machine on spin. Now that I've been on the east coast and have gone through it, my heart goes out to everyone who is watching these storms roll off. Everyone is in my thoughts.
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Quoting KEEPEROFTHEGATE:



This is an official U.S. Navy web site. Security & Privacy Policy is in place


Lol, you sound like some kind of CIA agent.
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2260. Relix
Quoting philliesrock:
Can you guys stop posting that loop of 1-minute updates, and start linking it instead? It's taking a few minutes to load and slowing down my internet connection.


Someone needs a better internet! =P
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Those latest model runs are taking Danielle disturbingly close to the east coast.

On the plus side, though, it does appear that Danielle is beginning to feel the effects of the weakness in the high pressure ridge, and has been drawn a bit farther to the north since this morning. So only time will tell.
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2258. KEEPEROFTHEGATE (Mod)
Quoting XStormX:
keeper can you send me that link? pretty please with sugar on top? :D



This is an official U.S. Navy web site. Security & Privacy Policy is in place
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ty
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Can you guys stop posting that loop of 1-minute updates, and start linking it instead? It's taking a few minutes to load and slowing down my internet connection.
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Quoting ChrisDcat5Storm:
guys the NHC updates there pics every how many minutes?

30 min :15 and :45
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30
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guys the NHC updates there pics every how many minutes?
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Yah, eye will show up soon you can clearly see were it will pop up and it will be a good sized eye.


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WHEW HOOOOOOOOOO the tropics are SMOKIN tonight!!! and so is the drama I LOVE HURRICANES the fact that the models are shifting around is making stomach shift around too!
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Stsimons - miss your sense of humor!!! I'm feeling rather darstic tonight myself. Perhaps a certain shower curtain would do the trick.
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Quoting stormwatcherCI:
LOL. In Cayman if you mop your floors with the windows open the floor never dries. I always have to mop with the a/c on in order for it to dry.


Paint NEVER dries here! Lol. Be careful where you sit.
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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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