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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2449. xcool
Tropical Cyclone Formation Alert

96L
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2448. xcool
traumaboyy lmao
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting CosmicEvents:
I'm starting to get the schpulkies.


You are one mashugganah schmagehgie. I'm just sayin'....!
Member Since: Posts: Comments:
2446. alfabob
I think the Lesser Antilles may have a slight chance of high winds in the near future. Waiting to see how the 200-500mb plays out over the next 24 hours.
Member Since: July 5, 2010 Posts: 0 Comments: 1347
2445. xcool
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.//

Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting xcool:


That a fly swat or spatula??
Member Since: Posts: Comments:
2443. JLPR2
Quoting scott39:
Danielle doesnt care about models. She is an independent Woman!


LOL!
Member Since: Posts: Comments:
2442. hydrus
Quoting StormJunkie:
Night all...
G,night.S.J.
Member Since: Posts: Comments:
2441. scott39
Danielle doesnt care about models. She is an independent Woman!
Member Since: Posts: Comments:
2440. TXEER
Quoting Amanda44:
Hello weather peeps! I am new here and have been reading this blog because yall all seem to be weather rocket scientists to me. I have lived in Houston TX all my life.. been through Alicia, and Ike...and this may sound crazy but I ALWAYS wish for a hurricane every year to come here! Even after living for 2 weeks with no power in the heat after Ike.. I still am ready for another one to blow through here.

Here is my question.. I don't understand any of the lingo or know what any of the blobby looking maps with various looking blobs and squiggly lines mean, so can any of you tell me if you think any of these lovely blobs that you all are talking about have a chance of coming to my town (Houston)for a visit?

Also why do they call them "invests"? Why do they call some of the colored blobs invests and others not? I got all excited about that new yellow blob in the GOM (see I can learn some lingo) but wondered how come it wasn't an "invest".

Love a good storm and hoping for one to come my way! I know I am not supposed to admit that though!! Not PC!

Back to your regularly scheduled weather mumbo jumbo talk! (no offense.. just wish I knew what yall were talking about!)


I live in Kingwood..and...dude you are NUTZ!!
Member Since: Posts: Comments:
2439. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2438. hydrus
Quoting will45:
Link
Nice. Three named storms and a 1010 mb low right off the African coast. Four storms with names at the same time?????
Member Since: Posts: Comments:
2437. will45
Link

not fast do i see a loop?
Member Since: July 18, 2009 Posts: 1 Comments: 994
Night all...
Member Since: Posts: Comments:
wow, 00Z GFS takes Earl directly over Bermuda
Member Since: March 10, 2010 Posts: 1 Comments: 7874
2434. smuldy
bartender, i'll take whatever the GFS has been having the last 12 hours
Member Since: Posts: Comments:
2433. xcool
okay now w'e need cmc % ECMWF
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2432. TXEER
Quoting Relix:
Pre-Fiona looks good. May just be the caribbean storm of the year!


Well we can all hope and pray for it, right?
Member Since: Posts: Comments:
Quoting Hurricanes101:
ok 18Z was just meant to scare us

00Z takes Danielle east of Bermuda, but close enough to Bermuda that they should get impacts


It also looks like the Leewards, especially the northern islands are potentially at risk.
Member Since: Posts: Comments:
2430. xcool
no ny hit.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2429. JLPR2
Quoting crashingwaves:


I think Danielle looks like trouble too.jmo


I'm talking about me. XD
So far the GFS is saying all the systems will be troublesome for someone, somewhere.
Member Since: Posts: Comments:
Hello weather peeps! I am new here and have been reading this blog because yall all seem to be weather rocket scientists to me. I have lived in Houston TX all my life.. been through Alicia, and Ike...and this may sound crazy but I ALWAYS wish for a hurricane every year to come here! Even after living for 2 weeks with no power in the heat after Ike.. I still am ready for another one to blow through here.

Here is my question.. I don't understand any of the lingo or know what any of the blobby looking maps with various looking blobs and squiggly lines mean, so can any of you tell me if you think any of these lovely blobs that you all are talking about have a chance of coming to my town (Houston)for a visit?

Also why do they call them "invests"? Why do they call some of the colored blobs invests and others not? I got all excited about that new yellow blob in the GOM (see I can learn some lingo) but wondered how come it wasn't an "invest".

Love a good storm and hoping for one to come my way! I know I am not supposed to admit that though!! Not PC!

Back to your regularly scheduled weather mumbo jumbo talk! (no offense.. just wish I knew what yall were talking about!)
Member Since: Posts: Comments:
2427. will45
no east coast on this run
Member Since: July 18, 2009 Posts: 1 Comments: 994
2426. scott39
Models are worse than politicians! Flip--Flop!
Member Since: Posts: Comments:
How is the ULL to the north of Danielle going to effect her?
Member Since: Posts: Comments:
2424. will45
Link
Member Since: July 18, 2009 Posts: 1 Comments: 994
2423. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2422. flsky
Quoting CosmicEvents:
I'm starting to get the schpulkies.

Good word....
Member Since: Posts: Comments:
Tropics are ACTIVE folks!!
Member Since: Posts: Comments:
ok 18Z was just meant to scare us

00Z takes Danielle east of Bermuda, but close enough to Bermuda that they should get impacts
Member Since: March 10, 2010 Posts: 1 Comments: 7874
2419. smuldy
Quoting cheetaking:
0z GFS takes Danielle straight into Bermuda as a category 2 hurricane five days from now, with potentially-future Earl almost directly behind it. An interesting week ahead indeed.
that is more than a cat 2, look at the tightness of concentric circles not the mb number the mb number is for the global low not a fixed center, one of several reasons I am having a hard time with the 0z run, again
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2418. will45
sorry bad link
Member Since: July 18, 2009 Posts: 1 Comments: 994
2417. xcool
okay
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2416. scott39
Quoting scott39:
xcool is that a trough coming off the E coast or Just storms?
Im looking at a live Satt.
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2415. xcool
StormJunkie hmm ? opps sorry
Member Since: September 26, 2009 Posts: 2 Comments: 15684
I'm starting to get the schpulkies.
Member Since: Posts: Comments:
2413. smuldy
Quoting will45:
bigggggggggggggggg weakness at 150 hrs
ya, caused by a storm the same run grows to a major and parks in more or less one place for 36 hours lol
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2412. will45
she gets kicked out on this run
Member Since: July 18, 2009 Posts: 1 Comments: 994
xcool, those last two images you posted are from the 18z run.
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2410. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting JLPR2:


Earl a little too close for comfort and possible Fiona looks like trouble.


I think Danielle looks like trouble too.jmo
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2408. xcool
scott39 ? posting nunmber ?
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2407. hydrus
Quoting emeraldcoast:
2384. KEEPEROFTHEGATE

KOG ... these bright-red-blood images give me the creeps ... they always look like a colonoscopy gone really bad. Just sayin.
Rollin them extra fat tonight E.C.? lol
Member Since: Posts: Comments:
0z GFS takes Danielle straight into Bermuda as a category 2 hurricane five days from now, with potentially-future Earl almost directly behind it. An interesting week ahead indeed.
Member Since: Posts: Comments:
2405. xcool
JLPR2 4 .bigg time.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting F4PHANTOM:
old run; we're on the oz run now


ok and the 0Z looks pretty similar
Member Since: Posts: Comments:
2403. scott39
xcool is that a trough coming off the E coast or Just storms?
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2402. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15684
2401. JLPR2
Quoting xcool:


Earl a little too close for comfort and possible Fiona looks like trouble.
Member Since: Posts: Comments:
2400. will45
bigggggggggggggggg weakness at 150 hrs
Member Since: July 18, 2009 Posts: 1 Comments: 994
2399. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684

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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.