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 alpha992000:


Ah, Churumba Weather... Yes, I remember. Who can forget? LOL

I spent all day away from the PC and now I get back to a significant shift in models. Scary stuff. Not too sure our infrastructure is strong enough to stand a tropical storm/hurricane and I don't particularly fancy another 2 weeks without power nor water. And don't even get me started on surviving this heat without at least a fan! :(


I spend a lot of time in the major hotels after a storm. At least they have cisterns and generators. I am blond and originally from the states so they think I am just one of their guests. Got to keep the tourists happy.

But seriously, I hope that the movement to the west is minimal and that all the storms recurve and do not affect land (including Bermuda)
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1797. angiest
Quoting AtHomeInTX:


That doesn't sound very south Texas. Unless it goes that far west first.


You and I know where South Texas is, but a lot of people would consider all of the coast to be South. :)
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1795. Levi32
Quoting StormW:


Did you see Bastardi's Long Ranger?

Explains about the current recurvature pattern.


Haven't had a chance to see it yet, will have to go take a look.
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Quoting StormW:


clwstmchasr

Based on what JG just posted here...it makes sense...it's going to be due to a change in the steering currents. Basically, the trof is south of a stationary front, so it's not really moving...much. In about 36 hours or so, the steering pattern is forecast to change in the GOMEX. Steering is weak right now, but a NW to NNW flow is forecast later on. So, initially, when the steering first picks up, it should move in a general westward direction, and once the flow becomes established, it should move NW or NNW.


That doesn't sound very south Texas. Unless it goes that far west first.
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1790. jonelu
Quoting Halon056:
No gaps, and GFS not looking good. Is this a viable solution? Or an errant run?


Too soon to know. But If I were in Bermuda I would pay attention. its looking like its going to be close...but she has ALOT of dry air to get past first...so we will see.
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1789. will45
if NHC track holds true HH should be able to fly in Thursday
Member Since: July 18, 2009 Posts: 1 Comments: 994
1788. XStormX
Quoting Levi32:


Evening Storm, thanks again! Yours was of high quality as well.


Wow, the GFS has Danielle hitting the North East and Earl out to sea, Fiona hitting the northern leewards and then another system hitting puerto rico and the DR
Member Since: August 19, 2010 Posts: 0 Comments: 171
Quoting Ossqss:
Interesting, click to enlarge





NAM turns it to the west in the later part of the run.

Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting barotropic:


at 150 -168 hours the gfs oddly shows almost no ridge which allows the storm to jog due west...thats why it shows possible eastern seaboard brush. Oddly the 18z GFDL and HWRF do the complete opp and show a solid ridge to the west and turn the storm ne...recurving it. The gfdl actually trended east this run.


The NGP model has been very consistent showing Danielle blocked in with High pressure to her north....at the end of the last model run...Danielle starts moving toward the West. The Outer Banks of NC, NY and for sure Boston better watch this and make sure she remains out to sea.
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1785. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15624
Quoting Halon056:
No gaps, and GFS not looking good. Is this a viable solution? Or an errant run?


Other models are showing this, so this is not something out of the blue.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
1783. Ossqss
Interesting, click to enlarge



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No gaps, and GFS not looking good. Is this a viable solution? Or an errant run?
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something from the cimss site that was posted on here is really causing my computer to slow down
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1780. will45
i think 0z GFS will still have a Bermuda hit but will back off of the east coast smash
Member Since: July 18, 2009 Posts: 1 Comments: 994
Quoting clwstmchasr:


I doubt it will. But what is more interesting is all of the storms parading behind it.


I agree, its been flip flopping all season.
Member Since: May 27, 2009 Posts: 0 Comments: 4436
Wow Danielle is certaintly coming together now.
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Storm,

Do you think the gfs is right at all on this last run?
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This what I am thinking of right now..

GOM potential storm - Probably going to bring lots of rains to texas and texas would love that.. Idk about too much rain at once tho.. But would cool off half of texas.. maybe southwest of LA..

Danielle.. Most likely get back where she was b4 and get stronger.. I would say Bermuda needs to watch out tho.. As Levi has said could reach Major Hurricane status.. and Most likely curve out to sea..

96L - will probably be a TD soon and then the next Tropical Storm.. We def have to watch this the next few days..

As I can see.. there is a lot more waves behind 96L..

As you can see below here..


I sure hope they turn out to be fish storms tho..
Member Since: August 15, 2008 Posts: 0 Comments: 2133
1775. Levi32
Quoting StormW:
Evening Levi!

Just to reiterate, great update today...as always!!


Evening Storm, thanks again! Yours was of high quality as well.
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Danielle is probably a 75 mph Category 1 Hurricane. This may peak at a weak Cat. 3, maybe higher the farther west it goes...

Invest 96L is very close to Tropical Depression status. All it needs is some organized convection, and it needs a well-defined center. I beleive we will have TD #7 tomorrow.

The area in the Gulf is really disorganized at this time. I really dont see development, just a rainmaker...Thats change though.

The wave over Africa needs to be watched closely too. Could pull a 96L and organize fast off the coast. We could have Fiona by mid week next week.
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Weewoo...Weeewooo...1756 needs a waambulance...
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1772. KEEPEROFTHEGATE (Mod)
06L/H/D/C1
MARK
17.57N/49.23W

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Quoting JavPR:

lol i remember that....and the late Ponce Mayor Churumba Cordero who also said George wasn't a threat....


Ah, Churumba Weather... Yes, I remember. Who can forget? LOL

I spent all day away from the PC and now I get back to a significant shift in models. Scary stuff. Not too sure our infrastructure is strong enough to stand a tropical storm/hurricane and I don't particularly fancy another 2 weeks without power nor water. And don't even get me started on surviving this heat without at least a fan! :(
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Quoting barotropic:


at 150 -168 hours the gfs oddly shows almost no ridge which allows the storm to jog due west...thats why it shows possible eastern seaboard brush. Oddly the 18z GFDL and HWRF do the complete opp and show a solid ridge to the west and turn the storm ne...recurving it. The gfdl actually trended east this run.


The NAM is another model that trended slightly west. Also keep in mind that the HWRF and GFDL have poleward biases, meaning that to get an accurate track from them, adjust the track south and west, which would mean an East Coast Storm.

-Snow
Member Since: April 1, 2010 Posts: 9 Comments: 2699
1768. bjdsrq
Quoting KEEPEROFTHEGATE:
WARFIGHTER GFS 18Z 180 HRS OUT


Maybe New York is going to get it's first storm in a long long time.
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1767. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15624
Quoting Greyelf:

I think he may be pulling your leg. If not, well...I won't say it.


Me too...but just in case...I threw in an apology
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1765. Greyelf
Quoting angiest:


Another trough split in a similar location:





Wow. Just as he gets an answer, he huffed off.
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For those who missed it earlier!

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Going to be interesting when we get the 0z GFS run... see if the GFS sticks to this.
Member Since: May 27, 2009 Posts: 0 Comments: 4436
1762. Greyelf
Quoting traumaboyy:


LOL.....and NOLA is not a typical non drinking invironment...lol....sorry about your brother's liver!

I think he may be pulling your leg. If not, well...I won't say it.
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1761. hercj
Quoting StormW:


COOL! That will be some great info if they can do it.

Im still waiting on the drone. I want to see how they do this. 60.000 feet is along way up and they may be able to pull that off. If they do that will be some of the must see data.
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1760. angiest
Quoting washingtonian115:
The system over the gom won't amount to much but a heavy rain maker.Nothing serious.The storms off of africa are a different story though.


Another trough split in a similar location:



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1758. centex
Quoting HaboobsRsweet:
A rain maker in the Gulf...that is what I make of it at this point.
I hope so, but to really be a rain maker it needs to get close to TD.
Member Since: August 10, 2007 Posts: 0 Comments: 3225
Quoting Levi32:


The GFS shows fairly solid ridging over the southeast US for the next week at least.


at 150 -168 hours the gfs oddly shows almost no ridge which allows the storm to jog due west...thats why it shows possible eastern seaboard brush. Oddly the 18z GFDL and HWRF do the complete opp and show a solid ridge to the west and turn the storm ne...recurving it. The gfdl actually trended east this run.
Member Since: August 22, 2010 Posts: 0 Comments: 652
1755. KEEPEROFTHEGATE (Mod)
WARFIGHTER GFS 18Z 180 HRS OUT
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Quoting WeatherNerdPR:

:o WoW!


Yep. The NOGAPS also shows an East Coast landfall.

It doesn't show the chain of storms though, like the GFS shows. Keep in mind that the GFS is a better CV hurricane storm than the NGP.



http://moe.met.fsu.edu/cgi-bin/ngptc2.cgi?time=2010082412&field=Sea+Level+Pressure&hour=Animation

and moving to the NW. O.o
Member Since: April 1, 2010 Posts: 9 Comments: 2699
1752. RJT185
Quoting alpha992000:


She already said so?! O_o OK, time to run to the nearest store and get as much canned food and batteries as possible then. Poor Susan, I like her but I still remember her saying early on that Georges wasn't a threat. Yeah, sure.


That woman is a terror! I remember Georges like it was yesterday, it was the experience that made me a weather weenie.
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A rain maker in the Gulf...that is what I make of it at this point.
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Quoting XStormX:
lol, i still see it moving west northwest, you know what's sad and funny, everyone on this blog has no lifes........


Everyone meaning yo?
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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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