Danielle a hurricane; TD 7 forming off coast of Africa

By: Dr. Jeff Masters , 2:18 PM GMT on August 24, 2010

Share this Blog
2
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 3149 - 3099

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68Blog Index

Quoting DestinJeff:


Yes. And Leroy got larrrrrrrger.


Leon... giggle
Member Since: Posts: Comments:
If you are TX and LA residents, you shall know that there is a possibility of a tropical system in our backyard. Nothing at the moment but be aware that there is some potential for development close to home.
Member Since: Posts: Comments:
So its pretty much beautiful outside here in SELA... It will probly still be hot later this afternoon but its definately cooled down!
Member Since: Posts: Comments:


eyewall is redeveloping on Danielle
Member Since: Posts: Comments:
Quoting angiest:


It's Leon!

There's a sale at Penney's!


and don't call me Shirley! lol
Member Since: Posts: Comments:
bad time of year for something to form there,
Member Since: Posts: Comments:
3141. Bonedog
am I on ignore?

wierd...
Member Since: Posts: Comments:
Quoting StormW:


Good morning!
Good Morning Stormw . Is Danielle acually mowing west or is it looking like that because the clouds are spreding out over her .
Member Since: Posts: Comments:
Might have a US impact lot sooner than Danielle, Gulf is homegrowing a system as we type
Member Since: Posts: Comments:
Quoting RitaEvac:
already have west winds in the western gulf at the low levels



Yup - posted this last evening. No shear to speak of either.


Quoting moonlightcowboy:
25n, 92.5w development?

RGB LOOP
Member Since: Posts: Comments:
Some kind of circulation south of Western LA and east of TX/MX border.
Member Since: Posts: Comments:
Quoting DestinJeff:


see, told you.

That makes 1 so far.


Ah, but are deliberate misspellings part of the count?
Member Since: Posts: Comments:
3134. breald
Quoting AllStar17:


That's TD Six (which is now Danielle). TD Seven's track will come out at 11am.


Duh!! I thought it was the track for the soon to be Earl. Thanks.
Member Since: Posts: Comments:
Quoting breald:


I am looking at the site and don't see this up yet. Where did you pull that from?


That's TD Six (which is now Danielle). TD Seven's track will come out at 11am.
Member Since: June 29, 2009 Posts: 13 Comments: 5315
3131. angiest
Quoting Neapolitan:
All this talk of the blog eating posts sounds like an ID-Ten-T error, or maybe a problem with Layer 8. Before you hit the 'Post Comment' button on any comment--especially a long, well-thought-out one--it's always a good idea to highlight the entire post and copy it to your clipboard. (On a Windows machine, just hit the CTRL-A combination when still in the 'Your Comment' box, followed by CTRL-C) That way if the "blog eats your post", you can simply go back to the 'Your Comment' box, paste the comment (CTRL-V on Windows), and resubmit it. Voila! You've then successfully fixed this particular ID-Ten-T error.


It's definitely not an ID-Ten-T error since it is happening to me as well.
Member Since: Posts: Comments:
3130. Patrap
..or maybe use the 'Preview Comment" button?
Member Since: Posts: Comments:
3129. Patrap
..Lordy..

LOL
Member Since: Posts: Comments:
All this talk of the blog eating posts sounds like an ID-Ten-T error, or maybe a problem with Layer 8. Before you hit the 'Post Comment' button on any comment--especially a long, well-thought-out one--it's always a good idea to highlight the entire post and copy it to your clipboard. (On a Windows machine, just hit the CTRL-A combination when still in the 'Your Comment' box, followed by CTRL-C) That way if the "blog eats your post", you can simply go back to the 'Your Comment' box, paste the comment (CTRL-V on Windows), and resubmit it. Voila! You've then successfully fixed this particular ID-Ten-T error.
Member Since: Posts: Comments:
3127. breald
Quoting jason2010xxxx:


I am looking at the site and don't see this up yet. Where did you pull that from?
Member Since: Posts: Comments:
3126. Prgal
Quoting StormW:


Good morning!


Good morning Storm! I am looking forward to read your synopsis. I see that TD7 might be a problem for the Caribbean and the wave behind it. We will see...
Member Since: Posts: Comments:
3125. angiest
Quoting DestinJeff:


Yes. And Leroy got larrrrrrrger.


It's Leon!

There's a sale at Penney's!
Member Since: Posts: Comments:
already have west winds in the western gulf at the low levels
Member Since: Posts: Comments:
3123. Patrap




Member Since: Posts: Comments:
Quoting StormW:


Good morning!


Heya Storm! Great call of the further westward movement of Danielle!! You really did your homework (not that you don't always)!
Member Since: Posts: Comments:
Quoting AllStar17:
4 of the 6 models on this graphics now hook Danielle back west very close to Bermuda. Those include the GFDL and HWRF. Only the UKMET and GFS sharply curve Danielle out. This should be monitored VERY closely.


I really wish I could dig back into some posts where the model guidance was the holy grail and some were shouting fish and forecasting hooks before or at 45 W. Danielle is still not above 20 N and is beyond 45 W. I don't want those individuals who were calling this storm to hook /fish to begin feeling bad. Nor do I want them to feel like I am calling them out because they are all my friends (yes including jason)but I will say however that model guidance is a good indicator but not the gospel. I didnt stay in a Holiday Inn Express last night. I just listened to one "grumpy old man"....
Member Since: Posts: Comments:
Quoting StormW:


Lookin at things now...I'll have it in my synopsis.


Looking forward to it as usual.! Long time lurker
Member Since: Posts: Comments:
Morning. I see the GFS is still favoring a parade of CV-type systems, with "Earl" developing from TD7 soon and "Fiona" on its tail. Danielle would have to be one monster storm to bust right through a building ridge and then evidently undermine most of the A/B high over the Atlantic, as 06Z looks like it is showing. I expect Danielle will stay off the CONUS coastline, but the destruction of the high is really hard for me to believe at this juncture. 06Z depicts there pretty much not being a high until after the passage of all three hurricanes.

And I find it interesting that a few runs ago, the GFS was saying that Danielle would feed on "Earl" and prevent it from becoming anything significant, whereas now it is suggesting that the proximity of "Fiona" to "Earl" could result in "Fiona" being weaker and smaller.
Member Since: Posts: Comments:
3114. RickWPB
Quoting jrweatherman:


StormW being a bit sarcastic again this morning:)


LOL. Yeah, Storm's 'sarcastic flag' is on... "(fish)" and "Sure glad the season is slow:".
Member Since: Posts: Comments:
3113. angiest
Quoting CycloneUK:
That is some tasty vorticity with TD 7



Did the vorticity in the Gulf get stronger?
Member Since: Posts: Comments:
3111. Relix
Quoting barotropic:
WOuldn't be completely surprised if 96L went directly to TS status. It looks that good.


it was renamed a TD. NHC just hasn't updated yet.
Member Since: August 3, 2006 Posts: 0 Comments: 2741
3110. Ossqss
Click to enlarge



Member Since: Posts: Comments:
3109. Bonedog
glad we are finally getting rain up here in the NE we needed it.

Danielle will surprise folks, not StormW of course ;) but the fish talkers might see something change.

TD7 (earl) I think will get a name by 11am if not at 2pm. Has a nice look to it, strong core structure, havent looked at winds yet though, but with yesterdays 25mph in the CVs I dont see why it wouldnt be named soon with a better apperence right now.

Let It Blow
Let it Blow
Let It Blow
Member Since: Posts: Comments:
StormW - Do you have any insight as to the GOM this week/end?

tia
Member Since: Posts: Comments:
3106. b4dirt
http://www.nhc.noaa.gov/archive/2010/graphics/al06/loop_5W.shtml

Tells the story!
Member Since: Posts: Comments:
Safe to say that the Advisory #8 (Monday at 11:00 am) forecast track was a bit off:
(the hurricane symbol marks the current center position)
Member Since: June 29, 2009 Posts: 13 Comments: 5315
3102. Times2
Cool weather sweeping across the plains. Enjoy it! No hurricanes impacting the US until maybe late Sep. Take your final vacations!! Enjoy life!!
Member Since: Posts: Comments:
3099. Prgal
Good morning! I see we have TD7 already.
Member Since: Posts: Comments:

Viewing: 3149 - 3099

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68Blog Index

Top of Page

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.

Local Weather

Overcast
29 °F
Overcast