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 fmbill:


LOL!!! Isn't a "fish storm" one that stays out to sea? I don't see any land masses in its path. :-)



other fishcaster / none mode run looking caster
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Quoting DestinJeff:


oh no. one thing of major concern is that it looks like we may have to deal with several hundred instances of Hebert being misspelled as Herbert.


Gasp.. dirty word :)
Mind you... it might hit one of the red boxes :)
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Wait till Herbert comes up on the naming lists.
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2994. RJT185
...EDIT FAIL...

oy.
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2992. RJT185
Quoting Orcasystems:


I would say its got a 50/50 chance of a CONUS hot somewhere.



30 to 40% if you go by Dr. Master's map on his post.
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Quoting DestinJeff:
We simply have no way of knowing where TD7 will track until Reed tells us.


how could anyone 'ignore' you?!?!?
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2989. RJT185
Quoting tkeith:
No caplocks, and no fishcasting...

who is this? and what did you do with the real Jason?


Don't quote the trolls, it only neglects the usefulness of the ignore feature! haha.


On a more serious note, Outer Banks vacation for Labor Day weekend and week ... looking like a FAIL.
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Quoting wayfaringstranger:


Bingo. It seems that it is just not good idea to futurecast out 200+ hrs. Dont get me wrong, model guidance while its better than before and is very useful, the tracs of most of our storms (not sure about Alex) but most tracs have had to be shifted some west. With Danielle, they have shifted at least twice to the west. Generally this time of season there is a massive H ridge across CATL. I was looking at the model runs yesterday and once this front leaves the east coast there is a decent H ridge.

At this point unless someone can show information proving otherwise, Id have to say given the location of 96L that it would take more of a westerly movement for now based also upon the steering enviroment.


I would say its got a 50/50 chance of a CONUS hot somewhere.

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2986. fmbill
Quoting jason2010xxxx:
TD 7 will not be a fish storm at all for the next five days. its moving west.


LOL!!! Isn't a "fish storm" one that stays out to sea? I don't see any land masses in its path. :-)
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Quoting HarryMc:

This one didn't show up either. :)


I can't see it either
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Quoting surfmom:

maybe TAZ will have an EYE to Spy!!!!



TD 7 has a pine hole eye
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Quoting Neapolitan:
TD7 will definitely be TS Earl later today, perhaps even by noon; he's wrapping up quickly and nicely.



this will be be a vary long track hurricane
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2981. surfmom
Quoting Neapolitan:
TD7 will definitely be TS Early later today, perhaps even by noon; he's wrapping up quickly and nicely.

maybe TAZ will have an EYE to Spy!!!!
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2978. surfmom
Cot, it's looking REAL GOOD -- just have to get my seat work done & I'm OUT --ohhhhLalalaaaaa
Weather & Waves - Surfers Perspective
Gomex/SWFL - Surf Report - Aurasurf/Micah Weaver
Buoys are still 4-5ft and not quite so short period as yesterday. Could be a fun wave somewhere today. If I was going to surf I would look at that incoming tide around 10 or 11am. Hopefully it does not peter out too quick. After high tide(2pmish) the swell will back off slowly with the outgoing tide this afternoon and go back to 1ft or flat.
Weekend Outlook: Really bad timing for the EC as Danielle's swell will meet heavy 20knt onshore winds. This will bring 6ft plus choppy waves, lots of rips and beach erosion to the EC this weekend. If you like surfing those kind of waves then head on over. The east flow on the gulf means good beach fishing and very flat conditions with cooler breezy WX in store for us... yes.
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TD7 will definitely be TS Earl later today, perhaps even by noon; he's wrapping up quickly and nicely.
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Quoting mydiapersarefull:
With 'soon to be named earl' following Danielle, there is the potential for surf all the way through the Labor Day weekend, meaning:

-red flag days throughout
-over 300 saves by lifeguards
-over 50 saves by surfers
-extra 500 idiots in the water



lol on the the last part
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Quoting Tazmanian:




TD 7 is not going out too sea not this time not all storm gos out too sea


Bingo. It seems that it is just not good idea to futurecast out 200+ hrs. Dont get me wrong, model guidance while its better than before and is very useful, the tracs of most of our storms (not sure about Alex) but most tracs have had to be shifted some west. With Danielle, they have shifted at least twice to the west. Generally this time of season there is a massive H ridge across CATL. I was looking at the model runs yesterday and once this front leaves the east coast there is a decent H ridge.

At this point unless someone can show information proving otherwise, Id have to say given the location of 96L that it would take more of a westerly movement for now based also upon the steering enviroment.
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2973. tkeith
Quoting jason2010xxxx:
TD 7 will not be a fish storm at all for the next five days. its moving west.
No caplocks, and no fishcasting...

who is this? and what did you do with the real Jason?
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2972. HarryMc
Quoting P451:
Blog eating posts again?

Wonderful....why do I bother typing then.

This one will post, of course, because it's worthless.

:/


This one didn't show up either. :)
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With 'soon to be named earl' following Danielle, there is the potential for surf all the way through the Labor Day weekend, meaning:

-red flag days throughout
-over 300 saves by lifeguards
-over 50 saves by surfers
-extra 500 idiots in the water
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TD 7 sure is comeing togeter vary nic
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Quoting jitterboy:
Thanks Taz. Is there any relationship to intensity as far as progression of the convection burst or is it relatively random?


not sure i would ask stormW that one
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000
NOUS42 KNHC 241300
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0900 AM EDT TUE 24 AUGUST 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 25/1100Z TO 26/1100Z AUGUST 2010
TCPOD NUMBER.....10-085

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
3. REMARKS: THE NASA DC-8 WILL FLY AN 8-HR RESEARCH
MISSION IN THE GULF OF MEXICO TODAY AT 38,000 FT.
TAKEOFF TIME IS 24/1400Z
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Thanks Taz. Is there any relationship to intensity as far as progression of the convection burst or is it relatively random?
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2963. KEEPEROFTHEGATE (Mod)
Quoting Tazmanian:
mode runs where right about forcasting two name storms and look what we got
still one more yet to come triple systems in atlantic to end august
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Quoting surfmom:

are you still in tinder conditions????
Quoting AllyBama:
lol - Jeff.

Orca - I will send you some rain. We have been "rain free" since Sunday - thank goodness!
But I know that the chances are creeping back into the forecast. I will make arrangements with Mother Nature Express Service and ship you some ASAP!..lol


We need it big time... right now the province is just one great big pile in kindling waiting for a match. Numerous large forest fires burning... and more starting each day.
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Quoting StormW:


And you honestly believe this?



hes a fishcaster
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Hey Surfie.

Hope the waves are nice and clean for ya.
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2957. Michfan
Quoting jason2010xxxx:
WE NEED TO WATCH TROPICAL D SEVEN BECAUSE ITS MOVING WEST AT 15 MPH ITS WANTED TO MOVE WEST FOR THE NEXT 5 DAYS OR MORE


Your caps lock key is broken :P
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Quoting jitterboy:
I noticed on a recent visible loop of 96 L that a burst of convection was progressing around the 'center of circulation'? Is this typical/ Has anyone every noticed a burst of convection retrograding around the COC? Thanks



yes


96L is now TD 7
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AL, 07, 2010082512, , BEST, 0, 142N, 303W, 30, 1007, TD, 34, NEQ, 0, 0, 0, 0, 1010, 200, 40, 0, 0, L, 0, , 0, 0, SEVEN, M,
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Quoting TOMSEFLA:
models show another system behind td7. but all pay follow the leader out to sea.were lucky to have a weak a/b high during this time otherwise a pattern like 2004 we would be looking down the gun
[s}.




TD 7 is not going out too sea not this time not all storm gos out too sea
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Quoting NovaScotia33:


Excuse my ignorance, but looking at this chart, I only see one path that veers away from Nova Scotia.Does anyone think there is still a chance that Nova Scotia will get affected at all? Thanks


Right now, all of the models bring it east of NS. That being said.. things change hourly. Love to be out at Peggy's if this thing was to pass a 100 miles offshore.
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I noticed on a recent visible loop of 96 L that a burst of convection was progressing around the 'center of circulation'? Is this typical/ Has anyone every noticed a burst of convection retrograding around the COC? Thanks
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2949. surfmom
Quoting NovaScotia33:


Excuse my ignorance, but looking at this chart, I only see one path that veers away from Nova Scotia.Does anyone think there is still a chance that Nova Scotia will get affected at all? Thanks


HOPE NOT - got friends up there and your ocean is mean even w/out a storm
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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.