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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399. Skyepony (Mod)
Quoting nrtiwlnvragn:


I was somewhat suprised the UKMET Office called for tropical development off the east coast. Last I looked at some cyclone phase did not show that. Guess it is possible.

NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 12 HOURS
FORECAST POSITION AT T+ 12 : 34.5N 74.9W


That ULL over NC/VA is kinda close to there. Lotta dry air too. But yeah slim chance, there & the GOM.
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To my untrained eye, it looks like the COC is currently at 16.8N 46.9W.
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GOES-15 Super Rapid Scan visible image of Danielle Link
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Quoting Levi32:
I love it when we start the debate of whether people with degrees can ever be questioned or called out lol. Seriously some of the stupidest people I have heard about have honors and flying colors from big-name universities but that doesn't prevent them from being dumb.

That is not to say the NHC is dumb, but that shouldn't stop people from discussion or questioning some decisions they make. If they were the rule of law, why should any other tropical Meteorologists exist? What would be their purpose? To echo whatever the NHC says? No, their purpose is to formulate their OWN opinion, and their OWN forecast. If you want that forecast to always agree with the NHC, then there is no point in having any other forecasters.

Would you rather that the times the NHC actually is wrong, that you weren't warned by someone else who saw what they didn't? Or would you rather have 2nd opinions who may catch something that could affect YOU, that warned YOU about a danger that the NHC happened to miss. Everyone misses sometimes....NHC is the best we have, but the more opinions floating around in the pond, the more information YOU have to protect yourself.


I gave up...It's like playing jenga with the pieces glued together. No Hope.
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Quoting Hurricanes101:
353. Krycek1984 4:44 PM GMT on August 24, 2010

Actually no because those who think this will be an active season have shown reasons why it will be active

Those who say its a bust, just site that we have only had 4 named storms and repeat that the season is a bust. They never back up their claim with any sort of reasoning.


Sometimes those people are just as blind and not as "scientific" as they would think.

I've asked several times for people to add some input as to what RESTRAINING factors are out there/going to be out there this season IN ADDITION to the well-laid out theories and forecasts on increased activity. Even with a period of increased activity, which, I agree, should happen this year, based on all of the observations that professionals have made, there are ALWAYS going to be restraining factors or we'd have a hurricane every day.

So I ask again, in addition to the multitude of positive factors out there that will lead us to an active season, what negative factors are out there that will act to somewhat reduce it?

Do note that by asking for negative factors does not assume that one is saying it is going to be slower than normal...any period, in the absence of perfection, would have broad negative influences in addition to positive influences.
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For the forlorn a goodie from the CFS Analog catalog for about Sept. 19.
Link
Of course this will be gone in a day or two.
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Quoting StormW:


So? I can respect that, and I can respect anyone who has one, cause it's a lot of hard work...I was working toward my meteorological degree, but circumstances with my son, required me to withdraw and take care of his medical needs..., but ya don't need a degree to forecast Hurricanes and tropical storms, or don't you read and comprehend my blog?


Although I am no expert at all and would never attempt to forcast weather I totally agree. Remember Isaac in Galveston?
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389. DVG
I was just looking at the steering layers. It seems that the two high pressure areas are reaching across to each other. Is there a block building to the north, or is it nothing?
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StormW, why is everybody after you today. I for one think are one of the best forecasters, I have ever seen. You have alot of questions on your blog today.
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Quoting nrtiwlnvragn:


I was somewhat suprised the UKMET Office called for tropical development off the east coast. Last I looked at some cyclone phase did not show that. Guess it is possible.

NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 12 HOURS
FORECAST POSITION AT T+ 12 : 34.5N 74.9W


That's on my door step. I'm at 35N 77W.
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353. Krycek1984 4:44 PM GMT on August 24, 2010

Actually no because those who think this will be an active season have shown reasons why it will be active

Those who say its a bust, just state that we have only had 4 named storms and repeat that the season is a bust. They never back up their claim with any sort of reasoning.
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384. Relix
Holy @##@ guys stop bashing StormW for God's sake. He has done nothing to deserve it. At all. All his points are valid and people with at least some degree of logic can understand it. Jesus with your constant bickering you might just scare one of the most valuable resources we have here in WU.

STOP IT
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Quoting ShenValleyFlyFish:


And I'm with you on the Ph.D. thing. I've known a lot of fools with the paper, and a lot of very smart and sophisticated people without it.

WTO

May be because both are outliers. We tend to notice them more.


Yeah but I wish the tails were a little thinner :-)
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I love it when we start the debate of whether people with degrees can ever be questioned or called out lol. Seriously some of the stupidest people I have heard about have honors and flying colors from big-name universities but that doesn't prevent them from being dumb.

That is not to say the NHC is dumb, but that shouldn't stop people from discussion or questioning some decisions they make. If they were the rule of law, why should any other tropical Meteorologists exist? What would be their purpose? To echo whatever the NHC says? No, their purpose is to formulate their OWN opinion, and their OWN forecast. If you want that forecast to always agree with the NHC, then there is no point in having any other forecasters.

Would you rather that the times the NHC actually is wrong, that you weren't warned by someone else who saw what they didn't? Or would you rather have 2nd opinions who may catch something that could affect YOU, that warned YOU about a danger that the NHC happened to miss. Everyone misses sometimes....NHC is the best we have, but the more opinions floating around in the pond, the more information YOU have to protect yourself.
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You know, I'm on GardenWeb forums a lot and we don't have these sorts of problems over there. So what's the problem here? Maybe a psychologist can tell us.
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Quoting DestinJeff:
Why is everybody so freakin edgy?

Careful or I'll whop you upside the head with my chart!



LOL, a chartcaster?
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378. MahFL
Quoting TOMSEFLA:
experts perdicted 500 ft homeruns instead looks like lot of ground balls to short....


It's "too" short, not to....
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Quoting Levi32:
You guys should feel exceedingly privileged to have someone such as Storm even stick around through all the crap (excuse the word) that goes on in here. A lot of professionals would never stick around on a board like this.


I 2nd that!!
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Storm, Levi, Drak, and Hurr09 keep up the good work. I try to learn, but on a learning curve up to this point.
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Quoting sdcbassman:


Actually your comments make you seem like you have a chip on your shoulder storm. What do you have against their (NHC Forecaster) degrees. They worked hard and achieved their Phd in Meteorology. You, on the other hand, were an Aerographers Mate ... if memory serves me correct. You have your own set of achievements as well. No one bashes them ... why do you care if someone correctly points out the achievements of the NHC METEOROLOGISTS. Are there any Aerographers Mates at the NHC????

Just wondering. You do your thing well ... so does the NHC. Difference is ... their responsibility is HUGE. Your input is valuable to many ... but let's not bash the PROFESSIONALS that make life and death decisions. IMHO .. you are classier than that Storm.

$.02


I think the point is that PhDs are put on a pedestal just because of their degrees, and people without formal degrees may be just as well educated but don't get the respect.

We used to not attach so much significance to pieces of paper:

Justice Robert Jackson
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Quoting WatchingThisOne:


I too beg to differ. I like the "new StormW" ... all you are doing differently is expecting people to do some minimal amount of reading and thinking before throwing time-consuming questions at you. I think that is more than reasonable. You do go out of your way to answer reasonable newbie (as opposed to troll) questions. You expect more from people who have been around longer. If that means being snarky to get the point across, so be it.

I don't recall you doing much in the way of NHC bashing either, although you state that you rely less on models. Models are becoming more reliable with time, but I've learned a heck of a lot more following your thoughts on steering patterns than I have from any model.

And I'm with you on the Ph.D. thing. I've known a lot of fools with the paper, and a lot of very smart and sophisticated people without it.

WTO


Hear, Hear!
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the experts missed something or there are unknowns. but u must agree the tropical environment has kept some secrets for the scientist.
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Link

GFS on 96L out 240 hrs. Long ways away but something to watch
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Quoting Krycek1984:


If no one can possibly know what the rest of the season will bring, wouldn't we want to put those who think it will be more active than usual on the ignore list too? duh.
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. WatchingThisOne 11:46 AM EST on August 24, 2010
And I'm with you on the Ph.D. thing. I've known a lot of fools with the paper, and a lot of very smart and sophisticated people without it.

WTO

May be because both are outliers. We tend to notice them more.
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I think it's interesting that people bash Storm, yet the first time there's something to be concerned about, it's suddenly "Storm, what do you think about..."? Kinda like how people are atheists until the excrement hits the oscillating device. Just my opinion, and I'll keep watching for your comments, Storm.
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Quoting Krycek1984:


If no one can possibly know what the rest of the season will bring, wouldn't we want to put those who think it will be more active than usual on the ignore list too? duh.
or ignore everyone who doesnt agree with you
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Quoting DestinJeff:
Why is everybody so freakin edgy?


Careful or I'll whop you upside the head with my chart!



Pleese don't hurl that globe either !!
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Quoting StormW:
A lot of "hobbyists" keep saying it will go further west than what the NHC says. Have you ever seen the inside of the Center? It is 23rd century. They are the pros with the degrees, brains and large salaries to boot. They are doing their jobs giving us cutting edge forecasts. We are allowed to discuss and debate, this is America, but remember they wear the pants.

Oh geez...here we go with the Ph.d stuff again...may I gag now or later?


Actually your comments make you seem like you have a chip on your shoulder storm. What do you have against their (NHC Forecaster) degrees. They worked hard and achieved their Phd in Meteorology. You, on the other hand, were an Aerographers Mate ... if memory serves me correct. You have your own set of achievements as well. No one bashes them ... why do you care if someone correctly points out the achievements of the NHC METEOROLOGISTS. Are there any Aerographers Mates at the NHC????

Just wondering. You do your thing well ... so does the NHC. Difference is ... their responsibility is HUGE. Your input is valuable to many ... but let's not bash the PROFESSIONALS that make life and death decisions. IMHO .. you are classier than that Storm.

$.02
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you got it
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Quoting StormW:


Well, I beg to differ. What is most irritating is. there are a lot of folks that come in here for good, honest. scientifically backed information, and when you have to wade through a lot of garbage...it's annoying. Yeah, folks can out folks on ignore, or do this and that, but why should they have to?

And your unsubstantiated comment in bold is out of line...as Jeff knows that is meant jokingly. He and I have conversed numerous times throughout the year.


I too beg to differ. I like the "new StormW" ... all you are doing differently is expecting people to do some minimal amount of reading and thinking before throwing time-consuming questions at you. I think that is more than reasonable. You do go out of your way to answer reasonable newbie (as opposed to troll) questions. You expect more from people who have been around longer. If that means being snarky to get the point across, so be it.

I don't recall you doing much in the way of NHC bashing either, although you state that you rely less on models. Models are becoming more reliable with time, but I've learned a heck of a lot more following your thoughts on steering patterns than I have from any model.

And I'm with you on the Ph.D. thing. I've known a lot of fools with the paper, and a lot of very smart and sophisticated people without it.

WTO
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351. TOMSEFLA 4:43 PM GMT on August 24, 2010

and you have determined this on August 24th after what 6 systems?

Your comment is part of what is wrong with this blog; you automatically assume the experts are wrong now just because we have yet to have a US impact this year. Like StormW said, you are in for a rude awakening in the next 2 months if you feel this will continue.
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Quoting DestinJeff:
Why is everybody so freakin edgy?

Careful or I'll whop you upside the head with my chart!

Flat on or edgewise?
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356. JavPR
darn 95...98...2004....those three years were not good for puerto rico especially 98...
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Quoting Neapolitan:
Triplets?

Click for larger image:


1995 redux coming?
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Quoting divdog:
If anybody is saying the seaon is a bust just put them on the ignore list where they belong. Nobody can possibly know what the rest of the season will bring so it becomes obvious they are just trying to elicit a response from us. Just ignore them and the blog becomes a more useful place.


If no one can possibly know what the rest of the season will bring, wouldn't we want to put those who think it will be more active than usual on the ignore list too? duh.
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Storm,

not sure if I ever introduced myself to you. My name is Prerak Dave
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Quoting Hurricanes101:
328. divdog 4:35 PM GMT on August 24, 2010

well ok its not that no one listens to him, but there have still been plenty who just continue to say the season is a bust despite all the evidence he keeps showing to the contrary.

This blog can really wear on a person over time
experts perdicted 500 ft homeruns instead looks like lot of ground balls to short....
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96L seems like a potential near future concern
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349. RMCF
Quoting Levi32:
You guys should feel exceedingly privileged to have someone such as Storm even stick around through all the crap (excuse the word) that goes on in here. A lot of professionals would never stick around on a board like this.

You to are one of the great ones that takes low blows from less educated.
Levi i love your emphasis on the affect on the US. keep up the good work.
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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.