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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949. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting StormChaser81:
Well fellow blogger's, I'm taking a long break from blogging and might not come back at all.

Stay safe and hope everybody avoids the storms of 2010.

Oh no! Another one gone forever.
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StormW, we appreciate your input, your guidance, and your humor.
Agreed! StormW is great!!!
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946. wjdow
quoting... 'but any time the models make a massive mistake in unison, the NHC is right there making it with them, and that is why they aren't as good as they could be if they dared to defy the models.'

So when in the last couple years, say, has NHC made a massive mistake? I don't remember any. There's a potential for over-reliance on models to lead to a mistake, but I don;t remember it actually happening, at least not recently.
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Quoting btwntx08:
nope


nope what?
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944. shauntanner (Admin)
You can listen to Dr. Masters on the Hurricane Haven go going here.
http://www.wunderground.com/wxradio/wubroadcast.html

Questions for Dr. Masters can be asked here, on his blog.
i havent posted in awhile but i read the blog every day. forecasting is the art of an educated guess. stormw is very educated in the tropics and he is an artist in his forecasts. no one ever knows for sure what these storms are going to do. living near a coast in florida i listen to what stormw has to say and take his word seriously. he is not here for a contest. hang in there stormw.
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yea center is at 17N, not 17.4
Member Since: March 10, 2010 Posts: 1 Comments: 7874
WOW major computer model shift for 96L its headed toward the islands and into the caaribean
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She's got a new blow up of convection.

She's trying.

Bring out the Holy Hand Grenade of Antioch, Ike...
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Quoting IKE:
Center is easy to see. Look at 17.4 and 48W....



Thats not the center imo, i think its still riding right along the 17N line
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Quoting eliteforecaster:
I know the blog doesn't want GW/climate change talk. But I saw some rather irritating posts on the last blog towards the end, and figured I'd give a shot at it. And please read the post before simply "Poof"ing



Well that solves the US, too bad it ain't called US Warming instead of Global Warming. Wtf is it with people thinking America is the only place in this planet which matters? America has 3,717,813 sq miles of land area which is only 6.5% of the earth's total surface area, which equals to less than 1/15th of the total surface area. Here is the graph for the globe, the one that really matters:



This is the temperature for the entire globe, not just the us, you can see since a little before 1980 the line is going up. There are a few years where it goes down or levels off, but by the next few years it continues back up. You can't blame a 30 year period of general warming entirely on teleconnections. If you want to link that to some teleconnection, then by all means go ahead and try, here is the Link to all the teleconnections and their values since as long as they have been recorded.

Anyway, do notice I said you can't blame it entirely on these things, meaning, I acknowledge and realize the fact that teleconnections have a significant effect on our weather patterns, but you can't put sole blame on these things, because if that were the case we should be seeing an equal downward motion in that graph within a few years of that initial rise (because teleconnections are always changing phases and never take longer than 30 years to do so). Yet, it's been over 30 years and we have not seen an equivalent drop in that temperature graph. Yea there have been slight drops lasting a year or two, but nothing significantly downward equal to the significant upward motion.

Here is the Link for the land area reference.



You forget that the amount of Methane is much less than the amount of Carbon Dioxide. So much lower that they measure it in parts per billion, not million like with CO2. So while it is 25 times more effective at retaining heat than CO2 (taken from the link provided further below), it is over 200 times less prevalent (385 ppm divided by 1780 ppb) in the atmosphere, making it more than 8 times less of a problem.







Link and Link



Anyway, sorry blog, I realize how much everyone here hates the gw argument. But I saw some gems and I couldn't resist the counter attack.

And StormW, I have no idea where you stand on Global Warming, but I thought I would clear up the picture you were painting.



Also, a reminder, the only real things we know for a fact about Global Warming:


A. Our planet as a whole is warming. (It has been measured-you can't deny that. And sure it is not going straight up, but looking at the last 35 years, in general, the line is going up).
B. CO2 is a greenhouse gas, so it retains warmth in our atmosphere.
C. Humans release amounts of CO2 into the atmosphere when burning fossil fuels.

As for how significant of an impact we have, what lies in the ahead as far as weather, and what our weather would be like without humans, it is nearly impossible to tell.

However, from the above 3 facts, we can say that however small and insignificant, humans have contributed to at least a tiny fraction of the warming of our planet.

And also, we should strive to become less dependent on non renewable fossil fuels and more dependent on alternative energies like renewable energies or nuclear energy, because they are less harmful to the environment and a more realistic solution for the long term (fossil fuels, in case you didn't know, will run out eventually).

Edited to fix apostrophes.


Very interesting read actually, and i disagree but good points
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934. IKE
Center is easy to see. Look at 17.4N and 48W....

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Storm...thats not like you to bite when the children are at play...come on now...
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A BIT OF A PATTERN CHANGE OVER THE WEEKEND AS AN UPPER LEVEL RIDGE
SHIFTS TO THE NORTHEAST AND A RATHER POTENT TROUGH DEVELOPS OVER
THE WESTERN U.S.. THIS WILL ALLOW A DEEP FETCH OF TROPICAL
MOISTURE TO TAKE AIM ON THE TEXAS COAST. AN INVERTED TROUGH OF LOW
PRESSURE WILL DEVELOP AT THE SURFACE AND ALSO MOVE SLOWLY INLAND
SAT/SUN. THE ECMWF...GFS AND CAN SHOW THE SFC TROUGH AND ASSOICATED
WEAKNESS ALOFT. LONG RANGE MODELS DIFFER SIGNIFICANTLY WITH THE
PLACEMENT OF THE HEAVIEST PRECIPITATION. THE 12Z ECMWF/CAN ARE IN
GOOD AGREEMENT OF DISPLACING THE PRECIP TOWARD LOUISIANA...WHILE
THE GFS PLACES THE GREATEST RAINFALL ON THE TEXAS COAST. THE
ECMWF/CAN HAVE NOT SHOWN MUCH CONSISTENCY AND PREFER THE MORE
STABLE GFS. THE GFS SHOWS PW VALUES OF 2.4 TO 2.6 INCHES AND A
NEARLY STATIONARY BOUNDARY ALONG THR COAST. IF THE GFS PANS OUT...
HEAVY RAIN WILL BE POSSIBLE ALONG THE COAST WITH A SHARP QPF
GRADIENT. COULD SEE EXCESSIVE RAIN AT THE COAST AND LESS THAN AN
INCH OF RAIN WELL INLAND. WHICHEVER SUITE OF MODELS IS
CORRECT...AT LEAST SCATTERED SHOWERS SHOULD OCCUR WITH MORE CLOUDS
AND LOWER HEIGHTS TRANSLATING INTO LOWER TEMPERATURES. 43

&&

.MARINE...
NO SIGNIFICANT FCST ISSUES THRU WED. WINDS/SEAS WILL BEGIN
INCREASING LATE WED AS A SFC TROF (OR EVENTUAL SFC LOW) MOVES INTO
THE NW GULF AND THE GRADIENT TIGHTENS. EXPECT THIS FEATURE TO MOVE
SOUTH & WEST OF THE UPPER TX COAST THIS WEEKEND. DO HOWEVER EXPECT
INCREASING SHRA/TSTM CHANCES AS THIS OCCURS. MODERATE ONSHORE FETCH
WILL BE IN PLACE ON THE BACKSIDE OF THE SYSTEM...WHICH SHOULD ALSO
LEAD TO ELEVATED SEAS THRU THE WEEKEND. WILL PROBABLY NEED TO DUST
OFF THE CAUTION/ADVISORY FLAGS BY AS EARLY AS THURS. 47

&&
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Quoting StormW:


Ok...here's the global anomalies form the same article regarding what I posted...questions?:


That is interesting, but have you ever considered that it isn't the teleconnections effecting the temperatures, and rather the temperatures effecting the way the teleconnections behave?
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Quoting homelesswanderer:


I'll be gentle. :) I think you're right after looking at the models and the "inverted trough" supposedly headed our way.



I'm gonna go out on another limb here as I did before Ike hit the GOM and Galveston, for which I was called a doomcaster, wishcaster, westcaster..and a few other types of caster I can't repeat. Got so old I deleted my account but stayed around lurking. Anyway, the GOM is going to throw something at the Texas Coast this week through the weekend, strong tropical storm and a alot of flooding rains. Of course this is only my opinion and if I am wrong on this call, I will be the first to say so. OK, let the bashing begin.
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929. flsky
Quoting wayfaringstranger:
Interesting development in the GOM



Also showing a reasonable pressure drop within the last 24 hrs in the GOM.

To say the least!
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Well fellow blogger's, I'm taking a long break from blogging and might not come back at all.

Stay safe and hope everybody avoids the storms of 2010.
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Quoting clwstmchasr:


I would have every hurricane hitting Fl as a Cat 5:)


lol
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06L/H/D/C1
MARK
16.88N/47.99W

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924. xcool
Danielle wnw off forecast points.i'm used 3 Satellite Imagery
Member Since: September 26, 2009 Posts: 2 Comments: 15684
914. Gearsts 7:55 PM GMT on August 24, 2010

I dont see any clouds getting blown away at all, Danielle weakened due to dry air
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting Welling2000:
In Support of StormW

Forecasters / Mets are like doctors. Many doctors are well-educated, but make standard diagnoses based primarily on standard test results. Others (a minority) have something extra - a talent to assimilate the information gleaned from a myriad of test results and other sources, including a greater understanding based their own experience.

StormW is in the latter group, the group with something extra. He's got talent, understanding, and experience. And that translates into ability. He's also smart enough to avoid making predictions when there's not enough info to back them up.

When he outforecasts the industry leaders, he has every right to make that fact clear. You will note that he also acknowledges it clearly when his forecasts do not come to fruition.

StormW, we appreciate your input, your guidance, and your humor.
I concur
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Quoting Levi32:
You know what would really be a great learning experience.....set up a group of students, or whatever, independent of the NHC, to draw up a forecast for a tropical cyclone without looking at any model tracks (or the NHC's forecast). True the skill would be pretty bad by days 4 and 5, same as our's were before computer models came into existance, but talk about a great way to learn some real forecasting. None of this model consensus nonsense.


Agree totaly, learn the basic's and then get more high tech.
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Quoting PRweathercenter:
Puerto Rico Tropical Update and Effects from Hurricane Danielle
Link
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In Support of StormW

Forecasters / Mets are like doctors. Many doctors are well-educated, but make standard diagnoses based primarily on standard test results. Others (a minority) have something extra - a talent to assimilate the information gleaned from a myriad of test results and other sources, including a greater understanding based their own experience.

StormW is in the latter group, the group with something extra. He's got talent, understanding, and experience. And that translates into ability. He's also smart enough to avoid making predictions when there's not enough info to back them up.

When he outforecasts the industry leaders, he has every right to make that fact clear. You will note that he also acknowledges it clearly when his forecasts do not come to fruition.

StormW, we appreciate your input, your guidance, and your humor.
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Interesting development in the GOM



Also showing a reasonable pressure drop within the last 24 hrs in the GOM.
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DANIELLE is getting hit by alot of shear,just look at the sat loop north of the system look at the clouds getting blown away.
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913. IKE
...
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Quoting shauntanner:
Listen to Dr. Masters here on the Hurricane Haven. Ask questions for the Dr. on this blog.

Ok and thank you for the reminder should be interesting tonight.
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Quoting MiamiHurricanes09:
Anything past 45W is highly uncertain in terms of track for 96L.
i agree, however do see the models shifting a little more west
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Quoting VAbeachhurricanes:


hows school?
Good. Got social studies and math homework to finish, but good so far.
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906. IKE
I'd say Danielle is near 17.4N and 48W, headed right for the next forecast point....looks like the center is becoming partially exposed again...Link
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Quoting Levi32:


Just look at the NHC advisories and notice how they go down the model consensus every time....it's just their way. If the models were off to the north the NHC will be as well. Rarely, if ever, will you ever find their track outside of the model guidance envelope. True, our models have some skill which has been improved over the years and thus the NHC skill has improved as well, but any time the models make a massive mistake in unison, the NHC is right there making it with them, and that is why they aren't as good as they could be if they dared to defy the models. I can see why they don't though.....I mean I would be hesitant to as well if the world's eyes were watching my forecast.
The world is watching your forecast Levi, and your forecasts are fine!
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You know what would really be a great learning experience.....set up a group of students, or whatever, independent of the NHC, to draw up a forecast for a tropical cyclone without looking at any model tracks (or the NHC's forecast). True the skill would be pretty bad by days 4 and 5, same as our's were before computer models came into existance, but talk about a great way to learn some real forecasting. None of this model consensus nonsense.
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Quoting MiamiHurricanes09:
Anything past 45W is highly uncertain in terms of track for 96L.


hows school?
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Quoting MiamiHurricanes09:
Anything past 45W is highly uncertain in terms of track for 96L.



yup
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Greetings folks. I rarely post here, as I do not possess the knowledge to have an intelligent discussion about meteorology in general, much less tropical weather. I come here simply for information. Don't get me wrong I live in a hurricane area, the Gulf Coast of Alabama to be precise, and have been through quite a few hurricanes. For the information that I receive, I thank those in know here on the board. From what I've read here, most folks know who I am speaking of...so I won't name any names, but you guys are aces in my book.

As for those that seemingly come here to cause trouble, I guess this question is for the admins. I realize that you can ban people, but why are the bans temporary? These troglodytes do nothing but bring the board down. Why not an IP address ban, or every permutation of their existing name, etc.? I've run a few boards here and there, and when a board starts showing signs of more in-fighting amongst its users, rather than the sharing of information, things usually do not wind up very well for the average "law-abiding" user. I guess my question is why use a velvet glove in handling these vermin, when an iron fist seems more effective.

Anyways, sorry to stick my nose where it might not belong (ignore me if you must), but it's been bugging me for a little while now... OK, back into the shadows.
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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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