Earl a Category 4 storm again

By: Dr. Jeff Masters , 9:23 PM GMT on September 01, 2010

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Hurricane Earl has regained Category 4 strength this afternoon, and continues on a steady northwest path towards the North Carolina coast. Recent satellite imagery shows that Earl has become more symmetrical, with improved upper-level outflow and no signs of dry air wrapping into the core. The improved appearance is probably due to lower wind shear. Latest wind shear tendency imagery from the University of Wisconsin CIMSS group shows that shear on the southwest side of Earl has fallen by about 10 knots over the past 24 hours.


Figure 1. Afternoon satellite image of Earl.

Forecast for Earl
The latest set of model runs from 8am EDT (12Z) this morning shows little change to Earl's track. Thus, my write-up of the possible impacts to North Carolina, New England, and Canada in this morning's post remain unchanged. The latest SHIPS model forecast shows wind shear will remain moderate, about 15 knots, through Friday afternoon. This should allow Earl to maintain major hurricane status as it passes North Carolina early Friday morning. By Friday night, as Earl gets caught in the jet stream and accelerates to the northeast, wind shear will rise to 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 1 or 2 hurricane early Saturday morning, when it will make its closest approach to New England. Earl is more likely to be a strong tropical storm or weak Category 1 hurricane early Saturday afternoon, when it is expected to make landfall in Nova Scotia, Canada.

Earl is a large hurricane, which gives it a higher potential for storm surge damage than a smaller hurricane with the same top winds. One measure of a storm's power, useful for gauging storm surge threat, is to measure the speed of the winds and multiply by the area over which those winds blow. This total is called the Integrated Kinetic Energy (IKE). Based on the storm's IKE, one can come up with a scale from 0 - 6 rating the storm's destructive power from its storm surge. A separate rating can be given to the destructive potential of the storm's winds. The IKE value of 112 Terrajoules for Earl, at 3:30pm EDT today, gives its storm surge a destructive power of 5.0 on a scale of 0 - 6. Earl's winds have a lower destructive power, 3.4 on a scale of 0 - 6. Let's hope the right front quadrant of Earl, where the main storm surge would occur, stays offshore! For comparison, the small Category 5 Hurricane Camille of 1969 had an IKE of 80 Terrajoules, and the very large Category 2 Hurricane Ike of 2008 had an IKE of 116 Terrajoules--similar to Category 3 Earl's.

Fiona
Tropical Storm Fiona is struggling due to high wind shear, courtesy of strong upper-level northerly winds from Hurricane Earl's outflow. The latest Hurricane Hunter center fix at 1:29pm EDT found Fiona had weakened some, with a central pressure of 999 mb. This is a rise of 1 mb from this morning. The wind shear analysis from the University of Wisconsin CIMSS group shows that shear has increased to a moderately high 15 - 20 knots this afternoon. Satellite loops show the classic signature of a tropical storm experiencing high wind shear--an exposed center of circulation, and all the heavy thunderstorms pushed to one side (the south side in this case). Martinique radar shows that the outer bands from Fiona are bringing heavy rain squalls to the same islands of the northern Lesser Antilles that were affected by Earl. Our wundermap for the northern Lesser Antilles shows no stations recorded winds over 20 mph this afternoon, though there was no reporting station on Barbuda, the island closest to Fiona.

Forecast for Fiona
Moderate wind shear and dry air should keep Fiona from attaining hurricane status over the next two days, as big brother Earl continues to bring high wind shear. The shear may be strong enough to destroy Fiona, as predicted by the NHC. However, by this weekend, Earl may pull far enough away for shear to drop and Fiona to survive. The 4 - 5 day track forecast is highly uncertain, as there is a large spread in the model solutions. It is possible Fiona may pose a threat to Bermuda on Saturday or Sunday, and the storm could wander for a week or more in the waters between Bermuda and the U.S. East Coast.


Figure 2. Afternoon satellite image of Fiona.

Tropical Storm Gaston forms
Tropical Storm Gaston developed enough heavy thunderstorms near its center this afternoon to get a name, and appears destined to become Hurricane Gaston by early next week. Water vapor satellite images show a large area of dry air to the north and west of Gaston, and this dry air will be the dominant inhibiting factor for development. The latest SHIPS model forecast predicts shear will remain moderate, 10 - 15 knots, for the next four days, and perhaps fall to the low range 4 - 5 days from now. Gaston is over warm 28°C waters, and should be able to steadily intensify into a hurricane by Saturday or Sunday, as predicted by the many of the intensity models. Gaston may threaten the northern Lesser Antilles Islands as early as Tuesday.

Next post
I'll have an update in the morning, and Dr. Rob Carver will have a late night update tonight.

Jeff Masters

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My thinking exactly...
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Quoting leo305:


more westerly movement evident because the high is stronger to its east


Yep west of track a greater chance of a direct hit and yes it is still doing a stair step course NW then W then NW maybe N in their to you get the picture this is not going to be a good day or night when and where it hits still even with a side swipe going to do damage no doupt about it.
Member Since: August 23, 2008 Posts: 0 Comments: 1918
2303. Hhunter
WHAT STORM MEANS IS IF THE RIDGE IS STRENGTHENING TO THE EAST THEN THE STORM MAY GO MORE WEST...FOLKS TAKE IT SERIOUSLY..IF YOUR IN A SURGE RISK AREA GET OUT. I THOUGHT DR MASTERS DID A GOOD JOB IN HIS POST OF LAYING OUT THE SURGE POTENTIAL..THAT WAS BEFORE REGAINED CAT 4 STRENGTH..DON'T UNDERSTIMATE THE POTENTIAL..YOU ONLY HAVE ONE CHANCE TO BAIL OUT..
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Quoting KanKunKid:


Yeah, but it doesn't seem to make much difference, it still looks like someone dumped over a box of snakes and they're all crawling away from the ugly one.


Now that's funny..I don't care who you are...
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Let's just hope Gaston does not get in the Caribbean.
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Quoting KerryInNOLA:
Didn't you hear? An alien spaceship crashed in France.


Link please. I just checked CNN and they did not even mention this at all.




j/k
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Thanks mudder, appreciate it!

So was your fadder a mudder too?
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Quoting hydrus:
Does the forward speed effect surge too? I would think so.
Of course. Hmmm, might have to dig up a paper we did 6 (?) years ago.

But, that has an interaction with the shoreline, and bays, etc. along with approach angle. Little effect where there is nowhere for the water to "pool". Big effect on a concave shoreline, and large bays, lakes, etc.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
THE EYE OF THE HURRICANE WOBBLED NORTHWARD A COUPLE OF HOURS
AGO...HOWEVER THE MEAN MOTION APPEARS TO BE ABOUT 330/16. NO
SIGNIFICANT CHANGES HAVE BEEN MADE TO THE FORECAST TRACK OR
SYNOPTIC REASONING FROM THE PREVIOUS ADVISORY PACKAGE...ALTHOUGH
THE MULTI-MODEL CONSENSUS FORECAST HAS NUDGED EASTWARD ABOUT 20 N
MI ON THIS CYCLE. EARL IS EXPECTED TO GRADUALLY TURN TOWARD THE
NORTH AND SLIGHTLY EAST OF NORTH AS IT MOVES ALONG THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE FOR THE NEXT DAY OR SO.
THEREAFTER...A STRONG 500 MB TROUGH MOVING THROUGH THE GREAT LAKES
SHOULD CAUSE THE HURRICANE TO TURN TOWARD THE NORTH-NORTHEAST AND
ACCELERATE. ONE SHOULD NOT FOCUS ON THE EXACT FORECAST TRACK OF
THIS LARGE AND INTENSE HURRICANE. SIGNIFICANT IMPACTS ARE LIKELY
TO BE FELT WELL AWAY FROM THE CENTER.




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Quoting stormhank:
Does anyone feel Gaston could be a potential threat to Florida?? Models dont recurve him like they did with earl n Fiona??


It's way too early to tell.
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2289. 2ifbyC
Quoting atmoaggie:
For those that wish to analyze the entire cycle of NHC 5 day forecasts from Earl's beginning:


Excellent!!!
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2288. ussual
Very nice with the 5 day loop atmoaggie
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2287. leo305
Quoting rwdobson:


Nope. The high has winds blowing clockwise around it. To the west of a high, the winds are coming from the south...so if the high to the east is stronger it will propel Earl north.


if the high is stronger it will push low pressure systems farther away from the high.. hence a more westerly movement..



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2286. hydrus
Quoting atmoaggie:
For those that wish to analyze the entire cycle of NHC 5 day forecasts from Earl's beginning:
The West-casters were on track with the forecast track.
Member Since: September 27, 2007 Posts: 1 Comments: 20539
Does anyone feel Gaston could be a potential threat to Florida?? Models dont recurve him like they did with earl n Fiona??
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Quoting atmoaggie:
For those that wish to analyze the entire cycle of NHC 5 day forecasts from Earl's beginning:


WOWW
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Quoting StormJunkie:


Not if you use the Goes 15 Science Test

That's one kick ... Sat
Thanks SJ..I use your site just about every day of hurricane season..great resources...I'm glad you are actively blogging :)
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2282. bassis
Hey Super Chart Man, Keep them under control, I'll see ya'll in the morn
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If you go to this site, and select infrared, pick 12 animations, and click on the storm, its a 3 hr loop..... turn off all the frames except the first and last, and you will see his movement.

Link
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Goes 15 image...Notice the image is from 3:20

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Quoting atmoaggie:
Fitzpatrick is one (MSU, look him up).

And, yes, I did realize that, but thanks anyway.

Did you know that Ike wasn't a stronger storm offshore? Yet, had a surge not usually associated with a cat 2? All about radius of TS force winds. Really.
(Surge modeling is what I do. No kidding.)


I suspect that the water level rise due to atmospheric pressure is very small compare to that water pushed by the wind...correct?
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Quoting leo305:


more westerly movement evident because the high is stronger to its east


Nope. The high has winds blowing clockwise around it. To the west of a high, the winds are coming from the south...so if the high to the east is stronger it will propel Earl north.
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Thank you for a bit of rational advice!
Love WU, but amazed at the "wonder-casting" that goes on... After years of watching these twirling monsters, I've learned to look, watch, stop - come back in a hour, look, watch & stop again... the old tracking maps would help a lot of "the new to hurricanes watchers" *a better understanding the wobbles. There's nothing like a pencil and a chart..... to give you a true perspective of the wacky wobbles the twirling can cause.
Thank you!
*sorry had to modify my grammer.
Quoting rwdobson:


Try comparing the last 2 sets of coordinates.

Then try responding with some actual science instead of personal attacks.
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Quoting redUK:


Does this satellite not have a blackout?!


Nope...But they are only testing it...I think the plan is to test it, then turn it off for a couple years before going operational.?. I think...
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For those that wish to analyze the entire cycle of NHC 5 day forecasts from Earl's beginning:
Member Since: August 16, 2007 Posts: 6 Comments: 12461
2271. hydrus
Quoting atmoaggie:
Fitzpatrick is one (MSU, look him up).

And, yes, I did realize that, but thanks anyway.

Did you know that Ike wasn't a stronger storm offshore? Yet, had a surge not usually associated with a cat 2? All about radius of TS force winds. Really.
(Surge modeling is what I do. No kidding.)
Does the forward speed effect surge too? I would think so.
Member Since: September 27, 2007 Posts: 1 Comments: 20539
Quoting leo305:


more westerly movement evident because the high is stronger to its east


Well that is a bad thing.
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I agree KEEPER, which means I am off to bed. Goodnight.
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Ok Im out can't stand it any more. Too many super adequacys in here tonight Night regulars and good luck East Coast. Talk to you all tomorrow.
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2266. redUK
Quoting StormJunkie:


Not if you use the Goes 15 Science Test

That's one kick ... Sat


Does this satellite not have a blackout?!
Member Since: August 18, 2008 Posts: 0 Comments: 53
2264. leo305
Quoting CaneWarning:


What does this mean?


more westerly movement evident because the high is stronger to its east
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2263. bwat
Well, goodnight all, I know the blogs gonna be a little tense until we start getting some nne motion. Off to bed to see what 5am brings. L8r
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Quoting DestinJeff:


spoken like a true pro.


UNLESS it name is Charley!
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Quoting oracle28:


Who are these good researchers?

You do realize that Cat 5's have lower barometric pressure and therefore can "lift" (re:suction effect) ocean water more easily that Cat 3's. So Katrina had already lifted more water than the typical Cat 3 max storm.
Fitzpatrick is one (MSU, look him up).

And, yes, I did realize that, but thanks anyway.

Did you know that Ike wasn't a stronger storm offshore? Yet, had a surge not usually associated with a cat 2? All about radius of TS force winds (and wind speeds at landfall, of course). Really.
(Surge modeling is what I do. No kidding.)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting blsealevel:


exactly what Bob and StormW was seeing earlier this evening in their talk.


What does this mean?
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Quoting tinkahbell:


Dear Oz,

Sorry I called you an idiot. I hope you can find it in your hear to forgive me. I am just thankful that I didn't use the adjective I was thinking of when I called you that. Just sayin'. K? Bye.

<3 Tink


LOL
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Quoting TheDawnAwakening:
Latest steering maps for a hurricane less than 940mb suggests the ridge has strengthened east of Earl.


exactly what Bob and StormW was seeing earlier this evening in their talk.
Member Since: August 23, 2008 Posts: 0 Comments: 1918
Quoting KEEPEROFTHEGATE:
last image will be 315 utc till about 6 15 utc


Not if you use the Goes 15 Science Test

That's one kick ... Sat
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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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