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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2556. xcool


this NJ2S:NJ2S:yellow 34-50

red 64

blue 50 -60
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting SCwannabe:


I've been wondering that same thing, but the models don't hint to that at all.


It (the ULL in the gulf) is quite visible on the water vapor loops..actually noticed earlier today dropping south through LA and wondered...now it is indeed pulling SW on the trough even as Earl pushes the VA based high ridge back into the trough degrading its flank from TN, KY North to IN. It seems it will be extremely hard for the trough to push forward now to catch earl and turn him fully clear of the coast.
Member Since: June 26, 2008 Posts: 0 Comments: 383
The motion of Earl is closer to NW then NNW right now.
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2552. leo305
Quoting NJ2S:
if earl comes within 5o miles of NYC what kind of winds miht we expect>?


hurricane force winds extend 90 miles from the center
tropical storm force winds extend up to 200 miles from the center
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2551. twooks
I feel like not enough attention is being paid to this storm, except on the TWC. I'm more than concerned about this storm. I feel too many ppl will take Earl for Granted on the East Coast.
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Hurricane Force!
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The storm surge is much greater to the right of track. Ergo, wind makes a huge diff.
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2548. robj144
Quoting SkinnyKnockdown:


What? I have always thought that the surge was almost ENTIRELY due to the low barometric pressure, with very little to do with the wind. If the wind was a significant player, then you'd have a "negative" surge on the clean (west) side of the storm. Of course, the surge is larger on the dirty side due, in part to the wine, but it only serves to amplify the surge. Am I way off on this? If so, then my world is rocked, and my 2.0 cumulative GPA as a met major for 5 semesters was, in fact, a fairly accurate representation of my knowledge base!


From the link Link:

"The storm surge is an abnormal rise in sealevel due to two effects. First, a minor effect is the fact that the very low pressure at the center of hurricanes causes an upward bulge in the ocean at the center of the storm. Thus, the ocean levels are higher there than in the surrounding areas, often by a matter of 5 feet or so.

In addition, the major effect has to do with the augmented winds on the right forward margin of the storm physically pushing the ocean against the coastline for a storm moving from southeast to northwest. The combination of these two effects makes, in particular, the forward right quadrant of a hurricane very prone to significant storm surges, sometimes of nearly 25 feet or so."

I think you need to go back to school... :)
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Quoting Orcasystems:


Your aware its not fair to have an intellectual disagreement with an unarmed person right?


LOL!!
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2546. NJ2S
if earl comes within 5o miles of NYC what kind of winds miht we expect>?
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2383. ROFL!
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2544. dmaddox
strong cat 4:
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2543. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting atmoaggie:
Knock, knock. Charley had a tiny radius of hurricane and TS force winds. Exactly the point. And his surge was based on the wind conditions.

You basing what surge should have been on the SS scale? Bad idea. And since removed from the scale as such fallacy has become well known.


Your aware its not fair to have an intellectual disagreement with an unarmed person right?
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2541. xcool
traumaboyy .lol .
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2540. wjdow
Quoting SkinnyKnockdown:


What? I have always thought that the surge was almost ENTIRELY due to the low barometric pressure, with very little to do with the wind. If the wind was a significant player, then you'd have a "negative" surge on the clean (west) side of the storm. Of course, the surge is larger on the dirty side due, in part to the wine, but it only serves to amplify the surge. Am I way off on this? If so, then my world is rocked, and my 2.0 cumulative GPA as a met major for 5 semesters was, in fact, a fairly accurate representation of my knowledge base!


i think i read in issac's storm that people stood at the shore in galveston 1900 in astonishment as all the water in the bay went out before the eye passed and the wind shift allowed the water to come back in.
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Quoting xcool:
traumaboyy .all news care about politics anyway


very true....waiting to see what the kin.....excuse me...president has to say about it...lol
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2538. xcool





two more storms
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting oracle28:


Right! and if 99% of the surge is based on current/lanfalling conditions, as atmoaggie stated, then Charley should have had a higher surge.

Thank you!
Knock, knock. Charley had a tiny radius of hurricane and TS force winds. Exactly the point. And his surge was based on the wind conditions.

You basing what surge should have been on the SS scale? Bad idea. And since removed from the scale as such fallacy has become well known.
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Yeah, I'm in Charleston too and find it hard to believe we are not even under a TS watch.
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Quoting hydrus:
That is a scary looking loop. I would venture to say that if there is not a turn to the north in the next 3 or 4 hours, North Carolina will feel the full force of the hurricane. This is just my honest opinion. I hope Earl turns soon.


Me, too. That's getting to be a mighty fine needle Earl has to thread. I just don't know if it's going to happen.

Member Since: August 18, 2008 Posts: 0 Comments: 884
2534. leo305
The models may have missed that ULL in the gulf..

this is why the core of the circulation may be moving west of the forecast..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2533. xcool
traumaboyy .all news care about politics anyway
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2532. robj144
Quoting SkinnyKnockdown:


What? I have always thought that the surge was almost ENTIRELY due to the low barometric pressure, with very little to do with the wind. If the wind was a significant player, then you'd have a "negative" surge on the clean (west) side of the storm. Of course, the surge is larger on the dirty side due, in part to the wine, but it only serves to amplify the surge. Am I way off on this? If so, then my world is rocked, and my 2.0 cumulative GPA as a met major for 5 semesters was, in fact, a fairly accurate representation of my knowledge base!


Isn't there a pressure based surge right underneath eye and a larger, wind-driven surge, ahead of the eye? Also, I believe the SLOSH models taken into account wind direction.
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2531. OBXgirl
Mainland Dare County here...about 15 miles west of the Nags Head coast. The local mets here need to get together for a forcast pow-wow and get on the same page. One TV guy says that it will be "No Biggie" for mainland Dare while another wants to go door-to-door here advising us to run for the hills. Now I am so confused I don't know whether to plan a garden party or go jump in the tub with a mattress over my head.
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High pressure building to the west
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Quoting jlp09550:


It's a developing ULL? Our local met said it was dropping from the north..?


I've been wondering that same thing, but the models don't hint to that at all.
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2527. leo305
looks like it jogged WNW on the last frame..

overall movement still is NW, the further west it goes the more of a chance of hit hitting land
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting xcool:
why no live tv on this storm wt beep beep .


Too early....gonna wait till it is about two hours out to really let people know there is a beautiful MONSTER headin in bent on Killin Folks!!
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Quoting oracle28:


To most people...some on here don't seem to grasp the concept.
Yeah. Whatever.
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2524. ussual
I would think that unless this turn comes before to much longer we may even feel some TS winds here in Charleston and we don't even have watches or warnings.


But then again maybe it will hit Washington DC wash away all the polititions would be great for the country.
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2523. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15684
2522. hydrus
Quoting RitaEvac:
NW

That is a scary looking loop. I would venture to say that if there is not a turn to the north in the next 3 or 4 hours, North Carolina will feel the full force of the hurricane. This is just my honest opinion. I hope Earl turns soon.
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2521. dmaddox
Quoting RitaEvac:
NW

wobble wobble to the west! wow! scary as the eye comes into the picture!
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Will be really interesting to see new models at 5am!
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10AM tomm is when the shock will take place of what is about to bare down on the east coast
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2518. Zeec94
Quoting CaneWarning:


Super close... Shouldn't they be putting up high wind warnings well inland???


TS Wind Warnings are at coast. None inland yet nor do I expect to see any.
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Quoting xcool:




Wait.. whaaaa?
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Quoting Legion:


Charlie was much smaller in size, though, than either Katrina or Ike.


Right! and if 99% of the surge is based on current/lanfalling conditions, as atmoaggie stated, then Charley should have had a higher surge.

Thank you!
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Quoting SkinnyKnockdown:


What? I have always thought that the surge was almost ENTIRELY due to the low barometric pressure, with very little to do with the wind. If the wind was a significant player, then you'd have a "negative" surge on the clean (west) side of the storm. Of course, the surge is larger on the dirty side due, in part to the wine, but it only serves to amplify the surge. Am I way off on this? If so, then my world is rocked, and my 2.0 cumulative GPA as a met major for 5 semesters was, in fact, a fairly accurate representation of my knowledge base!

Happens all the time.

In fact, we had a -6 foot surge around Grand Isle, LA during part of Katrina. And Lake Pontchartrain sloshed back towards Slidell after Katrina passed precisely because the wind pushed all of the water to the SW corner of the lake and setup a plus 7 foot surge there and a minus 7 foot surge at Slidell. Change the wind direction after the eye passes, well, like having all of the water on one end of a bathtub.

I know people that actually saw the water recede well beyond any normal water movements 2 hours before...saw mud where there had always been water.
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2513. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
2512. dmaddox
Quoting RitaEvac:
NW

wobble wobble to the west! wow what a sat shot! scary as it comes into the picture!
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2511. twooks
Quoting MZT:
It's appears to me that Earl's outflow has been disrupting the upper levels of the trough, and impeding its progress. I can't believe what a photo finish this is becoming. Guess I'll check the outcome in the A.M.


I'm at the point where I don't want to see what happening with Earl when I wake up.
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from what i can tell this is heading right for NC
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2509. xcool
why no live tv on this storm wt beep beep .
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2508. leo305
Quoting Alockwr21:


Solidly NW


yep.. NW movement
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2507. JP2010
Quoting stormhank:
Does anyone feel Gaston could be a potential threat to Florida?? Models dont recurve him like they did with earl n Fiona??


Yes
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2506. KEEPEROFTHEGATE (Mod)
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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.