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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2506. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting RitaEvac:
NW



He's running out of turning room.
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2504. 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.
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Quoting RitaEvac:
NW



Solidly NW
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2500. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting oracle28:


Um ok, guess all that 20-29 feet of water with Katrina just came out of nowhere then.

Charley, a Cat 4 at landfall, was only a Cat 4 two hours before landfall and had a surge WELL BELOW cat 4 standards.
Of course it didn't come out of nowhere, but it's good to consider all possibilities. Radius of hurricane force winds and radius of TS force winds are very important.

Charley was little, by windfield breadth, and hit the coast at a steep angle.

I work in this field. But you don't have to believe me, do some research on it. No, not the wiki kind. The http://www.ametsoc.org/pubs/ kind.
Member Since: Posts: Comments:
----------->lurker running in------->

Just heard from my young nephew who is also a sailor in Norfolk. He says they have been filling sandbags all night and doesn't look to stop anytime soon.

Praying for his little country a$$ he's never seen anything like this! He's only 19!!

Oh and sick puppy, I'm on that train too!

(Tappahannock)

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Quoting hydrus:
That looks bad.....I really hope that does not pan out. That would be a devastating path. And I have to mention, with all that warm water up there, it might not weaken very much at all. Earl would pound a huge part of the coastline.

Warm water goes very far north:

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Quoting oracle28:


Um ok, guess all that 20-29 feet of water with Katrina just came out of nowhere then.

Charley, a Cat 4 at landfall, was only a Cat 4 two hours before landfall and had a surge WELL BELOW cat 4 standards.


Ike was a Cat-2 at landfall... but had an 18-foot storm surge. It devastated the Bolivar Peninsula.

Rita was a Cat-3 at landfall and had a storm surge in excess of 18-feet. It completely wiped Cameron, Louisiana off the map.

You are absolutely correct. The storm surge height depends on how broad the wind fields are, how strong the winds have been in the past, it's direction relative to the shore and the slope of the off-shore waters.

From experience, I can tell you that Hurricane Earl is pushing a LOT of water. The surge potential along the East coast near landfall will be in the Cat-3 to Cat-4 surge range.
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Quoting Xyrus2000:


Very long range gfs shows gaston riding the east coast like Earl, only more west.



ouch ok thanks
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
By developing, I meant strengthening.
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2493. Acorna
Blech, and I'm supposed to work tomorrow too. I'm basically right on the line between the TS warning and hurricane warning since they revised it to Bogue Inlet instead of Surf City. Power going out is a near-given since we haven't had a good blow in quite a while...I hope that's the worst of what we see. Go east, Earl, go east!
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NW

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Quoting atmoaggie:
~ 1/10. But, at sea, nearly all of it is the inverted barometer effect.

At the coast, ~10%, roughly.

And big increases in central pressure in deep waters would have the result of the pressure-induced surge level having the chance to dissipate.


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!
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2490. leo305
well if he tracks along the east coast, a major disaster is in the ropes.. the media isn't going full force on this.. and I fear that if the time comes when they have to, they will be too late.. that's if it does hug the coast.
Member Since: April 17, 2010 Posts: 0 Comments: 1753
2489. Ryuujin
Quoting KEEPEROFTHEGATE:
07L/MH/E/C4
nearing coast


That's a GD scary sight.
Member Since: August 20, 2010 Posts: 0 Comments: 405
2488. hydrus
Quoting xcool:
That looks bad.....I really hope that does not pan out.
Quoting CaneWarning:
That GFS run hates the east coast... Geez that is near worst case scenario.
That would be a devastating path. And I have to mention, with all that warm water up there, it might not weaken very much at all. Earl would pound a huge part of the coastline.
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Quoting medic11402:
I think the overall message is this, the NHC said in there public advisory at 11pm NOT TO FOCUS ON THE TRACK... Unless Earl went to school, He is not reading the NHC Track map following through. The NHC took the line out of there map to prevent people from focusing on the "PATH", they would much rather that you focus on the cone and pay attention to your local Emergency Management Agency. Hurricane forecasting with the scientific study and data still has an element of art to it. Preparedness means paying attention, heeding the warnings and responding appropriately. If you live on the East Coast, let me clue you in, there is a threat to your area. FEMA has already begun positioning people and supplies for a possible response. Anyone know why they are doing that, because there is enough concern with Hurricane Earl that it may impact the East Coast. The bottom line is this, ARE YOU READY? DO YOU HAVE A PLAN? WHAT IS YOUR LIFE WORTH? if the NHC is right, then so bi it and you have just had an opportunity to exercise your plan. If the NHC is off, then you are going to be well ahead of the curve by executing your plan when the local Emergency Management Agency alerts you to the threat. If you do not have a plan IT IS TIME TO MAKE ONE AND BE PREPARED TO INITIATE IT, it may just save your life.....
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FIONA has had it
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
2484. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2483. KEEPEROFTHEGATE (Mod)
07L/MH/E/C4
nearing coast
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting DoctorDave1:
In looking at the Eastern US WV loop, it appears that a developing ULL in the NE GOM is inducing a westerly component in the movement of Earl and will continue to do so until the TROF arrives.


It's a developing ULL? Our local met said it was dropping from the north..?
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Quoting Tazmanian:
what do the mode runs show for Gaston


Very long range gfs shows gaston riding the east coast like Earl, only more west.
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2480. Ryuujin
Looking at the RGB feed from the Tropical Floater, it looks like Earl is going to clip 75W before he hits 30N and is looking to be a little south and west of the next forecast point of the NHC. Man this is going to be crazy close.
Member Since: August 20, 2010 Posts: 0 Comments: 405
Big storm...wow.
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Quoting DoctorDave1:
In looking at the Eastern US WV loop, it appears that a developing ULL in the NE GOM is inducing a westerly component in the movement of Earl and will continue to do so until the TROF arrives.


You think so? I noticed that this afternoon and thought the same thing.
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Quoting StSimonsIslandGAGuy:
Thanks! What do y'all think about Gaston's slow motion---the 120 hour forecast point places it still more than 400 miles east of the Leeward Islands. Tropical systems in the deep tropical Atlantic usually whip along at 15-20 mph. The 5 day average speed for Gaston will be less than 10 mph.


Storms doing strange things really mess with the models.
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Quoting DoctorDave1:
In looking at the Eastern US WV loop, it appears that a developing ULL in the NE GOM is inducing a westerly component in the movement of Earl and will continue to do so until the TROF arrives.


In that animation the trough looks like a big arm trying to give Earl a hug. :P
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what do the mode runs show for Gaston
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
With all due respect and concern for those in the outer banks and throughout the effected areas of the Carolinas, the meat of this forecast is the angle that the storm takes from OBX onwards. 5 degrees one way or the other in heading makes all the difference to much more densely populated areas. 10 degrees to the left means catastrophe.
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2473. o22sail
Quoting SickPuppy:
Go east strong man, go east!!!

SickPuppy,
Richmond, VA

I'm chanting with you SP.

(Richmond)
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Quoting PrivateIdaho:


...makes sense.


To most people...some on here don't seem to grasp the concept.
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2471. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting jlp09550:
He's a monster.



ughhhh...man, that looks really bad.....please be safe everyone and please evacuate if asked too.
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2469. twooks
Quoting jlp09550:
He's a monster.

>


I'd say he's a beauty.
Member Since: August 14, 2008 Posts: 0 Comments: 92
2468. leo305
I guess the cone may shift west again..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting atmoaggie:
Watch the presentation in my link.

What happens in deep water, including peak wind speed and central pressure, doesn't make it to shore in the surge. Conditions of the storm at landfall have 99% to do with the surge that we actually experience.


Um ok, guess all that 20-29 feet of water with Katrina just came out of nowhere then.

Charley, a Cat 4 at landfall, was only a Cat 4 two hours before landfall and had a surge WELL BELOW cat 4 standards.
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In looking at the Eastern US WV loop, it appears that a developing ULL in the NE GOM is inducing a westerly component in the movement of Earl and will continue to do so until the TROF arrives.
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This is the best advice I've heard all night MEdic11402
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He's a monster.

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Closest approach to Cape Cod:

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Quoting PrivateIdaho:


good point...a 2 foot tidal range on the La delta is on the high side...just sayin'
Many areas up the east coast can have a total tidal range of up to 6 feet. If we had that in LA...well, many things simply wouldn't be where they are.
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Go east strong man, go east!!!

SickPuppy,
Richmond, VA
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Quoting oracle28:


Yes and a post-Cat5 will have had (at some point)stronger winds to push water in its path than a Cat3 storm that never reached 145mph in its lifetime.


...makes sense.
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Keep looking at that SW quad - if it goes annular, that's where you will see it first.
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2458. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
That GFS run hates the east coast... Geez that is near worst case scenario.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
dont for get it all ways take one too make it a bad year
Member Since: May 21, 2006 Posts: 5091 Comments: 115456

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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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