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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GETTIN CLOSER
Member Since: Posts: Comments:
2605. dmaddox
BIG!!!
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2604. leo305
I wish norcross was on right now..

he would be pointing out the latest developments constantly
Member Since: Posts: Comments:
Quoting xcool:


gets stronger


Hi xcool....you think Gaston will end up getting pulled out to sea or do you think this could getting into the Caribbean and possibly GOM?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting oracle28:


Also a common phrase is "you can't cure stupid"
and as my profession would say: "You can't put in what the good Lord didn't"
Member Since: August 16, 2007 Posts: 1 Comments: 2337
Xtrap its current motion its heading towards Jacksonville NC,
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Quoting SiestaCpl:


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.


Yep, you can see all of that quite clearly on the Eastern US Water Vapor Loop. Link
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2599. xcool


ooh my
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Sea, Lake, and Overland Surge from Hurricanes (SLOSH) is a computerized model developed by the Federal Emergency Management Agency (FEMA), United States Army Corps of Engineers (USACE), and the National Weather Service (NWS) to estimate storm surge depths resulting from historical, hypothetical, or predicted hurricanes by taking into account a storm's pressure, size, forward speed, forecast track, wind speeds, and topographical data.

SLOSH is used to evaluate the threat from storm surge, and emergency managers use this data to determine which areas must be evacuated. SLOSH output is used by the National Hurricane Program (NHP) when conducting Hurricane Evacuation Studies as a hazard analysis tool for assisting with the creation of state and local hurricane evacuation plans or zones. SLOSH model results are combined with roadway network and traffic flow information, rainfall amounts, river flow, or wind-driven waves to determine a final analysis of at-risk areas.
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Quoting SkinnyKnockdown:


Thanks, Aggie. I can imagine water being shoved back out to sea when the storm passes, but I guess it must be all a timing thing, surely the surge pushes out in front of the storm regardless of the wind direction...but this is my gut talking. And I enjoyed the talk that you posted. I have a post doc met friend up at College Station...are you that breed of atmo-aggie?
That I am.

Want to see the Karina surge modeling results with wind overlaid on surge contours? http://www.nd.edu/~adcirc/katrina.htm

Pretty evident there.

Oh, and one final point. Of Katrina's surge, highest on the MS gulf coast, the top ~4 feet have everything to do with the shape of the shoreline. That water would have escaped to the west, if it could. But LA is in the way. (As if the Ole Miss/LSU game needed to be bigger)
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2596. xcool


gets stronger
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting btwntx08:
back


Hey how was that pizza earlier...?
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Quoting KEEPEROFTHEGATE:
07L/MH/E/C4
MARK
28.11N/74.11W
nearing coast


after looking at this- I would be freaking out if I lived in the SC lowcountry. What are the chances?
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There is overwhelming consensus in tonight's 0z global models of Earl coming less than 30 miles away from Cape Hatteras.
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2592. leo305
Quoting NJ2S:


i know it is not im just asking in a almost worst case scenario if it happens to be closer than expected im hoping the local mets are right and we just get some breezy showers....ive never been through hurricane and have family livin at the jersey shore so thats why i ask....dont mean to speculate or westcast or watever :)


No =P, I meant his map wasn't with the center being 50 miles away.

If the eye is 50 miles east of new york, you could get hurricane force winds.
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Its a feeder band being thrown out on the west side
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2590. xcool
. leo305 i meaning NJ2S:
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Does anyone have a link to SLOSH?
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Quoting oracle28:


No, just based on previous Cat 4 storms. Never did I mention a scale.
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Quoting SCwannabe:
Yeah, I'm in Charleston too and find it hard to believe we are not even under a TS watch.


we shouldn't be...we're not even gonna know it's out there ..
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2586. NJ2S
Quoting leo305:


that's not 50 miles away from NYC


i know it is not im just asking in a almost worst case scenario if it happens to be closer than expected im hoping the local mets are right and we just get some breezy showers....ive never been through hurricane and have family livin at the jersey shore so thats why i ask....dont mean to speculate or westcast or watever :)
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2585. xcool
btwntx08 about time.you very close getting fired ,,,
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2584. jswfl09
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.


All I know is that surge forecasting changed a lot due to that storm. For here in Bonita Beach and northward, the mets were throwing out possible storm surges of 15-20+ feet (at the last minute assuming a near head-on collison, once it made its infamous right-hand turn).

In the end, the surges for most of Lee and Charlotte county were 4-8 feet, with some of the highest actually occuring to the south on Vanderbilt Beach (I believe it was 10-12 feet or so). Luckily, due to tide and wind direction, there was almost no flooding there. The storm surge flooding was isolated on Bonita Beach and a bit more widespread on Fort Myers Beach.
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Good night all. Tomorrow should be interesting.
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2582. ussual
SCwannabe someone turned on a vacuum to suck the storm towards us making elongate.
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2581. dmaddox
if (and when) it gets west of 75W we should be very concerned...
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2580. robj144
Quoting LAlurker:

SLOSH models take wind speed, direction of movement, and speed of movement into account.


Right, but he was saying that wind plays no role in the storm surge, so I pointed out it is used in SLOSH, so it must play a role. I know it also uses topology of the coast and direction of impact, but the wind was the key thing.
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2579. leo305
Quoting xcool:
. leo305 oh i dnot see Comments oops


you don't see my comments?
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"Why is earl's west side bowing out like that??"

That's what I keep asking, but no one is listening.
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NW

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Quoting atmoaggie:
>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.


No, just based on previous Cat 4 storms. Never did I mention a scale.
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2574. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Why is earl's west side bowing out like that??
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Quoting 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!


That is exactly what caused people during Hurricane Ike to lose their homes or even their lives. The state and local government offices didn't close until time was running short to prepare & evac. Schools held session, businesses didn't close, etc... .

I'm betting a LOT of local governments and businesses here aren't paying much heed. However, the employees will have really short time to board up and evacuate if they are going. The responsible ones will close tomorrow and let their employees go home and prepare.
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2571. xcool
. leo305 oh i dnot see Comments oops
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2570. KEEPEROFTHEGATE (Mod)
07L/MH/E/C4
MARK
28.11N/74.11W
nearing coast
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2569. hydrus
G,night all.
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2568. leo305
Quoting NJ2S:


will the windfield be that wide when he is passing this latitude?


doubt it, but it shouldn't drop SIGNIFICANTLY
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Quoting robj144:


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... :)


If you think about it in terms of raising water with a vacuum pump, a perfect vacuum can raise water about 32 ft (I think) a hurricane is not close to a perfect vacuum so 5 ft seems reasonable.
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2566. dmaddox
looking at the last 3 hours of IR sat and "smoothing" the wobbles... the heading appears to be back to NW IMO....
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2565. ussual
Important rule for arguing with poeple

"Never argue with an idiot, for they will bring you down to thier level and beat you with experience."
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the way thing are going we could be up too the W storm by the end of SEP
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Quoting robj144:


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.

SLOSH models take wind speed, direction of movement, and speed of movement into account.
Member Since: Posts: Comments:
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.


Exactly, you have to consider size and direction and PREVIOUS intensity.

So you think a Katrina that never reached Cat 5 and a Katrina that was Cat 5 for nearly 24 hours(all else being equal) will have the exact same surge?

Fine by me, goodnight...

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2561. NJ2S
Quoting leo305:


hurricane force winds extend 90 miles from the center
tropical storm force winds extend up to 200 miles from the center


will the windfield be that wide when he is passing this latitude?
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2560. leo305
Quoting xcool:


this NJ2S:NJ2S:


that's not 50 miles away from NYC
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2559. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15620
Here is a link to the webcam on my favorite pier in Surf City, NC. They shut it down at 9 pm and turn it back on at 6 am. I think a friend told me that only a handful of piers had been replaced after the last major hit there.

Surf City Pier - Click Here
Member Since: December 6, 2001 Posts: 0 Comments: 24
Quoting atmoaggie:

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 pass percisely 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.


Thanks, Aggie. I can imagine water being shoved back out to sea when the storm passes, but I guess it must be all a timing thing, surely the surge pushes out in front of the storm regardless of the wind direction...but this is my gut talking. And I enjoyed the talk that you posted. I have a post doc met friend up at College Station...are you that breed of atmo-aggie?
Member Since: Posts: Comments:
2556. xcool


this NJ2S:NJ2S:yellow 34-50

red 64

blue 50 -60
Member Since: September 26, 2009 Posts: 2 Comments: 15620

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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.