Category 3 Hurricane Earl pounding northern Lesser Antilles and Puerto Rico

By: Dr. Jeff Masters , 2:40 PM GMT on August 30, 2010

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An intensifying Hurricane Earl is pounding Puerto Rico and northern Lesser Antilles Islands with heavy rain and high winds this morning. The eye of Earl passed just north of Anguilla at 9am EDT, and Juliana airport on neighboring St. Martin Island recorded sustained winds of 47 mph, gusting to 68 mph at 8am EDT before going silent. An Air Force Hurricane Hunter aircraft currently in Earl just found a central pressure of 960 mb at 9:42 am EDT. This is a significant drop of 25 mb in 25 hours. Top flight level winds at 10,000 feet seen by the Air Force aircraft were 128 mph. Using the usual rule of thumb that the surface winds are 90% of the 10,000 foot flight level winds gives one surface winds of 115 mph, which is right at the border of Cat 2/ Cat 3 strength. Top winds seen at the surface by the Air Force's SFMR instrument were lower, 104 mph. Recent satellite imagery shows that Earl is not perfectly symmetrical--there is still fewer heavy thunderstorms on the hurricane's north side, suggesting that upper-level northerly winds are bringing 5 - 10 knots of wind shear to the storm.


Figure 1. Radar image of Earl taken at 7am EDT 8/30/10 from the St. Maarten radar. Image credit: Meteorological Service of the Netherlands Antilles and Aruba.

Outlook for the Caribbean islands today
Latest radar animations out of Puerto Rico and St. Marten show that the eye of Earl is on track to pass just to the northeast of the islands of Anguilla, St. Maarten, and The Settlement in the British Virgin Islands today. The periphery of Earl's southern eyewall will probably bring Category 1 hurricane conditions to some of these islands today. NHC is giving its highest odds for hurricane-force winds to Saint Maarten--a 99% chance. These odds are 4% for St. Thomas in the Virgin Islands, and 2% for San Juan, Puerto Rico. The main threat to Puerto Rico will be heavy rains--up to eight inches in isolated areas. Earl's rains, in addition to causing flooding and dangerous landslides, will also help alleviate drought conditions that have affected many of the islands this year.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast is nearly non-existent over Earl--just 3 knots--put is probably higher than that, based on the fact that the northern portion of Earl cloud pattern is ragged. Further evidence of this is the fact that Earl's eyewall had a gap in its west side, according to the latest report from the Hurricane Hunters. Ocean temperatures are a near-record 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. These nearly ideal conditions for intensification should bring Earl to Category 4 strength by Tuesday morning, and Category 5 is not out of the question. Earl should be able to maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. Sea surface temperatures are very warm, 29°C, along the U.S. East Coast, and wind shear is expected to remain low through Thursday. By Friday, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday, when it could potentially make landfall in Massachusetts or Nova Scotia, Canada.


Figure 2. Swath of surface winds from Earl predicted by the 2am EDT Monday August 30, 2010 run of NOAA's GFDL model. Hurricane force winds (yellow colors, 64 kt and above) are predicted to stay off the coast and tropical storm force winds (light green colors, 34 knots and above) are predicted to stay off the U.S. coast, but affect the coast of Canada. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
Once Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. None of the computer models show Earl hitting the U.S., but the storm will likely come uncomfortably close to North Carolina's Outer Banks and to Massachusetts. The latest set of model runs (2am EDT, or 6Z) project Earl will miss North Carolina by 200 - 300 miles on Thursday, and Massachusetts by a similar distance on Friday. Keep in mind that the average error in a 4 - 5 day NHC forecast is 200 - 300 miles, so the East Coast cannot breathe easily yet. The Outer Banks of North Carolina and Cape Cod, Massachusetts are both at the edge of the cone of uncertainty. NHC is giving Cape Hatteras a 9% chance of receiving hurricane force winds. These odds are 14% for Nantucket, 4% for Boston, and 2% for New York City. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea late in the week, with the storm just missing landfall in the U.S., but possibly making landfall in Nova Scotia, Canada.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to waves that will reach 10 - 15 feet in offshore waters (Figure 3.)


Figure 3. Wave forecast for 8am Friday, September 3, 2010, as produced by the 8pm EDT August 29 run of NOAA's Wavewatch III model. The model is predicting waves of 4 - 5 meters (13 - 16 feet) in the offshore waters from North Carolina to New Jersey.

Hurricane History for the northern Lesser Antilles
The last Cape Verdes-type hurricane to affect the Barbuda and the surrounding northern Lesser Antilles Islands was Hurricane Debby of 2000, which passed over the islands on August 28 as a Category 1 hurricane. Damage was less than $1 million, and no fatalities were reported. The last hurricane of any kind to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar took an unusual track, moving towards the northeast, and the storm's eyewall missed all of the islands. Omar did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Wundermap of the northern Lesser Antilles Islands
Long range radar out of San Juan, Puerto Rico
Visible rapid scan satellite loop

97L
The tropical wave (Invest 97L) now 1000 miles east of the Lesser Antilles Islands has a well-defined surface circulation and enough heavy thunderstorms to be classified as a tropical depression, if it can maintain that state for another six or so hours. Satellite loops show the surface circulation clearly, but also that heavy thunderstorm activity has been slow to build. The storm is experiencing low wind shear of less than 5 knots, and is over warm 29°C waters. The main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Tuesday, and this should allow 97L to organize into a tropical depression today or Tuesday. NHC is giving 97L a 90% chance of developing into a tropical depression by Wednesday.

97L is moving quickly to the west, at about 20 mph. This means it is catching up to Earl, which has slowed down to 14 mph. By Tuesday night, Earl is expected to be a large and powerful major hurricane with a well-developed upper-level outflow channel heading clockwise out from Earl's center at high altitudes. These strong upper-level winds will bring high levels of wind shear, 20 - 30 knots, to 97L, and probably arrest the storm's development. The most likely scenario depicted in the computer models is for 97L to be drawn into the low pressure wake of Earl and pass to the northeast of the Lesser Antilles. Earl would then eventually destroy 97L through high wind shear, and by robbing the storm of its moisture. An alternative scenario is that 97L will stay far enough away from Earl that it will be able to pass through the northern Lesser Antilles islands as a tropical storm on Wednesday and Thursday, then bend northwestwards to potentially threaten the Bahamas and U.S. East Coast. There is a very high degree of uncertainty on what may happen to 97L. History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast.


Figure 4. Morning satellite image of 97L.

Danielle
Hurricane Danielle is on its way to oblivion over the cold North Atlantic waters, and is only of concern to shipping interests.

Elsewhere in the Tropics
Over in the Western Pacific, tropical cyclone activity is ramping up, with two named storms expected to affect land this week. As is typical in a La Niña year, these storms have developed close to mainland Asia, and don't have a lot of time over water to intensify into strong typhoons. The storm of most concern is Typhoon Kompasu, which is expected to hit Okinawa today and recurve northward into Korea on Thursday. It now appears the Kompasu will not have major impacts on China's largest city, Shanghai. In the South China Sea, the fearsome sounding Tropical Storm Lionrock is forecast to hit the Chinese coast near Hong Kong on Tuesday, but is not predicted to develop into a typhoon.

The GFS model is predicting formation of a tropical depression off the coast of Africa about seven days from now.

Jeff Masters

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1881. KEEPEROFTHEGATE (Mod)
07L/MH/E/C4
MARK
19.37N/64.78W
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Quoting K8eCane:
Im in Wilmington NC...How Worried should I be...anybody?


I would be dusting off your Hurricane Plans for the "just in case"
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Assuming 97L gets the upgrade at 5pm, I can't wait to see how the NHC handles the cone. Do they put more weight on the ECMWf or just go with consensus....
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1877. markot
get real
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Quoting angiest:


Throw a glob of jello into a pool of water and give it a nudge. tropical cyclones are not rigid bodies and have a lot of different things acting on them, including their own spin, their steering currents, and various other things.
throw a jello shot in your mouth and it will do the same thing....lol couldn't resist
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Quoting K8eCane:
Im in Wilmington NC...How Worried should I be...anybody?


well, if its cat 5, and so large that its gonna hit a large portion of coast, I would definitely leave as soon as it defnitely turns north and you are even near the cone. But thats just me.
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1872. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Disturbance Summary
TROPICAL DEPRESSION XX
3:00 AM JST August 31 2010
==================================

At 18:00 PM UTC, Tropical Depression (1010 hPa) located at 8.0N 173.0E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The depression is reported as moving northwest at 20 knots.
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...DANIELLE WEAKENS TO A TROPICAL STORM OVER THE OPEN ATLANTIC OCEAN...
5:00 PM AST Mon Aug 30
Location: 41.3°N 49.0°W
Max sustained: 70 mph
Moving: ENE at 15 mph
Min pressure: 973 mb
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Quoting reedzonemyhero:
Models are just that MODELS.

1) Katrina ended up West than forecast.

2) Rita ended up North than forecast.

3) Charley ended up South than forecast.

4) Ivan ended up East than forecast.

That about covers it.


When Katrina emerged into the GOM after crossing southern Florida, the NHC track forecast had it going straight into New Orleans. Don't know how many days out that was, but it was very impressive.
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Quoting reedzonemyhero:
Models are just that MODELS.

1) Katrina ended up West than forecast.

2) Rita ended up North than forecast.

3) Charley ended up South than forecast.

4) Ivan ended up East than forecast.

That about covers it.


And Earl is wayyy West of forecast, and will continue to be.
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1867. Asta
Quoting GetReal:


They act like a tire that is out of balance... The heavier convection continuously wrapping around the center interferes with the rotation, causing friction with the sea surface and the atmosphere...

Nicely put metaphor..
NorthWest Atlantic Water Vapor Loop( Flash)
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1866. Drakoen
Earl has been wobbling as hurricanes of this strength do and he is on the forecast track right now.
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Quoting reedzonemyhero:
Models are just that MODELS.

1) Katrina ended up West than forecast.

2) Rita ended up North than forecast.

3) Charley ended up South than forecast.

4) Ivan ended up East than forecast.

That about covers it.


"It's only a model.."
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Dani clings to tropical status.
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My location (Providenciales)
is currently
460 Nautical miles (530 statute)

on a bearing of 290 degrees

from the eye of Earl.

He has my attention.
Member Since: July 12, 2007 Posts: 0 Comments: 5984
Quoting OracleDeAtlantis:
The Fujiwhara effect can make two cyclones, in close proximity .... very difficult to forecast. Two whirlwinds, within a larger whirlwind.

In essence, a marriage of wind moving around a common center.


Thanks for that
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Quoting clwstmchasr:


Looking at the visible loop Earl is about to be right on top of the next forecast point.


Do remember that the change those forecast points daily..so Earl is not hitting the forecast points set yesterday...he would need to cross the 20N at 65W, which he will miss to the South...
Member Since: June 26, 2008 Posts: 0 Comments: 357
1859. angiest
Quoting iammothernature:


But why???


Throw a glob of jello into a pool of water and give it a nudge. tropical cyclones are not rigid bodies and have a lot of different things acting on them, including their own spin, their steering currents, and various other things.
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1858. Asta

The Danielle / Earl "relationship"
clearer on this AVN image,
me thinks..
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1857. hydrus
Quoting srada:


I agree..first it was 384 miles off the NC coast just yesterday in our local advisory..now its 200 miles off the NC Coast..and we aint even On Tuesday yet and this storm gets here on Thursday??..
Floodman had a good post earlier today. You have to remember that these models will only do what they are programed to do. They just outline the possible scenarios with the current atmospheric conditions. Of course they will shift. Sometimes dramatically. Storm seems to focus on the latest developments and observations. Thats probably why he gets paid. And why so many here ask his opinion.jmo
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1856. Drakoen

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1855. GetReal
Quoting iammothernature:


But why???


They act like a tire that is out of balance... The heavier convection continuously wrapping around the center interferes with the rotation, causing friction with the sea surface and the atmosphere...
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1852. kwgirl
Quoting Relix:
To weatherman455

Sorry, these are not 3 frames.



W > WNW> W> WNW again.
All storms wobble. You need to plot long/lat to see which direction it is truly going. Once you plot the points, take a ruler, draw a line and then you have your overall heading. And not always a straight line.
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Quoting K8eCane:
Im in Wilmington NC...How Worried should I be...anybody?


Worried? not at all.

aware and planned? yes.
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Models are just that MODELS.

1) Katrina ended up West than forecast.

2) Rita ended up North than forecast.

3) Charley ended up South than forecast.

4) Ivan ended up East than forecast.

That about covers it.
Member Since: Posts: Comments:
1849. HCW
30/1745 UTC 15.3N 48.1W T1.5/1.5 97L
Member Since: August 10, 2002 Posts: 0 Comments: 1346
1848. markot
eye is getting that stadium effect look....
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The Fujiwhara effect can make two cyclones, in close proximity .... very difficult to forecast. Two whirlwinds, within a larger whirlwind.

In essence, a marriage of wind moving around a common center.

Member Since: Posts: Comments:
Quoting clwstmchasr:


I give praise to the NHC and bash them when they miss. I believe they have missed it on Earl.


Wow...that does say it all...NHC are not gods but they must daily "eat their own crow" and change their maps to stay up with the facts on the ground (or ocean)...we must look at these and be ready to take their estimated movements of future hurricanes with the appropriate grain of salt and respect...hard to balance those some days.
Member Since: June 26, 2008 Posts: 0 Comments: 357
1844. Drakoen
Quoting StSimonsIslandGAGuy:


Thanks Drak, I put that in bookmarks. I knew there had to be a reason why Earl would go off to the north! Glad you could take the time to be on today.


No problem :)
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Quoting HadesGodWyvern:
msmoma

Link

It means that an invest has become better organized to become identified as a tropical cyclone.. in this case TC 08L has been identified by the NRL.


thank you for the explanation. I followed the link, but did not understand it. still in kindergarten here. lol
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Quoting clwstmchasr:
I read a story once that when Donna past east of Tampa that the winds were so strong out of the NE that it basically emptied Tampa Bay.


FYI - Donna is also the only hurricane on record to bring hurricane force winds to every state on the eastern seaboard...
Member Since: June 20, 2005 Posts: 22 Comments: 1050
1841. Relix
Quoting Asta:

Interesting, where are you Relix?


Toa Baja, PR. Btw getting strong winds and rain now.
Member Since: August 3, 2006 Posts: 0 Comments: 2639
Quoting Clearwater1:
Quoting washingtonian115:
We have Fiona finally...well can't ask any questions since the arrogant ones are on,Where's storm, levi,or miami09 anyway the wave behind Fiona needs to be mentioned because that could indeed develop.

***

And not long for this world if it catches Earl's wake. . . . and looking at sat imagery, I think it will.

They don't call it the wave train for nothing.
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Quoting HurricaneIsabel:


all storms wobble


But why???
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1838. Drakoen
Quoting DestinJeff:
I posted something similar earlier, so forgive the repeat... but look at the difference in the GFS forecast for the trough on Sep-3 00UTC. Also note the position of Earl.

12Z Run (current) 700mb level


6Z Run 700 mb level


What I see is a weaker trough depicted, and that trough will be the main player on down the road.


The trough in the top picture is more positively titled than the trough in the bottom picture. The more the trough tilts in a negative direction the greater the risk will be. Similar to Miller-A cyclogenesis steering factors.
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I see the WPAC is active, but heck why am I surprise it's always active over there!
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Quoting clwstmchasr:
I read a story once that when Donna past east of Tampa that the winds were so strong out of the NE that it basically emptied Tampa Bay.
True! I was a young man when it happen. Fish were flopping around in the mud of Tampa Bay
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invest_RENUMBER_al972010_al082010.ren
Link
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1833. BDAwx
Quoting Asta:

you can pick out the gulf stream in that!
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1832. Asta
Quoting Relix:
Amazing!

Over 15 birds have tried to take shelter in my house. Wow I didn't really believe those things but there are countless birds all around the house trying to take refuge. Man that's amazing. First time I go through that.

Interesting, where are you Relix?
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1831. srada
Quoting HurricaneIsabel:
with each update on earl, the more westerly track it takes :(


I agree..first it was 384 miles off the NC coast just yesterday in our local advisory..now its 200 miles off the NC Coast..and we aint even On Tuesday yet and this storm gets here on Thursday??..
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.