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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Quoting StormW:


I think what they are looking at is not so much the current trof pulling him northward, as much as the break in the ridge being in place. IF, that fails, we have one other possibility as a saving grace...but yes, the track would be further west. As to an east coast landfall, my thinking at the moment if it does, may still only be OBX/Hatteras.

IF this current weakness fails, the next trof that is forecast to swing in per the NHC discussion, will act in tandem with the current CONUS ridge, as in the most current forecast I saw for the 500 mb situation, would orient that ridge, with the subtropical ridge in such a manner, that we get the NW turn, and then the trof comes in and turns him NE.

Again, I'll have to reassess that in the a.m....closely.


Thank you.
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Quoting kshipre1:
If Fiona has formed then why hasn't the NHC updated their website?



they dont do it in tell 5 lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115099
Quoting MississippiWx:


4-2-2 in August...September could be a doozy.

will
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1678. markot
watches warnings for se bahamas east dom republic
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1676. Asta
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correct. either Earl better zoom out quicker or Fiona has to slow herself down or she will be a short lived tropical storm
Member Since: July 12, 2010 Posts: 0 Comments: 1130
Quoting BobinTampa:


just saw a long radar loop on t.v. Very clearly moving at least wnw. One of the westers this a.m. said it would be 35 miles north of PR. It will clearly be much more than that.

I guess you have to look at more than three frames of radar.

Exactly...Some people get stuck trying to pin a hurricane down to straight line movement, when in fact they almost always "wobble" If you look at NHC forecast advisory..It always uses terms like "overall motion" or "general"
motion..
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Quoting kshipre1:
If Fiona has formed then why hasn't the NHC updated their website?


They will initiate advisories @ 5pm
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1671. Drakoen
Earl continuing to strengthen and looking quite impressive. And now 97L Fiona.



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Fiona's development will likely be rather slow until Earl accelerates and begins to move more northwesterly away from the Leeward Islands and Puerto Rico.
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How that we have Fiona, I'm eager to see what type of track the NHC puts out. We have the dynamical guidance in a consensus through 3 days, but a few are showing a hook west towards day 5. The statistical guidance on the other hand is considerably further south. We then have the global models mainly all over the place, some developing it, some aren't. We shall see I guess.
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1668. angiest
Quoting tornadolarkin:
"Fiona" looks awful.


Earl looked awful most of his life.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1667. Scimet
Scimet on St. Croix

Good afternoon all

Here's an update from St. Croix U.S. Virgin Islands. Presently, as of 3:45 p.m., winds have picked up with occasional wind gusts of over 50 mph. The peak wind gust measured by my anemometer was 59 mph this afternoon. Raining heavily on the island for the past hour and a half with rainfall totals between four and five inches for the day. B/Pressure has been falling steadily since mid morning. It's presently at 29.26 inches on the south coast of the island. Police and emergency officials have reported some downed trees, fallen telephone and power lines and a few utility poles downed by Hurricane Earl. There is significant beach erosion on the north and east of the island. Marine conditions are really bad with pounding waves and dangerous surf. Breaking waves on the east of the island is at least 10 feet above nornal. Flooding has been reported around the island with some roadways rendered impassible. One vessel (a sail boat) has been washed ashore in Frederiksted and is totally destroyed, according to Deputy Police Chief Christopher Howell. Everyone is hunkered down for at least three more hours of inclement weather.

I'll give another update later.

SB
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1665. angiest
San Juan radar recently had a peak gust of 123kts.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1664. hydrus
Quoting Cotillion:
Now to 6-3-2.

I put my bets on Earl not reaching Cat 5 (hey, someone's got to disagree).
Hey Cotillion!..:) I already put My Cat-5 prediction up. If he does not reach cat-5 by 11am tomorrow, it is a crow sandwich for my lunch.:)
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"Fiona" looks awful.
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Quoting Waltanater:
Earl has been going West for the past 2 hours now! http://www.ssd.noaa.gov/goes/flt/t2/flash-vis.html

It seems that the expert forcasters are "hanging on" to those models until the very last minute. Every new run, the paths are looking more and more crunched up together as they stay conveniently off shore and not even making landfall. No outlier here. Is this to avoid\minimize mass panic? I feel there is something wrong here, in general. Something has to, and will give. If and where this hits, it will be very, very bad.

Anyone else feel the same way? I welcome your opinions (based on fact of course)




I agree with you. I believe they won't say anything until at least 48 hours of any landfall. That is my opinion.
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1661. KEEPEROFTHEGATE (Mod)
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Quoting markot:
weathermanplz look at radar it is moving west.... ok


Look at the satellite Keeperofthegate posted, it's very clearly moving WNW, the eye crosses the line going slightly North, it can't get anymore obvious than that!
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So is the soon to be Fiona going out to see to? Shouldn't that be stopping soon? Just curious...
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Quoting Flyairbird:
Hasn't the Atlantic had some crazy tracks like that? I think it was either jeanne or Francis that did a loop-de-loop


Jeanne in 04...

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Quoting markot:
weathermanplz look at radar it is moving west.... ok


Look at post 1628.....it is not
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The only reason why I am arguing about the movement of Earl is because it is extremely important. The further west Earl moves, the bigger impact he could have on the eastern United States.

Secondly, I am a weather forecaster. I have gone to school, and I have won awards in weather forecasting.

Thirdly, I just want to lay the rules out: Earl is moving WNW. NOT WEST. He has not moved completely NW yet. That probably will not occur until tomorrow.

I feel like it is important for everyone to share their opinions on the tropics, and I am not attacking anyone. 3 frames on radar is not enough proof to make a judgement that this system is moving west. Look at the overall system and where the center has moved through latitude.

I'll bow down to you guys if the NHC puts "WEST" as Earl's movement at the next advisory.
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1655. Asta
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If Fiona has formed then why hasn't the NHC updated their website?
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Quoting tornadolarkin:

Most of those have been within the past couple weeks.
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http://www.baynews9.com/video?clip=http://static.baynews9.com/newsvideo/bn9/web_video/Tropical_Update _4pm_830.flv

I think this is the loop I saw on tv. It's flash and I'm on my iPhone so I'm not 100% sure.
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Quoting MississippiWx:


4-2-2 in August...September could be a doozy.

Most of thos have been within the past couple weeks.
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1650. jasblt
Forgot to mention...I was wrong about the Gulf disturbance...so I guess I need to quit forecasting.
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1649. hydrus
Quoting KEEPEROFTHEGATE:
07L/MH/E/C4
MARK
19.27N/64.51W
Awesome loop Keep....
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1648. snotly
http://rammb.cira.colostate.edu/ramsdis/online/loop_640.asp?product=tropical_ge_1km_center_relative_v is_floater
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Another letter going poof to something that looks like that.

Oh well... I am generally a Miami caster. If it gives me reason to believe it will survive being near Earl, I will jump on the wagon and base my projection on the NGPS and ECMWF model runs.

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Quoting CybrTeddy:
Fiona puts us at 6-3-2.


4-2-2 in August...September could be a doozy.
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1645. Asta
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Quoting unf97:


Yes he did answer is own question LOL..


Was just asking Storm to verify if I was thinking right. Or left, as the case may be.
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Look at the eye well is really beginning to fill in on the radar echo screen.

Link
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I wouldn't be surprised to see the NHC mention the wave behind Fiona at 8:00 pm.
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Fiona is going to have to slow down if she wants to survive. Earl will end up killing her if she keeps at this pace.
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They just renumberd 97l
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Fiona puts us at 6-3-2.
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1637. unf97
So, NHC finally upgrades to T.S. Fiona. I will be interested to see the advisory within the hour.
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Now to 6-3-2.

I put my bets on Earl not reaching Cat 5 (hey, someone's got to disagree).
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Quoting clwstmchasr:
Earl is a wobbler. Took a west wobble and now back to the north. Overall still moving WNW.


just saw a long radar loop on t.v. Very clearly moving at least wnw. One of the westers this a.m. said it would be 35 miles north of PR. It will clearly be much more than that.

I guess you have to look at more than three frames of radar.
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Tropical Storm Fiona is born according to ATCF. Now 5 PM is really gonna be interesting.

invest_RENUMBER_al972010_al082010.ren
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this what i been waiting for


invest_RENUMBER_al972010_al082010.ren
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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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