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Hurricane Earl takes aim at Lesser Antilles; 5-year anniversary of Katrina

By: Dr. Jeff Masters, 2:35 PM GMT on August 29, 2010

Hurricane warnings are flying for the islands in the northern Lesser Antilles, as they hunker down a prepare for the arrival of the 3rd hurricane of the 2010 Atlantic hurricane season, Hurricane Earl. Earl, a classic Cape Verdes-type Atlantic hurricane, is a potentially dangerous storm for the islands in its path, should its eyewall pass directly overhead. Earl could intensify significantly as it moves through the islands late tonight and on Monday. An Air Force Hurricane Hunter aircraft found a central pressure of 978 mb at 1:21 pm EDT. This is a significant drop of 7 mb in four hours. Top surface winds were 75 mph, and they noted an eyewall open to the northwest. The incomplete eyewall can also be seen on Martinique radar (figure 1.) Recent visible satellite imagery shows the storm has continues to increase in organization this afternoon. The amount and intensity of Earl's heavy thunderstorms is increasing, low-level spiral bands are steadily building, and upper level outflow is becoming more established in all quadrants except the north. This lack of development on Earl's north side is due to strong upper level northerly winds from the outflow of Hurricane Danielle to the north. These winds are creating about 15 knots of wind shear over Earl, according to the wind shear analysis from the University of Wisconsin CIMSS group. Water vapor satellite images show a large region of dry air from the Sahara lies to the northwest of Earl, but Earl is successfully walling off this dry air with a solid circular region of heavy thunderstorms.

Figure 1. Radar image of Earl taken at 3:45 pm EDT. Image credit: Meteo France.

Intensity forecast for Earl
As Hurricane Danielle pulls away from Earl this afternoon and this evening, shear should fall to the low range, 5 - 10 knots, as predicted by the latest SHIPS model forecast. This should allow Earl to build a complete eyewall by tonight. Once a complete eyewall is in place, Earl will likely undergo a bout of rapid intensification, which could bring it to Category 3 or 4 strength by Tuesday morning. The ocean temperatures are at near record warmth, 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. 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.

Track forecast for Earl
Earl is being steered to the west by the same ridge of high pressure that steered Danielle. Earl is now approaching a weakness in the ridge left behind by the passage of Danielle and the trough of low pressure that pulled Danielle to the north. Earl should move more to the west-northwest today, likely bringing the core of the storm over or just to the northeast of the islands of Barbuda, St. Barthelemy, Anguilla, and St. Maartin in the northernmost Lesser Antilles Islands tonight and Monday morning. NHC is giving its highest odds for hurricane-force winds to Barbuda and Saint Maarten--a 44% and 42% chance, respectively. These odds are 11% for St. Thomas in the Virgin Islands, and 4% for Puerto Rico.

Figure 2. Wundermap view of the Lesser Antilles showing the NHC 5am wind radius forecast for Earl. Tropical storm force winds (dark green colors) were predicted to affect much of the northern Lesser Antilles, with hurricane force winds (yellow colors) predicted to pass just to the north of the islands.

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., and the 12Z (8 am EDT) set of model runs have mostly pushed the storm farther from the U.S. East Coast. It is not unusual for the models to make substantial shifts in their 5-day forecasts, and it is still possible that Earl could make a direct hit on North Carolina as a major hurricane on Thursday or Friday. One should pay attention of the cone of uncertainty, and the Outer Banks of North Carolina are in the 5-day cone. NHC is giving Cape Hatteras a 6% chance of receiving hurricane force winds. 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. However, five day forecasts can be off considerably on the timing and intensity of such features, and it is quite possible that the trough could be delayed or weaker than expected, resulting in Earl's landfall along the U.S. East Coast. The most likely landfall locations would be North Carolina on Thursday or Friday, or Massachusetts on Friday or Saturday. The GFS and ECMWF models predict that Earl will come close enough to North Carolina on Thursday to bring the storm's outer rain bands over the Cape Hatteras region. The other models put Earl farther offshore, but it currently appears that Earl will not pass close enough to Bermuda to bring tropical storm force winds to that island. It is possible that if 97L develops into Hurricane Fiona and moves quickly across the Atlantic, the two storms could interact and rotate counterclockwise around a common center. Predicting these sorts of interactions is difficult, and the long-term track forecast for Earl will be difficult if a storm-storm interaction with Fiona occurs.

In any case, the U.S. East Coast can expect a long period of high waves from Earl beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to very high waves from Earl (Figure 3.)

Figure 3. Wave forecast for 8am Thursday, September 2, 2010, as produced by the 2am 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 Central Florida to Virginia.

Hurricane History for the northern Lesser Antilles
The last hurricane to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar's eyewall missed all of the islands, but the storm 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
Martinique radar
Wundermap of the northern Lesser Antilles Islands
Long range radar out of San Juan, Puerto Rico (current down for repair.)
Visible rapid scan satellite loop

The tropical wave (Invest 97L) now midway between Africa and the Lesser Antilles Islands has developed a well-defined surface circulation, and appears destined to develop into a tropical storm and follow the path of Danielle and Earl. Satellite loops show the surface circulation clearly, but also reveal that there is not enough heavy thunderstorm activity associated with 97L for it to be called a tropical depression. The storm is experiencing low wind shear of 5 - 10 knots, is over warm 28°C waters, and is battling a region of dry air associated with the Saharan Air Layer (SAL) to its northwest. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Wednesday, and this should allow 97L to organize into a tropical depression today or Monday. The storm will follow a track very similar to Danielle and Earl westward towards the Lesser Antilles Islands, and the storm should arrive near the northern Lesser Antilles Wednesday or Thursday. A more northwesterly path is likely for 97L as it approaches the Lesser Antilles, as the storm follows a break in the high pressure ridge steering it, created by Danielle and Earl. It currently appears that the Northern Lesser Antilles Islands may be at risk of at close brush or direct hit by 97L. If 97L moves relatively quickly, arriving at the Lesser Antilles on Wednesday, it is likely to be a weaker system, since it will have less time over water, and will be closer to big brother Earl. Earl is likely to be a large and powerful hurricane at that time, and the clockwise upper level outflow from Earl will bring strong upper-level northerly winds to the Lesser Antilles, creating high wind shear for 97L. However, if 97L moves relatively slowly, and arrives in the Lesser Antilles on Thursday, Earl will be farther away, the wind shear will be lessened, and 97L will have had enough time over water to potentially be a hurricane. Depending upon how fast they have 97L moving, the computer models have a wide variety of solutions for 97L, ranging from a making it a Category 1 hurricane five days from now (GFDL model) to a weak tropical storm five days from now (several models.) History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast. NHC is giving 97L a 80% chance of developing into a tropical depression by Tuesday.

Figure 4. Morning satellite image of 97L.

Hurricane Danielle blew past Bermuda late Saturday night, bringing one rain squall to the island that brought top winds of 26 mph, gusting to 39 mph. Danielle is now on its way out to sea, and will not trouble any more land areas. High surf will continue to affect Bermuda and the east coast of the U.S. and Canada's Maritime Provinces today. The latest near shore water forecast for Cape Hatteras calls for 6 - 8 foot waves today. These waves will gradually subside during the week, then ramp up to 6 - 8 feet again on Thursday, as Hurricane Earl's wave field begins to pound the U.S. East Coast.

Elsewhere in the Tropics
Tropical Storm Kompasu is headed for China, and is predicted to intensify into a Category 2 typhoon by Wednesday and potentially threaten China's largest city, Shanghai. Over 16 million people live in the city, many of them in low-lying areas, and the Chinese will need to take this storm very seriously. 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.

Katrina, five years later
It hardly seems possible that five years have elapsed since that cruel day in 2005 when the world changed forever for so many people in Louisiana, Mississippi, and Alabama. Recovery from the great hurricane is nowhere near complete--the destruction wrought by Katrina still scars the land terribly, and the proud people of the Gulf Coast still suffer tremendously in the aftermath of the disaster. The scale and intensity of the destruction the hurricane brought is truly breathtaking, and can best be appreciated by viewing two of the best chronicles of Katrina's record storm surge--Margie Kieper's remarkable city-by-city aerial tour of the destruction, and extreme weather photographer Mike Thiess' 13-minute video of his storm surge experience in Gulfport, Mississippi. Katrina did do some good, though--it taught us that our nation can unite in the face of an overwhelming challenge to help our fellow citizens in need, and taught us not to be complacent about living in the realm where great hurricanes come.

Figure 5. A man wearing a tiny life jacket and clutching a neon green noodle and a pet dog floats on the remains of a house in Waveland, MS, during Hurricane Katrina. The photo was taken from the second floor window of a home, and the water is close to the roof line of the first floor. The home was at an elevation of about 17 feet, and the surge is close to ten feet deep here. There are electric lines running down from a pole to a home from left to right. In the distance on the right is a home with water up to the roof line. The eye is probably overhead, as the water is relatively calm and there appears to be little wind or rain, even though the pine trees are bent from the recent force of the eyewall winds. The photo was taken by Judith Bradford. Her husband, Bill Bradford, swam out and rescued the man and his dog, and two other people who floated by. He reported that the water was nothing like white water, but was a gentle, continuous flow. He was lucky. In the nearby Porteaux Bay area, a woman watched her fiance get pulled from a tree by the force of the current. The man was washed out into the Gulf and drowned. The image above is described in more detail in Part 9 of Margie Kieper's Katrina storm surge web page.

I'll share with you my personal story of blogging about Katrina. I starting writing blogs during the spring of 2005. For the first few months of this effort, it was a slow time for interesting weather events, and I had trouble finding things to write about. I was relieved when June of 2005 brought me two Atlantic tropical storms to discuss. But as July wore on, and the bombardment of the great Hurricane Season of 2005 began--a record five named storms, three hurricanes, and two major hurricanes, Dennis and Emily, both the strongest hurricanes ever recorded so early in the season--I was ready for less to write about! History was in the making, and the peak part of hurricane season was still a month away. I managed to take advantage of a slight break in the action in mid-August to travel for vacation and business, and the day Katrina was named found me in New York City. I was attending meetings with the Associated Press, who had just signed up to use Weather Underground as the weather provider for their 5000 newspapers. I wasn't able to follow the storm very closely that day, due to the all the meetings. Still, I had a very uneasy feeling about this storm. When one of the AP staff members made the remark, "It sure has been a slow summer for news. We need a big story!" I looked at her hard and thought, "Be careful what you wish for--you might get it!"

I flew home that Thursday afternoon, then made the decision Friday to drive up north with my family and spend a 4-day weekend at my father's house. The Hurricane Season of 2005 had kept me so busy that I hadn't made it up north to see him that summer, and this was my last chance. High speed Internet was not available in his small town of Topinabee on beautiful Mullet Lake, so I knew I'd be spending some slow hours blogging on his dial-up connection. Still, I figured Katrina would quickly recurve to the north and hit the Florida Panhandle before it had a chance to become a major hurricane. It wasn't like this storm would be worst disaster in American history or anything! Wrong. I spent virtually the entire weekend holed upstairs in the computer room, writing increasingly worried and strident blogs, exhorting people in New Orleans and Mississippi to evacuate. Every now and then, I'd emerge downstairs and say hi to everyone, then head back up to my cell to watch really slowly loading pages and write new blogs. Finally, I couldn't take it any more, and talked my family into returning home a day early. My wife couldn't fully understand why I was so agitated--wasn't this just another hurricane like Frances, Jeanne, Charlie, Dennis, or Emily? But, she agreed that we'd better go home that Sunday night before Katrina hit, since I was such a basket case. The next day, when Katrina hit and the full magnitude of the greatest disaster in American history unfolded, she understood. Indeed, three weeks later my wife headed down to the Louisiana disaster zone as a Red Cross volunteer, and she REALLY got an appreciation of why I had been so agitated in the days before Katrina hit.

It is difficult for me to read my Katrina blog posts again, as I relive those days and remember the terrible suffering this storm brought to so many. Let us not forget the people affected by Katrina, and the lessons the great storm taught. My thoughts and prayers are with all of Katrina's survivors on this fifth anniversary of the storm.

Next update
I may be able to post a quick update on Earl late this afternoon or early this evening.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.