If you recall, yesterday I mentioned that one aspect of the forecast regarding Hurricane Earl was the dry air in which Earl was moving into. I had thought that perhaps dry air might work its way into the circulation of the hurricane and perhaps limit its intensity potential or even bring it down a notch or two. At 5 AM on Wednesday September 1, 2010 the National Hurricane Center included this bit of information near the end of it’s discussion: ” …WATER VAPOR IMAGERY SHOWS A TONGUE OF MID/UPPER-LEVEL DRY AIR WRAPPED MORE THAN HALFWAY AROUND THE CYCLONE.” I honestly had been surprised that they had not mentioned that potential earlier because the the scale of the dry air ahead of the storm was rather large. Nevertheless, by Wednesday afternoon, the outflow symmetry of Earl looks to have improved and the dry air looks to have been absorbed without a whole lot of disruption; perhaps it hurt Earl a bit. But, Earl overcame the dry air and at 5pm EDT on Wed Sept 1 had maximum winds of 135 mph with gusts to 160 mph. Central pressure was 941mb and was moving at 310 -320 degrees (NW) at 17 mph. The dry air was one of the “challenges” that I referred to that I felt Earl would face in maintaining its intensity. There are other issues at play as well that suggest the storm has seen its better days and its ferocity will not be as great as it once was, or even feared it would be, when it affects the US Coast. Nevertheless, I would not take the storm lightly and it would be advisable to get out of its way if you may be in the path of Earl.
As of 5 PM EDT Wednesday, Hurricane Warning flags have been hoisted from Bouge Inlet, North Carolina to the North Carolina/Virginia. A Hurricane Watch extends from the North Carolina/Virginia border to Cape Henlopen, DE and from Woods Hole, MA to Sagamore Beach, MA. Tropical Storm Warnings are posted from the North Carolina/Virginia border to Sandy Hook, NJ. A Tropical Storm Warning means tropical storm conditions are likely within 36 hours, A Hurricane Watch and a Tropical Storm Watch means that those conditions are possible within 48 hours. A Hurricane Warning means that hurricane conditions are expected in the warned area with the onset of tropical storm force winds expected within 36 hours. Tropical Storm winds are considered to be 40 to 73 mph and winds are considered hurricane force at 74 mph. Remember, these are sustained winds, not gusts. Winds can gust to at least 20% higher than the sustained winds. It is not uncommon with a hurricane for a region to experience continuous hurricane force winds for many hours. Most people who survive “riding out” a hurricane swear they will never do so again. Wind is only part of the story as torrential rain is always a part of a hurricane and the storm surge associated with any hurricane is typically the gravest life taker. People generally have no idea just how powerful the sea can be. Click here for to find the storm surge probability forecast for your region.
By midday on Wednesday, Hurricane Earl had continued its gradual curvature around a big fat ridge extending from the Atlantic. As the ridge continues to move eastward, Earl will continue its right hand shifting and will eventually be moving due North. By late Thursday, the long anticipated trof moving across the northern United States will be close enough to pick up Earl. The result will be an increase in forward speed as well as a turning of the storm; first North-Northeast and eventually Northeast. The timing of the trof will be the determining factor as to the precise track of Earl up the East Coast, particularly off of New England. The variable is so slight that no one can say with certainty how it will play out. An hour or so timing difference of the trof’s influence on Earl can make the difference between the storm staying offshore or running over land. Suffice it to say, it will be at least a close call and no one along the NE Coast of the United States will escape some affect of Hurricane Earl.
While the shearing winds from the Southwest ahead of the trof and the dry air trying to work its way into Earl may serve to limit its intensity, forecasts continue to call for a major hurricane with winds of 100 to 120 mph running just off the North Carolina, Virginia, Maryland and Delaware coasts. By the time its off the New England coast, it will be probably scooting along at least at 30 mph and winds will have diminished from weakening due to the shearing winds that mess up its upper support as well as colder water. Tropical Cyclones need surface water temperatures of at least 80 F current coastal conditions from off of Delware northward fall below that level. Farther out though, in the Gulf Stream, waters remain above 80 F extend a shade farther north. However, hurricane conditions may still be probable for Long Island and Cape Cod, if not the mainland of the New England states. The official track keeps the storm offshore but it would not take much of a deviation, say 20 miles, for the eye of the hurricane to run right over Long Island and perhaps Cape Cod or Nantuckett Island. While its not entirely likely, it is not totally out of the question for Earl to actually make at least a partial landfall on some portion of the mainland.
While the winds may back off as it heads farther North, the increase in forward speed may serve to enhance the storm surge to the right of the storm. Further, given that Earl was a big bopper, the sea will not necessarily react as quickly to diminishing winds so the surge may be on the top end of the normally expected storm surge associated with a minimal hurricane running up the East coast. So, when you hear the forecasts call for a category 1 hurricane off the Jersey shore of off of the New England coast, it would be advisable not to pooh-pooh it as the destructive potential of a category 1 hurricane can be somewhat excessive.
Behind this is Tropical Storm Fiona which has been experiencing some difficulty as the outflow from Earl has been disrupting its outflow. Aside from its intensity, the same trof that is picking up Earl will most likely pick up Fiona as well, regardless of its strength, and should turn it north well before it threatens the US coast. Behind Fiona is a Tropical Wave (Invest 98) and Tropical Depression 9 which was designated at Tropical Storm Gaston at 5pm EDT September 1. Invest 98 appears to be running over the same worked-over water as Danielle, Earl and Fiona and may have a difficult time developing. However, Tropical Storm Gaston is farther south and the initial modeling data suggests its track will be more westerly and as it will be far enough south as to not be influenced by any trofs farther North. While there is no data currently showing a rapid intensification, a few models do indicate that it will develop into a hurricane and the general track would suggest the potential exists for it to some day affect the US coast from the Gulf of Mexico to the East Coast. It’s a long way out and there are many scenarios so there will be time to monitor its development.
HURRICANE EARL DISCUSSION NUMBER 30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010
500 PM EDT WED SEP 01 2010
VISIBLE SATELLITE IMAGES INDICATE THAT THE EYE HAS BECOME VERY
DISTINCT…WITH OJECTIVE T-NUMBERS OSCILLATING AROUND 6.0 FOR THE
PAST FEW HOURS. AN AIR FORCE PLANE MEASURED FLIGHT-LEVEL WINDS OF
138 KNOTS AND A MINIMUM PRESSURE OF 941 MB IN THE LAST FIX.
HOWEVER…SFMR MEASUREMENTS WERE A LITTLE LOWER. A COMPROMISE OF
THESE DATA SUPPORTS AN INITIAL INTENSITY OF 115 KNOTS.
HOWEVER…EARL COULD FLUCTUATE IN INTENSITY DURING THE NEXT 12 TO
24 HOURS BUT SHOULD BEGIN TO GRADUALLY WEAKEN AS IT REACHES
COOLER WATERS AND MOVES INTO HIGHER SHEAR BEYOND 36 HOURS. BY DAY 5
THE HURRICANE SHOULD HAVE BEEN ABSORBED BY A LARGE EXTRATROPICAL
CYCLONE WELL NORTH OF CANADA.
SATELLITE AND RECONNAISSANCE AIRCRAFT FIXES INDICATE THAT EARL
HAS BEEN MOVING RELENTLESSLY TOWARD THE NORTHWEST OR 310 DEGREES
AT 15 KNOTS. THE HURRICANE IS ABOUT TO REACH THE WESTERN EDGE OF
THE SUBTROPICAL RIDGE AND SHOULD BEGIN TO TURN MORE TO THE
NORTH-NORTHWEST AND NORTH LATER TONIGHT AND THURSDAY. IN ABOUT 36
HOURS OR SO…THE HURRICANE WILL ENCOUNTER THE BASE OF THE
MID-LATITUDE WESTERLIES AND SHOULD BEGIN TO RECURVE OR TURN TO THE
NORTHEAST WITH AN INCREASING FORWARD SPEED. THIS IS THE SOLUTION
CONSISTENTLY PROVIDED BY TRACK MODELS…WHICH HAVE EARL PASSING TO
THE EAST BUT NOT FAR FROM THE OUTER BANKS OF NORTH CAROLINA ON
THURSDAY NIGHT. ONLY A SMALL WESTWARD DEVIATION OF THE TRACK TO THE
WEST WOULD BRING THE CORE OF THE HURRICANE TO THE COAST.
GIVEN THE FORECAST TRACK…THE LARGE SIZE OF THE WIND FIELD…AND
THE EXPECTED INCREASE IN FORWARD SPEED WATCHES AND WATCHES HAVE
BEEN EXTENDED NORTHWARD ALONG THE EAST COAST OF THE UNITED STATES.
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/2100Z 26.3N 73.3W 115 KT
12HR VT 02/0600Z 28.4N 74.7W 115 KT
24HR VT 02/1800Z 31.7N 75.4W 110 KT
36HR VT 03/0600Z 35.1N 74.7W 100 KT
48HR VT 03/1800Z 38.5N 72.2W 90 KT
72HR VT 04/1800Z 46.5N 63.5W 60 KT
96HR VT 05/1800Z 58.0N 57.0W 40 KT…POST-TROP/EXTRATROP
120HR VT 06/1800Z…DISSIPATED