Earl significantly weakening
Hurricane Earl has significantly weakened today. The Hurricane Hunters found a central pressure of 948 mb at 4:06pm EDT, a large 20 mb rise from the 928 mb pressure of the 5am EDT advisory this morning. The aircraft found flight level winds at 10,000 feet of 124 mph, which translates to surface winds at the boundary between Category 2 and Category 3 strength, 112 mph. However, the SFMR instrument on the aircraft saw top surface winds of just 98 mph. Satellite imagery shows that Earl is no longer as impressive--the eye is less distinct, and the hurricane has a lopsided appearance. Dry air and wind shear of 15 - 20 knots have chewed away at Earl's southwest side.
Earl has made its turn to the north, and is headed for a close brush with North Carolina's Outer Banks. Rain bands from the hurricane have reached the coast, as seen on long-range Cape Hatteras radar.
Figure 1. Afternoon satellite image of Earl.
Forecast for Earl
If you're wondering about your chances for receiving hurricane force or tropical storm force winds from Earl, I highly recommend the NHC wind probability product. The highest odds of hurricane force winds for any location on the U.S. coast are for Nantucket--25%. Yarmouth, Nova Scotia has the highest odds for Canada, 15%, and Cape Hatteras has the highest odds for North Carolina, 19%. The latest set of model runs from 8am EDT (12Z) this morning show little change to Earl's track, and the latest SHIPS model forecast also shows no surprises. Wind shear will remain moderately high, 15 - 20 knots, through Friday morning. This should allow Earl to maintain Category 2 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 hurricane early Saturday morning, when it will make its closest approach to New England. Earl is more likely to be a strong tropical storm early Saturday afternoon, when it is expected to make landfall in Nova Scotia or New Brunswick, Canada. The expected impacts on the coast should somewhat less than what I outlined in this morning's blog post, because of Earl's recent weakening.
Figure 2. Wind field analysis of Hurricane Earl from 3:30pm EDT Thursday, September 2, 2010. Note the asymmetry in Earl's wind field, caused by the storm's forward motion of 18 mph to the north at the time. The highest contour has top winds of 80 kt (92 mph) surrounding the "+" on the NNE side of Earl--the strong right front quadrant of the storm. However, winds in the left front quadrant (on the west side) were just 75 knots (87 mph.) The asymmetry is not nearly as great as what was observed at 9:30am this morning. Image credit: NOAA/AOML/Hurricane Research Division.
Fiona
There is little change in the forecast for Tropical Storm Fiona, which is struggling due to high wind shear, courtesy of strong upper-level northerly winds from Hurricane Earl's outflow. 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). Wind shear from Earl and dry air should keep Fiona from attaining hurricane status, and the shear may be strong enough to destroy Fiona.
Gaston dies
Tropical Depression Gaston lost its battle with dry air. Satellite imagery shows that Gaston no longer has a surface circulation, and NHC has declared the system dead. The latest SHIPS model forecast predicts shear will remain low to moderate, 5 - 15 knots, for the next five days, so it is possible Gaston could regenerate.
Figure 3. Afternoon satellite image of Gaston (left) and the latest tropical wave to move off of Africa (right).
New tropical wave
A large and well-organized tropical wave moved off the coast of Africa last night, and this wave has the potential to follow the pattern set by Danielle, Earl, Fiona, and Gaston. Several models do develop this system into a tropical depression early next week, and NHC is giving the wave a 10% chance of developing by Saturday afternoon. Wind shear is currently too high, 30 - 40 knots, for the wave to develop. However, once the wave reaches a point a few hundred miles southwest of the Cape Verdes Islands two days from now, wind shear will drop and development will be more likely.
There is also a tropical wave over Central Africa which will emerge from the coast in 4 - 5 days. Some of the models are predicting development of this wave, 7 or so days from now.
Links to follow today
Cape Hatteras weather
Cape Hatteras radar
Next post
I'll have an update in the morning, and Dr. Rob Carver will have a late-night update.
Jeff Masters
Reader Comments
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I once saw a hurricane grow out of a small cloud just like like that South of the Cayman Islands. Don't be fooled by appearances. It has happened before.
It's not just that one cloud. Look at the 850 vort and the upper level conditions. The cloud is not the reason I believe it will refire but it is indicative that regeneration is certainly more of a possibility than you might otherwise think.
Green:
This is true. I hope Gaston doesn't regenerate now or ever, but that may not be reality here as it could come back. However, I think Gaston is/was destined for the Caribbean whether or not it was strong or weak due to the strong ridge at 30N60W (see my Gaston projected path & discussion)
LOL, I was also trying to say its not the cloud that convices me, but the environment that convinces me. I guess I will be on standby to see if that clouds erupts at DMAX tonight.
? ... Not sure I understand your question...MJO is an oscillation, sort of a movement of energy through the atmosphere. It has a positive (upward) and negative (downward, unfavorable) phase. If it's strong it's well-defined, if it's not it's in the background. Hope that helps...
Gaston has struggled it's true and stalling has not helped but I still think he is more likely than not to recover.
Unfortunately things look favorable for the wave behind Gaston.
Kman for what it's worth, I consider you the "E.F. Hutton" of this blog when it concerns the tropics....jmo
I think you're right, I fear Gaston and the wave right behind him, I can only imagine if they tap into the warm waters from Eastern to the western Caribbean, frightful and worrisome to the least!
Needs to reclose its circulation, but yeah, I agree with the prognostication of regeneration.
For a more scientific viewpoint, the WUndermap shows the windfield to have moved the TS force winds about 20 miles to my SE - leaving me with the local mets and NWS forecast of 25-35 mph.
what is that in the gulf????
There's a whole lotta CAPE to work with in the Eastern Caribbean, from 2400 to 2800 Joules.
There's a slight capping inversion out ahead of him which could prevent him from firing good cells until Sunday.
Shear forecast to start relaxing gradually starting Sunday. The map shows the TUTT in the central Carib. so we'll have to see how that goes.
Steering shows a continued danger to the Windward and Leewards and a strong ridge setting up shop smack in the middle of the Atlantic.
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