WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Earl significantly weakening

By: Dr. Jeff Masters, 9:54 PM GMT on September 02, 2010

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

Hurricane

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

Reader Comments

Quoting robj144:


What's the sustained winds there... like 50 to 60 mph?


I think he had a gust to 62 mph.
Quoting pottery:

Yeah. And I hope you are ded wrong!
I am going to keep watching Gaston, until.......


lol

Well I had a major forecast bust with Gaston, probably one of the biggest in my career. I was expecting him to be near Category 3 status five days from now.

Not likely to happen at this point.

Maybe he'll fool me again? :P
Quoting CosmicEvents:
I don't know nearly enough about these things to say if it's anythng more than a 2% chance of a NYC hit, so I'm not disputing the result of what some model says.
.
.
I would say that if a major model like the GFS showed that(a NYC landfall) at this stage in the ballgame, it would require immediate and unprecedented action by the local authorities as they followed the lead of the NHC. If it's there, and it continues in the next run, we'd be talking mass evacs on a scale we've never seen before. Starting 5AM tomorrow.



Local met just said the NHC has written Gaston off, fizzled, blah, blah! He also said Earl had weakened because of land interaction. OK - I'm upstate, and it's the late broadcast, what the heck does this guy know about the tropics! ;-P
Frisco NC
2 am
Thunderstorms/Wind
76° F
Thunderstorms/Wind
76° F
100%
100%
From NNW 51 mph
1505. JLPR2
Quoting KoritheMan:


The MJO is a 30-60 day cycle of anomalous moisture/subsidence that originates in the Indian Ocean and gradually moves eastward across the globe, eventually reaching the Atlantic. The upward motion favors enhanced precipitation (rainfall and convection), which tropical cyclones need to thrive, and the downward motion favors decreased precipitation, and thus creates stable sinking air (known as "subsidence). This generally decreases the likelihood of storm formation in relation to the climatological norm.

What's really frightening though, is that we've had Colin, TD5, Danielle, Earl, Fiona, and Gaston develop during the downward MJO. When the upward motion gets here, look out. That dry air Gaston died from? Not a problem.


O.o
Now I'm nervous. XD
Quoting KoritheMan:


The MJO is a 30-60 day cycle of anomalous moisture/subsidence that originates in the Indian Ocean and gradually moves eastward across the globe, eventually reaching the Atlantic. The upward motion favors enhanced precipitation (rainfall and convection), which tropical cyclones need to thrive, and the downward motion favors decreased precipitation, and thus creates stable sinking air (known as "subsidence). This generally decreases the likelihood of storm formation in relation to the climatological norm.

What's really frightening though, is that we've had Colin, TD5, Danielle, Earl, Fiona, and Gaston develop during the downward MJO. When the upward motion gets here, look out. That dry air Gaston died from? Not a problem.

Okay I see.. so upward motion is expected and then we will really see action...right?
1507. pottery
Quoting smuldy:
i am just talking about the end of the run where it is off the coast of long island and then heads due west into southern CT and NYC. Storms air clouds nothing moves due west up there except airplanes. That synoptic setup would be a once in 100 years pattern and there is just no way that it will happen I would bet my life on it. Lived up there most of my life and never saw any weather move like that, it just doesn't happen.

OK I see now.
Thanks.
I wonder what the model is seeing to suggest that though?
Quoting KoritheMan:


The MJO is a 30-60 day cycle of anomalous moisture/subsidence that originates in the Indian Ocean and gradually moves eastward across the globe, eventually reaching the Atlantic. The upward motion favors enhanced precipitation (rainfall and convection), which tropical cyclones need to thrive, and the downward motion favors decreased precipitation, and thus creates stable sinking air (known as "subsidence). This generally decreases the likelihood of storm formation in relation to the climatological norm.

What's really frightening though, is that we've had Colin, TD5, Danielle, Earl, Fiona, and Gaston develop during the downward MJO. When the upward motion gets here, look out. That dry air Gaston died from? Not a problem.


I agree. This is just the beginning, unfortunately.

Quoting alexhurricane1991:
Like storm says this is the pre game to the main event.


Yup.

Quoting KerryInNOLA:
flak you, TaZ! Flak you!


LOL
Quoting btwntx08:


hmmmmmmm
Quoting smuldy:
i am just talking about the end of the run where it is off the coast of long island and then heads due west into southern CT and NYC. Storms air clouds nothing moves due west up there except airplanes. That synoptic setup would be a once in 100 years pattern and there is just no way that it will happen I would bet my life on it. Lived up there most of my life and never saw any weather move like that, it just doesn't happen.
Agreed.
No chance of weather moving like that. I lived there for 20 years. There's as much chance of the system moving west that quickly in that spot as there is that you could move that quickly on the LIE at 5PM on a Friday
1513. robj144
Quoting CaneWarning:


I think he had a gust to 62 mph.


That's not going to take out the awning. Although why is he in a gas station? That's the last place I'd be chillin' watching a storm.
new blog.
Just make it thru tonight and tmw and the east coast will be ready for visitors to vacation! The peak of the storm is coming soon and no big deal for them. :)
Quoting JLPR2:


O.o
Now I'm nervous. XD


We might end up tying or surpassing the record set by 2002 and 2007 of 8 storms in September.
1517. smuldy
Quoting pottery:

OK I see now.
Thanks.
I wonder what the model is seeing to suggest that though?
I only viewed it once but it appeared that it had a monster high north and east impeeding any movement but west, but it is wrong that pattern just doesn't happen. There would be a split between the high pressure in the Atlantic and the high pressure over northern new england that would allow for future Gaston to charge through, if it even did make any turn that far north to begin with. I really think that was just a bogus run and certainly feel both the ECMWF and 6z will have very different things to say.
Quoting SeniorPoppy:


I agree. This is just the beginning, unfortunately.



I beg to differ about the "unfortunately" part. I love to track these things. It's what I do for a living. I don't wish harm on anyone, but I absolutely love tracking.
NEW BLOG!!!!!!!!!
1520. pottery
Quoting KoritheMan:


lol

Well I had a major forecast bust with Gaston, probably one of the biggest in my career. I was expecting him to be near Category 3 status five days from now.

Not likely to happen at this point.

Maybe he'll fool me again? :P

That area of "gaston-weather' is about to enter 86 degree water temps....
Quoting txsweetpea:

Okay I see.. so upward motion is expected and then we will really see action...right?


Yep. Here's what the upward MJO currently is (green):



The brown colors indicate subsidence (sinking air, downward MJO).
1522. JLPR2
Quoting KoritheMan:


We might end up tying or surpassing the record set by 2002 and 2007 of 8 storms in September.


I think we are ahead of 98 right now and that's our best analogue year, maybe we'll have to change to 1995. :\
1523. smuldy
Quoting CosmicEvents:
Agreed.
No chance of weather moving like that. I lived there for 20 years. There's as much chance of the system moving west that quickly in that spot as there is that you could move that quickly on the LIE at 5PM on a Friday
as much chance as someone moving that quickly on the lie at 5pm on friday if the gfs showed that happening at 5pm saturday
Quoting KoritheMan:


What's really frightening though, is that we've had Colin, TD5, Danielle, Earl, Fiona, and Gaston develop during the downward MJO. When the upward motion gets here, look out. That dry air Gaston died from? Not a problem.


Would that have had an impact on Earl's troubles with dry air as well?
Moved to "1603"