Category 4 Earl headed for a close brush with North Carolina

By: Dr. Jeff Masters , 3:16 PM GMT on August 31, 2010

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Powerful Category 4 Hurricane Earl is pulling away from Puerto Rico and the northern Lesser Antilles Islands, and is eyeing its next potential landfall--North Carolina's Outer Banks. Earl brought heavy rain and high winds to Puerto Rico and much of the northern Lesser Antilles yesterday, though it appears that the islands were spared major damage. One exception may be Anegada in the British Virgin Islands, population 200. The eye of Earl passed just north of Anegada at noon yesterday, and Earl's south eyewall probably brought sustained winds of 100 mph to the island. Second hardest hit was probably Anguilla. Amateur weather observer Steve Donahue at anguilla-weather.com estimated gusts of 100 mph on Anguilla; his anemometer broke at 88 mph. Winds in St. Thomas in the U.S. Virgin Islands remained above tropical storm force (39 mph) for five hours yesterday afternoon, peaking at 52 mph, gusting to 62 mph, at 4:49 pm. Heavy rains hit Puerto Rico, where radar-estimated rainfall amounts of up to 5 - 7" occurred. Earl brought waves of sixteen feet to San Juan, and waves at buoy 41043 offshore of Puerto Rico reached 31 feet early this morning.


Figure 1. Morning satellite image of Earl, taken at 10:30am EDT 8/31/10. Image credit: NASA/GSFC.


Figure 2. Radar estimated rainfall for Earl from the San Juan, Puerto Rico radar. Isolated regions of 5 - 7 " of rain occurred in three locations on Puerto Rico. The rays fanning out to east from the radar location marked with a "+" are due to mountains blocking the view of the radar.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast shows a moderate 10 - 20 knots of wind shear over Earl, due to upper level winds out of the southwest from a trough of low pressure to Earl's west. This moderate shear is predicted to continue through Friday, but should not appreciably affect Earl, since the hurricane is so large and strong. Ocean temperatures are a near-record 29.5 - 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content favorable for intensification. Earl is undergoing an eyewall replacement cycle, which may diminish its winds by 10 -20 mph for a day or so. However, the storm will probably regain strength after completing this cycle, and it is likely Earl will be a major Category 3 or 4 hurricane at its closest approach to North Carolina Thursday night and Friday morning. By Friday night, 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 night, when it could potentially make landfall in Massachusetts. Earl is more likely to be a Category 1 hurricane on Saturday morning, when it could potentially make landfall in Maine or Nova Scotia, Canada.


Figure 3. Swath of surface winds from Earl predicted by the 2am EDT Tuesday, August 31, 2010 runs of NOAA's GFDL model (left) and HWRF model (right). Hurricane force winds (yellow colors, above 64 knots) are predicted to stay off the coast. Tropical storm force winds (light green colors, above 34 knots) are predicted to affect coastal North Carolina, Massachusetts, and Eastern Maine. Winds between 58 mph - 73 mph (dark green colors) are predicted to small portions of the coast. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
The latest set of computer models runs from 2am EDT (6Z) this morning push Earl's projected track a little closer to the U.S. East Coast, and we now have two of our six reliable models predicting a U.S. landfall. The latest NOGAPS run shows Earl hitting the Outer Banks of North Carolina late Thursday night, then striking Southeast Massachusetts late Friday night, and Eastern Maine on Saturday morning. The HWRF model predicts a strike on Eastern Maine Saturday morning, but keeps Earl offshore from North Carolina and Massachusetts. None of the other computer models show Earl hitting the U.S., but several models bring Earl within 100 - 200 miles of North Carolina's Outer Banks and Southeast Massachusetts. It is likely that Earl will being a 12-hour period of heavy rain and tropical storm force winds of 39+ mph to North Carolina's Outer Banks, beginning on Thursday evening. NHC is giving Cape Hatteras a 12% chance of receiving hurricane force winds. By Friday evening, western Long Island, Rhode Island, and Southeast Massachusetts can expect a 6 - 8 hour period of heavy rain and tropical storm force winds of 39+ mph. NHC is giving Nantucket a 11% chance of receiving hurricane force winds. These odds are 4% for Boston, 6% for Providence, 5% for Eastport, Maine, and 11% for Yarmouth, Nova Scotia. 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. Keep in mind that the average error in position for a 3-day NHC forecast is 185 miles, which is about how far offshore Earl is predicted to be from Cape Hatteras three days from now. The average error in a 4-day forecast is 255 miles, which is about the distance Earl is expected to be from the coast of New England four days from now.

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 currents will be the rule, due to waves that will reach 10 - 15 feet in offshore waters. Waves from Hurricane Danielle killed two swimmers in the U.S. over the weekend and forced hundreds of water rescues along the U.S. East Coast. Earl's waves will be worse, and will likely cause millions of dollars in beach erosion damage.

Fiona
Tropical Storm Fiona is speeding west-northwest towards Hurricane Earl, but is unlikely to bring tropical storm force winds to the Lesser Antilles. Satellite loops show that heavy thunderstorm activity has increased in some of the outer bands this morning, but remains limited near the center. Wind shear is currently moderate, 10 - 15 knots, and the main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm.

Forecast for Fiona
Fiona is moving quickly to the west-northwest, at about 24 mph. This means it is catching up to Earl, which is moving at 15 mph. By tonight, Fiona will be beneath Earl's upper-level outflow channel. Strong upper-level winds from Earl's upper-level outflow and a ridge of high pressure to the northwest of Fiona will bring high levels of wind shear, 20 - 30 knots, to Fiona tonight through Friday, and probably arrest the storm's development. The scenario now called for by all the models is for Fiona to be drawn into the low pressure wake of Earl and turn to the northwest. Fiona will pass to the northeast of the Lesser Antilles, and will probably not bring tropical storm force winds to the islands. Fiona should then continue to the northwest and then turn north, passing very close to Bermuda on Saturday morning. It is possible Earl could destroy Fiona through high wind shear before Saturday.


Figure 4. Morning satellite image of Fiona. High level cirrus clouds flowing out from the center of Earl as part of its upper level outflow can be seen starting to impinge upon the western side of Fiona's circulation.

Danielle is dead
Tropical Storm Danielle has succumbed to the cold North Atlantic waters, and is no longer a tropical storm.

98L
A new tropical wave (Invest 98L) moved off the coast of Africa yesterday, and is centered a few hundred miles south of the Cape Verdes Islands. Strong easterly winds from the African Monsoon are creating a moderate 10 - 20 knots of shear, and the disturbance is currently disorganized. A large area of dry air lies to the north and west of 98L, and this will interfere with development. The latest SHIPS model forecast predicts shear will remain moderate, 10 - 20 knots, for the next five days, and some slow development of 98L is possible as it moves westward at 15 mph. NHC is giving a 10% chance of this system developing into a tropical depression by Thursday, and none of the computer models develop it.


Figure 5. Morning satellite image of 98L.

A rare triple threat in the Western Pacific
Over in the Western Pacific, we have an unusual triple feature--three named storms all within 700 miles of each other. A 3-way interaction between these storms is occurring, making for a very tough forecast situation. The storm of most concern is Typhoon Kompasu, which hit Okinawa today as a Category 2 typhoon. Kompasu is expected to recurve northeastward and hit North Korea on Thursday as a Category 2 typhoon. It is unusual for a powerful typhoon to thread the tight Yellow Sea and hit North Korea, and I don't know how prepared they are for strong typhoons. Kompasu is expected to hit the most populous region of North Korea, but the country is pretty mountainous, and a significant storm surge disaster is probably unlikely. In the South China Sea, Tropical Storm Lionrock and Tropical Storm Namtheun are moving through the straights between Taiwan and China towards each other. Neither are predicted to develop into typhoons, but heavy rains are occurring in Guangdong and Fujian Provinces, further exacerbating the flood conditions China has suffered this summer.


Figure 6. An unusual triple feature over the Western Pacific--three simultaneous named storms all within 700 miles of each other. Image credit: NOAA/SSD.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

I may have a short update this afternoon, once the latest models runs are available.
Jeff Masters

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Hi everyone!! Eow what a very active season!!!!
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Ok listen, I'm talking about overall is forcasting. If there is a chance of New England getting a direct hit does it matter who is telling me what is going to happen?

NHC - Should turn north any min now.

Local Met - Oh it not going to hit us?

Storm - going west on the next run

Who has been right so far.

Not that I don't believe the NHC cuz I do but I think Storm looks at things different and He is very good at it.
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1081. beell
Earl stationary for an hour or two. Then a jog to the N.
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Questions for Hurricane Have:

1) What is the strongest storm to strike the Tidewater VA area,....I grew up there and remember Donna in Sept. 1960, and Isabel in 2003, both were Cat IIs. Has anything stronger hit there?

2) At what point before Friday morning, can we feel confident of the Earl track prediction?
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1079. Walnut
The blog is really degrading... anyway, hope we can get back on track. When I see that model run that shows pretty much a clear basin in 10 days, that just seems off. Hard to believe the hot bathwater in the GOMEX will remain storm-free that long.
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Quoting sammywammybamy:
Why is Earl still moving Wnw... He Should have made the NW turn Monday night...


Looks like the gfdl might b on to something. Landfall Jacksonville NC
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Quoting Krycek1984:


Yes, as I stated once, I much prefer the night time on here...less drama and bickering, and it isn't as busy so you can be a little more free with what you say...and models come out around 1 AM too (or somewhere around there, I lose track of time after 11)! Only part that sucks is no visible satellite at night :(.


Past couple nights it was nice to have the radar...A rare bonus.
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Quoting NOLALawyer:


Are YOU joking? You think just because they are the NHC they know more than anyone? Do you think that the NHC is not partially steered by political and economic ramifications when predicting storms, paths and intensities? Someone like Storm is not beholden to many of the same restrictions as Mets at the NHC may be. I trust his assessments as much, if not more, than the NHC.


Well said.

The quality of forecasts (or decisions) is directly proportional to the experience of the forecasters, but inversely proportional to the # of people making the forecast.

If a politician or a self-important TV weatherman is "helping" to make the forecast decisions, confidence goes to zero.
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Quoting sammywammybamy:
Why is Earl still moving Wnw... He Should have made the NW turn Monday night...


The high has re-oriented and is stronger than forecast.

waiting game now to see if the weakness is still there.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting snotly:


Yep 57 states. What 18 letters of the alphabet does he need to use to make it clear to you guys?


Y so defensive.. lmao
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Quoting StormJunkie:


Hey SM, good to see you. You going to head over this way? Should have a crazy large break for the next few days.

Night shift also = no silver-backing

I think the drama starts up during the "in between data times" No more models, or updates for a few hours. Only thing to keep folks occupies is imagery, and the HH missions.


Yes, as I stated once, I much prefer the night time on here...less drama and bickering, and it isn't as busy so you can be a little more free with what you say...and models come out around 1 AM too (or somewhere around there, I lose track of time after 11)! Only part that sucks is no visible satellite at night :(.
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I thought some of you said Fiona was going to be the troublemaker for the CONUS but it is expected to head out to sea.
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Quoting StormW:


POOF!


not falling for that again huh storm? LOL
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting CosmicEvents:
I think that if you're looking for info about tropical weather and how it may effect you the smart thing to do is to listen to the following in this order:
1. NHC
2. Your local authorities
3. Dr. Masters
4. Anyone else of your choice on the Internet, be it weatherguy03, JB, Levi, StormW, me(lol), etc.
.
.
Use #3 and #4 to supplement what the NHC says. To me, this is just plain old fashioned good advice. Not knocking anybody, not even JB.
.
.
To each his own though, and if you want to trust your life/family/property to some guy on the Internet over the NHC, you can do that.


thank you. i will.
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Quoting DestinJeff:


depends on the time frame you're looking at. two or three days ago, he wasn't supposed to be where is he now.... barely in the cone, if at all.


I have been looking at track error and Earl has pretty much stayed in the cone for the forecasts for the last three days. Before that, not so much.

Data
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1056. 10Speed
Good old Earl really, really doesn't want to go where he has to go, does he. Quite a balker.
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Quoting surfmom:


Thank YOU!!! I shuddered when he typed that and thought "be patient -- he just doesn't know...."

those waves heights by the PR buoy are frightening
though I'm sure the Big Wave Boys are waxing their boards

Earl seems a lot like IKE in disposition - Nasty & Needs careful watching -

back2wrk lurk


Hey SM, good to see you. You going to head over this way? Should have a crazy large break for the next few days.

Night shift also = no silver-backing

I think the drama starts up during the "in between data times" No more models, or updates for a few hours. Only thing to keep folks occupies is imagery, and the HH missions.
Member Since: Posts: Comments:
1047. snotly
Quoting HadesGodWyvern:
57 states?


Yep 57 states. What 18 letters of the alphabet does he need to use to make it clear to you guys?
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Quoting angiest:


I've posted it several times in the last couple of days, showing how far off track he has been through his life. As have you.


A few of us have. Earl has remained west and south of the models the entire time. That's why I say observation is just as important as the math when forecasting
Member Since: July 23, 2010 Posts: 0 Comments: 133
1043. hcubed
Quoting StormW:


You don't think I know as much as them?


Not downplaying your experience and knowledge, but I can't walk up to my job and say "StormW's saying it's gonna be a bad one, can I evac?"

They'll only release us when the NHC tells us.

I use YOUR updates to get the "between-the-lines" data. Anything to get a few more hours to prepare.
Member Since: Posts: Comments:
Quoting CosmicEvents:
I think that if you're looking for info about tropical weather and how it may effect you the smart thing to do is to listen to the following in this order:
1. NHC
2. Your local authorities
3. Dr. Masters
4. Anyone else of your choice on the Internet, be it weatherguy03, JB, Levi, StormW, me(lol), etc.
.
.
Use #3 and #4 to supplement what the NHC says. To me, this is just plain old fashioned good advice. Not knocking anybody, not even JB.
.
.
To each his own though, and if you want to trust your life/family/property to some guy on the Internet over the NHC, you can do that.


Good point
Member Since: June 29, 2007 Posts: 0 Comments: 1136
1034. angiest
Quoting DestinJeff:


depends on the time frame you're looking at. two or three days ago, he wasn't supposed to be where is he now.... barely in the cone, if at all.


I've posted it several times in the last couple of days, showing how far off track he has been through his life. As have you.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1033. CJ5
Fiona needs a shape change..quickly..lol
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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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