Category 3 Hurricane Irene tracks northwest through the Bahamas

By: Dr. Jeff Masters , 8:55 PM GMT on August 24, 2011

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Hurricane Irene remains a powerful category 3 this afternoon, with maximum sustained winds of 120 mph. Irene is moving northwest through the Bahamas at 12 mph, and its center has cleared the northern edge of Crooked Island. The next islands in the path of Irene are Rum Cay (population 80) and Cat Island (population 1700), which it will encounter later tonight. Irene will track northeast of Long Island (in the Bahamas) over the next 24 hours. George Town has been reporting wind gusts up to around 40 mph this afternoon, and wind speed will likely increase during the next 12 hours as Irene's center passes about 30-40 miles to their northeast. Long Island in the Bahamas will likely see category 1 winds, which begin at 74 mph. Shelters on New Providence and Grand Bahama are open and ready for business, and Grand Bahama International Airport will remain closed until Irene passes.

Irene continues to look well-organized on satellite, especially compared to yesterday afternoon. Since then, intense upward motion, and therefore strong thunderstorm activity, has encompassed the center on all sides, which has led to a well-defined eye. Throughout the morning, Irene's eye wall has shrunk, and a new eye wall could be developing, although it remains unclear at this point. If this is the case, it could lead to some temporary weakening of the hurricane, which would be good for the Bahamas. This afternoon, Irene's hurricane-force winds extend 50 miles from the center, and tropical storm-force winds extend up to 205 miles from the center. Earlier this morning, an Air Force Hurricane Hunter mission investigated Irene and a NOAA Gulfstream (Gonzo) is currently collecting data around the hurricane.


Figure 1. Microwave satellite imagery of Irene captured at 8am this morning. Image source: Naval Research Laboratory.

Track forecast for Irene
NOAA has continued dropsonde missions today, scouring the atmosphere for data as far north as the waters off of South Carolina. Every bit of upper-air data that the models can ingest will lead to better forecasts and decreased uncertainty. These missions are an investment that pay off. Irene will track through the central Bahamas today, the northwestern Bahamas on Thursday, and approach the Outer Banks of North Carolina on Friday. Beyond this there is a bit of divergence in the models. Both the GFDL and the HWRF are forecasting a landfall on Long Island, New York, and the ECMWF continues to suggest a landfall even further west than that. NOGAPS is still the eastern outlier, which misses the U.S. all together and makes landfall in Canada. Today the official track forecast from the National Hurricane Center agrees with the GFS forecast through Saturday morning, and then diverges ever so slightly to the west of that through Monday. It has become clear over the past 3 days that everyone on the East Coast from North Carolina to Maine should be prepared to feel impacts from Hurricane Irene.


Figure 2. Official track forecast provided by the National Hurricane Center.

Intensity forecast for Irene
Irene continues to be embedded in a large envelope of moisture, and wind shear is expected to remain low to moderate, 5 - 20 knots, for the next three days. With water temperatures very warm, 28 - 30°C, these conditions should allow for intensification to a category 4 hurricane (winds of 131 to 155 mph). The only reliable model that's not forecasting this intensification is the GFS, and this is likely due to its relatively course spatial resolution. The National Hurricane Center expects Irene to intensify to a category 4 tomorrow, with a decrease in intensity back to a category 3 on Friday.

Links
For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, check out the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

Our Wundermap is also a great resource for tracking hurricanes, with the ability to turn on multiple layers of data, including satellite, official track forecast, and current weather observations from not only the U.S. but the Caribbean and Bahamas, as well. Here's a link to get you started.

Angela

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3068. jonelu
Quoting GaleWeathers:


I don't see any problem with being cautious. I, too, am on the SE coast of Florida and am keeping an eye on it. That doesn't mean we are freaking out, but just wondering what is possible.

Luckily, I'm assuming most SoFla people took care of their preps earlier in the week when the models were pointing at a Palm Beach landfall. With this in mind, most should be able to rest easy. The only sticking point is if it were to come ashore as a Cat 4.

I'm still thinking the most we will get is a swipe up the coast. Still, it doesn't hurt to keep an eye on her.
I agree...you never know...better safe than sorry..
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Quoting jonelu:
Can someone post the latest Euro?


Link to the 00z Euro loop.
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Quoting DFWjc:


And if by morn it's at 79W, what then?


Given the N tendency, you just put everything from Savannah to the OBX in the cone, depending on the timing and strength of the shortwave; it won't happen though; she'll end up west of the track point, the trof will move in start to lift her and the net result will be Wilmington back in the crosshairs, most likely. The high is building in from the east but that pesky little trof will have a pretty noticeable effect (in fact, already is)
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New surf forecast for the northeast, with analysis of trough coming from Canada:

http://www.nesurf.com/reports.html
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3064. jonelu
Can someone post the latest Euro?
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I posted a blog a couple days ago that gives the time and height of the highest tide of the day almost the southeast coast including North Carolina.

I guess I should have included all points up to Maine!

Sheesh I can't do all that. Too tired.
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Quoting jonelu:
I agree...but it's scary with her so close. I should just trust it and go to bed.


I don't see any problem with being cautious. I, too, am on the SE coast of Florida and am keeping an eye on it. That doesn't mean we are freaking out, but just wondering what is possible.

Luckily, I'm assuming most SoFla people took care of their preps earlier in the week when the models were pointing at a Palm Beach landfall. With this in mind, most should be able to rest easy. The only sticking point is if it were to come ashore as a Cat 4.

I'm still thinking the most we will get is a swipe up the coast. Still, it doesn't hurt to keep an eye on her.
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3060. JLPR2
Well I'm off to bed.
Also, dang! Not bad at all.

25/0545 UTC 12.3N 30.3W T2.5/2.5 90L

Satellite estimates love 90L
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Thanks everyone, going to sleep now. Interested to see if I have tropical storm watches or hurricane watches tomorow. That'll let me know how to prepare
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Quoting Dunkman:


I'm sitting at 72h so I can't see exactly but looks really close to Morehead. However, given the westward trend, I wouldn't exactly feel safe in Wilmington.


Thanks, keep me posted what happens with the rest of the run if you don't mind. Or atleast the next frame
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Quoting CarolinaHurricanes87:


May I ask where exactly? Sittin here in Wilmington getting nervous...


A tad inside of the Outer Banks. Overall not much of the change for the ECMWF, it's been the western solution for several runs now. There would be minimal effects in New England according to this model, since the system would go over New Jersey and have a slight west component.
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Quoting Skyepony:


Well it's good to see you.. You've been missed.

I'm off to sleep.


Thanks skyepony have a good night!
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Quoting CarolinaHurricanes87:


May I ask where exactly? Sittin here in Wilmington getting nervous...


Right around Morehead City as a Category 4 storm. Remember though it is just one run of one model. If it becomes a trend with the rest of the global models and if Irene continues NW-ward for a little longer later today then it might be time to get a little more concerned in NC.
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3054. Skyepony (Mod)
Quoting atmosweather:


Thanks much appreciated! I used to come here every night...particularly from 2005-2008. Been really busy with working and other things the last couple of years so I rarely get a chance to spend time blogging. I try to come when there is a storm that might threaten land areas or for major winter storms and severe weather outbreaks.


Well it's good to see you.. You've been missed.

I'm off to sleep.
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Quoting comments is messing up for me. Sorry.
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3052. scott39
If Irene continues to travel the same rate of speed she is now at the same direction....she will be about 20 to 40 miles S of the next forecast point. This could be significant for S/N Carolina IMO. Then again she could slow down turn and hit it. Im not going there with the Fl. scenerio. NO NEED IMO.
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3051. Dunkman
Quoting CarolinaHurricanes87:


May I ask where exactly? Sittin here in Wilmington getting nervous...


I'm sitting at 72h so I can't see exactly but looks really close to Morehead. However, given the westward trend, I wouldn't exactly feel safe in Wilmington.
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Quoting Floodman:
Yo make a very good point...Irene is very large and carries a great deal of atmosphere with her...hard to turn that much mass on a dime. Storms that make fairly drastic aspect changes tend to stall or sloow to a crawl before making a move like that. And again, as I said earlier, she appears to be moving a bit west of the forecast track; Levi made mention of 77W being critical and in looking at the map one has to agree; if she start that tendency northward she will not clear the OBX and in fact would tend to make landfall somewhere between Morehead and Wilmington...Camp Lejeune?

Back in 1991 when watching the weather channel, when it was still good, John Hope was talking about Hurricane Bob which had just passed west of 77 W. John Hope said that if Bob made it to 78 W a landfall on NC was practically inevitable, because hurricanes west of 78 W off the south Atlantic coast almost always make landfall from Cape Hatteras southward. Not always, there are some exceptions. But John Hope considered 78 W to be the key.

And of course, Hurricane Bob never reached 78 W and never made landfall in North Carolina. But he did hit New England.
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Quoting ConnecticutWXGuy:


Looks like more impacts for the NC coastline, according to the new ECMWF run. A direct hit, in fact.


May I ask where exactly? Sittin here in Wilmington getting nervous...
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Quoting Grothar:


You are quite adept at this. You should come on more often. Good analysis.


Thanks much appreciated! I used to come here every night...particularly from 2005-2008. Been really busy with working and other things the last couple of years so I rarely get a chance to spend time blogging. I try to come when there is a storm that might threaten land areas or for major winter storms and severe weather outbreaks.
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3047. Skyepony (Mod)
Quoting HurricaneHunterJoe:



what do the white lines just north of irene mean? they go west or sw. i see the lines around the highs go clockwise,its airflow and steering, right? why aew we paying attrntion to the bermuda high,but it seems the lines that go west dont count? or are they someting else?


Your looking at the steering chart for a storm between 990-999mb. You should be looking at this one.

Quoting Remek:


That's kind of tiny.

Unless you mean across rather than total length! :D


It was about 1/2 grown. Adults are only like 3foot. The younger & smaller the more poisonous. I don't remember seeing a snake awake like that at night. It's breezy..
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Quoting petewxwatcher:
Between 11 p.m. and 2 a.m. Irene moved 0.4 degrees N and 0.6 degrees W.

When looking at the 12 hour forecast position from the 5 p.m. NHC discussion on August 24 Irene is already 0.2 degrees west of the forecast position for 5 a.m.

I still don't think this is a Florida, Georgia or even South Carolina threat. But it's going to be very hard for Irene not to hit North Carolina. Already 0.4 degrees west of Cape Hatteras.


I'm figuring somehting between 77W and 77.2W at the 5AM point...not huge, by map standards, but tremendous in hurricane terms...
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3045. nigel20

Night guys.
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Quoting TheNewGuy:
00z ECMWF is looking very interesting so far.

I'll let it be a surprise for ya'll.


Looks like more impacts for the NC coastline, according to the new ECMWF run. A direct hit, in fact.
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Quoting Grothar:
Either dry air pocket or another EWRC.



The hurricane circulation has grown so much that cuba mountains are now in the way, upsetting Irene's symmetry.
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3042. Grothar
Quoting DFWjc:


And if by morn it's at 79W, what then?


Look for the fan.
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Decided to check - All day people have posted about the forecasts for Irene not showing it going further west than 77.0. Over the last few forecast advisories, the figure is now 77.4, at 26/1200Z so they have adjusted the forecast track westward due to the continued W component of Irene's motion, and expect it to retain some westward component for the next 24-36 hrs.
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3040. DFWjc
Quoting Floodman:


Yo make a very good point...Irene is very large and carries a great deal of atmosphere with her...hard to turn that much mass on a dime. Storms that make fairly drastic aspect changes tend to stall or sloow to a crawl before making a move like that. And again, as I said earlier, she appears to be moving a bit west of the forecast track; Levi made mention of 77W being critical and in looking at the map one has to agree; if she start that tendency northward she will not clear the OBX and in fact would tend to make landfall somewhere between Morehead and Wilmington...Camp Lejeune?


And if by morn it's at 79W, what then?
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Quoting Grothar:


I am a professor, but not of meteorology. Force of habit.


Lol it all makes sense :p
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3038. emguy
Quoting ConnecticutWXGuy:


18 hours ago it was moving at 290 degrees, now it's at 315. That is a curve and a change in mean direction in progress.


That directional information you are mentioning is a 6 hour mean. Not the direction the storm is actually moving on at this moment, it's just the longer term average.

It's probably a wobble that Irene has been on, but she has been running at about 285 degrees the last 3 hours. She is far enough west that she would have to move NNNW (alomst due North) to hit her next forecast point. Which she could accomplish if she is just wobbling due to eyewall dynamics and angular momentum due to islands. That said, she is closer to Nassau now than expected and she is currently west of track considering the shorter term guidance. By no mean does this mean a track change though. Even though there is still a small upper lavel cutoff in the Carolinas and another one gathering some pretty good steam in the eastern gulf (digging SW).
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Quoting atmosweather:


That's because those lines are showing the airflow existing from the circulation of Irene. The loop is from the 500-850 mb layer which is shallow and not the correct layer that will steer an intense hurricane, therefore Irene's circulation has a huge influence on the general shallow steering winds.
thank you . the highs are deep layer muchas gracias
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3036. Grothar
Quoting atmosweather:


That's because those lines are showing the airflow existing from the circulation of Irene. The loop is from the 500-850 mb layer which is shallow and not the correct layer that will steer an intense hurricane, therefore Irene's circulation has a huge influence on the general shallow steering winds.


You are quite adept at this. You should come on more often. Good analysis.
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Quoting Remek:


There is no "turn". It will be a gradual curve further NW, then N.


Yo make a very good point...Irene is very large and carries a great deal of atmosphere with her...hard to turn that much mass on a dime. Storms that make fairly drastic aspect changes tend to stall or sloow to a crawl before making a move like that. And again, as I said earlier, she appears to be moving a bit west of the forecast track; Levi made mention of 77W being critical and in looking at the map one has to agree; if she start that tendency northward she will not clear the OBX and in fact would tend to make landfall somewhere between Morehead and Wilmington...Camp Lejeune?
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3034. jonelu
Quoting petewxwatcher:
Between 11 p.m. and 2 a.m. Irene moved 0.4 degrees N and 0.6 degrees W.

When looking at the 12 hour forecast position from the 5 p.m. NHC discussion on August 24 Irene is already 0.2 degrees west of the forecast position for 5 a.m.

I still don't think this is a Florida, Georgia or even South Carolina threat. But it's going to be very hard for Irene not to hit North Carolina. Already 0.4 degrees west of Cape Hatteras.
She is still going thru eye wall replacement..so we have a wobble to the left. Maybe she will come 30 miles closer...not much of a game changer.
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Quoting AllStar17:
All I know is this is no turn:
LOL .... about as matter of fact as we ever see around these parts.

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3032. Grothar
Quoting scott39:
Will that raise the pressure?


It can. But as you know, storms do that frequently. Even very intense storms do not maintain that long. Some have broken records, but most fluctuate like this one has been doing for days. If any of you ever bothered to read my blogs, the answers are all there. :):):):)_
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Quoting ConnecticutWXGuy:


which is precisely what I was trying to say.


Yeah I know I was trying to educate the wishcasters a little lol.
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Quoting Remek:


A better Q might be - "Is it heading a solid due N yet?"


The answer is no and yes that would've been better.
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Quoting scott39:
will it go NNW first?


that would be logical lol
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3028. Remek
Quoting victoriahurricane:


But this isn't about when it's going to turn, it's about if it truly is a turn and not a bend or a curve and all sorts of nonsense like that. Asking when it will turn is different.


A better Q might be - "Is it heading a solid due N yet?"
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3027. KRL
2AM here in Delray Beach, FL. Just outside walking my dog and the first bands of gusty winds are now coming ashore in Palm Beach County.

You can already sense the ominous force of nature upon us.

Prayers out to all those who are going to experience the full brunt and wrath of Irene in the coming days.
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Quoting HurricaneHunterJoe:



what do the white lines just north of irene mean? they go west or sw. i see the lines around the highs go clockwise,its airflow and steering, right? why aew we paying attrntion to the bermuda high,but it seems the lines that go west dont count? or are they someting else?


That's because those lines are showing the airflow existing from the circulation of Irene. The loop is from the 500-850 mb layer which is shallow and not the correct layer that will steer an intense hurricane, therefore Irene's circulation has a huge influence on the general shallow steering winds.
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Quoting Ryuujin:


Those outer bands are really getting close to F...

Oh I almost said the "F" word.

Lets say the state where there are a lot of old people and oranges.. and a Mouse.


That starts with a C ;)
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Quoting petewxwatcher:
Between 11 p.m. and 2 a.m. Irene moved 0.4 degrees N and 0.6 degrees W.

When looking at the 12 hour forecast position from the 5 p.m. NHC discussion on August 24 Irene is already 0.2 degrees west of the forecast position for 5 a.m.

I still don't think this is a Florida, Georgia or even South Carolina threat. But it's going to be very hard for Irene not to hit North Carolina. Already 0.4 degrees west of Cape Hatteras.
12 miles out of position
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3023. Remek
Quoting Skyepony:
Had a 1 1/2' water moccasin at my back door at 1:50am. Kinda odd.


That's kind of tiny.

Unless you mean across rather than total length! :D

Oh, I see that's in feet. (Emily)Nevermind!(/Emily)


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3022. DFWjc
Quoting ConnecticutWXGuy:


The due north isn't supposed to happen for another 12 to 24 hours


I'll believe it when it happens, so far, it was supposed to turn more north two days ago and it didn't happen..
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3021. scott39
Quoting ConnecticutWXGuy:


The due north isn't supposed to happen for another 12 to 24 hours
will it go NNW first?
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Quoting Remek:


Where you been? People have been posting (yelling) questions and looking for a curve or turn N since early yesterday!


But this isn't about when it's going to turn, it's about if it truly is a turn and not a bend or a curve and all sorts of nonsense like that. Asking when it will turn is different.
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3019. Ryuujin
Quoting Grothar:


Not really, she just took a bite of dry air and she is trying to fix herself up again. See, they do that many times, especially on the western side, because most of the time they have already moistend their atmosphere to the east


Those outer bands are really getting close to F...

Oh I almost said the "F" word.

Lets say the state where there are a lot of old people and oranges.. and a Mouse.
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3018. Grothar
Quoting scott39:
Will that raise the pressure?


Wish you had not posted that. I made a spelling error. I had to go back and correct it. Give me a B- on this post please.
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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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