Hurricane Irene Approaches the Bahamas

By: Dr. Jeff Masters , 7:42 AM GMT on August 24, 2011

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As of 2AM EDT, Hurricane Irene was located at 21.3N, 72.6W, 400 miles southeast of Nassau. It was moving west-northwest at 9 mph with maximum sustained winds of 100 mph, making it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 966 mb. Hurricane warnings have been issued for all of the Bahamas and the Turks and Caicos Islands. Tropical storm warnings are in effect for Haiti from Le Mole St. Nicholas to the Dominican Republic border.

Satellite Views
Figure 1 shows that Irene has a large eye visible in infrared imagery, (26 miles across accoring to a report from the Hurricane Hunters at 130AM) with well-defined outflow cirrus bands. Tuesday evening, TRMM, NASA's tropical research satellite, flew directly overhead Irene, getting a radar scan of the storm using it's downward pointing radar, shown in Figure 2. It is immediately apparent that Irene has well-developed bands of rain showers, with strong storms present in the eyewall.


Figure 1 IR satellite view of Irene taken at 113AM EDT, August 23, 2011


Figure 2 TRMM radar overpass of Irene at 713PM EDT, August 22, 2011. Image courtesy of the Naval Research Laboratory

Track Forecast

Irene is forecast to move to the northwest, passing over all of the Bahamas by Thursday evening, then curving to the north. Irene then makes landfall in the US near or at the Outer Banks Saturday afternoon, then traveling along the mid-Atlantic coastline of the US. After Saturday, Irene may pose a threat to Long Island and the New England coastline. However, NHC is quick to remind us that the average forecast error for day 4 is 200 miles, so don't stop your hurricane preparations if you aren't in the immediate area of landfall. It is also important to note that the windfield of Irene is expected to be large, affecting areas distant from the immediate track of Irene's center. Tropical storm forces winds are expected to be found out to at least 150 miles away from Irene's center on Friday afternoon.

NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours.


Figure 3 Official track forecast of Irene at 2AM EDT.

Forecast models and adaptive observations
The different forecast models are in fairly good agreement about Irene's track through the Bahamas and along the east coast of the US. The GFDL, a dynamical hurricane forecasting model, which had been a western outlier from the other models is now agreeing with them. When a set of weather models using slighly different initial views of the atmosphere and slightly different ways of simulating how the atmosphere works all agree on a forecast, then meteorlogists tend to believe that the forecast is more likely to occur. The 00Z GFS and ECMWF (wind swath shown in Figure 4) forecasts are nearly identical, which furthur boosts forecaster confidence.

In the 11PM forecast discussion, the NHC forecaster praises the NOAA Gulfstream IV (aka Gonzo) for providing infomation about the atmosphere around Irene that will influence it's track. Looking at the plan of the day valid for today, it will be a busy day for airborne reconnaissance. Three flights for the Air Force hurricane hunters, two flights for the Gulfstream IV, and two flights for NOAA 42, a WP-3D (aka Kermit).


Figure 4 Plot of the maximum sustained winds in mph over the next week from the 00Z ECMWF forecast.

Impacts

In the immediate future, Irene will have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are ongoing over the Turks and Caicos islands and southeastern Bahamas. These locations can expect storm surges that are 5-8 feet above tide levels. The northwestern Bahamas can expect hurricane force winds Thursday, and storm surges that are 7-11 feet above tide levels. The Turks and Caicos islands and all of the Bahamas can expect 6-12 inches of rain over the next two days.

I still think people living along the east coast of the US should closely monitor Irene and review their hurricane preparations. Irene will be a large storm, impacting areas far from the storm center track.

Dr. Masters will have a new blog entry this morning, and Angela Fritz will be covering the afternoon. I'll be back on third shift tonight.

Thanks for reading,

Dr. Rob Carver

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I will say this much for everyone living in FL, GA, SC, NC. Even if the storm does not make a direct landfall on your location, it is important to remember that outer rain bands in tropical systems already contain some level of rotation due to the spin of the storm. Small short lived tornadoes are not out of the question as the storm makes it's closest approach to your respective areas. Just something to keep in mind..
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1377. hamla
strong>Quoting ph34683:My dad is and will be on OBX tomorrow through the storm (even though I told him not to!)WB3CWK is his call sign/handle/ whatever you call it.

hi my call sign is N1RG been a ham since 1957
dont orry about ur dad us hams can handle these type of situations,is he from pa. with the wb3 call sign??
tks rick
n1rg bay st. louis ms.he can look me up on the qrz database
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2 hours of west wobble
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weather channel showing Irene is now moving NW at 12mph
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Irenes' satellite silouette reminds me of Andrews'...awesome. definately strengthening i believe
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1372. Ninj4

Quoting heavyweatherwatcher:

T-ville here as well... my 85 yo Mom is in Satellite Beach... If things change, I'll be makin speed to her place... for now its a 25% chance for low end TS force winds... but that was with a storm running up 77W... the wind feild (TS) is projected to be about 160NM to the NW/120 nm to the SW... each degree west of 77 moves the storm ~66 nm closer...
Bingo. I'm not going to delude myself or anyone else by saying we're going to get a direct hit, because that would just be stupid. But you're point is spot on, and it exactly why I'll be watching our girl until she's well out of our way. 50+mph winds are nothing to be willy nilly about, especially when I have a giant oak tree in my back yard waiting for a reason to come down.
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Quoting trinigal:
I just wanted to jump in here and say that while some like to mock others as 'Florida Wishcasters', I for one appreciate their posts. Being in Florida, I find it reassuring when people take time to explain WHY they don't believe that person is correct or what specifically would have to happen for that to occur. Until this girl is safely past, I don't mind Florida being kept in the discussion at all.


That actually holds true for each and every state that was and still is in the cone..not closing both eyes until she is due east of me and i am feeling no effects...
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Quoting FLWaterFront:
It probably is not a good idea to get all caught up in the wobbles. It is very common for a strengthening hurricane to wobble along its path, particularly when it is also in the process of making a significant turn. Philliesrock correctly pointed out a while back that for every wobble to the W or WNW there is a more or less equal wobble to the NNW.

So if you are going to fixate on the wobbles, thinking that this may mean that the storm is failing to follow the forecast track, don't forget to notice the wobbles that take place in any and all directions, not just one.


ALL wobbles do not have an equal and opposite wobble. Wobbles can be caused by many things and they may not be simple wobbles, but something more significant impacting the storm. Agreed, one cannot fixate simply on 1 wobble, but has to be looked at over time. In this case the last 2 or 3 satellite pics have shown a westward jog. Just have to see what happens next.
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Again....Just checking in. I will stick to what I have been saying...Irene will not make that sharp turn and clear 25N by 78W like the track has been saying for two days...East coast of Florida needs to watch this storm closely...
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here is another predict for the day....as the storm moves closer and closer to florida, we will see an exponential increase in south floridians coming in here trying to wishcast when what they need to be doing is battening down the hatches....



amazes me,....absolutely amazes me...
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Quoting Ninj4:
Titusville here and watching this thing like a hawk.

T-ville here as well... my 85 yo Mom is in Satellite Beach... If things change, I'll be makin speed to her place... for now its a 25% chance for low end TS force winds... but that was with a storm running up 77W... the wind feild (TS) is projected to be about 160NM to the NW/120 nm to the SW... each degree west of 77 moves the storm ~66 nm closer...
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I just wanted to jump in here and say that while some like to mock others as 'Florida Wishcasters', I for one appreciate their posts. Being in Florida, I find it reassuring when people take time to explain WHY they don't believe that person is correct or what specifically would have to happen for that to occur. Until this girl is safely past, I don't mind Florida being kept in the discussion at all.
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Quoting ackee:
90L looking good this morning


Good! At least a little interest in 90L, Yes it is looking healthy and moving west.
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Quoting RitaEvac:


that is a pretty good sized windfield there...ummm, includes even SC...BLAH!!!
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It probably is not a good idea to get all caught up in the wobbles. It is very common for a strengthening hurricane to wobble along its path, particularly when it is also in the process of making a significant turn. Philliesrock correctly pointed out a while back that for every wobble to the W or WNW there is a more or less equal wobble to the NNW.

So if you are going to fixate on the wobbles, thinking that this may mean that the storm is failing to follow the forecast track, don't forget to notice the wobbles that take place in any and all directions, not just one.
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Quoting Vero1:
And every 6 hrs NHC moves the points to the eye.



yah isn't it nifty how NHS can just make their best line, call it gospel, then when it doesnt happen they back up and say...naaa we had it called all along, look at our huge cone of predict....we know better....now washington fund us.......lol


and if nothing else, shift the cone....how can we ever be wrong?


bureaucratic job security = why even think, try, or care?
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I really can't see this getting to Florida, but I am relying on the NHC's expertise. I have a feeling it may stay a bit West of the guidance, but you never know. Like last year with Earl, it is all about timing.
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1360. Ninj4

Quoting SCwannabe:


Has the GFS gone a bit west...wasn't that one of the more easterly models??
Yes, the GFS has had a consistent easterly bias for a few days now.
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1359. snotly
GFS tends to be an east-caster sometimes, no one should let their guard down in the Continental US, NHC is still predicting landfall in NE, hopes and prayers for the SE Bahamas, they don't have the luxury of wish-casting at this point.

Quoting VAbeachhurricanes:
After 24 hours the 12 GFS is south and west of the 6z...

12z:


6z:
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Quoting waynehelpardNS:
We will have killer surf in NS if this pans out 120-144hrs

http://www.stormsurfing.com/cgi/display.cgi?a=nat la_height

Maybe literally as well as figuratively.
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Quoting hurricanejunky:
12Z NOGAPS and GFS both have Irene getting pretty close to FL coast...



Has the GFS gone a bit west...wasn't that one of the more easterly models??
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1356. Ninj4
Titusville here and watching this thing like a hawk.
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Quoting odinslightning:




yah, NHS i bet is hoping for a hard turn. but what's there 2 do it? nothing....and now she enters the shallow waters around Bermuda (hottest water in the Gulf Stream) with a bullseye on Miami.....


Bermuda? I think you musta skipped out on geography...
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Quoting odinslightning:



by friday??? it's wednesday morning. It's almost to 75W. Miami is 80w......r u sure about what your saying?


Yep, positive. Irene is not going to Miami.

The 2nd TROF (1st one just left) is coming down and will reinforce the weakness that pulls her NW/NNW and then N over the next two days... on Friday/Saturday, the 3rd TROF comes down into the Great Lakes, as stated by the NHC Discussion I posted.

Whether or not Irene continues to move NORTH instead of NNE/NE will be determined by how the TROF sets up at the Great Lakes... and the models won't have a good idea on that until Friday although they seem to favor a NNE motion as of now.
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1353. rv1pop
Quoting ILwthrfan:


Are you right in line with the NHC forcast? Or do you this still possible swaying furthur east or west with time? I have noticed that the trough over the midwest is a bit weaker than forcasted. I don't know what implications if any this would have?
NURTZ--- read the message--- do not brush off this storm "Just because it might miss you." your question might have a place, but not on this post.
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1352. KEEPEROFTHEGATE (Mod)
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Quoting Indialanticgirl:


yup same here!


Brevard county represents! :)
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More like due west


Quoting cat5hurricane:

Not significant. Right.
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Quoting MoltenIce:
A bit like 2003 I assume?


To be honest I don't remember the 2003 season. I remember 2004 when I was sationed in Jacksonville FLorida and we felt Frances as a Tropical Storm (Strong one). I will research on what he said and will post shortly. But US East Coast should be aware of this.
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Quoting kshipre1:
sorry, this is a dumb question on my part, but how do you read this map?

Take for example the down arrow lines to the left of florida and the kind of looping lines to the SE of SE Florida.

I am trying to learn more as I am not as experienced as most everyone on here, thanks

Don't assume that everyone else knows what they are talking about either. There are some with a good understanding, and you will soon work out who they are, but many really don't know that much and are here to learn and pick up information. I include myself in the latter category.
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NEW BLOG
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I can't figure this Blog stuff. Someone quoted Winston Churchill on 5 min. talk with average voter. He also said never never never give up. Read the Pulitzer Prize lists. America by far has more than any other two nations in the sciences. Must of them in one way or another where funded by the government. You should check out NOAA's draft of their plan of scientific integrity. This is obviously being done to prevent what you where talking about. The meddling of the uneducated in the science of the educated.
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Quoting ecflweatherfan:


Same here, Chris. I live just a few miles north of you, in Merritt Island. I will not be fully comfortable until this thing is past our latitude. Gusty winds on the way for us though, regardless, and the threat for isolated tornadoes... so just because we may not get the full fury, we are also not necessarily going unscathed, either.


yup same here!
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Quoting VAbeachhurricanes:
After 24 hours the 12 GFS is south and west of the 6z...

12z:


6z:




the 1st z run u have shown there doesn't even look accurate. how can that be. it shows it at 25N 75W its already almost to 75 w and no trough in sight.....models can't deal with the anomaly that started yesterday.
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Regardless of what happens, this storm is going to have a GIGANTIC wind field by the time it's in the NE, and that alone is gonna shock people up there. Put it this way, after the quake, and what is awaiting the NE, these folks will think the world is coming to an end literally.
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We will have killer surf in NS if this pans out 120-144hrs

http://www.stormsurfing.com/cgi/display.cgi?a=nat la_height
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Quoting philliesrock:
In the last 3 hours, Irene has wobbled almost due WNW rather than NW.

Also, the GFS is out to 33 and no major changes so far, except that it's a little SW of 6z so far.

Not significant. Right.
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NEW BLOG ENTRY
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In the last 3 hours, Irene has wobbled almost due WNW rather than NW.

Also, the GFS is out to 33 and no major changes so far, except that it's a little SW of 6z so far.
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ULHP is the first model to shift west.

Closer to Florida
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Quoting ecflweatherfan:


Same here, Chris. I live just a few miles north of you, in Merritt Island. I will not be fully comfortable until this thing is past our latitude. Gusty winds on the way for us though, regardless, and the threat for isolated tornadoes... so just because we may not get the full fury, we are also not necessarily going unscathed, either.


Very true neighbor, very true!
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Also, Irene's east side is flattening somewhat in latest satellite images. Shows it is being pushed west by the ridge just as suspected.
Member Since: September 2, 2008 Posts: 0 Comments: 744
Quoting CaneHunter031472:
Bastardi said yesterday that this year was going to be a East Coast year and now by looking at how the ridge is positioning itself I can see what he meant.
A bit like 2003 I assume?
Member Since: August 11, 2010 Posts: 0 Comments: 784
1334. rv1pop
Quoting Smikey:


'Ignore' is not working on Internet Explore 9 with Jason, its the embedded videos that are causing a major mess for me on the forum.
There is to 'strong' a cache in IE. Delete the current cache not just 24+ hours cache and it should be gone.
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Bastardi said yesterday that this year was going to be a East Coast year and now by looking at how the ridge is positioning itself I can see what he meant.
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1332. wxdrone
...which is why I won't discuss the OBX or NE today lol


"AND USERS ARE ONCE AGAIN REMINDED NOT TO FOCUS ON SPECIFIC FORECAST POINTS THREE TO FIVE DAYS DOWNSTREAM."
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Quoting VieraChris:
I live on the FL east coast just above Melbourne. Even if it is on NHC track, I'm not taking my eye off this one until it makes that more northerly turn. She's at 74WW Now and still moving slightly more west than north. I don't fully trust the model at this time.

Best wishes to and praying for all you folks in the Bahamas.


Same here, Chris. I live just a few miles north of you, in Merritt Island. I will not be fully comfortable until this thing is past our latitude. Gusty winds on the way for us though, regardless, and the threat for isolated tornadoes... so just because we may not get the full fury, we are also not necessarily going unscathed, either.
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Anticyclone is moving back over Irene. Which will mean shear will lessen and intensification will continue and will even ramp up more. Cat 4 Irene in the making.

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1329. snotly
cloud tops warming slightly...

Link
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1328. Mucinex
Quoting E46Pilot:



People still use IE, thats the problem. Use Mozilla Firefox, it is much better, and no problems.

The problem is that some of us are at work or accessing the site from locations were there is no choice but to use IE. The Admins have known this for years but have done nothing to fix it.

However, for those on IE, if you wait for the page to turn over, the blog will return to it's normal appearance.
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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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