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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728. CarolinaHurricanes87
1:53 PM GMT on August 24, 2011
Quoting cat5hurricane:

Very interesting observation. From what I can tell you now, I believe a track closer to the coast would ensue if that holds true. I'm gonna spend some more time looking at these and similar maps in the next couple updates of them.

I will say when this thing gets across the 75 degree latitude and has not resumed a true NW (310 degree) motion and/or more poleward, I will really start doubting the NHC current track for Irene.


Looks to me like shes already taking a bend NW. I believe the turn has begun, just may not be a sharp turn because of her strength
Member Since: August 4, 2011 Posts: 0 Comments: 631
727. hamla
1:52 PM GMT on August 24, 2011
has the stadium effect started in the eye yet???
Member Since: August 29, 2008 Posts: 0 Comments: 167
726. HiWay
1:52 PM GMT on August 24, 2011
Quoting knightdog:


For whom?


I'm believe like most that she's going to continue trending a bit more east, but if it followed the HWRF/GFDL path having the north eastern eye wall hit long island, the damage could be along the lines of the history channel show that came out last year. That's who.
Member Since: August 17, 2007 Posts: 0 Comments: 55
724. overwash12
1:52 PM GMT on August 24, 2011
Quoting OuterBanker:
OK, so it appears it is making landfall along the outer banks (OBX). Anyone willing to take a chance on where along the OBX? The OBX runs VA to rt 12, roughly 40 miles, rt 12 to Hatteras Ferry, add another 74 miles, plus 10 ish miles of
Ferry, plus Ocracoke and uninhabited islands (formerly Plymouth [cool ghost town]- 30ish?), so when you say the outer banks, you are speaking of 144 miles. Any chance that someone, anyone can get a little more specific?
Well it can only come ashore from Hatteras to the south as it will be coming up from the south.
Member Since: June 24, 2007 Posts: 0 Comments: 1479
723. WeatherfanPR
1:52 PM GMT on August 24, 2011
I just want to point out that even if Irene moves far from Florida. Some parts in Florida could feel some outer bands with rain, gusty winds or even Tornadoes.
Member Since: August 23, 2006 Posts: 0 Comments: 1592
722. Cat5Hurricane250
1:52 PM GMT on August 24, 2011
Flight level winds up another 5 knots
115 knots
(~ 132.2 mph)
Member Since: August 4, 2010 Posts: 0 Comments: 101
721. Stats56
1:52 PM GMT on August 24, 2011
Quoting FLdewey:


That story has been around for 40 years.


One reason I don;'t think muxh of you. Too full of yourself., imho

Texas residents told to write their SSN on their arms with a sharpie
Texans evacuate and hunker down

Associated Press - September 12, 2008 4:13 PM ET

GALVESTON, Texas (AP) - Instructions to write their name and Social Security number on their forearm in case of "something bad" were enough to finally persuade at least one couple to get out ahead of Hurricane Ike.

That was the request of the police chief in Surfside Beach, Texas, as Ike approached. The streets of the small coastal town were already knee-deep with water at that point.

An ominous warning from the National Weather Service that those staying behind in low-lying areas could be facing "certain death" has persuaded most in the evacuation zones to leave. A handful have stayed behind with the TV news crews.

Meanwhile, in Houston, residents have been streaming in and out of stores, stocking up on water, batteries, food and other emergency supplies. One man who had cut short a California vacation says he got home a bit late to board up the windows. He says he'll use tape to hopefully "keep things from flying around" and "hunker down."
Member Since: September 18, 2010 Posts: 0 Comments: 69
720. nrtiwlnvragn
1:51 PM GMT on August 24, 2011
Since Irene became a tropical cyclone (TD), HWRF has the lowest average track errors of the major models through 72 hours at about 125 km (~78 miles). Next would be the GFS at about 230 km (~145 miles). The ECMWF is not included since they will not allow their data to be made public, so no error available.
Member Since: September 23, 2005 Posts: 14 Comments: 11262
719. atmoaggie
1:51 PM GMT on August 24, 2011
Quoting Gorty:
IT MUST BE NOTED THAT THE GFDL HAS BEEN CONSISTENT WITH ITS WEST TRACK. THIS IS WHY I AM VERY CONCERNED FOR A HIT ON US AND FOR DEVASTATION IN NEW ENGLAND AND NORTHEAST.

THE HWRF HAS SHIFTED CLOSER TO THE GFDL.

THIS SITUATION SHOULD NOT BE TAKEN LIGHTLY.
If this makes you shout, then you should probably evacuate to Salt Lake City and do so right this very minute. I'm afraid you haven't the right mindset to effectively deal with the situation.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
718. HarryMc
1:51 PM GMT on August 24, 2011
Quoting OuterBanker:
OK, so it appears it is making landfall along the outer banks (OBX). Anyone willing to take a chance on where along the OBX? The OBX runs VA to rt 12, roughly 40 miles, rt 12 to Hatteras Ferry, add another 74 miles, plus 10 ish miles of
Ferry, plus Ocracoke and uninhabited islands (formerly Plymouth [cool ghost town]- 30ish?), so when you say the outer banks, you are speaking of 144 miles. Any chance that someone, anyone can get a little more specific?


I wouldn't even try. The current cone covers over 1400 miles of the east coast so it's a little sketchy at the moment.
Member Since: March 30, 2010 Posts: 4 Comments: 341
717. Orcasystems
1:50 PM GMT on August 24, 2011




It "appears" to have sped up a bit.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
716. angiest
1:50 PM GMT on August 24, 2011
Quoting MoltenIce:
Question here.

What are McTavish numbers?


A myth. Something someone made up to get a rise out of people.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
715. ncstorm
1:50 PM GMT on August 24, 2011
Quoting CarolinaHurricanes87:


We will get quite a show from the Atlantic as far as waves are concerned.... but im not expecting anything more than weak tropical storm conditions as the wilmington NWS says. If the track shifts west again I may move the yard furniture inside, but looking like quite the false alarm and a non-event for SE NC.

OBX is another story, hope they stay safe, Irene could have a huge impact on them...


I dont think we will be seeing weak tropical force winds..any little deviation to the left would put us in another scenario..Models are not gospel and until its 400 miles north of me, then I will feel better..
Member Since: August 19, 2006 Posts: 13 Comments: 16021
714. angiest
1:50 PM GMT on August 24, 2011
Quoting CarolinaHurricanes87:


Exactly. This huge shift from the central gulf to eastern gulf to south florida to SC to NC to the NE...... is going to make millions of people in these areas more likely to ignore future warnings and delay preparations. I know a forecast is what it is, but when they have been dead wrong every day this week, its like the boy who cried wolf... I fear people will take the threat less seriously when they seem clueless on the forecasting


NHC never forecast Gulf, and most people probably don't pay attention to the super long range models.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
713. msgambler
1:49 PM GMT on August 24, 2011
Quoting FLdewey:


That story has been around for 40 years.
Don't give a fat rat's backside how long the story has been around. That is what I had to do for Ivan and Katrina. I know for some on here ( their age that is) it may sound "old school" but I can remember 2005 quite well THANK YOU.
Member Since: February 27, 2010 Posts: 0 Comments: 1125
712. Ryuujin
1:49 PM GMT on August 24, 2011
People have got to take the GFS models with a grain of salt. The have a know trough bias, and tend be the eastern outlier on most models. Please if you are in the path of this storm, pay attention to it and the NHC/local mets, not to models.
Member Since: August 20, 2010 Posts: 0 Comments: 378
711. MoltenIce
1:49 PM GMT on August 24, 2011
Quoting dader:
Does anyone have the newest McTavish numbers on Irene? Will they be as high as Earl last year?
Question here.

What are McTavish numbers?
Member Since: August 11, 2010 Posts: 0 Comments: 784
710. cat5hurricane
1:49 PM GMT on August 24, 2011
Quoting air360:
I will be the first to say i do not know exactly what im looking at...so im really just using my basic understanding with this (which is why im asking for someone to explain)

Essentially what im tying to understand is that it looks like the gap is starting to get blocked off a bit from the bermuda high/ridge to the east if you look at the 0z compared to the 12z. %uFFFDIn the 0z the gap was huge..now it looks like its pushing all the way onto the NC coast. %uFFFDam i right in seeing this? %uFFFDWould this hold it closer to the coast than forecast?

12z



0z

Very interesting observation. From what I can tell you now, I believe a track closer to the coast would ensue if that holds true. I'm gonna spend some more time looking at these and similar maps in the next couple updates of them.

I will say when this thing gets across the 75 degree latitude and has not resumed a true NW (310 degree) motion and/or more poleward, I will really start doubting the NHC current track for Irene.
Member Since: August 17, 2010 Posts: 21 Comments: 6939
709. Floodman
1:49 PM GMT on August 24, 2011
Quoting Gorty:


Well said Gorty.


Only one thing to say to that:

BWAHAHAHAHAHAHA!

Dude, the "quoting yourself for effect" thing is one of my faves...

I'm not laughing at your supposition; you have valid concerns...as long as any reliable models are outliers then there is a chance that a nasty surprise could be coming...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
708. Grandpato4
1:48 PM GMT on August 24, 2011
Governor Purdue is giving a live new conference in NC.
Member Since: May 21, 2011 Posts: 0 Comments: 203
707. dader
1:48 PM GMT on August 24, 2011
Does anyone have the newest McTavish numbers on Irene? Will they be as high as Earl last year?
Member Since: September 6, 2008 Posts: 0 Comments: 165
706. Gorty
1:48 PM GMT on August 24, 2011
IT MUST BE NOTED THAT THE GFDL HAS BEEN CONSISTENT WITH ITS WEST TRACK. THIS IS WHY I AM VERY CONCERNED FOR A HIT ON US AND FOR DEVASTATION IN NEW ENGLAND AND NORTHEAST.

THE HWRF HAS SHIFTED CLOSER TO THE GFDL.

THIS SITUATION SHOULD NOT BE TAKEN LIGHTLY.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
705. ncstorm
1:48 PM GMT on August 24, 2011
Quoting yonzabam:


Yes.


so the center right now is 40 miles wide where the hurricane force winds are..if the center is 70 miles east of us, we would be feeling some strong tropical force winds instead of the weak tropical force winds the NWS is saying..
Member Since: August 19, 2006 Posts: 13 Comments: 16021
704. FLdewey
1:48 PM GMT on August 24, 2011
Quoting aussiecold:
Oh the models!!!!

Five days ago,Tampa was in the middle of the cone ,in two more days Irene will go to Ireland .
The only real and reliable track is the day to day by the storm itself,other than that ALWAYS models are wrong!!!


Hahahaha... yeah the "evolution of the cone" animation shows just how good they nailed it. ;-)
Member Since: August 19, 2008 Posts: 42 Comments: 6269
703. SPLbeater
1:48 PM GMT on August 24, 2011
Quoting CarolinaHurricanes87:


Exactly. This huge shift from the central gulf to eastern gulf to south florida to SC to NC to the NE...... is going to make millions of people in these areas more likely to ignore future warnings and delay preparations. I know a forecast is what it is, but when they have been dead wrong every day this week, its like the boy who cried wolf... I fear people will take the threat less seriously when they seem clueless on the forecasting


This is what i was raisin sound bout on Monday, the entire SE coastline shift. not the NHC i used to know. Hmmm. if this thing does miss the Carolinas my dad will never listen to me until its too late!
Member Since: August 4, 2011 Posts: 46 Comments: 4488
702. interstatelover7165
1:48 PM GMT on August 24, 2011
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 24th day of the month at 13:35Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number & Year: 09L in 2011
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 14
Observation Number: 11
A. Time of Center Fix: 24th day of the month at 13:15:00Z
B. Center Fix Coordinates: 22°09'N 73°35'W (22.15N 73.5833W)
B. Center Fix Location: 164 miles (264 km) to the WNW (287°) from Cockburn Town, Turks and Caicos Islands (GBR).
C. Minimum Height at Standard Level: 2,714m (8,904ft) at 700mb
D & E. Estimated (by SFMR or visually) Maximum Surface Wind: Not Available
F. Maximum Flight Level Wind Inbound: From 213° at 102kts (From the SSW at ~ 117.4mph)
G. Location of Maximum Flight Level Wind Inbound: 13 nautical miles (15 statute miles) to the ESE (118°) of center fix
H. Minimum Sea Level Pressure: 956mb (28.23 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 9°C (48°F) at a pressure alt. of 3,051m (10,010ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 3,050m (10,007ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 8°C (46°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Closed
M. Eye Shape & Diameter: Circular with a diameter of 18 nautical miles (21 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile
Remarks Section:
Maximum Flight Level Wind: 110kts (~ 126.6mph) in the northeast quadrant at 11:42:10Z

Anybody post this yet?
Member Since: August 18, 2011 Posts: 0 Comments: 994
701. OuterBanker
1:47 PM GMT on August 24, 2011
OK, so it appears it is making landfall along the outer banks (OBX). Anyone willing to take a chance on where along the OBX? The OBX runs VA to rt 12, roughly 40 miles, rt 12 to Hatteras Ferry, add another 74 miles, plus 10 ish miles of
Ferry, plus Ocracoke and uninhabited islands (formerly Plymouth [cool ghost town]- 30ish?), so when you say the outer banks, you are speaking of 144 miles. Any chance that someone, anyone can get a little more specific?
Member Since: August 8, 2008 Posts: 0 Comments: 39
Irene really seeking latitude now. Without an unexpected stregthening of the Atl high to her north, I wouldn't expect more than 76W at her furthest west extent.
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699. Gorty
Quoting knightdog:


For whom?


For me in western Mass.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
Quoting ncstorm:
can someone answer this..if the NHC forecasts has the storm passing 70 miles to our east (wilmington), are they speaking of the center (eye) passing to our east?


We will get quite a show from the Atlantic as far as waves are concerned.... but im not expecting anything more than weak tropical storm conditions as the wilmington NWS says. If the track shifts west again I may move the yard furniture inside, but looking like quite the false alarm and a non-event for SE NC.

OBX is another story, hope they stay safe, Irene could have a huge impact on them...
Member Since: August 4, 2011 Posts: 0 Comments: 631
Quoting msgambler:
2005 is not "OLD SCHOOL urban legend".


That story has been around for 40 years.
Member Since: August 19, 2008 Posts: 42 Comments: 6269
Oh the models!!!!

Five days ago,Tampa was in the middle of the cone ,in two more days Irene will go to Ireland .
The only real and reliable track is the day to day by the storm itself,other than that ALWAYS models are wrong!!!
Member Since: Posts: Comments:
Quoting msgambler:
2005 is not "OLD SCHOOL urban legend".


Thanks.. now I have to go and find a towel.. do you have any idea how hard it is to get coffee off a laptop.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting DVG:


It was about there 2am this morning edt.

yep. i see that... but not in the most recent observations, if i must clarify upon your need to clarify.
Member Since: Posts: Comments:
Quoting CoopsWife:


ROFLMAO - Amen to that! :)


You remember the slaughter of the trolls, do you? LOL
Member Since: August 2, 2006 Posts: 10 Comments: 9922
691. Jax82
Irene need to shoot the gap between OBX and Bermuda, but then she's nova scotia's problem. Either way, lots of beach erosion to occur on the East Coast. Jax Beach just spent $11 million pumping sand onto the beach right before hurricane season. That was smart.
Member Since: Posts: Comments:
Quoting HiWay:


The new GFDL and HWRF models, if accurate, would be absolutely devastating.


For whom?
Member Since: Posts: Comments:
I here in Nassau - bright and sunny right now. Eleuthera will get it bad.
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Quoting robert88:
6Z GFS ensembles..How far E will she go???


00Z ECMWF ensembles has it west..NC/SC dont let your guard down..
Member Since: August 19, 2006 Posts: 13 Comments: 16021
Good morning guys, are there any reports coming out of Turks and Caicos?
Member Since: November 6, 2010 Posts: 11 Comments: 8314
Quoting ackee:
90L looking good this morning


...and the models don't really have a handle on it, all over the place.
Member Since: Posts: Comments:
685. Gorty
Quoting rkay1:
Don't worry its just a matter of time before they get in line with the rest of em'. 



Negative... HWRF went WEST of the model consensus. It's only a matter of time till the model consensus goes west with the HWRF.
Member Since: November 8, 2008 Posts: 12 Comments: 1058
Ok - clearing off the breakfast buffet now and heading out to do a couple of quick errands (bird seed, fill the last 2 gas cans). Back later with lunch to see what it looks like at 11.

Member Since: Posts: Comments:
Quoting FLdewey:
The SSN on the arm thing? That's old school urban legend stuff.

Good times.
2005 is not "OLD SCHOOL urban legend".
Member Since: February 27, 2010 Posts: 0 Comments: 1125
..Irene , the Atlantic Lurking Death Star
.

Irene will clear the Planets outer Banks and head for New Jersey.

Fill the Arks,,we sail East the fleet does in the Morn outta Norfolk.

The Fleet is Hoisting the Colors for Storm
Member Since: July 3, 2005 Posts: 426 Comments: 129089
Quoting air360:

I will be the first to say i do not know exactly what im looking at...so im really just using my basic understanding with this (which is why im asking for someone to explain)

Essentially what im tying to understand is that it looks like the gap is starting to get blocked off a bit from the bermuda high/ridge to the east if you look at the 0z compared to the 1200.  In the 0z the gap was huge..now it looks like its pushing all the way onto the NC coast.  am i right in seeing this?  Would this hold it closer to the coast than forecast?

12z



0z


See the trough in the hole? Shortwaves are supposed to amplify that which is supposed to weaken the western edge of the high and that is what is to turn it N.
Member Since: Posts: Comments:
Quoting angiest:


There's a shortwave moving in which may reopen the gap between the ridges. Remember, you are looking at a snapshot that's good for about three hours.


Thanks! That makes perfect sense. I thought it might be something like that but wanted to make sure.
Member Since: Posts: Comments:
Quoting rkay1:
This is great that its looking like there will be no direct hit.  On the other hand, these forecasts definitely pranked the entire East coast.




i said she was going to be a sea rider now im beginning to wonder about long island with the strong high pushing IRENE back towards the nnw
Member Since: June 24, 2011 Posts: 0 Comments: 896
Wind field of Irene as of 8 am EDT...
As of right now, TS-force wind extend about 100 miles to the west of the eye. Hurricane force, about 45 miles. Maximum winds, 102 knots, 21 miles straight north of the eye.

Member Since: August 16, 2007 Posts: 6 Comments: 12463

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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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