Category 2 Irene Approaches The Bahamas

By: Dr. Jeff Masters , 7:51 AM GMT on August 23, 2011

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As of 2am EDT, Hurricane Irene was located at 20.1N, 69.7W, 135 miles southeast of Grand Turk Island. It was moving west-northwest at 12 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 978 mb. Hurricane warnings have been issued for the northern coast of the Dominican Republic from the Haiti board to Cabo Engano, the southeastern and central Bahamas, and the Turks and Caicos islands. Hurricane watches have been posted for the north coast of Haiti from Le Mole, St. Nicholas to the Dominican border and the northwestern Bahamas. Tropical storm warnings are in effect for all of Haiti and the southern coast of the Dominican Republic from Cabo Engano to Santo Domingo.

5AM Update
As of 5am EDT, Hurricane Irene was located at 20.3N, 70.1W, 105 miles southeast of Grand Turk Island. It was moving west-northwest at 12 mph with maximum sustained winds of 100 mph, keeping it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 978 mb.

Figure 1 shows that Irene is maturing into a vigorous storm, with apparent waves in the western edge of the cirrus outflow.


Figure 1 IR satellite view of Irene taken at 135AM EDT, August 22, 2011

Track Forecast

Irene is forecast to move to the north-northwest, passing over all of the Bahama islands by Thursday evening, at which points it starts curving to the north. Irene is forecast to make landfall in the US near Wilmington, NC Saturday evening. However, it is important to note that this is not a definitive forecast, the average forecast error for day 5 is 250 miles. The timing of Irene's recurvature depends on how quickly several small troughs of low pressure in the Northeastern US move to the east. After Saturday, Irene may pose a threat to the mid-Atlantic coastline and locations further north, but it is too early to make a skillful forecast for those regions.

NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours, then reaching peak intensity at 130 mph (Category 4 storm) by 8pm EDT Thursday evening.

Forecast models and adaptive observations
The different forecast models are in rough agreement until Irene nears the Carolinas. The dynamical hurricane forecasting models, GFDL and HWRF, have Irene making landfall near Charleston, SC. NGFDL (a variant of the GFDL that uses NOGAPS for background conditions) has landfall near Morehead City, NC, and the GFS has Irene crossing the Outer Banks. The UKMET forecast track splits the difference, placing Irene near Myrtle Beach, SC at landfall.

To reduce the model spread, and improve the track forecast error, the NOAA Gulfstream IV and an Air Force WC-130J have been flying dropsonde missions north of Irene. A dropsonde is an meteorological instrument package dropped from a plane that can tell you the vertical profile of temperature, pressure, moisture, and winds. By flying these missions, the dropsondes can improve all of the numerical weather prediction models initial picture of the atmospheres, which improves the forecast. Also, NHC has asked NWS offices in the southeastern US that launch weather balloons to do so every 6 hours instead of the normal 12 hour frequency.


Figure 2 Official track forecast of Irene as of 2am.

5AM update
The 00Z ECMWF forecast is available and Figure 3 shows the maximum wind speed over the next week for the eastern coast of the US. Green indicates tropical storm force winds, while yellow and orange are hurricane-force winds. The important thing is not to fixate on the predicted landfall location, but to see that Irene's winds will affect areas far away from landfall. The GFS, not shown, agrees with ECMWF that Irene will have a large area of tropical-storm force winds associated with it.

Figure 3 Maximum wind-speed in mph from the 00Z August 23 ECMWF forecast for the next week.

Impacts

In the immediate future, Irene is expected to have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are forecast to reach the southeastern Bahamas and the Turks and Caicos sometime this afternoon or evening. These locations can also expect 5-10 inches of rain. Three to six inches of rain are forecast over northern Hispaniola, with isolated areas receiving up to 10 inches. This could lead to flash flooding and mudslides in mountaineous terrain. NHC is predicting a storm surge of 9-13 feet above normal tide level for the southeastern Bahamas and the Turks and Caicos.

Outside of the islands immediately impacted by Irene, it is my judgement that everybody living on the eastern coast of the US should monitor Irene and review their hurricane preparations over the next few days.

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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Gusting upto 40 on the TCI's

Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting charlottefl:
Well, I know what the slow down was once again:

The AB high has retreated slightly to the East, probably from the energy from the shortwave entering the picture, leaving her in fairly weak steering currents..



EDIT: Also of note, the Texas high continues to retreat into the GOM
thanks for posting that map. that was just what i was looking for. can you post some more for predicted and current. tia! what do you think irene is going to do?
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8 am models are still spread out from a SC hit to OBX. Im not buying a FISH storm yet. I think it will take a track similar to Hurricane Hanna.
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Hello to everyone. New recon has started.
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Quoting Waltanater:
So basically the opening is there for Irene to move up, but she has to have help in doing so, which may or may not be strong enough. If not, then would it safe to say that the system will be in a "neutral" steering environment, ie wnw @11mph as she has been moving? Maybe she won't be affected at all!


Correct. You could say that "pulses" in the overall circulation of the Bermuda/Azores high are little by little steering Irene to the WNW around its periphery until a larger force (i.e. TROF, upper level westerlies, etc...) picks it up.
Member Since: August 14, 2008 Posts: 4 Comments: 4972
Quoting Bayside:


Actually, some of the predicted paths for this storm look a lot like the path that Hurricane Hanna took in 2008, but that was a MUCH weaker storm than this one is (is going to be)...



Bayside - NOOOO, say it isn't so..... Seriously, take care and get your prep done. I'm taking the baby girl off to college (GMU) on Thursday, back after midnight, so I'm working my yard now. All these trees (and can't cut a single one - you and I are in the same boat with the CBP Act) - anyway, I'm prepping early and have reservations in place for a possible run to the west. May have to shift farther west if the track holds.
Member Since: June 19, 2006 Posts: 63 Comments: 4175
HH has taken off again.
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oh my bad gator23, was talking in general... wasn't going by the map..I should have said so...but i'm sure there are many that we can't all remember also..
Member Since: June 3, 2008 Posts: 0 Comments: 1930
Quoting Waltanater:
Yup. I saw that. Jogged WEST!!!


Definitely, Florida watch out!!
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P3 Orion



Formally know as "Lockheed Electra"

Member Since: October 26, 2003 Posts: 0 Comments: 363
Quoting Waltanater:
So basically the opening is there for Irene to move up, but she has to have help in doing so, which may or may not be strong enough. If not, then would it safe to say that the system will be in a "neutral" steering environment, ie wnw @11mph as she has been moving? Maybe she won't be affected at all!


15 years ago I would say yes. But now, the models have gotten so reliable, I would say the chances of it not going north are next to nil.
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724. CJ5
Quoting MahFL:
We've had 2 aircraft failures this year so far. Obviously not enough funding, sadly.


Mechanical issues are not directly related to funding, so I would say no, it is not obvious.
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Morning everybody.
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Quoting MahFL:
Jog left anyone ?
Yup. I saw that. Jogged WEST!!!
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Quoting TampaSpin:
As the old saying goes........"Strong Storm goes NORTH.....Weak Storm goes SOUTH" holds true again......and we need a trough too tho!!!!!


But because of the quickly growing size of Irene, it could affect it differently, I think....
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Quite a blowup of convection of the Georgia Coast that seems to have separated itself from the Trough. Not sure how this will affect anything but definitely something to check out!
Member Since: August 25, 2006 Posts: 1 Comments: 3025
719. MahFL
They only have 2 WD-P3's, I thought they had more.....
Member Since: June 9, 2004 Posts: 0 Comments: 3492
As the old saying goes........"Strong Storm goes NORTH.....Weak Storm goes SOUTH" holds true again......and we need a trough too tho!!!!!
Member Since: September 2, 2007 Posts: 178 Comments: 20439

Especially after Saturday...cant wait. Havent seen any good overhead waves in awhile..

Amen Gatorman98!!!
Member Since: June 3, 2008 Posts: 0 Comments: 1930
Quoting WxLogic:
Current steering level:



Next steering level (Cat3):



You can noticed on the above that a northerly component to Irene's motion is definitely possible in the short term as the weakness still quite open.

Yet currents are not moving things along it too fast as you can see in the WV SAT Loop.

In the image below, you'll see that Irene is elongated N to S and not "circular" in appearance which tells you that is attempting to get into that weakness but since it's so large it requires assistance to displace it from point A to point B. The yellow line represents a COL region or an area of low steering between a High and Low pressure.



Irene would continue to move slowly but the window is open for now for a more Northerly component if it wanted to.
So basically the opening is there for Irene to move up, but she has to have help in doing so, which may or may not be strong enough. If not, then would it safe to say that the system will be in a "neutral" steering environment, ie wnw @11mph as she has been moving? Maybe she won't be affected at all!
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Quoting Nolehead:

gator23

arnt the models bad at predicting large intense storms?


YES!! Prime example IVAN..goin N nope..kept on going west till it wanted to go north..models never had it right..


Well that and the Jeanne example someone posted. Heck even 1999 Irene was forecast for Tampa and was off by 300 miles. as was Charley
Member Since: August 26, 2008 Posts: 0 Comments: 2182
I just watched the archived NHC track for Hurricane Katrina to see how much it deviated from start to finish. Pretty interesting. They actually had a better handle on landfall at 4 days out than they did the day before it hit the coast. However the center of the cone shifted across 4 states in just the last 5 days prior to August 29th. A lot can change in a short amount of time.
http://www.nhc.noaa.gov/archive/2005/KATRINA_grap hics.shtml
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I love it when people think it's going out to sea...
Florida/Carolinas can still get direct hit at this point. Anyway, another HH took off.... without surface winds measurement or rain rate. *facepalm*
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Quoting Zaphod:
Why the expected drop from Cat 4 to Cat 3 as it approaches land? A slow moving big storm will move a lot of water. Even if the wind intensity drops a bit, I'd imagine surge will be unusually significant.


A mixture of increasing shear from the trough and dry continental air just off shore should weaken it slightly. But yes, you are correct in terms of storm surge. Katrina made landfall as a Cat 3, but produced a storm surge easily coherent with a Cat 5.
Member Since: August 10, 2010 Posts: 2 Comments: 1971

Quoting FLdewey:


Yeah that's where I was going.

Funding can't make an airplane failure proof.

Maybe they should buy a force field... yeah that's it.

*facepalm*
I bet it was the dam cappuccino machine the broke again
Member Since: September 9, 2010 Posts: 5 Comments: 1034
A lot can go wrong with an aircraft whether it is brand new or 30 years old.
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gator23

arnt the models bad at predicting large intense storms?


YES!! Prime example IVAN..goin N nope..kept on going west till it wanted to go north..models never had it right..
Member Since: June 3, 2008 Posts: 0 Comments: 1930
Anyone else find it strange that this storm has been a hurricane for nearly 24 hours and has yet to form an eye?
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Quoting Nolehead:
but just waiting to see which beach to go surf at...i do believe it's going to miss the E.C. but just always have that "well it could do...." but i'm sure there are a tone of boards getting ready for a good waxen!!


Especially after Saturday...cant wait. Havent seen any good overhead waves in awhile..
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H.Irene's_12pmGMT_ATCF : Starting 22August_12pmGMT and ending 23August_12pmGMT

The 4 shorter line-segments represent HurricaneIrene's path
and the westernmost line-segment is the straightline projection.

Using straightline projection of the travel-speed&heading derived from the ATCF coordinates spanning the 6hours between 6amGMT then 12pmGMT :
H.Irene's travel-speed was 11.3mph(18.2k/h) on a heading of 300.7degrees(WNW)
H.Irene was headed toward passage over DelectableBay(Acklins)Bahamas ~20&1/2 hours from now

Copy&paste 18.9n67.0w-19.3n68.0w, 19.3n68.0w-19.7n68.7w, 19.7n68.7w-20.1n69.7w, 20.1n69.7w-20.6n70.6w, axp, 20.1n69.7w-22.40n73.962w, upa, asd into the GreatCircleMapper for more info

The previous mapping (for 23August_6amGMT)
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Quoting Methurricanes:
100mph, 1978 mbs but no eye, lol



Still not Wrapped hard on the SE side......its coming tho.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting hurricanehanna:


Actually, some of the predicted paths for this storm look a lot like the path that Hurricane Hanna took in 2008, but that was a MUCH weaker storm than this one is (is going to be)...

Member Since: September 4, 2008 Posts: 0 Comments: 68
Jeff Masters - Flying into Hurricane Hugo Link at the top right of this page under links.
Link
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Member Since: September 10, 2007 Posts: 0 Comments: 11151
701. presslord
1:30 PM GMT on August 23, 2011
We will be having a conference call this evening at 8pm EDT to discuss Portlight's response to all this. We will focus tonight on how we may be of assistance to our friends in the Bahamas and T & C islands. If you'd like to join, please WU mail me and I'll send you the call in # and participant code.
Member Since: August 13, 2007 Posts: 0 Comments: 10490
700. Bobbyweather
1:30 PM GMT on August 23, 2011
Quoting Methurricanes:
100mph, 1978 mbs but no eye, lol

there is an eye, just not closed. See recon info from just a couple of hours ago.
Member Since: September 7, 2006 Posts: 89 Comments: 2655
699. WxLogic
1:30 PM GMT on August 23, 2011
Quoting Methurricanes:
Why dont the Hurricane Hunters use Jet airplanes?


Jets have a higher turbulence penetration speed than prop planes to ensure structural stability. Prop planes are easier to maneuver and have far better structural stability for such (not all prop planes of course, but those made for such severe/demanding) conditions.
Member Since: August 14, 2008 Posts: 4 Comments: 4972
698. overwash12
1:30 PM GMT on August 23, 2011
Quoting yesterway:


20 miles east of Gainesville, Fl in Melrose...
You should be fine according to the Track then,we will see how this plays out here in Knotts Island,N.C.
Member Since: June 24, 2007 Posts: 0 Comments: 1471
697. NCSaint
1:29 PM GMT on August 23, 2011
Quoting Orcasystems:


Those planes are not getting any younger... I wonder what the hour ratios are?

Hours Maint per hour flying?


Actually they are now flying the WC-130J which was initially fielded around 2003. Judging by the way the data stopped feeding shortly after takeoff from San Juan, my guess would be they lost their satellite link, possibly an onboard SatCom radio set issue, but it could have been any number of things. Anyway, they are new aircraft (in terms of typical aircraft life spans) that just had a problem. It's not any different than the new car you buy burning out a headlight the day you drive it off the lot...it happens. But you NEVER intentionally take an aircraft with a known problem into that type of flight environment, no matter how minor the problem may seem to the casual observer
Member Since: September 13, 2010 Posts: 0 Comments: 75
696. MahFL
1:29 PM GMT on August 23, 2011
Quoting charlottefl:


You do not want to use jet engines in heavy rain fall and strong turbulence, they're not designed for it.


They do have jet engines actually, driving a propeller, they are known as Turboprops. They give very good fuel efficency at the heights the HH fly.

Also the P3 was designed to fly slow and low hunting Soviet submarines, so they are built like brick shit houses. They are though like us all, getting older.
Member Since: June 9, 2004 Posts: 0 Comments: 3492
695. Zaphod
1:29 PM GMT on August 23, 2011
Why the expected drop from Cat 4 to Cat 3 as it approaches land? A slow moving big storm will move a lot of water. Even if the wind intensity drops a bit, I'd imagine surge will be unusually significant.
Member Since: October 5, 2005 Posts: 15 Comments: 3239
693. gator23
1:28 PM GMT on August 23, 2011
arnt the models bad at predicting large intense storms?
Member Since: August 26, 2008 Posts: 0 Comments: 2182
692. AllStar17
1:28 PM GMT on August 23, 2011
Quoting Methurricanes:
100mph, 1978 mbs but no eye, lol


Wow! Now that's HIGH pressure!
Member Since: June 29, 2009 Posts: 13 Comments: 5313
691. belizeit
1:28 PM GMT on August 23, 2011
Quoting MoltenIce:
Good God, that's massive. EF3-4 equivalent?
We here don,t know anything about tornados but it also looks huge to me i think this is probably the first tornado capured in a photo in Belize
Member Since: January 10, 2010 Posts: 0 Comments: 920
690. AllStar17
1:26 PM GMT on August 23, 2011
If Irene gets west of 75W, a Cape Hatteras scrape at least would seem likely.
Member Since: June 29, 2009 Posts: 13 Comments: 5313
689. Methurricanes
1:26 PM GMT on August 23, 2011
100mph, 1978 mbs but no eye, lol
Member Since: August 1, 2011 Posts: 0 Comments: 699
688. Diploid
1:26 PM GMT on August 23, 2011
Anyone else notice that there are no Dvorak T-numbers in any of the "discussion" statements made by NHC?

Are Dvorak numbers out of favor? I've always found them useful, especially when a storm is far out to sea and out of reach of direct measurement by the airplanes.
Member Since: September 27, 2010 Posts: 0 Comments: 4
687. NICycloneChaser
1:26 PM GMT on August 23, 2011
Quoting JNCali:

Soon it will be sub-contracted out to Jose's Crop Dusting


Let's try this again.

Speaking of Jose....

Member Since: August 10, 2010 Posts: 2 Comments: 1971
685. yesterway
1:26 PM GMT on August 23, 2011
Quoting overwash12:
Hey yesterway,where do you live,if I may ask?


20 miles east of Gainesville, Fl in Melrose...
Member Since: October 26, 2003 Posts: 0 Comments: 363

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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.