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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Check out Irene's beauty spots.

Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting charlottefl:


It's microwave data, not radar, just FYI.. :)

MIMIC MICROWAVE HURRICANE IRENE


Thanks. I lost a lot of bookmarks when I switched my CPU
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Quoting oakland:


I agree which is why I haven't taken my guard down.


All true, we've all seen em change tracks before. I think generally a good rule of thumb is to keep a close eye on them until they clear your latitude. (Now there are a few exceptions to that i.e. Jeanne), but for the most part.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting charlottefl:


Irene has slowed down a lot, so until she resumes a decent forward speed, you're gonna notice all kinds of wobbles in track. Slow moving TC's usually move fairly erratically.


Thank you timewise does anyone know when aprox it is suppose to start taking that northward turn am in ft lauderdale so am a bit concerned have a midterm on monday i do not need any loss of power!!!
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Low level recon just left Link

The Gulfstream IV is also out, but Tropical Atlantic is not showing the flight and when I try to copy and paste the raw dropsonde data it results in an error.
Member Since: September 23, 2005 Posts: 14 Comments: 11215
Yeah, I have friends over there too. Hoping to hear something from them this morning. Something like "we're on our way to your house!" Hope they stay safe.
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damage multi billion storm jb
Member Since: September 11, 2010 Posts: 1 Comments: 4728
Quoting nash28:
LOL Oakland!!!

Well it worked while I lived in Tampa. For direct hits anyways. Still got raked by Frances and Jeanne though...

Anyways...Not letting my guard down. All it takes is a 6hr extended trek WNW and we're back in the landfalling crosshairs.


I agree which is why I haven't taken my guard down.
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Quoting oceanblues32:
Why does it look to me hat she is heading on the westerly track of the cone more than in the middle am i just seeing things... Just a weather lover nothing more...


Irene has slowed down a lot, so until she resumes a decent forward speed, you're gonna notice all kinds of wobbles in track. Slow moving TC's usually move fairly erratically.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting splash3392:
Good idea Nash but we have to convince her of starting that turn!


I'm all for that! My parayers go out to all of our friends in the Bahamas. They're gonna get it first.
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Living in South Fla, I won't feel comfortable until she starts her turn. Does anyone know the time frame when that is supposed to happen? Tonight?, tomorrrow a.m.?
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Why does it look to me hat she is heading on the westerly track of the cone more than in the middle am i just seeing things... Just a weather lover nothing more...
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Quoting weatherguy03:


Nothing for Florida as far as Watches or Warnings go. Expect some Gusty winds along the immediate coast and probably the biggest factor with Irene will be beach erosion and high surf.


Not to mention, depending on how close she get's short lived tornadoes in outer rain bands.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting vital1:
I just read on Twitter that Reed Timmer is taking the Dominator to try to intercept where Irene makes landfall. He said he's bringing a vertical radar. I'm usually a lurker, but thought y'all may find this interesting......or not:).
What is a Dominator? Is that the Terminators nagging wife telling him to take out the trash and mow the lawn? LOL!
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Quoting hurricanehunter27:
Thats not entirly true, HH did report a closed eye wall.


Yeah looks like that image was a few hours old.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting nrtiwlnvragn:
Almost complete on the eyewall



That's very impressive given Irene's proximity to mountainous terrain. Sort of indicates just how well-established all the other ingredients are at the moment...
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Good idea Nash but we have to convince her of starting that turn!
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Quoting Edisonian:
So, probably no watches or warnings for Miami/Ft. Lauderdale you think?


Nothing for Florida as far as Watches or Warnings go. Expect some Gusty winds along the immediate coast and probably the biggest factor with Irene will be beach erosion and high surf.
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Hey Nash , Hey Oakland. Grab some coffee and breakfast off the sideboard and get to work figuring this track out. We don't like the "I" girls up here in Hampton Roads. :)

Nash - glad to hear you've got the go bags ready. I think it's probably all timing from here on out as far as the mainland goes. The islands are just going to get hammered though - plenty of thoughts and prayers for our friends down there.
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Quoting KeyWestwx:
The storm looks stalled to me or she has slowed way down. She is lagging behind her projected path, I'd say. Maybe a little jog to the West. Good God! Why am I up this early!!!!!


She has slowed. Many times, this indicates the beginning of a turn around the ridge. However, looking at the steering maps this morning, she should still be on the WNW heading.
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Issue DOOMCon advisory and set DOOM lvl 4 on Friday.
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Almost complete on the eyewall


Member Since: September 23, 2005 Posts: 14 Comments: 11215
I think coastal areas of Broward and Palm Beach will get Tropical Storm Watches later today... if the storm's tropical windfield is 200 miles wide and she is 100 miles off the coast at her closest approach to us, then it could be expected that some areas will get tropical storm conditions hence the watch/warnings might be necessary.
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Quoting Edisonian:
So, probably no watches or warnings for Miami/Ft. Lauderdale you think?

If everything were to stay as it is now, parts of the east coast of Florida would likely go under a tropical storm watch in the morning, followed by a TS warning/hurricane watch tomorrow night or early Thursday. But so much depends, of course, on Irene's where and when...
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Quoting TampaBayWX:


Looks like a slight west jog to me anyone else agree???
The storm looks stalled to me or she has slowed way down. She is lagging behind her projected path, I'd say. Maybe a little jog to the West. Good God! Why am I up this early!!!!!
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I had a feeling that I would wake up and find Florida just about out of the cone of DOOOOOOM...looks like I am right. Unfortunately, that means my friends in the Bahamas will not be so lucky. Good luck to everyone over there!!
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IR seems to show a loss of deep convection near the core of the storm. It's likely that land interaction with Hispanola is holding Irene back from strengthening. Something that will soon no longer be as much an issue, though it will also have the southerly flow disrupted by Cuba as well.. But there is plenty of very warm water in the Bahamas to fuel the storm. Outflow on the Western side looks excellent, so shear looks to be no issue for further intensification once it moves away from Hispanola.
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How many flights are schedulsd for today?
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Quoting charlottefl:


Nope, still open to the S-SE, probably won't happen till she clears Hispanola, it's disrupting inflow into the system.

Thats not entirly true, HH did report a closed eye wall.
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LOL Oakland!!!

Well it worked while I lived in Tampa. For direct hits anyways. Still got raked by Frances and Jeanne though...

Anyways...Not letting my guard down. All it takes is a 6hr extended trek WNW and we're back in the landfalling crosshairs.
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Quoting bassis:


Could you post the link to this radar. TIA


It's microwave data, not radar, just FYI.. :)

MIMIC MICROWAVE HURRICANE IRENE
Member Since: December 18, 2006 Posts: 7 Comments: 2686
I just read on Twitter that Reed Timmer is taking the Dominator to try to intercept where Irene makes landfall. He said he's bringing a vertical radar. I'm usually a lurker, but thought y'all may find this interesting......or not:).
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Quoting GoWVU:
Well I feel a little better here in Charleston this morning, I know we are still in the cone but things are looking better for us. I hope all is safe in the Bahamas and north of us if that is where she goes. Have a great day all


still not completley out of the woods yet
Member Since: August 14, 2007 Posts: 0 Comments: 535
Got everything ready to go last night just in case we need to hop on I-26 and beat feet.

I would prefer the GFDL and the HWRF to shift east. But the slowdown has me a bit concerned. It's now a matter of a foot race. Will Irene get to moving and feel the shortwave? Or will she keep the slow pace which would allow the ridge to slowly build the western periphery back in, forcing her further to the WNW before the turn?

Fun fun.
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So, probably no watches or warnings for Miami/Ft. Lauderdale you think?
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Member Since: August 14, 2007 Posts: 0 Comments: 535
Quoting charlottefl:


Nope, still open to the S-SE, probably won't happen till she clears Hispanola, it's disrupting inflow into the system.



Could you post the link to this radar. TIA
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197. GoWVU
Well I feel a little better here in Charleston this morning, I know we are still in the cone but things are looking better for us. I hope all is safe in the Bahamas and north of us if that is where she goes. Have a great day all
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Good morning everyone.

Nash-just your offer to return to return to Tampa scared her away. Maybe it would work for the Bahamas too. :-)
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Quoting nash28:
Good morning everyone.

Another fun day of "where is she going?"

Hey Nash been awhile. I know you will be watching.
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Aqua - I would say come on up and have breakfast, but I don't think we'll be having lovely weather in Va Beach this weekend.

Keep safe Water Dog - and BREATHE, breathe, breathe!
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She sure didn't move much during the overnight. I expected a little more past Hispaniola.
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Wind Field Continues to Expand:

H= 50 miles out
TS= 205 miles out

She's gonna be a very large hurricane when she clears Hispanola.
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting trHUrrIXC5MMX:
almost there



Never ending creeping sun .. :-)
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Good morning everyone.

Another fun day of "where is she going?"
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Quoting MoltenIce:
Don't feed the trolls...

Yeah, but I've got a hangover and since we're at Doomcon 1......
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almost there

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Quoting Hurricanes12:
Honestly, the true beauty of meteorology is attempting to forecast the near impossible and waiting for it to happen. Basically, everyone will be incorrect sometimes and that's normal. Something you would never understand, howtheweater.

I have been trying to guess these things since the late 90's. MAYBE i got 3 right in all these years.
I leave it up to the NHC. OH good morning to all
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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.