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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Anyone using the intellicast interactive map? I just found it while searching for caribbean radar and it has a alot of cool features. Overlaying the model tracks on the of the satellite really shows how precise the models are with this storm.
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UHHHHhhh  I experienced an earthquake in LV.  The earthquake was in Joshua Tree and the EQ shook the heck out of us on the 29th floor of the RIO.  I also lived there for a while too and experienced some flash floods too!  So not perfect.  But I do like it.
Quoting Misogynist:
To all those who fear the weather, move to Vegas. It only gets hot and windy. Last 10 days of over 105. No storms, tornadoes, earthquakes, nothing all ways.

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CBJeff, To be honest it would be a alot more meaningful it was to be on 9-11-11. But it isn't. No offense intended. I'm just trying to oint out that 9-1-11 isn't an important date in history (off the top of my head anyway).
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Your never going to see a better fix then this :)

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Igor last year had 945mb at 90mph,and IMO cat2 landfall near NYC is possible,so it can be hmmm...935mb at 100mph
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When does the new cimss model gets released?
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370. Vero1
Quoting atmosweather:
9-1-1.
And almost made NYC on 9/1/11
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Quoting EastTexJake:
The Weather Channel just announced Cat 3 as of 8 am.

You probably know but the NHC sitis faster than TWC
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NOAA plane comes through with another fix around 955 mb.
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Quoting atmosweather:
9-1-1.


I wish that wasn't so ominous…
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To all those who fear the weather, move to Vegas. It only gets hot and windy. Last 10 days of over 105. No storms, tornadoes, earthquakes, nothing all ways.
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Here is a good site to walk you through it.

http://www.gearthblog.com/blog/archives/2008/07/l ive_hurricane_hunter_missions_in_g.html

Sorry can't link.
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The Weather Channel just announced Cat 3 as of 8 am.
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8:00 AM EDT Wed Aug 24
Location: 21.9°N 73.3°W
Max sustained: 115 mph
Moving: WNW at 9 mph
Min pressure: 957 mb
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LOCATION...21.9N 73.3W
ABOUT 55 MI...85 KM SE OF ACKLINS ISLAND BAHAMAS
ABOUT 335 MI...540 KM SE OF NASSAU
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...957 MB...28.26 INCHES
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Location: 21.9°N 73.3°W
Max sustained: 115 mph
Moving: WNW at 9 mph
min pressure: 957mb
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Quoting atmosweather:
114630 2157N 07320W 6972 02754 //// +164 //// 282008 012 /// /// 05

Since the pressure readings are off I like to use the geopotential height as a guide, and its gonna end up being around 2690 meters which is a full 100 meters lower than the 1AM center fix.



am off can you PM if they find some major wind and lower mb
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9-1-1.
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Quoting nrtiwlnvragn:
06Z HWRF 108 hours





HOUR: 108.0 LONG: -73.10 LAT: 40.40 MIN PRESS (hPa): 930.00 MAX SURF WIND (KNOTS): 87.00


06Z HWRF 108 hours ....
that scares me if that were to actually happen
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the blog is about to go bananas..

SATELLITE ANIMATION AND CENTER FIXES SHOW THAT THE EYE OF IRENE HAS
BEEN WOBBLING BETWEEN A WEST AND NORTHWEST HEADING OVER THE PAST
SEVERAL HOURS.
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Category 3 folks!
..IRENE BECOMES A CATEGORY THREE HURRICANE....EYE HEADED FOR THE CROOKED AND ACKLINS ISLANDS...
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Quoting msgambler:
How dare you!!you could be kicked out of the club for such remarks....LOL Morning E-Fly

Morning Gambler.....  Ive been out of the Club for a while...  LOL
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Quoting polarcane:
Gotta love the end of the Houston are forecast discussion this morning if you are any kind of Star Wars fan.

"BUT OVERALL NOT A LOT OF NEW HOPE ON THE HORIZON AS THIS
TATOOINE-LIKE CLIMATE PERSISTS. 41"



Watch out for the sarlacc pit!!
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Quoting Grandpato4:
Good morning. The folks are here putting up my hurricane shutters. I think I will delay my evacuation until tomorrow though because Irene just keeps shifting to the east.


Did you have that grouper granwich for me? Keep us informed, my house is not too far from yours, so I live vicariously through you from Europe.
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Quoting victoriahurricane:


Ok gotcha.

Anyways it's almost 5 am here in Victoria, so I better get some sleep, night all.


Night!
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351. A4Guy
you know...after watching these storms for so many years, I figured out that the best place to be is in the dead center of the 4 - 5 day cone....because by the time days 4 and 5 get here, the storm track has changed! I think Wilma was an exception. We were not inthe cone at all in SoFla...but once the track shifted dramatically to the east, once we were in the cone, we never came out!
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Irene's a major.

000
WTNT34 KNHC 241157
TCPAT4

BULLETIN
HURRICANE IRENE INTERMEDIATE ADVISORY NUMBER 16A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
800 AM EDT WED AUG 24 2011

...IRENE BECOMES A CATEGORY THREE HURRICANE....EYE HEADED FOR THE
CROOKED AND ACKLINS ISLANDS...
Member Since: August 23, 2008 Posts: 7 Comments: 5300
114630 2157N 07320W 6972 02754 //// +164 //// 282008 012 /// /// 05

Since the pressure readings are off I like to use the geopotential height as a guide, and its gonna end up being around 2690 meters which is a full 100 meters lower than the 1AM center fix.
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Quoting atmosweather:


The NHC site updates quicker than the decoder that most people use lol.


Ok gotcha.

Anyways it's almost 5 am here in Victoria, so I better get some sleep, night all.
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Quoting earthlydragonfly:
Where are you Grandpato?  You should be listening to your local authorities for evacuation plans not to this web site for sure!!!!  This is mostly a amateur website and would not consider anyone on this site an expert as to when evacuation should happen in your area.

How dare you!!you could be kicked out of the club for such remarks....LOL Morning E-Fly
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Information overload... all 3 HH's



Click to enlarge
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Irene and 90L...



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hey look what recon found


956.0 mb
(~ 28.23 inHg)
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Quoting victoriahurricane:
atmos how did you get the recon data so quickly? I was refreshing like a madman! lol


The NHC site updates quicker than the decoder that most people use lol.
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956 mb center now.
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Quoting leelee75k:
Grandpa, avoid the traffic, rush and stress and go have some fun with your daughter and grandkids.


Yeah, The last thing you want is to wait too late and get stuck in traffic. During Rita here in Houston the North bound Interstates were gridlocked for over 24hrs. with thousands of cars stuck without water and food, some running out of fuel. We did better during Ike, but if Rita hadn't turned North it would have been REALLY bad.

Anyway, beat the traffic, don't wait too long.
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Quoting wunderweatherman123:
reason irene is trending left is causing there is an ULL by south carolina, it trying to pull it more to the west thats why i think the nw motion wont start till tonight. this is one very close and dangerous storm



I noticed that ULL to of SC last night. And you're right! Sometimes they can "Pull" a system a little bit towards them.
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Quoting nrtiwlnvragn:


Believe it or not, ECMWF is in the same general area, GFS at ~960mb.

Edit Add: 06Z GFDL is in that area also
HOUR:114.0 LONG: -74.61 LAT: 40.07 MIN PRESS (hPa): 931.51 MAX SURF WIND (KNOTS): 77.20


The pressure doesn't really add up much with the winds. You can get it, but only usually after a EWRC or perhaps a landfall, but the pressure catches up quick.

Not sure why they're making it so low.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
atmos how did you get the recon data so quickly? I was refreshing like a madman! lol
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Do you have Google Earth with the Hurricane Hunter plugin?
Quoting splash3392:
296 yes i have a mac. Good Morning all.

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336. Vero1
NYC need to start replaying this!

History Channel Mega Disaster.

Can been viewed at: http://www.history.com/shows/mega-disasters
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Staying for one more update from recon after it goes through the center and then I'm off to bed.
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Oh and that also is the last record so we may even go higher on the next set of obs before recon hits the center
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296 yes i have a mac. Good Morning all.
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Good advice too as long as they are out of the path of Irene.
Quoting leelee75k:
Grandpa, avoid the traffic, rush and stress and go have some fun with your daughter and grandkids.

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Quoting Cotillion:


HWRF should lay off the fry up, obviously causing indigestion.

Only time you'll see 930mb that high up is with a windstorm around Greenland, Iceland and the North Sea.


Believe it or not, ECMWF is in the same general area, GFS at ~960mb.

Edit Add: 06Z GFDL is in that area also
HOUR:114.0 LONG: -74.61 LAT: 40.07 MIN PRESS (hPa): 931.51 MAX SURF WIND (KNOTS): 77.20
Member Since: September 23, 2005 Posts: 15 Comments: 11341
Quoting WeafhermanNimmy:


Wow next advisory 130 mph then.


Those are flight level winds from 700 mb (10,000 feet). Take off 15-20% and you get 90-95 kts at the surface.
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Quoting atmosweather:
114200 2209N 07310W 6973 02840 //// 094 //// 127109 112 /// /// 05

There are your major hurricane force winds.


A lot of interference with that reading. Questionable.

That said, it is probably a major by now.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Somebody quote me if i am wrong, but looking at visible sat thats just coming out, does it look like she is developeing or a new eye to the west of the current?
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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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