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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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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Quoting wunderweatherman123:

i agree with you but as seen in recent images the ULL is trying to bring irene farther west but the gap i still open for the nw turn. this will be very close. 98L will be a key player to how much the southern periphery of the high weakens but 98L looks to be fizziling so we will have to see what comes out of that


That's the key... If the ULL is able to deteriorate the eastern flank of the C CONUS high and allow any incoming TROF to dig further W then more of the US E coast line could be in trouble, but if the ULL weakens and/or washes out then it would allow the C CONUS to build back to the E and keep the weakness in the SE coast which would imply a further offshore track on Irene's path.

Of course variables are not restricted to the above and there are some other factors, but in the short term the above should be a pretty good driving force.
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112 knt flight level winds... likely 100 knt surface winds


the 127 you see above is the wind direction and the 109 is sustained flight level winds.... the 112 is the flight level winds
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Grandpa, avoid the traffic, rush and stress and go have some fun with your daughter and grandkids.
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11:42:00Z 22.150N 73.167W 697.3 mb
(~ 20.59 inHg) 2,840 meters
(~ 9,318 feet) - - From 127° at 109 knots
(From the SE at ~ 125.3 mph) 9.4°C*
(~ 48.9°F*) -* 112 knots
(~ 128.8 mph)
-

Flight level, but oh dear god.
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Quoting atmosweather:
114200 2209N 07310W 6973 02840 //// +094 //// 127109 112 /// /// 05

There are your major hurricane force winds.


Wow next advisory 130 mph then.
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Quoting atmosweather:
114200 2209N 07310W 6973 02840 //// +094 //// 127109 112 /// /// 05

There are your major hurricane force winds.


127kt?
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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.
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.

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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 wonder if the NHC 8am discussion will mention it..the new player in the game
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114200 2209N 07310W 6973 02840 //// +094 //// 127109 112 /// /// 05

There are your major hurricane force winds.
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"
This is the Hydrometeorological Prediction Center's 5 Day Quantitative Precipitation Forecast
Link
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Gotta run.........everyone have a good day! Irene should start a more Northerly move soon!
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Oh My God...
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Quoting ExumaMET:
Just reporting from Exuma, Bahamas... we're getting squally conditions and have had a few wind gusts approaching 40kt.

I'm not liking the amount of wobbling to the west.


Hope everyone has completed their preparations in Exuma, still a lot to be done here in Nassau.
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Quoting scott39:
Looks like the gap is closing some.


Indeed... very close gap.
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Quoting WxLogic:


The evolution of that ULL (which is keeping he weakness open) could allow Irene to stay far off the US coast or bring it closer to the US coast.

We also have to keep in mind that 98L is assisting on weakening some the southern periphery of the Bermuda/Azores high so the bush being currently imposed onto Irene might be temporary as 98L gets closer to Irene and a more Northerly component to the track starts materializing by then.

i agree with you but as seen in recent images the ULL is trying to bring irene farther west but the gap i still open for the nw turn. this will be very close. 98L will be a key player to how much the southern periphery of the high weakens but 98L looks to be fizziling so we will have to see what comes out of that
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Quoting nrtiwlnvragn:


I haven't figured out how to display two yet. Thought you only got up this early for golf.


I only get up this early for Fishing... It has to be light out for Golf.
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Quoting victoriahurricane:
.75 degree north and .5 degree east of the center is 100mph flight level winds, how many miles is that from the center?


About 60 miles NNE
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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


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.
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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
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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


927 that far north...

someone better turn the bs flag on!
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Quoting OldGeezerRick:

I'm no expert here, but if I am looking at that graph right, those steering winds makes me think it'll stay on the WNW track by several more hours rather than the projected near immediate turn to the NW, this may perhaps slide the cone back in over south florida once more, at least for the coastal areas.


The evolution of that ULL (which is keeping he weakness open) could allow Irene to stay far off the US coast or bring it closer to the US coast.

We also have to keep in mind that 98L is assisting on weakening some the southern periphery of the Bermuda/Azores high so the bush being currently imposed onto Irene might be temporary as 98L gets closer to Irene and a more Northerly component to the track starts materializing by then.
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.75 degree north and .5 degree east of the center is 100mph flight level winds, how many miles is that from the center?
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Does anyone on here use Mac with Google earth?  Im looking for a google earth plugin so I can watch the Hurricane Hunters live.
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Quoting victoriahurricane:


Last year was ridiculously bad, by the end of the season I had over 100 users on my ignore list. This year I'm only up to 20, so not too bad so far.



Yeah....But it's still early.
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http://www.atmos.washington.edu/~ovens/loops/wxlo op.cgi?wv_east_enhanced+12


Here comes the nudger that yanks Irene North.....its a pretty flat trough tho........need some latitude to come pretty soon.
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Quoting Orcasystems:


I stand corrected.. your right..
3 HH and I can only display two at a time... not enough coffee... its only 4:35


I haven't figured out how to display two yet. Thought you only got up this early for golf.
Member Since: September 23, 2005 Posts: 14 Comments: 11215
299. 900MB
Quoting TampaSpin:
Just posted the below in my site.


We have a serious issue arrising it seems. It appears Irene may just scape the outer banks of North Carolina but, NY City is in serious trouble. Irene appears to be coming toward NY at a very bad angle and will cause some serious flooding. If these models don't change their could be some serious loss of life and major flooding coming in that damage. Currently Irene is forecast to be an uppper in Cat 1 nearly a Cat 2 moving into NY City. Not sure what else to say. Beyond NY City then becomes Boston with the same problem but, only a slightly weaker system but, not by much. The amount of damage and loss of power along the Eastern Seaboard might be something we have not seen for some time.


From NYC here, a beautiful day. I am concerned yes, and I wouldn't want to live in a house right on the water in the city (and we have plenty of coastline), but I am far more concerned about Long Island, the potential for devastating storm surge and wind damage. If Irene indeed hits us directly and avoids much interaction with NC, I think we could see a Cat 2 landfall up here, and it would likely have some decent forward speed to make matters worse.
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Quoting KirbyPuckett34:
All you wishcasters make me sick...practically praying for a huge hurricane to nail the U.S. mainland. Sorry for offending you by hoping otherwise you losers


There is where you are wrong.. I personally couldn't care less where it makes landfall.

I do care about people who get run over by them...

I just take offence to people who have their head stuck so far up.. that they forget that there are other people in the world other then CONUS.

Baha is going to have this thing over his house... but in your eyes he is a no one.. because its only a Fish.

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Quoting WxLogic:
Should hopefully be updating in 30min to 1HR... but latest steering for Irene:



Would yield a WNW to NW (at times).
Looks like the gap is closing some.
Member Since: June 13, 2009 Posts: 0 Comments: 6863
Does anyone on here use Mac?
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Anything that close isn't good, Tampa.  NYC will be a mess(glass mostly and some flooding), but they will act like it's nothing.  Only heavy snow shuts down that city.

Folks up here prepare and are well educated.  But since we rarely see DOOM, there is shock and disbelief first, but it goes away quickly once everyone gets to work.

I remember Gloria's eye going directly over my house.  That was the last time we saw any real wind from a 'cane inland.  Everything else was mostly a rain event.

The folks on the coast up here are used to Nor'easters and Glancing Blows from TC's.   So they at least have an idea what is coming.  It's been a while though.

Should be a wild ride out on Montauk and the Islands if that track holds up.

More coffee, please.
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Quoting ncstorm:


if this was the GFS saying this, I wouldnt be inclined to worry but the ECWMF ensembles is something you need to pay attention to because the operational is the outlier..SC/NC needs to pay attention to this storm..like I say a 40-50 mile shift to the left would make a difference in impact for the coastal residents
Lets hope this trend with the ECMWF does not continue.
Member Since: June 13, 2009 Posts: 0 Comments: 6863
good question about protection for windows in NY.
My mom is in an apt, no home depot or lowes around for her to get plywood and even if she did it wouldn't be feasible or possible to put them from the outside, she'd have to do it from the inside of the window.

I told her to put that plastic stuff you usually put over the windows in winter to protect from the cold, then nail a heavy blanket over that and then stay the hell away from any windows if the shtf.

not much protection, but if the glass breaks it might offer some.
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I feel for all of those who have been affected and who will be affected by Irene.

Just please do not make it to 80W Longitude before the turn. That's all I ask. Thank you.
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Quoting oracle28:
As I watch the forecast track move further east I'm less concerned with FL/SC/NC, but can anyone guess the intensity at Long Island if Irene misses any land before getting that far north?


Most likely Category 1 with a very outside shot at Category 2.
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Just posted the below in my site.


We have a serious issue arrising it seems. It appears Irene may just scape the outer banks of North Carolina but, NY City is in serious trouble. Irene appears to be coming toward NY at a very bad angle and will cause some serious flooding. If these models don't change their could be some serious loss of life and major flooding coming in that damage. Currrently Irene is forecast to be an uppper in Cat 1 nearly a Cat 2 moving into NY City. Not sure what else to say. Beyond NY City then becomes Boston with the same problem but, only a slightly weaker system but, not by much. The amount of damage and loss of power along the Eastern Seaboard might be something we have not seen for some time.
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Quoting OldGeezerRick:

I'm no expert here, but if I am looking at that graph right, those steering winds makes me think it'll stay on the WNW track by several more hours rather than the projected near immediate turn to the NW, this may perhaps slide the cone back in over south florida once more, at least for the coastal areas.



Exactly. That's what I would say.
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Just reporting from Exuma, Bahamas... we're getting squally conditions and have had a few wind gusts approaching 40kt.

I'm not liking the amount of wobbling to the west.
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As I watch the forecast track move further east I'm less concerned with FL/SC/NC, but can anyone guess the intensity at Long Island if Irene misses any land before getting that far north?
Member Since: July 25, 2008 Posts: 0 Comments: 596
Quoting nrtiwlnvragn:


Those two are Kermit and AF303, Gonzo is south of Cuba.


I stand corrected.. your right..
3 HH and I can only display two at a time... not enough coffee... its only 4:35
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Quoting Tropicsweatherpr:
PR has seen epic rainfall from Irene and it's tail. So far between 15-20 inches has fallen here.

CLIMATE...IMPRESSIVE RAINFALL TOTALS PAST FEW DAYS HAS RESULTED
IN NEW RAINFALL RECORDS BEING BROKEN AT THE LMM SJU INTL ARPT.

SO FAR THIS MONTH...A TOTAL OF 16.53 INCHES OF RAIN HAVE BEEN
MEASURED. AUG 2011 IS NOW THE WETTEST AUG ON RECORD BREAKING THE
OLD RECORD OF 14.10 SET BACK IN 1944. AUG 2011 IS ALSO THE THIRD
WETTEST MONTH OF ANY YEAR ON RECORD SINCE RECORD KEEPING BEGAN IN
1898. ONLY 0.35 INCHES OF RAIN NEEDED TO BREAK THE RECORD OF 16.88
INCHES MEASURED BACK IN MAY 1936. WITH STILL EIGHT DAYS LEFT THIS
MONTH IT IS PRETTY MUCH DEFINITE THAT THIS RECORD WILL BE BROKEN
BEFORE THE MONTH IS OVER. LASTLY...AN INCREDIBLE 61.07 INCHES OF
RAIN HAVE ALREADY BEEN MEASURED SO FAR THIS YEAR. THIS REPRESENTS
THE WETTEST START TO A YEAR ON RECORD WELL AHEAD OF 2010 WHEN
52.89 INCHES HAD BEEN MEASURED TO THE DATE.


Wow...
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Quoting scott39:
Noticing a jog to the left with Irene for the moment. Every little jog like this from now on will make a difference in making landfall for N/S Carolina or not. She should be starting to turn more to the NW today.


if this was the GFS saying this, I wouldnt be inclined to worry but the ECMWF ensembles is something you need to pay attention to because the operational is the outlier..SC/NC needs to pay attention to this storm..like I say a 40-50 mile shift to the left would make a difference in impact for the coastal residents
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946mb 45° (from the NE) 100 knots (115 mph)
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Quoting WxLogic:
Should hopefully be updating in 30min to 1HR... but latest steering for Irene:



Would yield a WNW to NW (at times).

I'm no expert here, but if I am looking at that graph right, those steering winds makes me think it'll stay on the WNW track by several more hours rather than the projected near immediate turn to the NW, this may perhaps slide the cone back in over south florida once more, at least for the coastal areas.
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Irene is currently in a tight spot... In the image below you'll see I've marked the C CONUS High being pushed back some.

You'll also notice an ULL attempting to take shape offshore GA/SC border which is assisting on weakening the eastern periphery of the C CONUS high as it attempts to slide underneath it (at least a piece of it, while the more pronounced vortex is stalled off the SC coast.

Finally, you'll see the NE quadrant of Irene being flatten out as the Bermuda/Azores High attempts to build back to the W as per the steering current just posted.

Given all this... Irene has 2 options... either attempt to go in a more Northerly motion to try to outrun the building High and squeeze through the weakness or head W to WNW towards the ULL and follow it which would put it closer to the US coast.

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Quoting Orcasystems:
Gonzo is making a Vortex run





Those two are Kermit and AF303, Gonzo is south of Cuba.
Member Since: September 23, 2005 Posts: 14 Comments: 11215
Recon headed into the NE eyewall.
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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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