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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Quoting weatherh98:
wow this looks good, and what is the ace up to

Irene:6.92
Year:18.5
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Morning all. Conditions early this morning in Nassau are overcast, with winds light, variable and increasing. We had a light rain just five minutes ago at my house. On the national radio, ZNS, they are interspersing songs with calls from the Southeast Bahamas in an attempt to get information about conditions there. The calls I have heard so far have been from Acklins and Crooked Island, and wind and rain are down there. This is going to be a long two days.
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The ECWMF ensembles are showing a western track..

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I am loving the GDFL: miss the entire east coast until it hits NY.

Hurray GDFL!
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Quoting islander101010:
it could go out to sea cloudburst has been saying that all along



Poof
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Quoting CTSkywatcher:
Mornin' WU.

If that GFS holds up, there will be some severe flooding here in S. NE.  My immediate area can handle it, but we have flood control measures not seen in many places outside of TN thanks to Connie and Diane in '55.

CRS check in yet?


Not yet, said my prayers for him during the night and hopefully he will stop by and all will be okay.
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Quoting Bassfishing123:
Morning to all, when is the turn north supposed to take place? thanks..



when the storm gets ready too
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Quoting cat5hurricane:

:)


Seems to me that some of the models...  NOGAPS, GFDL and HWRF seem to pushing to the west a bit on the early track giving FL a little more rain and wind.
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Well good morning bloggers!! Coffee in hand, relaxed at my office and hoping everyone is somehow safe in the Bahamas. What's the lates and greatest? I know today is the the "T" day T for turn. Has Irene turned already as predicted?
Member Since: August 1, 2007 Posts: 0 Comments: 167
when will we know for sure that Irene isnt going to possibly bend back to the west
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Quoting atmosweather:


She should turn NW later tonight and tomorrow and then make the N-ward turn by Friday.


ok thanks apprec. that
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Quoting atmosweather:


Mhmm been there done that a few times lol. At least there are far less trolls around here now than earlier this year and last year.


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.
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Mornin' WU.

If that GFS holds up, there will be some severe flooding here in S. NE.  My immediate area can handle it, but we have flood control measures not seen in many places outside of TN thanks to Connie and Diane in '55.

CRS check in yet?
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Quoting atmosweather:


Mhmm been there done that a few times lol. At least there are far less trolls around here now than earlier this year and last year.


Wait until this afternoon and this thing keeps gaining latitude... most are still sleeping.
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Quoting Bassfishing123:
Morning to all, when is the turn north supposed to take place? thanks..


She should turn NW later tonight and tomorrow and then make the N-ward turn by Friday.
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wow this looks good, and what is the ace up to
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Quoting Orcasystems:


One of these days I am going to get mad... and get a 24 hour vacation.


Mhmm been there done that a few times lol. At least there are far less trolls around here now than earlier this year and last year.
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Quoting Tazmanian:



STOP SAYING ITS A FISH ITS NOT A FISH IT HIT PR DEAD ON AND ITS HITING LAND NOW ALL SO ITS GOING TOO COME VARY CLOSE TOO THE USA OR MAY BE EVEN MAKE A FULL LANDFALL ALL SO EVEN IF IT DOS NOT MAKE A FULL LAND FALL A LOT OF DAMG COULD BE DONE LIKE MAJOR FLOODING INLAND HIGH WINDS AND DOWN TREES


THIS IS NOT A FISH
it could go out to sea cloudburst has been saying that all along
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Her cloud tops appear to be warming ever so slightly this morning... is that just normal swings or could she have injested some more dry air
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Quoting FLdewey:
Well at least you've given in to reality on Florida... baby steps. ;-)


LMFAO....It's headed south!! South!!

Florida DOOMED!!!
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Complete Update

Gonzo & Kermit on Task... let the fun begin :)

TS BUSTED FORECAST ALIBI





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Morning to all, when is the turn north supposed to take place? thanks..
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Quoting atmosweather:


Brilliant.


One of these days I am going to get mad... and get a 24 hour vacation.
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it rained so hard early this morning here in e cen fl. that if you had a metal roof you would of woke up the neighborhood
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Quoting Orcasystems:


And the other is your an idiot.


Technically it's "you're" :P, but from another Victoria native I'll let it slide this time ;)
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Quoting KirbyPuckett34:
One thing has become crystal clear....Irene=fish


This is also clear

KirbyPuckett34= idiot.
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Irene on visible.
Member Since: August 11, 2010 Posts: 0 Comments: 772
Quoting KirbyPuckett34:
One thing has become crystal clear....Irene=fish



STOP SAYING ITS A FISH ITS NOT A FISH IT HIT PR DEAD ON AND ITS HITING LAND NOW ALL SO ITS GOING TOO COME VARY CLOSE TOO THE USA OR MAY BE EVEN MAKE A FULL LANDFALL ALL SO EVEN IF IT DOS NOT MAKE A FULL LAND FALL A LOT OF DAMG COULD BE DONE LIKE MAJOR FLOODING INLAND HIGH WINDS AND DOWN TREES


THIS IS NOT A FISH
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Quoting Orcasystems:


And the other is your an idiot.


Brilliant.
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Quoting KirbyPuckett34:
One thing has become crystal clear....Irene=fish


And the other is your an idiot.
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Quoting KirbyPuckett34:
One thing has become crystal clear....Irene=fish


What a brilliant first post, welcome to my ignore list. That woman who died in Puerto Rico refutes your "fish" claim I bet.
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Quoting WeafhermanNimmy:
Despite no northerly turn, they still expect the outer banks to get hit?


The turn isn't due yet.
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Quoting cat5hurricane:
Intensity forecast is way overdone in the short term. I don't anticipate this thing to approach high-end category 3 until it is north of 30 degrees. The TCHP and depth of the 26 degree isotherm (with all the islands around and the shallower waters) is too shallow for that kind of intensification.

With that being said, a further westward movement may ensue. Florida is out of the woods, but I am still very concerned for the upper coast of SC, particular Myrtle Beach, SC on Northward to the OBX.


What about Chalreston, SC?
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Quoting victoriahurricane:
10:46:30Z 21.817N 73.217W 754.1 mb
(~ 22.27 inHg) 2,107 meters
(~ 6,913 feet) 957.1 mb
(~ 28.26 inHg) - From 266° at 14 knots
(From the W at ~ 16.1 mph) 19.5°C
(~ 67.1°F) 14.9°C
(~ 58.8°F) 17 knots
(~ 19.5 mph) 28 knots
(~ 32.2 mph)

O_O


30 mph surface winds so we're looking at around 954-955 mb.
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Time: 10:46:00Z
Coordinates: 21.85N 73.2333W
Acft. Static Air Press: 754.0 mb (~ 22.27 inHg)
Acft. Geopotential Hgt: 2,105 meters (~ 6,906 feet)
Extrap. Sfc. Press: 957.2 mb (~ 28.27 inHg)
D-value: -
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looks like the models are pushing off my house in CT to offshore :D
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185. MahFL
Daylight...

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Quoting nrtiwlnvragn:
GFS last four cycles




GFS is pretty much set for up to 48 to 72HR or so.
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10:43:30Z 22.017N 73.300W 749.8 mb
(~ 22.14 inHg) 2,211 meters
(~ 7,254 feet) 965.3 mb
(~ 28.51 inHg) - From 68 at 85 knots
(From the ENE at ~ 97.7 mph) 16.2C
(~ 61.2F) 16.3C
(~ 61.3F) 95 knots
(~ 109.2 mph) 81 knots
(~ 93.1 mph)


Found higher surface winds and this is in the northWEST quadrant, not northEAST. Irene very may well be a Cat 3 major now.
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10:46:30Z 21.817N 73.217W 754.1 mb
(~ 22.27 inHg) 2,107 meters
(~ 6,913 feet) 957.1 mb
(~ 28.26 inHg) - From 266° at 14 knots
(From the W at ~ 16.1 mph) 19.5°C
(~ 67.1°F) 14.9°C
(~ 58.8°F) 17 knots
(~ 19.5 mph) 28 knots
(~ 32.2 mph)

O_O
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Looks like the possible center fix would be a bit to the left than what I was expecting to be... and to be expected since is not like the SAT images I'm looking at are real time. That could put it right on track.
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One center reading for me and NE eye wall run and I'm off to bed. 4 am and should be sleeping, damn you WU, why must you be so addictive?
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957 mb from RECON...no winds strong enough to support an upgrade to major hurricane status yet, although they have not sampled the NE quadrant yet.
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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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