Hurricane Irene Approaches the Bahamas

By: Dr. Jeff Masters , 7:42 AM GMT on August 24, 2011

Share this Blog
11
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1128 - 1078

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29Blog Index




hmmmm....
Member Since: Posts: Comments:
1126. dipchip
Seems NHC knows of what they say.

Forecast positions and Max winds
11 AM CDT 23 A 2011
init 23/1500z 20.5n 71.0w 85 kt 100 mph
12h 24/0000z 21.3n 72.3w 90 kt 105 mph
24h 24/1200z 22.3n 73.8w 100 kt 115 mph

Forecast positions and Max winds
11 AM CDT 24 A 2011
init 24/1500z 22.4n 73.9w 100 kt 115 mph
12h 25/0000z 23.4n 74.8w 110 kt 125 mph
24h 25/1200z 25.1n 76.1w 115 kt 135 mph

24 hour forcast hit intesity on the button.
Missed position by 6 min of Lat and Log or about 8 mile error in position.
Member Since: Posts: Comments:
1125. Gorty
Quoting Bayside:


Yup, I know the feeling...


And I am in western Mass! How about you?
Member Since: Posts: Comments:
Presslord

from http://www.geobytes.com/CityDistanceTool.htm?d&pt_ 1=usnynyor&pt_2=usflmiam

1097 miles as a crow flies at 201 degrees south.

from
http://www.carbidedepot.com/formulas-trigright.as p

hypotenuse is 1097, angle A is 21 (201-180).

result is 393 miles West and 1024 miles South.

Hope this helps.
Member Since: Posts: Comments:
1123. IMA
Quoting Grandpato4:
Pornography on the blog? I cannot believe this.


Wow, I thought Press had retired from that particular profession
Member Since: Posts: Comments:
Quoting Jax82:


Its probably partly sunny, calm winds on Acklins Island at the moment, only because the Eye is right over top of it. :-\
except for andros island as you go nw from there the islands get more and more populated. I think the bahemians will need alot of help in the comming weeks
Member Since: Posts: Comments:
Quoting IMA:
For the vets on the block


Oh have mercy..brings back memories *sniff, sniff*
Member Since: Posts: Comments:
Quoting IMA:
For the vets on the block


LOL...now THAT'S funny
Member Since: Posts: Comments:
Quoting Grandpato4:
Pornography on the blog? I cannot believe this.


WHERE? WHERE?
Member Since: Posts: Comments:
Quoting Cotillion:


Ahh, I see.

So, if non-US countries installed sufficient radars, they'd also get the two hour advisories?

Thanks for the answer, nrti.


Yes Link that goes into detail on the text products.
Member Since: September 23, 2005 Posts: 14 Comments: 10875
1114. hamla
Quoting notabubba:
AB1JV, first licensed 1976

thats great,when max mayfeild was in nhc they had 4 to 5 hams in the center.dont know if any are licensed now qrz n1rg
Member Since: Posts: Comments:
Quoting atmoaggie:
Tip: On filter set to "Show Bad" none of these posts are visible without a click on "Show".

Thus, on a refresh, I see nothing posted by the worst of the blog.


in that case...How are you able to respond to me?!?!
Member Since: Posts: Comments:
Quoting Smikey:


'Ignore' is not working on Internet Explore 9 with Jason, its the embedded videos that are causing a major mess for me on the forum.


Ahhhh...IE9; I have resisted the upgrade lo, these many months and it has paid off handsomely, vis, my ability to banish the aforementioned indiviudal...
Member Since: Posts: Comments:
While is is not a TRUE NW (315 degrees) it is close. Since 8am it has moved 0.5N and 0.6W, so slightly west of northwest, however since 2am, she has moved 1.1N 1.3W, also slighty west of northwest... e.g. the 305 degrees.
Member Since: Posts: Comments:
Nothing..it can happen and has happened before regardless of the models


Quoting E46Pilot:
Whats to stop the trough from lifting and the high building in?
Member Since: Posts: Comments:
1106. IMA
For the vets on the block
Member Since: Posts: Comments:
1105. Nimitz
Quoting Smikey:


'Ignore' is not working on Internet Explore 9 with Jason, its the embedded videos that are causing a major mess for me on the forum.


Sounds like the admins need to do an IP block...
Member Since: Posts: Comments:
1104. Jax82
Quoting alvarig1263:
Acklins Island taking a direct hit from Irene's eye right now as it jumped west and is now pummeling them.


Its probably partly sunny, calm winds on Acklins Island at the moment, only because the Eye is right over top of it. :-\
Member Since: Posts: Comments:
Category 4 - good Lawdie....I sure hope all along the East Coast are prepared for what they could experience....I know it's been a while. And if they say get out - heed the warning.
Member Since: Posts: Comments:
Tip: On filter set to "Show Bad" none of these posts are visible without a click on "Show".

Thus, on a refresh, I see nothing posted by the worst of the blog.
Member Since: Posts: Comments:
1101. Bayside
Quoting Gorty:
I can't believe I am saying this but my house has a 50/50 shot at destruction... 50 chance it will get wrecked and 50 chance she will go east of me sparing me.


Yup, I know the feeling...
Member Since: Posts: Comments:
1100. Smikey
O
Quoting Floodman:


Use the ignore button...


ok now he is posting porn, I've got to call it quits on looking at the forum now until that is corrected, since my ignore is not working, and I'm at work.

I hope you all you can correct this so I can come back.

Member Since: Posts: Comments:
AND USERS ARE ONCE AGAIN REMINDED NOT TO FOCUS ON SPECIFIC FORECAST POINTS THREE TO FIVE DAYS DOWNSTREAM.
Member Since: September 23, 2005 Posts: 14 Comments: 10875
Whats to stop the trough from lifting and the high building in?
Member Since: Posts: Comments:
Quoting Smikey:


'Ignore' is not working on Internet Explore 9 with Jason, its the embedded videos that are causing a major mess for me on the forum.

Use Firefox. Much better. Or Google Chrome would work too.
Member Since: Posts: Comments:
1095. snotly
go to the top of the screen, click my blog, go to the bottom right, click ignored, add the user to the list... gotta love that!
Member Since: Posts: Comments:
Quoting angiest:


What do you mean? Anytime there is a coastal watch or warning anywhere in the NHC's area they issue the three hour intermediate advisory.

If they only do the 'b' advisory on final approach to US territory, well, their primary mission is to US taxpayers. Alex last year go 'b' advisories, as well as position fixes and update, while Karl did not, except for an update.. I'm not sure the exact criteria for the 'b' advisories.


Yeah, I meant the 'b' advisories for when they crop up. I just wondered why that appeared to be the case.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
ignoring him might be overrated
Member Since: Posts: Comments:
1092. wpb
http://www2.sunysuffolk.edu/mandias/38hurricane/nys _storm_surge_zones.pdf

long island storm surge map link above
Member Since: Posts: Comments:
Jason will be banned for life for posting a naked women he will be gone gone gone
Member Since: Posts: Comments:
Quoting RitaEvac:
If Irene speeds up this will have implications on any evacuations. Could you imagine if this thing were to start cranking up movement to 20-25 mph going due north for Long Island.
Long Island express, the sequel!
Member Since: Posts: Comments:
In the last hour or so irene has made a sharp left turn..I know it's the wobble but wobbles can add up
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:


Radar


Intermediate Public Advisories. Intermediate Public Advisories will be issued at 2- to 3-hourly intervals between scheduled advisories (see times of issuance below). Issue 3-hourly intermediate advisories whenever 1) a coastal tropical storm or coastal hurricane/typhoon watch/warning is in effect, or 2) a tropical cyclone is over land at tropical storm strength or greater. Issue 2-hourly intermediates whenever tropical storm or hurricane/typhoon warnings are in effect and coastal radars are able to provide responsible tropical cyclone centers with a reliable hourly center position.


Ahh, I see.

So, if non-US countries installed sufficient radars, they'd also get the two hour advisories?

Thanks for the answer, nrti.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
1086. Smikey
Quoting Floodman:


Worked for me...he now holds the distinction of being the one person most represented on my ignore list...and that's the last I'll say on that particular indiviual...LOL


'Ignore' is not working on Internet Explore 9 with Jason, its the embedded videos that are causing a major mess for me on the forum.
Member Since: Posts: Comments:
Acklins Island taking a direct hit from Irene's eye right now as it jumped west and is now pummeling them.
Member Since: Posts: Comments:
I wonder how many people in South FL on on there toes this morning knowing how close a major hurricane is to them and moving straight for them!? Yeah the forecast calls for it to turn but how much faith do you have in that forecast!? Sure glad I'm not anywhere along the East Coast for this one, it's going to be touch and go once Irene gets closer to the U.S. Coastline. She's still heading WNW from what I can tell.....How close is she going to get to Florida before she actually turns!?
Member Since: Posts: Comments:
1082. angiest
Quoting Cotillion:
Why is it only the US that ends up getting two intermediate advisories?


What do you mean? Anytime there is a coastal watch or warning anywhere in the NHC's area they issue the three hour intermediate advisory.

If they only do the 'b' advisory on final approach to US territory, well, their primary mission is to US taxpayers. Alex last year go 'b' advisories, as well as position fixes and update, while Karl did not, except for an update.. I'm not sure the exact criteria for the 'b' advisories.
Member Since: Posts: Comments:
1081. Gorty
I can't believe I am saying this but my house has a 50/50 shot at destruction... 50 chance it will get wrecked and 50 chance she will go east of me sparing me.
Member Since: Posts: Comments:
If Irene speeds up this will have implications on any evacuations. Could you imagine if this thing were to start cranking up movement to 20-25 mph going due north for Long Island.
Member Since: Posts: Comments:
000
WTNT44 KNHC 241450
TCDAT4

HURRICANE IRENE DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
1100 AM EDT WED AUG 24 2011

IRENE HAS CONTINUED TO STRENGTHEN THIS MORNING. THE EYE HAS BECOME
MORE DISTINCT IN SATELLITE IMAGERY AND IT IS SURROUNDED BY CLOUD
TOPS COLDER THAN -70 DEGREES CELSIUS. BOTH AIR FORCE AND NOAA
HURRICANE HUNTER AIRCRAFT HAVE BEEN INVESTIGATING IRENE THIS
MORNING. THE AIR FORCE PLANE MEASURED A PEAK 700 MB FLIGHT-LEVEL
WIND OF 112 KT JUST BEFORE 1200 UTC...AND THIS SUPPORTED THE
UPGRADE TO A 100-KT CATEGORY THREE HURRICANE AT THAT TIME. SINCE
THAT TIME THE NOAA AIRCRAFT REPORTED 115 KT AT 750 MB. THE
PRESSURE HAS REMAINED AROUND 956 MB...AND THE INITIAL INTENSITY
ESTIMATE REMAINS 100 KT.

THE OUTFLOW HAS BECOME WELL ESTABLISHED OVER THE HURRICANE AND IRENE
WILL BE MOVING OVER SEA SURFACE TEMPERATURES OF AROUND 29 DEGREES
CELSIUS DURING THE NEXT 24-36 HOURS. THESE ENVIRONMENTAL FACTORS
FAVOR ADDITIONAL INTENSIFICATION AND THE NEW INTENSITY FORECAST
CALLS FOR IRENE TO REACH CATEGORY FOUR STRENGTH WITHIN 24 HOURS.
AFTER THAT TIME...SOME FLUCTUATIONS IN WIND SPEEDS ARE LIKELY DUE
TO EYEWALL REPLACEMENTS. THE UW-CIMSS OBJECTIVE SECONDARY EYEWALL
FORMATION TECHNIQUE SHOWS A VERY HIGH LIKELIHOOD OF THAT OCCURRING
DURING THE NEXT 48 HOURS. SOUTHWESTERLY SHEAR IS EXPECTED TO
GRADUALLY INCREASE AND THE HURRICANE WILL BE MOVING OVER
SIGNIFICANTLY COLDER WATERS BY 96 HOURS. THIS SHOULD RESULT IN
GRADUAL WEAKENING...HOWEVER IRENE IS FORECAST TO REMAIN A LARGE AND
POWERFUL HURRICANE DURING THE NEXT 5 DAYS.

AIRCRAFT FIXES DURING THE PAST 12 HOURS INDICATE THAT IRENE HAS MADE
THE EXPECTED TURN TOWARD THE NORTHWEST...WITH AN INITIAL MOTION OF
305/10. THERE IS NO CHANGE TO THE TRACK FORECAST REASONING AND THE
MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT FOR THE FIRST 2-3
DAYS. AFTER THAT TIME...THERE IS SOME QUESTION AS TO WHETHER OR NOT
IRENE CONTINUES ON A NORTH-NORTHEAST HEADING OR TURNS BACK TOWARD
THE NORTH AHEAD OF A MID-LATITUDE TROUGH APPROACHING THE GREAT
LAKES REGION. THE GFDL AND HWRF MODELS REMAIN ALONG THE WEST SIDE
OF THE GUIDANCE ENVELOPE AND SHOW A TRACK OVER OR VERY CLOSE TO THE
MID-ATLANTIC COAST. THE UKMET AND NOGAPS ARE ALONG THE EASTERN SIDE
AND KEEP THE CORE OF THE HURRICANE WELL OFFSHORE. GIVEN THE TYPICAL
MODEL AND OFFICIAL TRACK ERRORS...BOTH SCENARIOS ARE VIABLE OPTIONS
AT THIS TIME...AND USERS ARE ONCE AGAIN REMINDED NOT TO FOCUS ON
SPECIFIC FORECAST POINTS THREE TO FIVE DAYS DOWNSTREAM. THE TVCA
CONSENSUS AND THE EXPERIMENTAL HURRICANE FORECAST IMPROVEMENT
PROJECT CONSENSUS WERE RELATIVELY CLOSE TO THE PREVIOUS NHC
FORECAST. THE UPDATED NHC TRACK HAS BEEN NUDGED EASTWARD AT 96 AND
120 HOURS AND LIES BETWEEN THOSE TWO CONSENSUS AIDS.




FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 22.4N 73.9W 100 KT 115 MPH
12H 25/0000Z 23.4N 74.8W 110 KT 125 MPH
24H 25/1200Z 25.1N 76.1W 115 KT 135 MPH
36H 26/0000Z 27.2N 76.9W 115 KT 135 MPH
48H 26/1200Z 29.3N 77.2W 110 KT 125 MPH
72H 27/1200Z 33.2N 76.2W 100 KT 115 MPH
96H 28/1200Z 38.5N 73.5W 85 KT 100 MPH
120H 29/1200Z 45.0N 69.5W 70 KT 80 MPH...INLAND

$$
FORECASTER BROWN
Member Since: Posts: Comments:

Viewing: 1128 - 1078

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Partly Cloudy
73 °F
Partly Cloudy