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 Floodman:


Exactly; all that "I'm a man and a man don't leave his stuff" can end actually meaning "A man has to die with his stuff when he don't understand limitations"
Put that on my tombstone then! LOL
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Quoting Cotillion:
Why is it only the US that ends up getting two intermediate advisories?


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.
Member Since: September 23, 2005 Posts: 14 Comments: 11305
Quoting HiWay:


Thank you. So the larger the wind field, especially a wide swath of strong winds instead of a small area of intense winds is far more telling for a large surge?
Exactly.

That, and the other usual factors, such as angle of approach, water depths just off the coast, the shape of the coastline.

Katrina made landfall quite perpendicular to the coast in an area where the water she set in motion could not escape the west or to the depths.

If Irene approaches any east-west coastline while moving north, the highest surge she will produce will be east of the eye at the coast, near the distance of her radius of maximum winds to the east. In that scenario, the surge to the west of her eye will be a negative surge (below normal water, some sea bed exposed in shallow areas).

And the wider her area of strong winds, above hurricane force, especially, the larger area experiencing the above.
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i usually just read but i must add this. this monster is bearing down on great exuma. i do believe a fairly large number of people live there. lets wish them safety as this approaches
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It seems to me the Eastern High is building back to the West a little.

Any thoughts? Temporary shift?



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Quoting alvarig1263:


For now, but I think Irene may slow back down just a little and possibly resume a WNW track. With these jumps to the west they can't keep the direction at NW when it's not even moving NW. We'll continue to watch it over the next hours.


Well any jog west would mean increase effects on south Fl. I remeber going to bed thinking Irene was going to skirt south of PR, and waking up and it was N of PR.
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Quoting yonzabam:


Mine doesn't work for Jason. Tried it four times in the past twenty minutes. He's getting smarter.


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
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1069. Gorty
Link

Now you all know why it is dangerous to say she will go ots.
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Quoting Neapolitan:

If you drew a line straight north from downtown Miami and another straight west from the tip of Manhattan, they'd intersect a few miles south of Pittsburgh International. That's 327 miles due west of Manhattan.


Thank you ( I think) for understanding the necessity of a simplistic answer when dealing with me
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Quoting scCane:
Already looks like it will go west of the next forecast point.


That's what I'm seeing...
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Quoting twooks:


One could argue that models have probably come along way in a decade too, so that has to be a factor in older 3-day models.


A 5-day model with no center line should be fine in my view as well.


It's not a matter of "probably come a long way", they have come a long way.

1 Day avg. error 1990 aprox. 100 miles, 2010 aprox. 50.
2 Day avg. error 1990 aprox. 200 miles, 2010 aprox. 75.
3 Day avg. error 1990 aprox. 300 miles, 2010 aprox. 125.
4 Day avg. error 2000 aprox. 275 miles, 2010 aprox. 150.
5 Day avg. error 2000 aprox. 350 miles, 2010 aprox. 200.

(Source: http://www.nhc.noaa.gov/verification/figs/OFCL_ATL _trk_error_trend_sm.gif)

Since hurricane storm-force winds can extend out for 150 miles for a large one and tropical storm-force winds can stretch out as far as 300 miles from the center of a large hurricane, the 200 mile avg. error for day five is well within a spatial scope of concern.

I'm in western MA, and today I'll begin some basic prep. If this storm misses me, any prep. I do is set aside for next time. No time or money wasted there.

I applaud the work forecasters at the NHC and academia are doing to improve their predictions.
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TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES

Expect this to expand to 300 miles when closer to CONUS
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1063. scCane
Already looks like it will go west of the next forecast point.
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*A note for all NHC bashers*

Up until 30-40 years ago, people who lived along costal areas in the CONUS, every island in the Caribbean, Mexico and CA purchased/stocked up on items they would need in case a major storm impacted them. They had no warning that something was coming down the barrel at them, relying instead on years of experience in handling cases like this. More often than not, their warning that something was coming did not give them enough time to flee to better areas. If they chose not to stock up, nobody else would probably help.

Now we have the NHC, a collection of experts that tracks every cloud between Africa and Hawaii. Up to the minute updates can be had from every person who has a computer. These experts can tell that there could be a problem with a particular cloud as it is leaving Africa.

When major storms to arise, they send off reports to everyone letting them know to PAY ATTENTION. They put out maps of where a storm could POSSIBLY go. They allow the public to have knowledge of what a storm is doing.

In fact, the NHC now allows people to NOT buy supplies for storms because of their forecasts. Just think......when you are complaining and saying "I'm glad I didn't buy supplies" that it was the NHC that saved you a bunch of money!

So, as a recap, the NHC lets you know about storms coming your way and allows you to do what you think is right. They save you money possibly, but also save your life if you need to go.

Keep on bashing them if you want.....just know there are quite a few people that think a bit differently.

BTW, I live in a snow belt. It would be quite irresponsible of me to get rid of all my snow throwing gear just because a model 5 days out says a storm won't hit us with a foot of snow.
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1061. Gorty
NHC:


"THE OFFICIAL FORECAST IS NOT SUBSTANTIALLY DIFFERENT FROM
THE PREVIOUS ONE AND LIES A LITTLE TO THE LEFT OF THE CONSENSUS."
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Quoting presslord:


What I wanna know is...How far west of NY is Miami?

If you drew a line straight north from downtown Miami and another straight west from the tip of Manhattan, they'd intersect a few miles south of Pittsburgh International. That's 327 miles due west of Manhattan.
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1059. MahFL
EAST :(...........bah humbug !
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POOF!
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I need to post a video of me ignoring/blocking JasonCoolMan2004 videos.
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1056. Gorty
Quoting Cotillion:
Not a pretty cone. A little west wobble brings a Cat 4 on Nassau.


NHC went slightly west for the north... not looking good especially since I could see a cat hurricane in western Mass now! Cat 1 in Maine!
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Quoting E46Pilot:


She actually is speeding up. and is now moving NW


For now, but I think Irene may slow back down just a little and possibly resume a WNW track. With these jumps to the west they can't keep the direction at NW when it's not even moving NW. We'll continue to watch it over the next hours.
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Quoting ecupirate:


Dont hate on the guy too much. He is clearly one of those individuals with "Special Needs"


Who's hating? I'm annoyed that the ignore function isn't working.
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Quoting presslord:
At 9:32am yesterday a high ranking FEMA official reached out to us about 'partnering' in response to Irene...I said "if FEMA can help, great!! If not, please just get out of our way"...as of this moment, we have not heard back from them..........I suppose that answers that....


you'd be hard pressed to imagine how much I love that story...
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Use the ignore button...


I can't he's displaying videos that are screwing up the format of the blog. I can't ignore the buttons are disabled, which is why he is doing what he's doing. I can't read crap on here right now.


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1050. Buhdog
can someone tell me what happened to Destin Jeff? Funny dude but has not been on...I miss his humor. Low level clouds streaming west in South Florida in front of Irene make for a nice view at the office today.

Good luck BAHA!!!!!!!!!!!!!!
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Not a pretty cone. A little west wobble brings a Cat 4 on Nassau.
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Quoting Floodman:


Use the ignore button...


Mine doesn't work for Jason. Tried it four times in the past twenty minutes. He's getting smarter.
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Quoting 69Viking:
Presslord, according to my calculations on Google Earth it's NY is approx. 390 miles East of Miami.


which fact makes their forecast look pretty good
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1044. Gorty
Cone looks like shifted a tad west... not looking good at the updated track and intensity.
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At 9:32am yesterday a high ranking FEMA official reached out to us about 'partnering' in response to Irene...I said "if FEMA can help, great!! If not, please just get out of our way"...as of this moment, we have not heard back from them..........I suppose that answers that....
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Quoting ILwthrfan:
Admin please do something about Jason, This is becoming a problem.


Use the ignore button...
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Quoting alvarig1263:


I've been saying this could happen for the past 24 hours but many berated me for even mentioning FL. Let's see if anything comes of it...


She actually is speeding up. and is now moving NW
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Atlantic wind analysis maps due out within the next 30 mins. Will post them here when available. Atlantic ridge continues to build west, as Texas ridge also retreats west towards Arizona. Could become a factor. Irene going NW now, but expecting a WNW track again before the full northward turn.
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Presslord, according to my calculations on Google Earth it's NY is approx. 390 miles East of Miami.
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1038. dmh1026
Quoting ILwthrfan:
Admin please do something about Jason, This is becoming a problem.

I un-poofed him...What a mistake!!!
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Can someone let me know what the current DOOM:CON level is? I haven't seen an update and with the Gulf Coast and Florida out of the picture, I would expect a substantial easing of the DOOM:CON. Heck maybe the lowest (safest) level of DOOM, what with this being a "fish storm" now. (Despite it hitting multiple islands already, currently hitting an island nation, and forecast to possibly hit the northeast or outer banks).

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1035. air360
Cat 4 Forecast! Slight East shift passing NC though

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Quoting Cotillion:
Why is it only the US that ends up getting two intermediate advisories?


Internal favoritism....
Member Since: May 27, 2009 Posts: 0 Comments: 4438
HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 50 MILES...85 KM...FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM.

Forget the cone. If you're within this range from the eye, prepare accordingly.
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Quoting flsky:
Go to Google Maps and get directions between the two - it will give you the mileage.



Mileage isn't the same as longitudinal distance; roads turn and twist and add distance
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1030. Gorty
Not liking this, Irene sped up and is going NW. I wonder how she will be affected the trough now.
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Quoting Misogynist:
I think everyone should embrace the bickering and debate. A public that is engaged is a lot more likely to finance the research that may one day get a handle on Weather Forecasting.


Hardly. Winston Churchill said that the biggest argument against democracy is a 5 minute conversation with the average voter.

Engaging the public in a scientific debate is like trying to discuss the weather with an angry swarm of bees. The bees don't understand, and you're most likely to get stung.

The general public does not have the knowledge and/or experience to make informed decisions about where scientific funding should go or how much. The growing anti-science and anti-intellectual movement has done a good job of creating an environment where "scientists are not to be trusted". That undermines ALL scientific endeavors, not just the ones you may or may not agree with. Just take a sampling of this blog, or look at the recent idiocy in cutting NOAA funding. Uninformed people (and sometimes even informed people) do not make good decisions.

Perhaps I'm just overly cynical, but when it comes to matters of science the general public is not a good judge. All it takes is a good FUD campaign and it seems like you can even convince people that gravity doesn't exist.

I think the general public should be more educated when it comes to science. Public outreach, programs, etc. are good at engaging the public. But until our population is more well informed when it comes to science, they should leave the decisions to people with more knowledge and experience on the subject.
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1028. 996tt
Quoting RickWPB:
I think the NHC do a great job. We need to remember that Wx prediction is not an exact science. It's fluid with lots of variables. We have computer models that help speed up the analysis, but we need the PhD's to make the final word. I thank them for their service.

Interesting to note that so far in this satellite/radar loop that Irene is tracking slightly to the right of the cone center line.

14 hr loop


They really are. NHC has gotten much better in just the last couple of years. I think they err on leaving the cone touching shore though on storms like this due to duty to public and politics if they don't warn. That being said, I would imagine the NHC individuals would have this storm even further East and off shore if off record.

The Weather Channel, on the other hand, are a bunch drama queens whose job is to over-hype anything and everything to get people to tune in. Even their tone and inflection (especially the big boned shrilly voice Abrahms) is specifically directed at evoking emotion, fear or excitment. This is exactly why she has the slot she has is her ability to stir emotion and captivate the viewer. Has nothing to do with actual weather.
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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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