Category 2 Irene Approaches The Bahamas

By: Dr. Jeff Masters , 7:51 AM GMT on August 23, 2011

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As of 2am EDT, Hurricane Irene was located at 20.1N, 69.7W, 135 miles southeast of Grand Turk Island. It was moving west-northwest at 12 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 978 mb. Hurricane warnings have been issued for the northern coast of the Dominican Republic from the Haiti board to Cabo Engano, the southeastern and central Bahamas, and the Turks and Caicos islands. Hurricane watches have been posted for the north coast of Haiti from Le Mole, St. Nicholas to the Dominican border and the northwestern Bahamas. Tropical storm warnings are in effect for all of Haiti and the southern coast of the Dominican Republic from Cabo Engano to Santo Domingo.

5AM Update
As of 5am EDT, Hurricane Irene was located at 20.3N, 70.1W, 105 miles southeast of Grand Turk Island. It was moving west-northwest at 12 mph with maximum sustained winds of 100 mph, keeping it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 978 mb.

Figure 1 shows that Irene is maturing into a vigorous storm, with apparent waves in the western edge of the cirrus outflow.


Figure 1 IR satellite view of Irene taken at 135AM EDT, August 22, 2011

Track Forecast

Irene is forecast to move to the north-northwest, passing over all of the Bahama islands by Thursday evening, at which points it starts curving to the north. Irene is forecast to make landfall in the US near Wilmington, NC Saturday evening. However, it is important to note that this is not a definitive forecast, the average forecast error for day 5 is 250 miles. The timing of Irene's recurvature depends on how quickly several small troughs of low pressure in the Northeastern US move to the east. After Saturday, Irene may pose a threat to the mid-Atlantic coastline and locations further north, but it is too early to make a skillful forecast for those regions.

NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours, then reaching peak intensity at 130 mph (Category 4 storm) by 8pm EDT Thursday evening.

Forecast models and adaptive observations
The different forecast models are in rough agreement until Irene nears the Carolinas. The dynamical hurricane forecasting models, GFDL and HWRF, have Irene making landfall near Charleston, SC. NGFDL (a variant of the GFDL that uses NOGAPS for background conditions) has landfall near Morehead City, NC, and the GFS has Irene crossing the Outer Banks. The UKMET forecast track splits the difference, placing Irene near Myrtle Beach, SC at landfall.

To reduce the model spread, and improve the track forecast error, the NOAA Gulfstream IV and an Air Force WC-130J have been flying dropsonde missions north of Irene. A dropsonde is an meteorological instrument package dropped from a plane that can tell you the vertical profile of temperature, pressure, moisture, and winds. By flying these missions, the dropsondes can improve all of the numerical weather prediction models initial picture of the atmospheres, which improves the forecast. Also, NHC has asked NWS offices in the southeastern US that launch weather balloons to do so every 6 hours instead of the normal 12 hour frequency.


Figure 2 Official track forecast of Irene as of 2am.

5AM update
The 00Z ECMWF forecast is available and Figure 3 shows the maximum wind speed over the next week for the eastern coast of the US. Green indicates tropical storm force winds, while yellow and orange are hurricane-force winds. The important thing is not to fixate on the predicted landfall location, but to see that Irene's winds will affect areas far away from landfall. The GFS, not shown, agrees with ECMWF that Irene will have a large area of tropical-storm force winds associated with it.

Figure 3 Maximum wind-speed in mph from the 00Z August 23 ECMWF forecast for the next week.

Impacts

In the immediate future, Irene is expected to have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are forecast to reach the southeastern Bahamas and the Turks and Caicos sometime this afternoon or evening. These locations can also expect 5-10 inches of rain. Three to six inches of rain are forecast over northern Hispaniola, with isolated areas receiving up to 10 inches. This could lead to flash flooding and mudslides in mountaineous terrain. NHC is predicting a storm surge of 9-13 feet above normal tide level for the southeastern Bahamas and the Turks and Caicos.

Outside of the islands immediately impacted by Irene, it is my judgement that everybody living on the eastern coast of the US should monitor Irene and review their hurricane preparations over the next few days.

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 Bluestorm5:
gater23, local radar is not a good proof... this storm got "eye", but it's not visible.

Visible image of Katrina shows it didn't have eye



Katrina did have an eye as it passed right over my house. Experienced that period of calmness and blue skies before the trailing edge of the "eye" came through.
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Quoting HurricaneHunterJoe:
dude, are you for real?


According to the president he has been to 57 of the states and has two more to go.
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983. ackee
I know we all focus on IRENE but notice that most of the other CV storm models show seem to be fish storm would be nice if the rest of the seasons ends up be a fish event
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981. 7544
could the new blob come into play on where irene could go its moving south from fl/ ga eastcoast and just showed up after the models were run hmmmmm anyone know what effect this could have on her path thanks
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Quoting WeatherfanPR:


yep, this is very true.
unless they are in a raft at birth! LOL
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Until I see that storm move past Latitude 28.3 deg N I won't sigh relief..this is a monster that everyone on the East Coast from the Keys to NY needs to pay attention too!
Hudson, Fl weather
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977. 900MB
Quoting mcluvincane:


Best model around ECMWF


Not if you live in the Northeast!
Member Since: June 11, 2006 Posts: 0 Comments: 660
Quoting libertygirl:
I live in Key West, Fl and we are watching this carefully. Until we see a direct turn towards the North...it's positioning makes it appear that it could come straight up the "alley" and with that big "blob" hanging up off coast of FL/GA - I am wondering if that thing will push it down and track it into the "alley"? Waiting for Wed. afternoon ... on pins and needles.


That's probably the smart thing to do.
Member Since: August 1, 2007 Posts: 0 Comments: 167
Quoting wolftribe2009:
I am going to kick myself in the rear if this storm misses the trough and plows into Florida and then into the gulf. I have been wanting to say that is what is going to happen but don't have any model support and every else is saying it is turning to; therefore, hey if i have to be wrong then it is better if we all are wrong and so I go with South Carolina Landfall.
We've seen hurricanes do this before in the past...just keep moving on defying all models no matter what! This is my point exactly. Just by listenting to the weather people on TV I am not convinced about their confidence level in the models, even though they keep stating the facts which is the storm is still going wnw and hasn't turned yet...comments like, "we are all waiting now to see what it does" doesn't help the model's credibility.
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Quoting HurricaneHunterJoe:
dude, are you for real?
No. I was being sarcastic.
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972. viman
Quoting sarahjola:
a good wobble can push a storm off its track a few hundred miles sometimes

Very true, as with OMAR - A small 10-15 mile wobble when it turned to travel NE at that point in the southern Caribbean Sea allowed it to thread the needle through the Anegada Passage and thus spared the islands most of its Cat3 winds.
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Looks like that today is as low as the negative NAO is going to go before sharply going up. You guys need to watch this one to the end as we could easily see a western shift if this storm moves slow enough.

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Quoting wolftribe2009:


I remember that she was a hurricane coming across Florida. Not sure I remember an eye though since I think the destruction of the gulf coast drown that out forever in my mind. It was awful seeing that.




Member Since: December 18, 2006 Posts: 7 Comments: 2685
969. Ninj4

Quoting smartinwx:


The XTRP model is consistently pointing to New Orleans, but it's clearly an outlier.
Seriously, XTRAP isn't a model. It's the current movement extrapolated.
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Quoting UpperLevelLOL:


Can we stop even mentioning XTRAP? All it is is the extrapolation of the current course and assumes no deviation thereof. It has absolutely no predictive value whatsoever


We all know. It's a joke.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting CaicosRetiredSailor:
Morning,

Still no classic "outer bands" have come through Provo, grey and blustry.
I don't expect to be on here a lot, but will update when I can.
Be safe!
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Quoting smartinwx:


The XTRP model is consistently pointing to New Orleans, but it's clearly an outlier.


Can we stop even mentioning XTRAP? All it is is the extrapolation of the current course and assumes no deviation thereof. It has absolutely no predictive value whatsoever
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Quoting whepton3:


Now THAT's a forecast I can rely on! Well done... even threw some dynamics in there for effect.

+1000

Well if I make it sound official enough, it's GOTTA be true, right? And that is "written in stone." lol (Ah the man we love to hate...)
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Quoting mcluvincane:


Open the door to what?


Watch the evolution of the E CONUS TROF and the C CONUS High. Their foretasted placement would allow a systems to track from SW to NE along the US coast.
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Quoting Bluestorm5:
ok, thank you. It's funny people are saying you are wrong, but you did joined in June of 2005 before Katrina. These people are maybe been too young to remember Katrina.


I remember that she was a hurricane coming across Florida. Not sure I remember an eye though since I think the destruction of the gulf coast drown that out forever in my mind. It was awful seeing that.
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Quoting mcluvincane:


Best model around ECMWF


Don't tell the Americans that,they tell us the EURO'S are all socialist who have it all wrong.
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960. MahFL
Quoting NICycloneChaser:


Worth bookmarking for tonight and tomorrow though.


Nah...the Cubans will turn it off as soon as it comes near, just watch.....
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Quoting cat5hurricane:
Irene continuing to entrain dry air into her center from her southern semi-circle, ultimately breaking down her southern and eastern eyewall and thus exposing her inner core to dry air. I expect a slight downgrade to 95mph at the next update from the NHC, at 11am EDT.

However, this does not change the longer-term intensity forecast. The intensification expected may be halted a little, but I still expect this to top out at low-end category 4, with a strong cat 2 or weak cat 3 upon landfall...if she makes landfall anywhere in the U.S.

Prayers and thoughts for those in the Bahamas.

click image for animation


They'll probably leave it at 100 mph because recon. won't have sampled the storm completely yet.

Also, I don't think there is such a thing as a "weak" Category 3 - but I know what you mean.
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Quoting ProgressivePulse:
12Z TVCN shifted east to OBX.






The XTRP model is consistently pointing to New Orleans, but it's clearly an outlier.
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956. HCW



Member Since: August 10, 2002 Posts: 0 Comments: 1406
Quoting Seflhurricane:
NHC is waiting For the track to be very confident before issueing any watches for the US , but its likely SE fla would be under TS watches the wind field is going to be quite large , lets wait and see but i do not see a direct hit on S florida at all


Me neither... but a tic left in the track should make it awfully windy here in a couple days time.

I think they just want to see their track confirm over a couple of runs... who knows... may get further east and we'll have Chamber of Commerce wx through the weekend.
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Quoting Seflhurricane:
NHC is waiting For the track to be very confident before issueing any watches for the US , but its likely SE fla would be under TS watches the wind field is going to be quite large , lets wait and see but i do not see a direct hit on S florida at all


I think we are in the clear as far as a direct hit, but the news stations here keep talking about tropical storm conditions on Thurs/Fri. I was just wondering if and when they would do that. Looks like we dodged another one, I feel bad for all of those in the bahamas and everywhere else in her path.
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I live in Key West, Fl and we are watching this carefully. Until we see a direct turn towards the North...it's positioning makes it appear that it could come straight up the "alley" and with that big "blob" hanging up off coast of FL/GA - I am wondering if that thing will push it down and track it into the "alley"? Waiting for Wed. afternoon ... on pins and needles.
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Quoting bocahurricane:


Think we are going to get any ts watches/warning down here?


AS OF THE 5am advisory:

FT PIERCE FL
Tropical Storm Force Winds (39 mph- 57 mph) = 58%
Strong Tropical Force Winds (58 mph – 74 mph) = 25%
Category 1 Force Winds (75 mph - 95 mph) = 9%
COCOA BEACH FL
Tropical Storm Force Winds (39 mph- 57 mph) = 54%
Strong Tropical Force Winds (58 mph – 74 mph) = 21%
Category 1 Force Winds (75 mph - 95 mph) = 8%

PATRICK AFB
Tropical Storm Force Winds (39 mph- 57 mph) = 54%
Strong Tropical Force Winds (58 mph– 74 mph) = 21%
Category 1 Force Winds (75 mph - 95 mph) = 7%
MIAMI FL
Tropical Storm Force Winds (39 mph- 57 mph) = 50%
Strong Tropical Force Winds (58 mph – 74 mph) = 19%
Category 1 Force Winds (75 mph - 95 mph) = 6%


ORLANDO FL
Tropical Storm Force Winds (39 mph- 57 mph) = 43%
Strong Tropical Force Winds (58 mph – 74 mph) = 12%
Category 1 Force Winds (75 mph- 95 mph) = 2%
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Quoting UpperLevelLOL:


Holy irony.


Also has the NHC gone to updates on 2/8 as well now?
they had been doing that for awhile now... like since before Puerto Rico landfall?
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IMO, Bahamians and Floridians can make a sound decision based on the 11am advisory track and reading the discussion. Points Nward stay tuned, still a lot of uncertainty.
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Wind Gusts to 43mph now in the TCI's:

Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting Seflhurricane:
looking at the projected windfield TS storm force winds would affect coastal SE Fla if the current track holds and so far she is on track , has the high pressure steering irene weakened at all ???? and the trofs have they been on time coming down or a bit delayed???


Gusty winds 20-30mph range at best over mainland sfl. Strong TS winds should stay over the coastal waters. Fairly deep trof currently digging across the southeast united states and another waiting in line (should) keep irene east of Florida.
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Quoting WxLogic:
12Z NAM @51HR:

Sharp TROF evolution across the mid ATL States opening the door:



Open the door to what?
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Quoting BahaHurican:
BTW, people on the radio are still saying "IF" Irene comes.... clear evidence that we haven't had a hurricane hit here for a while...
I think we have blow coming down here.I will keep in touch.
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Quoting UpperLevelLOL:


Hahahaha the grammar in this post is hilarious. Make it through high school first then come back.
First... my grammar is bad BECAUSE I'M DEAF. I learned English just few years ago. 2nd, I got 4.5 GPA in a public high school... I just got mail from VCU in Richmond few days ago.
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12Z NAM @51HR:

Sharp TROF evolution across the mid ATL States opening the door:

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Quoting quakeman55:

Then it will run into the Philippines, then Taiwan, China, pop back off and hit Japan, then move across the north Pacific as an extratropical cyclone and slam into the Pacific Northwest, move across the US and move off the coast of New England, then a ridge of high pressure will push it southward, regains tropical characteristics, then rebuilding ridge pushes it west into the GOM, bombs into a Cat 5 and slams into New Orleans.

How's THAT suit ya? LOL


Now THAT's a forecast I can rely on! Well done... even threw some dynamics in there for effect.

+1000
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Quoting Bluestorm5:
ok, thank you. It's funny people are saying you are wrong, but you did joined in June of 2005 before Katrina. These people are maybe been too young to remember Katrina.


Holy irony.


Also has the NHC gone to updates on 2/8 as well now?
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All, OK the position as of 0800am edt was Location: 20.6°N 70.6°W

Why??? Unless I can't read lat and long it is no where near that point.


Link
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If ECMWF solution were to occur. That would be a disaster for NC to VA to DC
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Quoting aimetti:

923 mb
whats that 135-140 mph ?


Easy
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Click on graphic for enlarged view
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Quoting naplesdreamer28:
So are we safe to say at this point FL is out of it? I'm in SW FL and glad to see the cone gone, but sad to see where its heading for the Carolinas. From what I'm reading these troughs and influences are pretty well where they will be in terms for FL not to worry, correct?


Nothing relating to weather is ever 100%. So the answer is no- not until it passes to our north.
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Quoting HurricaneHunterJoe:
are the 12Z models out yet?


yes, for some oh them. the BAMS
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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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