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 Neapolitan:

It would certainly appear so. With the more or less steady eastward movement of each succeeding forecast track, we may see the center of the five-day cone out in the open sea by this evening or the morning. A US landfall has shifted from the southern tip of Florida up the east coast to Miami, then Palm Beach, then Jacksonville, then Savannah, then Charleston, and--now--Wilmington. Of course, some of that is an illusion, as the cone narrows with time. But, still, the eastern migration is evident. Cone animation here.

At any rate, what is becoming more and more certain is that the Bahamas are in for as nasty a walloping as they've likely ever seen...


Poor Bahamas, when was the last time they took a Major hit?
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All; The 5am position shows 20.3n x 70.1w. The last image of the water vapor loop for 0445am or 0845am utc shows the center way south and east of the given position. Yes I am awake and have coffee in hand. What am I missing? Someone please educate me as to what I am seeing.

Thanks

BULLETIN
HURRICANE IRENE ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 AM EDT TUE AUG 23 2011

...IRENE LASHING THE NORTHERN COAST OF THE DOMINICAN REPUBLIC...
EXPECTED TO MOVE OVER THE TURKS AND CAICOS LATER TODAY...


SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...20.3N 70.1W


Link
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Quoting USAFwxguy:
Recurve more and more of a possibility.

It would certainly appear so. With the more or less steady eastward movement of each succeeding forecast track, we may see the center of the five-day cone out in the open sea by this evening or the morning. A US landfall has shifted from the southern tip of Florida up the east coast to Miami, then Palm Beach, then Jacksonville, then Savannah, then Charleston, and--now--Wilmington. Of course, some of that is an illusion, as the cone narrows with time. But, still, the eastern migration is evident. Cone animation here.

At any rate, what is becoming more and more certain is that the Bahamas are in for as nasty a walloping as they've likely ever seen...
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Quoting aspectre:
NICycloneChaser "Looks like Irene is still struggling because of Hispaniola this morning. As soon as she gets away from there later this afternoon, she is going to really start intensifying.
71 odinslightning "she is struggling? really?..."

Irene's convection and circulation extends farther south of Hispanola than it's center is located north of the island. The southernwestern quadrant of Irene's extent has been dominated by Hispanola's landmass and especially its mountains, hindering smooth convergence from that sector.
I think what he meant was that without Hispanola's disruptive landscape, Irene would have already undergone RapidIntensification, would already be a Cat.3 heading toward Cat.4.


Yep, that's what I was suggesting.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
NICycloneChaser "Looks like Irene is still struggling because of Hispaniola this morning. As soon as she gets away from there later this afternoon, she is going to really start intensifying."
71 odinslightning "she is struggling? really?..."

Irene's convection and circulation extends farther south of Hispanola than it's center is located north of the island. The southernwestern quadrant of Irene's extent has been dominated by Hispanola's landmass and especially its mountains, hindering smooth convergence from that sector.

I think what he meant was that without Hispanola's disruptive landscape, Irene would have already undergone RapidIntensification, would already be a Cat.3 heading toward Cat.4.
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Quoting USAFwxguy:
Recurve more and more of a possibility.
Agree
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06z GFS has her moving west @ 18 hours. Tad north of 0z
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Quoting odinslightning:



she is struggling? really? she is at least twice the size she was 18 hrs ago, has progressed from barely a cat 1 (75 mph) to a strong cat 2.....i don't see the eyewall anywhere near the D.R. coast so im not sure if your correct. Looks like it is getting stronger quickly.

the hurricane will go through bursts and decrease periods of convection as it stacks in the higher layers of the atmosphere. You will see that cycle run faster with this storm because there is no wind shear or upper level interference with venting upwards. Each cycle of the convection venting upwards will just increase the size of this monster.....


She is not struggling but she is not intensifying much either. That is to be expected though since her circulation is a little cut off by Hispanola to the south and there is a little dry air to contend with. However, she is expanding with every passing moment as you have said with increasingly favorable outflow in 3 of the 4 quadrants. As she moves towards the Bahamas later today she could really strengthen very quickly with no apparent obstacles in the upper level environment.
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Quoting atmosweather:


Don't think that is an eye feature just the regular pulsing of the convection in the CDO.


Agree.

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Nevermind, convection is weakening once again, likely do to the presence of Hispaniola disrupting the southerly inflow into Irene. I will be back after work today. Hopefully I would have passed my PT test and Irene will be moving away from the DR and Haiti.
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Quoting odinslightning:



she is struggling? really? she is at least twice the size she was 18 hrs ago, has progressed from barely a cat 1 (75 mph) to a strong cat 2.....i don't see the eyewall anywhere near the D.R. coast so im not sure if your correct. Looks like it is getting stronger quickly.

the hurricane will go through bursts and decrease periods of convection as it stacks in the higher layers of the atmosphere. You will see that cycle run faster with this storm because there is no wind shear or upper level interference with venting upwards. Each cycle of the convection venting upwards will just increase the size of this monster.....


Perhaps struggling was the wrong word, but there's no doubt that Hispaniola is slowing intensification, for now. At the last recon pass her eyewall was still open, and the high mountains are likely the cause of this. Once Irene gets a bit further away later today, intensification could become rapid.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting thedawnawakening3:
Link

Maybe an Eye trying to show up?


Don't think that is an eye feature just the regular pulsing of the convection in the CDO.
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thanks
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Quoting NICycloneChaser:
Looks like Irene is still struggling because of Hispaniola this morning. As soon as she gets away from there later this afternoon, she is going to really start intensifying.



she is struggling? really? she is at least twice the size she was 18 hrs ago, has progressed from barely a cat 1 (75 mph) to a strong cat 2.....i don't see the eyewall anywhere near the D.R. coast so im not sure if your correct. Looks like it is getting stronger quickly.

the hurricane will go through bursts and decrease periods of convection as it stacks in the higher layers of the atmosphere. You will see that cycle run faster with this storm because there is no wind shear or upper level interference with venting upwards. Each cycle of the convection venting upwards will just increase the size of this monster.....
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Link

Maybe an Eye trying to show up?
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Quoting oceanblues32:
i am in ft lauderdale so a bit concerned of course is it me or does it seem to be riding the western edge of the forecast cone. looks like it is over hispanola a littl emore than they thought it would.


At 11PM the forecast point for 8AM this morning was 20.4N 70.6W, and right now she is at 20.3N and 70.1W, so she looks to be on track if not a hair north of the previous NHC track.
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Quoting shfr173:
Did the trough flatten out that was pulling her more northward? does anyone have link to updated water vapor?


Here is the water vapor loop for the Eastern U.S. You can see the mean longwave trough begin to flatten out and slowly lift away in the last few frames as expected. The shortwave impulse you see in the far N-ern Plains is the first of a few shortwave troughs that will help deepen the longwave trough again off the east coast.
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i am in ft lauderdale so a bit concerned of course is it me or does it seem to be riding the western edge of the forecast cone. looks like it is over hispanola a littl emore than they thought it would.
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large circulation
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Quoting yonzabam:
I'm writing a thread on Irene in the news section of a local forum here in the UK. Been looking for some stats, but having a bit of trouble finding what I want.

I know Ike was the last hurricane to make landfall in the US and I think Wilma was the last major (correct me if I'm wrong).

However, can't find the last hurricane and last major to strike the east coast. Anyone know? Thanks in advance.


Last major hurricane to strike the east coast was Jeanne in 2004 (110 kts at landfall).
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I think Jeanne was the last major to strike the east coast
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Quoting shfr173:
Did the trough flatten out that was pulling her more northward? does anyone have link to updated water vapor?
I dont have link. Read a few posts back and you will see that the trough is on track to curve Irene. Dont know how to link.
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I'm writing a thread on Irene in the news section of a local forum here in the UK. Been looking for some stats, but having a bit of trouble finding what I want.

I know Ike was the last hurricane to make landfall in the US and I think Wilma was the last major (correct me if I'm wrong).

However, can't find the last hurricane and last major to strike the east coast. Anyone know? Thanks in advance.
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NHC 5am update is out...no real changes so I'm off to bed
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Quoting atmosweather:


Well the 00z model suite was in a lot better agreement at days 4 and 5 with regard to the timing of Irene's N-ward turn so they did not feel the need to adjust the track much at all. The TVCN consensus remained pretty much the same as it was 6 hours ago and they always prefer to stick close to that.


courtesy dropsonde data:THE
23/00Z G-IV JET AIRCRAFT AND AIR FORCE C-130 DROPSONDE DATA APPEAR
TO HAVE SETTLED DOWN THE MODELS...AND THERE IS CONSIDERABLY LESS
DIFFERENCE AMONG THE VARIOUS MODEL SOLUTIONS NOW.
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Did the trough flatten out that was pulling her more northward? does anyone have link to updated water vapor?
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Fl. is looking in alot better shape now. GA SC/NC under the gun!
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Thanks for the late night/early morning post Dr. M. I don't think I've ever seen a storm so large and strong without a visible eye on satellite. Is it due to land interaction? But I have a feeling there will be one when I get up in about 8 hours. See you then.
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Looks like Irene is still struggling because of Hispaniola this morning. As soon as she gets away from there later this afternoon, she is going to really start intensifying.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting atmosweather:


Very good analysis and I agree on most points. Environment near the Bahamas and E of FL should allow her to become a Category 4 or 5 storm without much problem. The question is how much SW-erly shear could impact the system late in the period as Irene moves N-ward and towards the coast with the mean trough over the E-ern U.S.
thanks, and yea I forgot to include that. The SSTs and TCHP will increase just before the coast, but shear and dry air will as well,so it will be interesting to see what happens.
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Quoting scott39:
large cone of error.


Well the 00z model suite was in a lot better agreement at days 4 and 5 with regard to the timing of Irene's N-ward turn so they did not feel the need to adjust the track much at all. The TVCN consensus remained pretty much the same as it was 6 hours ago and they always prefer to stick close to that.
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Quoting scott39:
If you look at the animation of the NHC track. The 5am E movement was alot less compared to all other runs. the models have it pegged in the water right at the border of SC/NC. But it still has a large cone of area. Could it be that they are getting a better grip on landfall and the cone will shrink, or do the models see a different trend with Irene?
Cancel this! The updated animation wasnt in it yet.
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Quoting scott39:
If you look at the animation of the NHC track. The 5am E movement was alot less compared to all other runs. the models have it pegged in the water right at the border of SC/NC. But it still has a large cone of area. Could it be that they are getting a better grip on landfall and the cone will shrink, or do the models see a different trend with Irene?
large cone of error.
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If you look at the animation of the NHC track. The 5am E movement was alot less compared to all other runs. the models have it pegged in the water right at the border of SC/NC. But it still has a large cone of area. Could it be that they are getting a better grip on landfall and the cone will shrink, or do the models see a different trend with Irene?
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The GFDL, HWRF and Euro models all continue to forecast Irene to approach the coast of the Carolinas with at least Category 4 intensity. I'm not going to rule this kind of strength out because I don't see many negative factors facing Irene in the 5-day period.
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IRENE IS FORECAST TO BECOME A LARGER THAN AVERAGE HURRICANE. IT IS
IMPORTANT TO REMIND USERS NOT TO FOCUS ON THE EXACT FORECAST
TRACK...ESPECIALLY AT DAYS 4 AND 5...SINCE THE MOST RECENT 5-YEAR
AVERAGE ERRORS AT THOSE FORECAST TIMES ARE 200 AND 250 MILES...
RESPECTIVELY.

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I do wish I was home though. 2AM sun point is probably 20 miles from my house.
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http://www.ssd.noaa.gov/goes/flt/t2/flash-avn.html
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looks almost like twins...did Irene split?
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Quoting atmosweather:
SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...20.3N 70.1W
ABOUT 105 MI...170 KM SE OF GRAND TURK ISLAND
ABOUT 50 MI...85 KM NE OF PUERTO PLATA DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...100 MPH...160 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...978 MB...28.88 INCHES


HURRICANE IRENE DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 AM EDT TUE AUG 23 2011

SMOOTHING THROUGH ALL OF THE AIRCRAFT FIXES SINCE IRENE MOVED OFF
THE COAST OF PUERTO RICO MORE THAN 18 HOURS AGO YIELDS A LONG TERM
MOTION OF 295/10 KT...WHICH IS USED FOR THIS ADVISORY. THERE IS NO
SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. THE
23/00Z G-IV JET AIRCRAFT AND AIR FORCE C-130 DROPSONDE DATA APPEAR
TO HAVE SETTLED DOWN THE MODELS...AND THERE IS CONSIDERABLY LESS
DIFFERENCE AMONG THE VARIOUS MODEL SOLUTIONS NOW. THE OVERWHELMING
CONSENSUS IS THAT IRENE WILL GRADUALLY TURN NORTHWESTWARD OVER THE
NEXT 2-3 DAYS AND THEN MOVE NORTHWARD THROUGH A DEVELOPING BREAK IN
THE SUBTROPICAL RIDGE OVER THE SOUTHEASTERN UNITED STATES. THE
OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND
LIES VERY CLOSE TO CONSENSUS MODELS TVCN AND TVCA.

AN EARLIER RECON FLIGHT INDICATED THE PRESSURE HAD ONLY FALLEN BY 2
MB DOWN TO 978 MB...AND THE OVERALL APPEARANCE IN SATELLITE IMAGERY
HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY. AS A RESULT...THE
INITIAL INTENSITY IS BEING HELD AT 85 KT...WHICH COULD BE GENEROUS.
IRENE IS FORECAST TO REMAIN IN A RELATIVELY LOW VERTICAL WIND SHEAR
ENVIRONMENT AND OVER SSTS NEAR 30C. THAT COMBINATION...ALONG WITH
EXPANDING OUTFLOW IN ALL QUADRANTS...SHOULD ALLOW FOR IRENE TO
BECOME A MAJOR HURRICANE WITHIN THE NEXT 24 HOURS ONCE THE CYCLONE
CLEARS THE EFFECTS OF HISPANIOLA...AND PROBABLY MAINTAIN MAJOR
HURRICANE STATUS THROUGHOUT THE REMAINDER OF THE 5-DAY FORECAST
PERIOD. THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY
AND CLOSELY FOLLOWS A BLEND OF THE HWRF AND GFDL MODEL INTENSITY
FORECASTS...AND CONVERSION OF THE SURFACE PRESSURES DEPICTED IN THE
GFS AND ECMWF MODELS.

WIND RADII WERE EXPANDED BASED ON A BLEND OF RECON FLIGHT-LEVEL
WINDS...SFMR WINDS...AND SURFACE OBSERVATIONS.

IRENE IS FORECAST TO BECOME A LARGER THAN AVERAGE HURRICANE. IT IS
IMPORTANT TO REMIND USERS NOT TO FOCUS ON THE EXACT FORECAST
TRACK...ESPECIALLY AT DAYS 4 AND 5...SINCE THE MOST RECENT 5-YEAR
AVERAGE ERRORS AT THOSE FORECAST TIMES ARE 200 AND 250 MILES...
RESPECTIVELY.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 20.3N 70.1W 85 KT 100 MPH
12H 23/1800Z 20.9N 71.5W 95 KT 110 MPH
24H 24/0600Z 21.7N 73.3W 105 KT 120 MPH
36H 24/1800Z 22.9N 74.9W 110 KT 125 MPH
48H 25/0600Z 24.3N 76.2W 110 KT 125 MPH
72H 26/0600Z 28.0N 78.0W 115 KT 135 MPH
96H 27/0600Z 31.5N 78.3W 105 KT 120 MPH
120H 28/0600Z 35.0N 78.0W 100 KT 115 MPH...INLAND


Sounds like pretty much the same over the past 5 hours?
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SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...20.3N 70.1W
ABOUT 105 MI...170 KM SE OF GRAND TURK ISLAND
ABOUT 50 MI...85 KM NE OF PUERTO PLATA DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...100 MPH...160 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...978 MB...28.88 INCHES


HURRICANE IRENE DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 AM EDT TUE AUG 23 2011

SMOOTHING THROUGH ALL OF THE AIRCRAFT FIXES SINCE IRENE MOVED OFF
THE COAST OF PUERTO RICO MORE THAN 18 HOURS AGO YIELDS A LONG TERM
MOTION OF 295/10 KT...WHICH IS USED FOR THIS ADVISORY. THERE IS NO
SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. THE
23/00Z G-IV JET AIRCRAFT AND AIR FORCE C-130 DROPSONDE DATA APPEAR
TO HAVE SETTLED DOWN THE MODELS...AND THERE IS CONSIDERABLY LESS
DIFFERENCE AMONG THE VARIOUS MODEL SOLUTIONS NOW. THE OVERWHELMING
CONSENSUS IS THAT IRENE WILL GRADUALLY TURN NORTHWESTWARD OVER THE
NEXT 2-3 DAYS AND THEN MOVE NORTHWARD THROUGH A DEVELOPING BREAK IN
THE SUBTROPICAL RIDGE OVER THE SOUTHEASTERN UNITED STATES. THE
OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND
LIES VERY CLOSE TO CONSENSUS MODELS TVCN AND TVCA.

AN EARLIER RECON FLIGHT INDICATED THE PRESSURE HAD ONLY FALLEN BY 2
MB DOWN TO 978 MB...AND THE OVERALL APPEARANCE IN SATELLITE IMAGERY
HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY. AS A RESULT...THE
INITIAL INTENSITY IS BEING HELD AT 85 KT...WHICH COULD BE GENEROUS.
IRENE IS FORECAST TO REMAIN IN A RELATIVELY LOW VERTICAL WIND SHEAR
ENVIRONMENT AND OVER SSTS NEAR 30C. THAT COMBINATION...ALONG WITH
EXPANDING OUTFLOW IN ALL QUADRANTS...SHOULD ALLOW FOR IRENE TO
BECOME A MAJOR HURRICANE WITHIN THE NEXT 24 HOURS ONCE THE CYCLONE
CLEARS THE EFFECTS OF HISPANIOLA...AND PROBABLY MAINTAIN MAJOR
HURRICANE STATUS THROUGHOUT THE REMAINDER OF THE 5-DAY FORECAST
PERIOD. THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY
AND CLOSELY FOLLOWS A BLEND OF THE HWRF AND GFDL MODEL INTENSITY
FORECASTS...AND CONVERSION OF THE SURFACE PRESSURES DEPICTED IN THE
GFS AND ECMWF MODELS.

WIND RADII WERE EXPANDED BASED ON A BLEND OF RECON FLIGHT-LEVEL
WINDS...SFMR WINDS...AND SURFACE OBSERVATIONS.

IRENE IS FORECAST TO BECOME A LARGER THAN AVERAGE HURRICANE. IT IS
IMPORTANT TO REMIND USERS NOT TO FOCUS ON THE EXACT FORECAST
TRACK...ESPECIALLY AT DAYS 4 AND 5...SINCE THE MOST RECENT 5-YEAR
AVERAGE ERRORS AT THOSE FORECAST TIMES ARE 200 AND 250 MILES...
RESPECTIVELY.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 20.3N 70.1W 85 KT 100 MPH
12H 23/1800Z 20.9N 71.5W 95 KT 110 MPH
24H 24/0600Z 21.7N 73.3W 105 KT 120 MPH
36H 24/1800Z 22.9N 74.9W 110 KT 125 MPH
48H 25/0600Z 24.3N 76.2W 110 KT 125 MPH
72H 26/0600Z 28.0N 78.0W 115 KT 135 MPH
96H 27/0600Z 31.5N 78.3W 105 KT 120 MPH
120H 28/0600Z 35.0N 78.0W 100 KT 115 MPH...INLAND
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Quoting atmosweather:


It's pretty much on track with regards to the eroding mid level ridge to the E of the U.S. and the strength of the longwave trough looks to be right on forecast.
Thanks for the help. Hopefully the short waves troughs will make it the hulk and carry Irene out to sea!
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5.5 hrs sleep. Waiting on the 5am update.

I might die by the time she gets to VA on Sunday at the rate I'm not sleeping...
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i am in ft lauderdale so a bit concerned of course is it me or does it seem to be riding the western edge of the forecast cone. looks like it is over hispanola a littl emore than they thought it would.
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Quoting scott39:
Thanks, after I looked at the water vapor loop again, I see where that shortwave is going to back it up. Do you think the first part of the trough fattened out faster than forecasted, which puts the timing off turning N late enough to put Fl. back in a higher risk of the cone?


It's pretty much on track with regards to the eroding mid level ridge to the E of the U.S. and the strength of the longwave trough looks to be right on forecast.
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Quoting atmosweather:


Keep asking questions lots of people are ready to help ya! Yes, the shortwave impulses are basically energy drinks for the mean trough in the E-ern U.S. Once they move along the trough down to the axis they will act to amplify it and deepen it.
Thanks, after I looked at the water vapor loop again, I see where that shortwave is going to back it up. Do you think the first part of the trough fattened out faster than forecasted, which puts the timing off turning N late enough to put Fl. back in a higher risk of the cone?
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Irene currenly moving from 84.2 Fahrenheit to 86.0 F waters. And eventually she'll be tracking to 87.8 degrees.
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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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