Hurricane Irene Prepares to Leave the Bahamas and Head for the US

By: Dr. Jeff Masters , 7:51 AM GMT on August 25, 2011

Share this Blog
17
+

As of 2AM EDT, Hurricane Irene was located at 24.2N, 76.0W, 105 miles east-southeast of Nassau or 760 miles south of Cape Hatteras. It was moving northwest at 12 mph with maximum sustained winds of 115 mph, making it a Category 3 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 950 mb. Hurricane force winds can be found up to 70 miles from Irene's center, and tropical storm force winds can be found out to 255 miles from the storm's center.

Hurricane warnings are in effect for all of the Bahamas. Hurricane and tropical storm watches will likely be posted for the Carolina coastlines later this morning. At this time, Dare County Emergency Management has issued a mandatory evacuation order for all visitors in their county. Dare County Schools will also be closed Thursday and Friday.

Satellite Views
Figure 1 is the infrared satellite image of Irene at 135EDT. The convection is a bit unbalanced around the storm center, which is going to cause Irene to wobble like an unbalanced clothes washer (Analogy courtesy of Angela Fritz) over the next few hours. At the time this image was taken, the convection around Irene's center appears to be getting more vigorous, as cold cloudtops are starting to increase around the storm center. This is important to note because microwave satellite imagery from Wednesday evening suggested Irene was starting an eyewall replacement cycle. Figure 2 shows passive microwave imagery from a Air Force DMSP polar-orbiting satellite. The two concentric green/yellow bands in the image suggest that two eyewall features are present in Irene, and Hurricane Hunter observations confirm this. This has important consequences for Irene's intensity, because in an eyewall replacement cycle, as the inner eyewall weakens, the storm's intensity drops. However, once the inner eyewall is gone, and the outer eyewall contracts to replace it, the storm intensity will increase again.


Figure 1 IR satellite view of Irene taken at 113AM EDT, August 23, 2011


Figure 2 DMSP F18 microwave overpass of Irene at 824PM EDT, August 24, 2011. Image courtesy of the Naval Research Laboratory

Track Forecast

Irene is forecast to move to the northwest, passing over the northwest Bahamas by Thursday evening, then curving to the northeast. 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. Sunday, Irene may make secondary landfall anywhere from New Jersey to Long Island and the southern New England coastline. In my opinion, New York City may be significantly impacted by Irene. 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 Category 4 storm (winds faster than 130 mph) by Thursday morning. As Irene moves northward into cooler water, the intensity is expected to drop slowly to a Category 2 storm before making landfall in the Outer Banks.


Figure 3 Official track forecast of Irene at 2AM EDT.

Forecast models and today's planned flights
The different forecast models are still in fairly good agreement about Irene's track through the Bahamas and along the east coast of the US. The 00Z GFS run is in close agreement with the 12Z ECMWF run, but the 00Z ECMWF run (shown in figure 4) is continuing the ECMWF's trend of shifting the track westward with each run. NHC forecasters have been placing emphasis on the ECMWF's forecast track when making their forecasts for IRene, so it is possible that the NHC track will shift westwards at the 5AM update.

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 (Gonzo), and two flights for NOAA 42, a WP-3D (Kermit). They may have to give NOAA a littering permit for all of the dropsondes used to monitor Irene and her environment, but the forecast improvements they generate are worth the effort.


Figure 4 Plot of the maximum sustained winds in mph over the next week from the 00Z ECMWF forecast.

Impacts

Hurricane force winds will arrive in the northwestern Bahamas today. Storm surge near the center of Irene will be 7-11 feet above tide level. The Bahamas can expect 6-12 inches of rain over the next day or so, and it looks like the Turks and Caicos islands will receive a total of 6-12 inches from Irene. Large, swells from Irene will start landing on the southeastern US coastline later today. Please don't go in the water, as these swells can cause dangerous rip currents. Dr. Masters has catalogued the worst-case storm surge surge scenarios as a function of storm intensity here.

In my opinion, people living from the Carolinas to Cape Cod should pay close attention to Irene and prepare for a wide range of impacts. I think that there is a 75% chance of Irene's secondary landfall will be somewhere between JFK airport and Cape Cod. That said, Irene's size will cause significant impacts for people living far from it's center.

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: 296 - 246

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22Blog Index

come on visible......
Member Since: Posts: Comments:
Quoting hotrods:
I think the NHC is being a little to conservative about watches and warnings for the east coast, regardless if the turn is going to happend. It's getting a little bit to close for comfort for me here in ECFL-Palm Bay. No turn yet!


Incorrect. Irene is moving NNW.
Member Since: Posts: Comments:
294. bwi
One thing I've been noticing on GFS is that the precipitation seems tilted to the west and north as the hurricane approaches the mouth of the Chesapeake. (Here is link to 6z GFS at 75 hours.)
This is not what I'd expect if it's undergoing southwesterly shear. Heavy rains in the DC/Baltimore area would bring down more wind, in my opinion, as the storm passes by to the east.

Others noticed this, and have explanation?
Member Since: Posts: Comments:
I think the NHC is being a little to conservative about watches and warnings for the east coast, regardless if the turn is going to happend. It's getting a little bit to close for comfort for me here in ECFL-Palm Bay. No turn yet!
Member Since: October 22, 2009 Posts: 0 Comments: 89
Turning NNW earlier than expected makes me think Irene's track will be on the E side of the models. It's still way too early but this may be a blessing for the EC.
Member Since: Posts: Comments:
Shear Map



What do you think?
Member Since: Posts: Comments:
Quoting tropicfreak:
Good morning all, watching Irene closely here in VA as I could see TS force winds. One of the models has it going straight into the Chesapeake Bay, wouldn't that be something!


Good morning tropicfreak..no doubt you will have a busy few days preparing as will my daughter. who would have thought that earthquakes and hurricanes would be instore of you this week..
Member Since: Posts: Comments:
Anybody remember this little spinner?

DISORGANIZED SHOWER ACTIVITY CONTINUES NEAR A LOW PRESSURE AREA
LOCATED ABOUT 1200 MILES EAST-SOUTHEAST OF BERMUDA. ALTHOUGH
UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE...THESE WINDS COULD
BECOME A LITTLE MORE CONDUCIVE FOR DEVELOPMENT IN A COUPLE OF DAYS.
THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES TOWARD THE
WEST-NORTHWEST AT ABOUT 15 MPH.
Member Since: Posts: Comments:
Quoting Tazmanian:


yes


Thanks Taz. I found what I needed to do.
Member Since: Posts: Comments:
Quoting dipchip:
The last vortex message compared to the 0400 NHC location shows the storm tracking nearly due north.


Vortex also shows the storm to have passed Nassau to the east at about 65 miles. Local wheather station on Nassau shows Max wind hovering near 50 MPH.


Winds are considerably higher on the eastern end of the island.
Member Since: Posts: Comments:
Quoting Autistic2:
I see she is past 75 w longitude and still moving NW. Any chance she will go to 79 or 80 w befor going due N?

Hope not. Florida and Georgia will be seriously affected then and WE are not truly prepared for a surprise visit from Irene. Of course, I remember the last Irene that hit us..NHC.."she is gonna turn, she is gonna turn, she is gonna turn.....well, folks, she is NOT turning." Fortunately she was a Cat 1 with minimal damage. Still, I did not have time to get my shutters up or do any preparation! I now get my hurricane kit ready in MAY!
Good morning to all. Getting breezy in Port St. Lucie, no rain yet. Clouds to the SE. Prayers and thoughts with all of those in Bahamas.
Member Since: Posts: Comments:
Heres my simple 2 cents worth. Irene is a big TC which makes her harder to turn. If she doesnt start dropping pressure and build up that W side and strengthening.....its going to take longer to make that turn and start going N.
Member Since: Posts: Comments:
The last vortex message compared to the 0400 NHC location shows the storm tracking nearly due north.


Vortex also shows the storm to have passed Nassau to the east at about 65 miles. Local wheather station on Nassau shows Max wind hovering near 50 MPH.
Member Since: Posts: Comments:
NCEP COUPLED HWRF HURRICANE MODEL FORECAST MADE FOR

HURRICANE IRENE 09L

INITIAL TIME 6Z AUG 25

FORECAST POSITIONS (FROM STATS.SHORT FILE...)

HOUR LATITUDE LONGITUDE MIN PRESS (hPa) MAX SFC WIND (KTS)

HOUR: 0.0 LONG: -75.80 LAT: 24.10 MIN PRESS (hPa): 933.00 MAX SURF WIND (KNOTS): 99.00
HOUR: 6.0 LONG: -76.50 LAT: 25.00 MIN PRESS (hPa): 928.00 MAX SURF WIND (KNOTS): 111.00
HOUR: 12.0 LONG: -76.80 LAT: 25.90 MIN PRESS (hPa): 921.00 MAX SURF WIND (KNOTS): 116.00
HOUR: 18.0 LONG: -77.00 LAT: 27.00 MIN PRESS (hPa): 923.00 MAX SURF WIND (KNOTS): 114.00
HOUR: 24.0 LONG: -77.10 LAT: 28.20 MIN PRESS (hPa): 923.00 MAX SURF WIND (KNOTS): 110.00
HOUR: 30.0 LONG: -77.10 LAT: 29.20 MIN PRESS (hPa): 925.00 MAX SURF WIND (KNOTS): 110.00
HOUR: 36.0 LONG: -77.00 LAT: 30.30 MIN PRESS (hPa): 926.00 MAX SURF WIND (KNOTS): 109.00
HOUR: 42.0 LONG: -76.70 LAT: 31.40 MIN PRESS (hPa): 928.00 MAX SURF WIND (KNOTS): 102.00
HOUR: 48.0 LONG: -76.60 LAT: 32.50 MIN PRESS (hPa): 927.00 MAX SURF WIND (KNOTS): 99.00
HOUR: 54.0 LONG: -76.40 LAT: 33.60 MIN PRESS (hPa): 927.00 MAX SURF WIND (KNOTS): 105.00
HOUR: 60.0 LONG: -76.10 LAT: 34.70 MIN PRESS (hPa): 925.00 MAX SURF WIND (KNOTS): 103.00
HOUR: 66.0 LONG: -75.70 LAT: 35.70 MIN PRESS (hPa): 929.00 MAX SURF WIND (KNOTS): 90.00
HOUR: 72.0 LONG: -75.30 LAT: 37.00 MIN PRESS (hPa): 929.00 MAX SURF WIND (KNOTS): 88.00
HOUR: 78.0 LONG: -74.90 LAT: 38.40 MIN PRESS (hPa): 931.00 MAX SURF WIND (KNOTS): 84.00
HOUR: 84.0 LONG: -74.40 LAT: 40.10 MIN PRESS (hPa): 934.00 MAX SURF WIND (KNOTS): 76.00
HOUR: 90.0 LONG: -73.50 LAT: 42.10 MIN PRESS (hPa): 948.00 MAX SURF WIND (KNOTS): 60.00
HOUR: 96.0 LONG: -72.50 LAT: 44.40 MIN PRESS (hPa): 963.00 MAX SURF WIND (KNOTS): 43.00
HOUR: 102.0 LONG: -71.10 LAT: 46.70 MIN PRESS (hPa): 974.00 MAX SURF WIND (KNOTS): 36.00
HOUR: 108.0 LONG: -69.40 LAT: 48.90 MIN PRESS (hPa): 979.00 MAX SURF WIND (KNOTS): 24.00
HOUR: 114.0 LONG: -67.60 LAT: 51.10 MIN PRESS (hPa): 982.00 MAX SURF WIND (KNOTS): 40.00
HOUR: 120.0 LONG: -65.10 LAT: 52.90 MIN PRESS (hPa): 983.00 MAX SURF WIND (KNOTS): 23.00
HOUR: 126.0 LONG: -61.60 LAT: 54.80 MIN PRESS (hPa): 988.00 MAX SURF WIND (KNOTS): 34.00
Member Since: Posts: Comments:
Quoting trHUrrIXC5MMX:
TWC strong language?
but no storm alert
http://www.weather.com/weather/videos/news-41/top -stories-169/forbes-first-thunderstorms-then-irene -21670

what the heck??


If you have TWC in HD the bottom bar is now red ever since Irene has begun to pose a threat.
Member Since: Posts: Comments:
why does she look flattish on her sw side?
Member Since: Posts: Comments:
looking at miami radar looks like another jog to the west?
Member Since: Posts: Comments:
278. Inyo
Looks like they slowed down the storm a bit. Good news for me personally as I'll be leaving the MA area on Sunday morning, but could be bad news for New England in general as a slower moving storm would cause more rain. It'll be interesting to see what happens here in Vermont. Most of Vermont hasn't been THAT wet but our watershed has had a bunch of rain.
Member Since: Posts: Comments:
Quoting Bassfishing123:
can someone be removed from the ignore list once they are put on it....thanks


yes
Member Since: Posts: Comments:
276. GoWVU
Quoting wxobsvps:


The "588" line you see is indicative of high pressure, generally a TC will be less likely to barrel right into a high pressure.

In that image you see the 588 bridged to the north of her (no break)... that doesn't mean there won't be, but the longer there isn't, the greater likelihood of longitudinal gains.


Thanks for the explantion
Member Since: Posts: Comments:
Very heavy rain bands coming through eastern Nassau now.
Member Since: Posts: Comments:
from 5 a.m. Forecast Discussion:
THE INITIAL MOTION CONTINUES TO BE ABOUT 315/10. THERE HAS BEEN NO CHANGE TO THE TRACK FORECAST REASONING.

IRENE SHOULD TURN NORTHWARD AS IT MOVES THROUGH A BREAK IN THE SUBTROPICAL RIDGE DURING THE NEXT 48 HOURS. THEREAFTER...A SHORTWAVE TROUGH MOVING THROUGH THE GREAT LAKES IS LIKELY TO TURN THE HURRICANE TOWARD THE NORTH-NORTHEAST.

IN THE LATTER PART OF THE FORECAST PERIOD...GLOBAL MODELS SHOW THE SHORTWAVE BYPASSING IRENE AND THE HURRICANE BECOMING EMBEDDED WITHIN A BROAD AND SLOW-MOVING MID-TROPOSPHERIC TROUGH OVER THE EASTERN UNITED STATES. THIS STEERING PATTERN SHOULD PREVENT IRENE FROM MOVING WELL OFFSHORE OF THE NORTHEASTERN STATES.

THE OFFICIAL TRACK FORECAST HAS BEEN SHIFTED VERY SLIGHTLY TO THE WEST OF THE PREVIOUS ONE AND IS
ROUGHLY IN THE MIDDLE OF THE GUIDANCE ENVELOPE
... WHICH IS BRACKETED BY THE U.K. MET. OFFICE MODEL ON THE EAST AND THE GFDL MODEL ON THE WEST.

HURRICANE AND TROPICAL STORM WATCHES ARE NOW NECESSARY FOR A PORTION OF THE SOUTHEAST AND CENTRAL U.S. EAST COAST.
Member Since: Posts: Comments:
273. Vero1
Quoting wxobsvps:


Agree. Really wanted to see her not get past 76, now I'm hoping for 77.

INIT 25/0900Z 24.6N 76.2W 100 KT 115 MPH
12H 25/1800Z 26.1N 77.1W 110 KT 125 MPH
24H 26/0600Z 28.2N 77.7W 115 KT 135 MPH
36H 26/1800Z 30.4N 77.5W 110 KT 125 MPH
48H 27/0600Z 32.3N 77.1W 100 KT 115 MPH
Member Since: July 21, 2008 Posts: 4 Comments: 2233
I got it thanks..
Member Since: Posts: Comments:
Good morning all, watching Irene closely here in VA as I could see TS force winds. One of the models has it going straight into the Chesapeake Bay, wouldn't that be something!
Member Since: Posts: Comments:


Member Since: Posts: Comments:
did not evacuate like most for floyd it got 50mph or so here in merritt island strong enough to blow in a neighbors front door who had evacuated expect about the same for irene
Member Since: Posts: Comments:
Quoting Tazmanian:


poof




(poof)
Member Since: Posts: Comments:
Short RSO Loop
Member Since: Posts: Comments:
263. GoWVU
Quoting wxobsvps:
RUC Model



What does this map mean?
Member Since: Posts: Comments:
261. beell
Quoting wxobsvps:


That is reassuring. Although, I think that ULL in the GoM is keeping Irene from taking full advantage of the weakness


At the least, it certainly would seem to prevent any movement E of N. Always the chance it could drag Irene back towards the coast some before its influence grows a weaker today as they put some distance between each other.

This does not look like an OBX "scraper" this morning.
Member Since: September 11, 2007 Posts: 142 Comments: 16627
260. Mikla
Just starting to pick up the center on long range Miami radar... link
Member Since: Posts: Comments:
Quoting CarolinaBeachGirl:
Okay--I do understand:-) Little too close for comfort here, but I am putting faith in what we are being told. I am 8 blocks back and have been lucky in the past. You stay safe as well!


8 blocks from a potential hurricane landfall is a very dangerous place to be. I have seen +12" trees snapped in half over 90 miles inland from Rita. Please take a look at these pictures of Bolivar Peninsula before and after Ike (the last storm to make US landfall). http://coastal.er.usgs.gov/hurricanes/ike/photo-co mparisons/bolivar.html

Also here is an article detailing the fates of people who stayed because they had been lucky in the past. The man from Port Neches (where I grew up) was 100 miles east of Ike's landfall. http://www.chron.com/neighborhood/baytown-news/art icle/Grisly-finds-put-Houston-area-Ike-death-toll- at-32-1583737.php

Please follow all your local emergency authorities' recommendations.
Member Since: Posts: Comments:
Quoting JrWeathermanFL:
At 8:00 Irene will be________.
A.115-125mph
B.130-140mph
C.145-155mph
D.Cat. 5
E.Weaker


a. same 115
Member Since: Posts: Comments:
I see she is past 75 w longitude and still moving NW. Any chance she will go to 79 or 80 w befor going due N?
Member Since: Posts: Comments:
Quoting coffeecrusader:
Looks like anything that forms east of the antilles will be destined for the fishes. Very weak Bermuda high this year. It was forecasted to be strong allowing for alot of action in the GOM. But looks like this forecast was inaccurate.


poof
Member Since: Posts: Comments:
Looks like anything that forms east of the antilles will be destined for the fishes. Very weak Bermuda high this year. It was forecasted to be strong allowing for alot of action in the GOM. But looks like this forecast was inaccurate.
Member Since: Posts: Comments:
Quoting JrWeathermanFL:
At 8:00 Irene will be________.
A.115-125mph
B.130-140mph
C.145-155mph
D.Cat. 5
E.Weaker


A - 115mph. Possibly slightly lower, though I think NHC will be reluctant to downgrade to Cat 2.
Member Since: Posts: Comments:
At 8:00 Irene will be________.
A.115-125mph
B.130-140mph
C.145-155mph
D.Cat. 5
E.Weaker
Member Since: Posts: Comments:
Quoting CarolinaHurricanes87:


I know, its crazy... tropical storm conditions om the left side of the storm... or if it pushes idk, 20, 30, 50 miles west? We would be getting the eye/eyewall of a major hurricane. Weird setup, hope the NHC is right... Im sure they must be or theyd have put us in the hurricane watch to be safe
Member Since: Posts: Comments:
South Florida Update:
Outermost bands of Irene now ashore in Broward County (Fort Lauderdale region) Sustained winds at Nova University (By I-595 and Fla Turnpike) 12-15 MPH with gusts to mid 20's This about 10-12 miles inland
Member Since: Posts: Comments:
scrubs did a couple shows in hope town walking bicycles only in its little historic downtown (developed by royalist who moved here after the revolutionary war) neat little bay safe harbour beachside community great fishing and surfing nearby. incredible place to visit expensive!
Member Since: Posts: Comments:
Quoting FLdewey:
Maybe we'll get some spouts...



woot woot

Did you ever see and/or use this NWS waterspout activity calculator (or one like it), Dewey? It works. I used it one day last summer, saw things were favorable, and went to the beach one afternoon and set up my camera while just a short line of cumulus drifted offshore. A curious passerby asked what I was shooting, and I said "waterspouts". Literally as he noted there were none, one started snaking down just a mile offshore. I think he thought I was magic... ;-)

- - - - - - - - - - - - - -
Note: The waterspout calculations do not include stability or moisture parameters. Before using make sure stability and moisture parameters are high enough to support at least widely scattered showers over the coastal waters.
ACARS / Sounding mean wind speed and direction______________

1.) If mean wind below 15,000 feet is (equal to or less than) 8 knots
and max layer wind speed 12 kt or below then.........................add 1.0
(If max layer wind is between 12 kt and 15 kt then only add 0.5)
If mean wind below 15,000 feet is between 9 and 11 kt and
max layer wind speed 15 kt or less then............................add 0.5
(If max layer wind above 15 kt then add 0)

If mean wind below 15,000 feet is greater 12 kt or greater then..add 0
Wind Speed Factor_________
2.) If mean wind direction below 15,000 feet is:

Between 010-069 degrees.............................add 0.5
Between 070-209 degrees.............................add 1.0
Between 210-289 degrees.............................add 0.5
Between 290-360 degrees.......................subtract 0.5

Wind Direction Factor_________
3.) If previous day had waterspout activity and no major synoptic
change expected then.............................................. ...............add 1.0
(Treat waterspouts in Keys and SE Coast Seperately)
Persistence Factor_________

TOTAL WATERSPOUT POTENTIAL________
If total equals 2.0 then waterspouts are possible.
If total equals 2.5 or 3.0 then waterspouts potential is high.
Member Since: Posts: Comments:

Viewing: 296 - 246

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22Blog 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
79 °F
Partly Cloudy