Irene continues to weaken

By: Dr. Jeff Masters , 8:46 PM GMT on August 26, 2011

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Satellite data and measurements from the Hurricane Hunters show that Irene continues to weaken. A 1:32 pm EDT center fix by an Air Force Reserve aircraft found that Irene's eyewall is still gone, and the central pressure had risen to 951 mb from a low of 942 mb this morning. The winds measured in Irene near the surface support classifying it as a strong Category 1 hurricane or weak Category 2. Satellite imagery shows a distinctly lopsided appearance to Irene's cloud pattern, with not much heavy thunderstorm activity on the southwest side. This is due to moderate southwesterly wind shear of 10 - 20 knots. This shear is disrupting Irene's circulation and has cut off upper-level outflow along the south side of the hurricane. No eye is visible in satellite loops, but the storm's size is certainly impressive. Long range radar out of Wilmington, North Carolina, shows that the outermost spiral bands from Irene have moved ashore over North Carolina. Winds at buoy 41004 100 miles offshore from Charleston, SC increased to 47 mph, gusting to 60 mph at 3 pm EDT, with significant wave heights of 25 feet.


Figure 1. MODIS satellite image of Hurricane Irene taken at 11:50 am EDT Friday August 26, when Irene was a Category 2 hurricane with 105 mph winds. The eyewall collapsed several hours before this image was taken, and no eye is apparent. Image credit: a href=http://rapidfire.sci.gsfc.nasa.gov/gallery/ NASA.


Figure 2. Distribution of Irene's wind field at 3:30 pm EDT Friday August 26, 2011, as observed by the Hurricane Hunters and buoys. The right front quadrant of the hurricane had about 90% of the storm's hurricane-force winds (yellow and warmer colors, bounded by the heavy black line between the "50" and "60" knot thin black lines.) Tropical storm-force winds (heavy black like bounding the light blue area) extended out 290 miles from the center of Irene. Image credit: NOAA/AOML/HRD.

Forecast for Irene
With its eyewall collapsed and just 18 more hours over water before landfall, Irene does not have time to build a new eyewall and intensify. The storm is too large to weaken quickly, and the best forecast is that Irene will be a strong Category 1 hurricane at landfall in North Carolina on Saturday. Based on the latest wind analysis from NOAA's Hurricane Research Division (Figure 2) and Irene's continued weakening trend, I predict that the 80-mile section of North Carolina coast to the right of where Irene makes landfall will receive sustained hurricane-force winds of 75 - 85 mph on Saturday at landfall; the 80-mile section of coast to the left will receive 55 - 75 mph winds. High wind shear of 30 knots will begin ripping into Irene Sunday morning when it is near Southern New Jersey, and more rapid weakening will occur. By the time Irene arrives on Long Island Sunday afternoon, it will probably have top sustained winds in the 65 - 75 mph range. However, since Irene is such a huge storm--tropical storm force winds extend out up to 290 miles from the center--it has set a massive amount of the ocean's surface in motion, which will cause a much larger storm surge than the winds would suggest. At 3:30 pm EDT this afternoon, a wind analysis from NOAA/HRD (Figure 2) indicated that the potential storm surge damage from Irene still rated a 5.0 on a scale of 0 to 6. This is equivalent to the storm surge a typical Category 4 hurricane would have. While this damage potential should steadily decline as Irene moves northwards and weakens, we can still expect a storm surge one full Saffir-Simpson Category higher than Irene's winds when it impacts the coast. Since tides are at their highest levels of the month this weekend due to the new moon, storm surge flooding will be at a maximum during the high tidal cycles that will occur at 8 pm Saturday night and 8 am Sunday morning. Wherever Irene happens to be at those times, the storm surge damage potential will be maximized. I continue to give a 20% chance that a 3 - 4 foot storm surge high enough to over-top the Manhattan flood walls and swamp the New York City subway system will occur on Sunday. The latest 11 am probabilistic storm surge map from NHC shows a 20 - 30% chance of a storm surge in excess of 3 feet in New York Harbor (Figure 4.) Keep in mind that these maps are calculated for normal tide level, and this weekend's high tides will be nearly 1 foot above normal.

Insurance company AIR-Worldwide is estimating that insured damages from Irene in the U.S. will be $1.5 - $6 billion. They estimate losses in the Caribbean at $0.5 - $1.1 billion from Irene.


Figure 3. Storm surge heights, in feet above normal tide level, which have a 20 percent chance of being exceeded during the next 3 days.  The graphic is based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the current National Hurricane Center (NHC) official hurricane advisory. The exceedance heights depend on the historical accuracy of NHCs forecasts of hurricane track, and wind speed, and an estimate of storm size. Image credit: NOAA.


Figure 4. Overall chance that storm surges will be greater than 3 feet above normal tide levels during the next 3 days.  The graphic is based upon an ensemble of Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model runs using the current National Hurricane Center (NHC) official hurricane advisory.  Storm surge probabilities depend on the historical accuracy of NHCs forecasts of hurricane track, and wind speed, and an estimate of storm size. Image credit: NOAA.

Links
For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Wunderblogger Mike Theiss is in Nassau, documenting the storm's impact on the Bahamas.

Internet radio show on Irene at 4:30pm EDT
Wunderground meteorologists will be discussing Hurricane Irene on a special edition of our Internet radio show, the Daily Downpour, today (Friday) at 4:30pm EDT. Shaun Tanner , Tim Roche, Angela Fritz, and Rob Carver will take your questions. The email address to ask questions is broadcast@wunderground.com.

Jeff Masters

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Quoting ConnecticutWXGuy:
What's ironic about the complaints I've seen in these forums about the precautionary actions being taken in NYC is.... most of them probably don't even live in NYC, or the Northeast for that matter! A few of my friends in Manhattan have told me most of the people there aren't too upset about the evacuation orders and transit being shut down. It's an excuse to miss work and go party somewhere out of the evacuation zone, to most of them.


I've been advocating this whole time for people to take this storm seriously and I'm not even in a city that can get Tropical Storms let alone Hurricanes. Victoria British Columbia here.
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1201. ncstorm
16th Street and Market Street (US 17) in Wilmington have been closed down due to flooding..WECT TV6
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The Topsail Pier cam is amazing. Does anyone know how tall the pier is? I didn't see it on their website. For wave height reference ...

I hope everyone stays safe. I'm another voice saying if you're told to evacuate - GO!! Things can be replaced; lives can't.
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Quoting hahaguy:


http://www.surfchex.com/index.php

Those are some huge waves. :O
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1198. hahaguy
Quoting Hoff511:


hey haha guy did I see you are from the pizzle (aka Port Saint Lucie)?


Yup
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1197. Patrap
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Quoting ncCANEiac:


WOW doesn't begin to express it! That pier floor is about 20' above water level and some of those waves are already hitting the floor! Hate to see tomorrow morning at high tide around 7 AM!!!!
its low tide right now?
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1195. Levi32
The swath of dry air between the inner and outer rain bands might be filling in a little bit on radar, but it is probably too little too late for Irene to strengthen much. However, she is in a steady state, and her central pressure is characteristic of a strong Category 3 hurricane. This speaks to how much water is being pushed by the storm and how large the circulation is. Prolonged exposure to Cat 1 winds can be just as bad as short-term exposure to winds of a category stronger.

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1194. hahaguy
anyone elses video freezing up?
Member Since: August 12, 2007 Posts: 2 Comments: 2838
1193. jdjnola
Quoting ConnecticutWXGuy:
Well here's a question.... how fast was Ike moving when it made landfall? I thought I remember it moving pretty slow as well... slower than Irene will move once it gets past NC


About 12mph:

Link
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1192. Hoff511
.
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1191. rv1pop
Quoting LAnovice:


It is clear that you have never lived where a hurricane landed. Please listen and do not use your inexperience to influence others. You know not what you speak.
I was a facilities manager at a high rise. The windows and structure (walls) are rated for a specific wind speed for either 0.1 or 0.2 hours. That is 6 to 12 minutes. Our 1 inch glass was rated at 110 MPH for 0.1 hour, then it was supposed to crumble so no one below was hit with large shards. A hurricane lasts longer than 6 minutes. Tornadoes, usually not. The windows, by the way, are part of the shear stability of the walls. When the windows go the walls have almost NO structure. Picture a 60 story building with the windows blown out at floor 35. Twenty-five stories probably are coming down on top of the others, then the rest come down - remember the towers.
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Quoting Skyepony:
A few tide gage readings. Beaufort got past the first high tide, but this one wasn't expected to be as high as the next. Wrightsville may have seen their worst surge they should see from Irene. Observations were 1- 1 1/2ft higher than expected. Overall the the new surge forecast has been lowered since earlier today.
Wrightsville, NC 7ft
Beaufort, Duke, NC 5ft




i know for charleston, it was astronomical...morning high was 8 steps higher on the beach access than normal and tonight...the water at the battery wall was higher than the street...if the wall wasnt there...ugh...
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Quoting mojofearless:


WOW. How long do you suppose that pier is going to hold?


WOW doesn't begin to express it! That pier floor is about 20' above water level and some of those waves are already hitting the floor! Hate to see tomorrow morning at high tide around 7 AM!!!!
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1188. Dennis8
Precipitation 2.81 in Wilmington rain so far..
Member Since: August 15, 2008 Posts: 0 Comments: 446
Quoting superpete:
Ok, it is time for a poll on when Topsail Pier is going down. Any takers for 12:00 am Saturday?


An hour tops...if not gone already. HUGE waves hitting it
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Quoting Hoff511:
I clicked on the link quick enough to watch the pier disappear.


I saw that too!!!!
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1185. Thrawst
Quoting violet312s:


Are you serious? Can't you hit a page like CNN or MSNBC? Or scroll back.


Chill .. I was out cleaning up my OWN damage from the hurricane.
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My take on Irene is I'll eat opossum not crow,since i'm from the the south...Brush with the coast of N.C. and out to sea......Stay safe....
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1183. Remek
Quoting Methurricanes:
i think part of the peir @ Topsail beach collpased you can see it in the water, i think.


It's the shadow from the lights on the taller waves.
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It has been E of forecast for a couple of hours now. this is good for the populated areas of NC.



In addition even though it is trying to intensify a bit now the dry air earlier prevented intensification that was expected.
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1181. Dennis8
Precipitation 2.63 in Cape Hatteras Rain today
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Quoting Levi32:


Beach cam? Please share :)


Here:

Link
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Quoting AllyBama:
I am lovin' the TS beach cam!
I'm thinking the ocean is gonna' take that pier down.
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1178. jdjnola
Quoting violet312s:


That is the best cam out there that I can find. And wow those waves are getting huge. (Topsail) That pier won't make it through the storm.


It's kind of scary seeing that much surge that far from the center... I said it before: Irene reminds me of a smaller Ike.
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Well here's a question.... how fast was Ike moving when it made landfall? I thought I remember it moving pretty slow as well... slower than Irene will move once it gets past NC
Member Since: November 17, 2010 Posts: 11 Comments: 527
Quoting 900MB:
Hey Levi and crew-
What are the odds that this landfalls as a major? I am putting it at 30%.

Wish that hurricane hunter would get back to the center, I think we are at 947 or 948 with a good accurate drop.

Presentation looks better, and notice the SW side, actual outflow! Looks like the SW shear is dying down.


Well RECON has been doing center fixes pretty much every hour for the last 24 hours (tons of kudos to their pilots and meteorologists for some outstanding work) and they haven't noted any strengthening or even an increase in the presentation of the inner core. She could still make one last attempt to intensify tonight before approaching the coastline, but I'd say the chances of a landfall as a Category 3 storm at only about 10%.
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Ok, it is time for a poll on when Topsail Pier is going down. Any takers for 12:00 am Saturday?
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1174. hahaguy
Quoting Levi32:


Beach cam? Please share :)


http://www.surfchex.com/index.php
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Quoting Thrawst:
HI guys, can someone update me on what has occurred w/ Irene today? TIA (:


Are you serious? Can't you hit a page like CNN or MSNBC? Or scroll back.
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1172. Dennis8
Quoting Skyepony:
A few tide gage readings. Beaufort got past the first high tide, but this one wasn't expected to be as high as the next. Wrightsville may have seen their worst surge they should see from Irene. Observations were 1- 1 1/2ft higher than expected. Overall the the new surge forecast has been lowered since earlier today.
Wrightsville, NC 7ft
Beaufort, Duke, NC 5ft



That is a devastating amount of water
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i think part of the peir @ Topsail beach collpased you can see it in the water, i think.

NVM, it was stairs of something.
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1170. Hoff511
I clicked on the link quick enough to watch the pier disappear.
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1169. Levi32
Quoting AllyBama:
I am lovin' the TS beach cam!


Beach cam? Please share :)
Member Since: November 24, 2005 Posts: 635 Comments: 26548
Quoting jdjnola:
Oh jeez it looks like that pier is about to be underwater...


That is the best cam out there that I can find. And wow those waves are getting huge. (Topsail) That pier won't make it through the storm.
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Quoting dogsgomoo:
This is a question for anyone that might be able to give a reasonable opinion.

I have some acquaintances living just a bit north of Seaside Heights New Jersey. I've visited them recently and even at regular tide the streets flooded so I've taken a look at the surge predictions for that area. They look high but these people say that they have seen those exact predictions before and all that happened was some decent winds, some street flooding, and the power went out. There will be a voluntary evac and curfew only. Once you're off the island you don't get back on. So they are staying. At least they are prepared with supplies for a week to ten days.

Now that Irene is weaker do you think that this is a reasonable decision on their part? I'm worried but it's hard for me to understand how the surge is really going to go.


There are mandatory evac zones directly north and south of this area. Given what others have said, and looking at the evac map and location, I don't know that I would be staying.
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1166. Levi32
West Beach, Bald Head Island, North Carolina (PWS)
Updated: 9:59 PM EDT on August 26, 2011

74.6 °F / 23.7 °C
Rain
Humidity: 100%
Dew Point: 75 °F / 24 °C
Wind: 54.0 mph / 86.9 km/h / 24.1 m/s from the NNE

Wind Gust: 63.0 mph / 101.4 km/h / 19.0 m/s

Pressure: 29.28 in / 991.4 hPa (Steady)
Member Since: November 24, 2005 Posts: 635 Comments: 26548
1165. Thrawst
HI guys, can someone update me on what has occurred w/ Irene today? TIA (:
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I am lovin' the TS beach cam!
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ok...i finally got pics of high tide here in Charleston from down at the battery...how do i get it from my album to here...inbox me the directions
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1162. Skyepony (Mod)
A few tide gage readings. Beaufort got past the first high tide, but this one wasn't expected to be as high as the next. Wrightsville may have seen their worst surge they should see from Irene. Observations were 1- 1 1/2ft higher than expected. Overall the the new surge forecast has been lowered since earlier today.
Wrightsville, NC 7ft
Beaufort, Duke, NC 5ft


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Time again for the multiple relative check-in. Phone calls non-stop from family in TX and WI. We're as prepped as we can be and I'm well inland (Durham, NC).

You folks on the coast stay safe, looking increasingly ugly.
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1160. 996tt
I dunno. Think worse case scenario is this thing takes a hard right, misses NC for most part and turns bak west when trough passes through for a direct hit on LI. Storm could feasibly stay 100 to 110 mph then and that would be very bad.
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Quoting mcluvincane:



Is that from today? :}



no its not from today
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1158. Verdog
Quoting Verdog:


YUP, lights still on.....

See for yourself


Remember, its is a PTZ controllable camera. It may or may not be looking at the pier.
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1157. jdjnola
Oh jeez it looks like that pier is about to be underwater...
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Quoting TropicalAnalystwx13:

Wow. Flooding already?
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Quoting Remek:


Topsail cam link:

cam


Yes, Topsail getting hammered and she's still about 12 hours off shore.
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1154. 900MB
Hey Levi and crew-
What are the odds that this landfalls as a major? I am putting it at 30%.

Wish that hurricane hunter would get back to the center, I think we are at 947 or 948 with a good accurate drop.

Presentation looks better, and notice the SW side, actual outflow! Looks like the SW shear is dying down.
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1153. Verdog
Quoting TropicalAnalystwx13:


No, it did not...Yet.


YUP, lights still on.....

See for yourself
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Dang, step away for an hour. Irene trying her darndest to get fully dressed again :(
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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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