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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2052. Levi32
I'm going to grab some sleep now. I'll be back in a while. Everyone stay safe!
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting Levi32:
Satellite blackout is over. No wonder the recon found nothing on the west side lol.



brutal dry air intrusion
Member Since: Posts: Comments:
Well, best as I can tell, she's still 60 miles off of Harkers island... Even if she's going straight north at her current speed, she's got 5 more hours over water.

It's starting to look like she'll just skirt the outer banks like Levi was pointing out. That would be good if it was the beginning of a larger NE turn, but bad if it basically continues going up the coast with the center just off shore.

The forecast points now look like that's exactly what's going to happen... Over Nags head, and skirt the coast all the way to the West end of Long Island, just East of NYC.

Could be an interesting 24 hours... She shouldn't weaken much more along that track. If she would just go inland now, she would probably drop off quick...

Is Irene a Fat Lady? If she is, I don't think she's ready to sing yet...
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2049. Levi32
Satellite blackout is over. No wonder the recon found nothing on the west side lol.

Member Since: November 24, 2005 Posts: 635 Comments: 26647
I think this was the first HH pass where the SFMR or any dropsondes did not record a single 75 kt wind. They obviously exist in the NE-ern portion of the convection but it shows how broadly her energy is sprawled out and how poorly the flight level winds are mixing down to the surface.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Levi32:
Well there is no temperature difference between the inside and outside of the eye, but at least it's not saturated inside the eye anymore lol.

000
URNT12 KNHC 270619
VORTEX DATA MESSAGE AL092011
A. 27/05:57:10Z
B. 33 deg 22 min N
076 deg 35 min W
C. 700 mb 2679 m
D. 54 kt
E. 221 deg 73 nm
F. 295 deg 61 kt
G. 212 deg 35 nm
H. 952 mb
I. 15 C / 3043 m
J. 16 C / 3044 m
K. 7 C / NA
L. NA
M. NA

N. 12345 / 07
O. 0.02 / 1 nm
P. AF306 3109A IRENE OB 03
MAX OUTBOUND AND MAX FL WIND 93 KT NE QUAD 06:10:40Z
MAX FL TEMP 17 C 212 / 9 NM FROM FL CNTR
;


Ive never heard of a 952 millibar hurricane that is barely at category 2 strength. Even stranger is that there is no temperature difference, do think that suggests Irene essentially has no inner core left? The "eyewall" is only showing convection with echotops to 35000 ft, which is way too shallow for normal inner core convection of a hurricane at 952 millibars.
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2046. JLPR2
Quoting sunlinepr:


Well, my family in Ponce, felt no TS force winds... (that's what they tell me) At least in the Pastillo - Fort Allen area...
In Caguas, we did felt TS force winds, but were sporadical...


I had sustained TS winds in Carolina,PR would dare to say there could have been a hurricane gust in there.

But yes, from what I heard the south didn't feel much.
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Once the center makes landfall it usually causes the winds to pick up because the middle starts to spread out and makes the wind field increase
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Quoting tarps3:
what is the link to oz's website again?
crazymother.tv
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Quoting HurricaneLovr75:
so Plymouth mass will be worse than where OZ is?


Wind gusts are expected to be around 90 mph where he is; around 65 mph in Plymouth.
Member Since: September 21, 2010 Posts: 1 Comments: 3690
LOL. As soon as I say good night, my new avatar shows up.
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Quoting JLPR2:


?

We had sustained TS force winds, did you mean Hurricane force gusts?


Well, my family in Ponce, felt no TS force winds... (that's what they tell me) At least in the Pastillo - Fort Allen area...
In Caguas, we did felt TS force winds
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Quoting atmosweather:


It is such a large storm and its pressure is still down near 950 mb...this is a powerful storm and will be slower to weaken than the average system moving up the east coast. I still expect her to remain at hurricane strength as she moves into Long Island and the rest of the NE.


Thank you for your explanation--as always, your post was very helpful!

This certainly is a fickle storm! Might have to rewrite a few textbooks on tropical cyclones...
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Quoting Levi32:
Well there is no temperature difference between the inside and outside of the eye, but at least it's not saturated inside the eye anymore lol.

000
URNT12 KNHC 270619
VORTEX DATA MESSAGE AL092011
A. 27/05:57:10Z
B. 33 deg 22 min N
076 deg 35 min W
C. 700 mb 2679 m
D. 54 kt
E. 221 deg 73 nm
F. 295 deg 61 kt
G. 212 deg 35 nm
H. 952 mb
I. 15 C / 3043 m
J. 16 C / 3044 m
K. 7 C / NA
L. NA
M. NA

N. 12345 / 07
O. 0.02 / 1 nm
P. AF306 3109A IRENE OB 03
MAX OUTBOUND AND MAX FL WIND 93 KT NE QUAD 06:10:40Z
MAX FL TEMP 17 C 212 / 9 NM FROM FL CNTR
;


Lol yeah that's weird...its basically not an eye anymore just a dry spot in the center.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2038. KEEPEROFTHEGATE (Mod)
Quoting tarps3:
what is the link to oz's website again?
www you need a drink .com
Member Since: July 15, 2006 Posts: 171 Comments: 53839
2037. help4u
lol
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Quoting QacarXan:


When it hits the NE will it be hurricane force or tropical storm based on the newest data?


It is such a large storm and its pressure is still down near 950 mb...this is a powerful storm and will be slower to weaken than the average system moving up the east coast. I still expect her to remain at hurricane strength as she moves into Long Island and the rest of the NE.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
so Plymouth mass will be worse than where OZ is?
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Dropsonde measures 952 mb and a 700 mb height of 2681 meters in the eye.

And the maximum flight level winds just found were 100 kts:

061730 3415N 07531W 6975 02955 9875 +067 +049 141099 100 065 011 00
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2033. Levi32
Well there is no temperature difference between the inside and outside of the eye, but at least it's not saturated inside the eye anymore lol.

000
URNT12 KNHC 270619
VORTEX DATA MESSAGE AL092011
A. 27/05:57:10Z
B. 33 deg 22 min N
076 deg 35 min W
C. 700 mb 2679 m
D. 54 kt
E. 221 deg 73 nm
F. 295 deg 61 kt
G. 212 deg 35 nm
H. 952 mb
I. 15 C / 3043 m
J. 16 C / 3044 m
K. 7 C / NA
L. NA
M. NA

N. 12345 / 07
O. 0.02 / 1 nm
P. AF306 3109A IRENE OB 03
MAX OUTBOUND AND MAX FL WIND 93 KT NE QUAD 06:10:40Z
MAX FL TEMP 17 C 212 / 9 NM FROM FL CNTR
;
Member Since: November 24, 2005 Posts: 635 Comments: 26647
2032. tarps3
what is the link to oz's website again?
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2031. Levi32
Quoting HurricaneLovr75:
Is Irene really this weak?


Don't be fooled. This is a 950mb hurricane and her power will be felt. The recon doesn't support more than Cat 1 winds, but stronger winds could come to the ground in gusts after landfall, and the very low pressure means that the overall power of the storm is immense and comparable to a Cat 3, which is what it would be if it had an eyewall without dry air. The size of the wind field means the coastline will get raked with 50kt or higher winds for many many hours straight, which is capable of doing substantial damage.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
2030. KEEPEROFTHEGATE (Mod)
Quoting HurricaneLovr75:
Is Irene really this weak?
yes and it will be getting even weaker as the morning goes by tommorrow may just be a strong tropical storm as she finishes the ride up the coast
Member Since: July 15, 2006 Posts: 171 Comments: 53839
Quoting atmosweather:


That just isn't true...the storm is still extremely powerful and will spread its impacts all the way up the eastern seaboard including in inland areas.


When it hits the NE will it be hurricane force or tropical storm based on the newest data?
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Have a great night, everyone! Hopefully I wake up to a much weaker Irene!
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Don't be surprised if the storm ramps up just a bit between now and the 5AM advisory period.

Atmospheric conditions have heretofore not been friendly to this storm since its trek through the Bahamas. But with the rapidly approaching trough, that could change. Being such an oddball storm it can provide surprises that one would not expect from reading the textbooks on tropical systems.

Also, the SST's are warmer than normal and we have contradictory SST readings for the waters north of NC up to near Long Island.
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Quoting KEEPEROFTHEGATE:
did oz stop by the liqour store for the wiskey you know that will make a cat 1 look like a cat 3 maybe a 4 the more drinks you have hic....
Now Thumper . . .
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Winds have picked up a fair amount here in Elizabeth City. Rain bands coming in are definitely stronger than the previous. Rain is now moderate to heavy, gusts are in the 30mph range. Lightning and thunder with this band.
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Is Irene really this weak?
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Quoting Levi32:
Very lackluster winds in the SW quad of Irene on this new pass from the hurricane hunters.



Not really surprised to hear that, convection is completely gone in the southwest quadrant as seen on radar.
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Quoting KEEPEROFTHEGATE:
did oz stop by the liqour store for the wiskey you know that will make a cat 1 look like a cat 3 maybe a 4 the more drinks you have hic....


You watching that too? holy ch!t he's freaking out...
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Quoting HurricaneLovr75:
this is going to be a rain event for Ny and New England!


That just isn't true...the storm is still extremely powerful and will spread its impacts all the way up the eastern seaboard including in inland areas.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Morehead City

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2019. KEEPEROFTHEGATE (Mod)
did oz stop by the liqour store for the wiskey you know that will make a cat 1 look like a cat 3 maybe a 4 the more drinks you have hic....
Member Since: July 15, 2006 Posts: 171 Comments: 53839
this is going to be a rain event for Ny and New England!
Member Since: Posts: Comments:
Tides running 3+ ft. above predicted at Wrightsville Beach, NC and Beaufort, NC and appear to be building. High Tide ~6am


Hurricane IRENE QuickLook
Posted: 00:00 EDT 08/27/2011



Storm Analysis

As of 08/27/2011 00:00 EDT, water levels at stations from northeastern Florida to North Carolina are elevated between 0.5 and 3.5 feet above predicted tide levels, with the exception of Oregon Inlet Marina, NC and USCG Station Hatteras, NC. Water levels along the North Carolina coast are rising. Levels along the Atlantic coast of Virginia and Maryland as well as the entrance to the Chesapeake Bay remain at or slightly above predicted. Winds are generally increasing from Georgia to the Carolinas, especially at Wrightsville Beach, NC and Springmaid Pier, SC where sustained winds of 40 kts and gusts close to 50 kts have been measured over the past few hours. Barometric pressure continues to fall accross the region.

Water Level and Meteorological plots available below are updated automatically.
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061030 3357N 07553W 6958 02906 9776 +085 +053 147090 093 072 018 00

Still not very impressive even in the NE quadrant.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2015. Levi32
The northeast eyewall still has 90 kt flight-level winds:

000
URNT15 KNHC 270612
AF306 3109A IRENE HDOB 19 20110827
060300 3338N 07617W 6967 02783 9597 133 067 148069 070 063 008 00
060330 3339N 07615W 6961 02794 9622 115 067 149071 073 064 010 00
060400 3340N 07614W 6967 02791 9637 108 066 147071 073 066 014 00
060430 3342N 07612W 6969 02802 9642 112 064 148072 075 067 011 00
060500 3343N 07610W 6967 02814 9665 100 063 148077 080 067 013 00
060530 3344N 07609W 6965 02822 9672 102 062 150083 084 068 013 00
060600 3346N 07607W 6966 02831 9680 104 060 150082 084 069 009 00
060630 3347N 07606W 6967 02838 9690 103 059 150082 082 069 008 00
060700 3348N 07604W 6967 02846 9695 108 059 153083 084 070 008 00
060730 3349N 07603W 6963 02861 9709 103 059 153085 086 069 014 00
060800 3351N 07601W 6982 02846 9732 091 059 149086 087 069 019 00
060830 3352N 07559W 6956 02878 9735 092 057 153087 088 069 019 00
060900 3353N 07558W 6970 02875 9745 093 055 150087 088 069 016 00
060930 3355N 07556W 6966 02886 9747 098 054 151089 091 070 015 00
061000 3356N 07555W 6979 02877 9762 091 054 151087 088 070 022 00
061030 3357N 07553W 6958 02906 9776 085 053 147090 093 072 018 00
061100 3359N 07552W 6964 02908 9785 082 051 147088 089 071 015 00
061130 3400N 07550W 6969 02908 9786 089 049 148091 092 067 016 00
061200 3401N 07549W 6968 02915 9785 096 049 148089 091 069 014 00
061230 3402N 07547W 6966 02922 9782 105 048 149086 086 069 009 00
Member Since: November 24, 2005 Posts: 635 Comments: 26647
2014. tarps3
Don't know if any of this has been posted or not but here are some Tweets from AP and other news sources:

32 minutes ago: "Morehead City, NC, just went dark as wind from intensifies. Battery power only from here on out. "

3 hours ago: "Brunswick NC EOC is on generator power, buzzing along while the rest of the government complex is dark."
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2013. cwf1069
Irene is moving almost due north. For the last couples of hours she resume her track a little be to the left.
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Station 41036
NDBC
Location: 34.206N 76.952W
Conditions as of:
Sat, 27 Aug 2011 05:50:00 UTC

Winds: ENE (70°) at 42.7 kt gusting to 58.3 kt
Significant Wave Height: 28.2 ft
Dominant Wave Period: 15 sec
Mean Wave Direction: S (181°)
Atmospheric Pressure: 28.87 in and falling rapidly
Air Temperature: 79.9 F
Dew Point: 76.1 F
Water Temperature: 80.6 F
Member Since: Posts: Comments:
2010. JLPR2
Quoting sunlinepr:


The same happened when it was a storm over PR.... We had some TS gusts in the North east but in the SW they felt no winds at all.. The tail, did really bring a lot of rain to that area...


?

We had sustained TS force winds, did you mean Hurricane force gusts?
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Quoting AllStar17:
It appears that Irene's southwestern quadarant lacks any hurricane force winds.


The same happened when it was a storm over PR.... We had some TS gusts in the North east but in the SW they felt no winds at all.. The tail, did really bring a lot of rain to that area...
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2008. Mucinex
Not that I'm completely oblivious or insensitive with whats going on with Irene.
But as my main interest is cyclogenesis, anyone have any thoughts on the GFS and ECMWF runs from 66-336 hours (ie Bermuda)?
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Quoting MSweatherguy:
Great website Tampa

Tropical Links? Thanks! I find it very useful. :)
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2006. Levi32
Quoting VAbeachhurricanes:


Yeah, local news was calling this worse than isabel all day. It wont even come close to isabels power.


Well it's not a perpendicular hit to the NC coast so it's not going to beat Isabel in North Carolina. That won't be true farther north though.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting JRRP:


here we go again


Yeah here we go again....can't see links from that site anymore.....been going on all day.
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Quoting Levi32:


These are a lot weaker than even earlier today, though, which is good news. However, it is the very weakest quadrant of the storm. We'll see if they are weaker elsewhere as well. We're about to get a pressure reading in the eye.


Yeah, local news was calling this worse than isabel all day. It wont even come close to isabels power.
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Pretty much the same as it has been all evening:

055730 3324N 07634W 6967 02715 9509 +150 +070 131009 012 009 003 03
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2002. Levi32
950.9mb extrapolated:

055730 3324N 07634W 6967 02715 9509 150 070 131009 012 009 003 03

She's still holding steady, amazingly.
Member Since: November 24, 2005 Posts: 635 Comments: 26647

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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.