Hurricane Irene Weakens on its Approach to North Carolina

By: Dr. Jeff Masters , 7:58 AM GMT on August 27, 2011

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As of 300AM EDT, Hurricane Irene was located at 33.7N, 76.5W, 60 miles south of Cape Lookout. It was moving north-northeast at 14 mph with maximum sustained winds of 90 mph, making it a Category 1 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 952 mb.

Hurricane warnings are in effect for the US Atlantic coast from the Little River inlet in North Carolina to Sagamore Beach, Massachusetts. Tornado watches are also in effect for the North Carolina/Virginia/Maryland coast. Figure 1 shows the hurricane, tropical storm, and tornado watches and warnings for Irene. Remember, a hurricane warning means hurricane conditions are expected, and tropical storm force winds (greater than 34 mph) will occur within 36 hours. Tropical storm warning means that tropical storm force winds are expected in the next 36 hours, but hurricane conditions are not. A tropical storm watch means tropical storm force winds are possible within 48 hours.

To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes. FEMA also has a blog describing their response to Irene.


Figure 1 Map of watches and warnings taken at 225AM EDT, August 27, 2011

Satellite Views
Figure 2 shows that Irene is a large storm, with outflow reaching from South Carolina to Long Island, NY. Irene's eye is not visible.


Figure 2 IR satellite view of Irene taken at 226AM EDT, August 27, 2011

Track Forecast

Irene is forecast to make landfall on the North Carolina coast Saturday morning as a category 1 storm with sustained winds around 90 mph. I believe that Irene's center of circulation will make landfall somewhere between Cape Lookout and Okracoke on the Outer Banks around 9-10 am. Irene should then move roughly north, along the mid-Atlantic coastline before making landfall in western Long Island. However, it is important to not focus solely on the track forecast. Irene is a large storm with a large windfield and equally large areas of storms and showers. It's impact will be felt over a wide swath of the northeastern US.


Figure 3 Official track forecast of Irene at 11PM EDT, Aug. 26.

Irene and Flooding
Six to ten inches of rain are possible along Irene's track from North Carolina north into New England, with 15 inches possible in isolated areas. Radar estimates indicate at least 5 inches have already fallen near Morehead City, NC. As a result, flooding is very likely. The Hydrometeorological Prediction Center (HPC) has issued their Significant River Flood Outlook for the next five days shown in figure 4. HPC thinks that river flooding from the Delmarva peninsula to northwestern Maine is likely, while river flooding in much of the rest of the northeastern US is possible.


Figure 4 Significant River Flood Outlook issued by HPC.

Impacts

Tropical storm forces winds are occuring at Cape Lookout now, with hurricane force winds expected on the North Carolina coast later today. Use this Wundermap to keep track of how the winds are behaving around the North Carolina coastline. Within the hurricane warning area in North Carolina, storm surge is expected to be 6-11 feet above ground. This is our storm surge forecast map. To see how high the tides are running, NOAA has an excellent page collecting all of the relevant tide gauges.

People living on the the east coast of the US from the Carolinas to Cape Cod should continue monitoring Irene and be in the process of finishing their hurricane preparations. If you have not started preparing for this storm, start immediately. If an evacuation order is given, please follow it, unless it is unsafe to do so. Irene will be a large storm, impacting areas far from the storm center track.

Links

If you're curious about power outages, here are some maps: Dominion Power Outage Map (NC/VA), Progress Energy Outage Map (NC/SC), and NOVEC Outage Map (Northern Virginia).

Dr. Masters will have a new blog entry this morning, and there will be another blog this afternoon. I'll be back with another blog entry late tonight.

Stay safe,

Dr. Rob Carver

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Quoting nola70119:
I wonder if that Aussie is still having a suck on his fag,.....?

Sorry, I don't smoke.
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Quoting WeatherNerdPR:


It would be very helpful to the blog (and keep the number of "idiot" posts like this one to a minimum), if images had either contained within them, or as a poster's comment, a description at least of what the image is. Even better would be, as someone asked yesterday, a note saying what we should be looking at, specifically. Just think how much help that would be to those of us working on an informal weather education. Thank you for being one of our teachers.
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Quoting FLdewey:


I cannot imagine how much hog poop is floating around right now... will be an environmental mess.
,wiat to you see the juice nyc produces with over 5" is less than 24hrs
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Quoting NoVaForecaster:


Well said. People really need to get their facts straight before claiming "weakening" or "strengthening" and even "FISH!". Regardless of the appearance it is still a major event for the whole east coast that doesn't happen that often. The behavior of intense systems like this is way different in northern latitudes than southern ones.


This could be the Godzilla of Nor'easters.......not technically a nor'easter of course.
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Quoting QacarXan:


Will it be worse than Isabel?

Also, when is she going to turn toward the NE? She looks like she's headed further west than predicted.


Yeah she's drifting a little west of forecast...I expect she will try to hug the coast and stay pretty close to the water. Let's just say that I don't see her going deep into New York State. She should theoretically start moving more northeastward after she passes Virginia Beach, but you never know lol. She's already pulled some short-term motions that weren't predicted by any model.
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Quoting aquak9:
Quoting 996tt:
Guys saying people are stupid for being on the streets in their cars, but wait, he is standing in the streets with nothing but googles on.


GOGGLES go on the eyes...but where do GOOGLES go?


I thought he was wearing a computer and performing internet searches in the middle of the storm..
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Quoting aquak9:
Quoting 996tt:
Guys saying people are stupid for being on the streets in their cars, but wait, he is standing in the streets with nothing but googles on.


GOGGLES go on the eyes...but where do GOOGLES go?
Searching for answers?
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Just browsing through some of the posts this morning, and it seems as though people are of the opinion that friction due to landfall increases the wind speed. But can that be right? I had thought that friction would slow the wind down.

Maybe people are referring to the fact that the air that piles up at landfall is inclined to rise, leading to additional convection and a burst of local strengthening. But to me, that's different. Clarification, anyone?

Quoting Titoxd:


Actually, there is a third variable there: size. If we look at a one-dimensional Navier-Stokes equation, you have ∂u/∂t +u*∂u/∂x = -(1/ρ)*dP/dx + ν*((∂^2)u)/(∂(x^2)) - friction. From there, we can see that an increase in dP can be offset simply by increasing dx by a similar amount.

Irene for some reason decided to expand its radius instead of increasing its winds, and is now a gargantuan storm. If it hadn't expanded as much, you'd have a storm with stronger winds.


Although I'm not sure you're analysis is strictly correct, since the dx occurs in other parts of the equation, consider your self +1'ed! I'm not terribly familiar with the Navier-Stokes equations, but I do know that they're extremely important, and are notoriously unwieldy. In three dimensions, mathematicians can't even prove if physically realizable solutions exist!

From Wikipedia:

  • Prove or give a counter-example of the following statement:
    In three space dimensions and time, given an initial velocity field, there exists a vector velocity and a scalar pressure field, which are both smooth and globally defined, that solve the Navier–Stokes equations.


  • The real world, of course, leads one to conjecture 'yes'. But mathematically, we cannot answer why. The understanding gained from a proof would go a long way in nailing down one of the trickiest unsolved problems in physics: turbulence.

    Solve this problem, and folks from all walks of science would want to shake your hand. Oh, and you'd also net a cool $1 million.
    Member Since: Posts: Comments:
    Quoting P451:


    There's no reason to doubt it.

    These folks trying to equate Irene to a storm that makes landfall down in the tropics are out of their league. Period.

    They don't understand baroclinic forcing. They don't understand how a jet stream can ventilate the system. They don't understand extratropical transition. They don't understand the expanding wind field situation.

    None of this is in their league so they just see an 85mph cane, with a somewhat ragged appearance, that made landfall, is entering cooler waters, undergoing shear, and they expect it to wind down quickly - as a storm in the tropics under those conditions would.

    What they don't understand is some of these conditions are helping Irene maintain strength or even deepen.


    They get all upset when someone forecasts's a storm's intensity and path when it comes over their homes but now they seem free to tell us all up north it's just a fart in the breeze.

    Their opinions are neither reality nor fact and when the storm is over and done with they will all be proven to be incorrect in their assumptions.

    Even as they are reading the storm reports of damage, seeing the incredible rainfall totals, and now reading of injuries and fatalities, they are still claiming it's a nothing storm doomed to weaken rapidly.

    It's ignorance at it's best.
    Lets not forget to add a big ole helping of arrogance to inflate these same folks ego.
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    Quoting h0db:


    That's probably true for the NE US, but for folks living in the Outer Banks, whether the surge comes up the sound or the Atlantic is a big deal, and it could be for Va Beach and the Delmarva.

    NBC Affiliate WAVY10 showing tornado damage at Sandbridge Beach VA now, BTW.


    I didn't mean to minimalize the surge......I am afraid all that water is going to pile up against Long Island that runs east/west.....
    Member Since: Posts: Comments:
    Quoting FLdewey:


    I've spent a lot of time in Eastern NC... they have no shortage of the pig.

    OOOoooo and good BBQ.

    Scotts BBQ in Goldsboro is worth the 10 hour drive!


    Poole's BBQ in Ellijay, Ga. Finest kind.
    Member Since: August 18, 2008 Posts: 0 Comments: 884
    Does anyone have pics or links to cams for Chesapeake Bay Bridge?
    Member Since: Posts: Comments:
    Quoting CanesfanatUT:
    P451 - are you a met? You speak quite eloquently. :)

    Just learned a new word.
    Member Since: Posts: Comments:
    925. jpsb
    Quoting weatherwart:
    I posted this early this morning, but what do y'all think?

    Instead of just issuing the Saffir-Simpson scale for a storm when it begins to threaten land, perhaps they should issue a second rating, a "Threat Scale" as it were.
    Excellent idea, IMHO Saffir-Simpson is inadequate.
    Member Since: Posts: Comments:
    Quoting Levi32:


    Wow - 115mph gust. That's what we were talking about with those higher winds mixing to the surface once in a while. Irene is capable of surprising a few folks with random gusts well over Cat 1 force.
    ,unoffical,i see no other reprts even close,85-90 mph max,and in 12 hrs we should have a strong ts imo,i would like to add great job you and bob did with irenee,easily 12-24 hrs ahead ofthings ,great job!!!
    Member Since: Posts: Comments:

    Quoting FLdewey:


    But... but Reed has Jesus on his side.

    In more important news, All Starbucks closed in NYC. Now this is getting serious.
    Some one needs to set Jesus back on his feet!
    Member Since: Posts: Comments:
    Quoting Levi32:


    I agree. Some of the hype has been too apocalyptic for this situation, but it's still going to be one of the worst storms in recent memory for the northeast United States.


    Will it be worse than Isabel?

    Also, when is she going to turn toward the NE? She looks like she's headed further west than predicted.
    Member Since: Posts: Comments:
    P451 - are you a met? You speak quite eloquently. :)
    Member Since: Posts: Comments:
    Quoting weatherwart:
    I posted this early this morning, but what do y'all think?

    With Irene, I was thinking maybe the NHC might think about updating/changing their warning system. Instead of just issuing the Saffir-Simpson scale for a storm when it begins to threaten land, perhaps they should issue a second rating, a "Threat Scale" as it were.

    That scale could take into account the size, forward speed, direction, tides, barometric pressure, land features ahead of landfall, where the eye will be (landfalling or over water), etc. Maybe just a color code, i.e. Cat 1, Threat Red.

    Some kind of married warning system would give a better picture to folks that just a SS scale would. Because this CAT 1 storm certainly will do more damage than say some small, fast-mover coming across the GOM and watering a dry Texas.


    Yes, and add rainfall too that......everyone is looking at the windspeed, but look at the size of that and the pressure is still low. You have a Cat 3 energy field spread out over hundreds of miles.,,,
    Member Since: Posts: Comments:
    Quoting norfkstreetdoc:


    Apologize for giving that impression...however for this area even a slight wobble/jog whatever to the west means the difference between mid-tropical storm winds and mid-cat 1 winds as the current track has CoC missing us by only a handful of miles. Not trying to doomcast.


    i was not singling out anyone in particular,it just tends to happen on here quite often.
    Member Since: September 18, 2010 Posts: 0 Comments: 5100
    Quoting sullivanweather:
    91L has had the appearance of an erupting volcano.



    Loop


    IT does look cool.
    Member Since: Posts: Comments:
    since I'm link deficient I don't know how to post this, but looking at the Wunderground map for the North Carolina area the bands are showing increased rain amounts. There are several red areas, and many more orange. Earlier today they weren't that strong.
    Member Since: Posts: Comments:
    Glad I moved my car earlier. There's now a tree where it was...

    Hurricane Irene Live Stream Raleigh, NC
    Member Since: Posts: Comments:
    912. h0db
    Quoting nola70119:


    Irene now a huge system.....the energy is spread over hundreds of miles. This is not an eyewall event, so looking at any single point is a mistake in my opinion.....its going to be the water that does the damage.


    That's probably true for the NE US, but for folks living in the Outer Banks, whether the surge comes up the sound or the Atlantic is a big deal, and it could be for Va Beach and the Delmarva.

    NBC Affiliate WAVY10 showing tornado damage at Sandbridge Beach VA now, BTW.
    Member Since: Posts: Comments:
    Quoting Levi32:




    Now that is an impressive span of winds.
    Member Since: Posts: Comments:
    909. 996tt
    Quoting P451:


    Can't be happening. I was assured yesterday on this blog that the storm was rapidly fading and weakening and would be a weak TS by morning.

    :|



    Sad story. Pray for his family. Wouldn't be good taste to use someone's tragedy to sarcastically try and prove point. Even a thunderstorm can down trees and be threat to life so of course this is serious whether a TS or cat 1.
    Member Since: Posts: Comments:
    Looks like an 82kt gust in Cape Hatteras:

    Member Since: Posts: Comments:
    Quoting FLdewey:


    I cannot imagine how much hog poop is floating around right now... will be an environmental mess.

    lol Gross.
    Member Since: Posts: Comments:
    I posted this early this morning, but what do y'all think?

    With Irene, I was thinking maybe the NHC might think about updating/changing their warning system. Instead of just issuing the Saffir-Simpson scale for a storm when it begins to threaten land, perhaps they should issue a second rating, a "Threat Scale" as it were.

    That scale could take into account the size, forward speed, direction, tides, barometric pressure, land features ahead of landfall, where the eye will be (landfalling or over water), etc. Maybe just a color code, i.e. Cat 1, Threat Red.

    Some kind of married warning system would give a better picture to folks that just a SS scale would. Because this CAT 1 storm certainly will do more damage than say some small, fast-mover coming across the GOM and watering a dry Texas.
    Member Since: August 18, 2008 Posts: 0 Comments: 884
    Quoting zoomiami:
    All the damage that is being reported through Hampton roads, Virginia Beach etc -- and they aren't even in the worst of the weather.

    I agree with the post earlier that people are saying not so bad right now, but I think when its over it will be worse than people believed.

    Discussing this yesterday, my opinion is that people judge these storms against Andrew or Katrina, and then think its not so bad. Which it isn't, but doesn't make this storm less dangerous.


    In New Orleans most of the damage from Katrina was from flooding, and from the looks of Irene, she might surprise some people. 10-12inches of rain is an extremely dangerous flood situation locally, regionally it could be a Biblical flood...
    Member Since: Posts: Comments:
    Quoting FLdewey:


    I cannot imagine how much hog poop is floating around right now... will be an environmental mess.


    What a lovely thought.
    Member Since: Posts: Comments:
    Just saw the Hurricane Irene Tropical Update intro, love that track. VERY large storm.
    Member Since: Posts: Comments:
    Quoting zoomiami:
    All the damage that is being reported through Hampton roads, Virginia Beach etc -- and they aren't even in the worst of the weather.

    I agree with the post earlier that people are saying not so bad right now, but I think when its over it will be worse than people believed.

    Discussing this yesterday, my opinion is that people judge these storms against Andrew or Katrina, and then think its not so bad. Which it isn't, but doesn't make this storm less dangerous.


    I agree. Some of the hype has been too apocalyptic for this situation, but it's still going to be one of the worst storms in recent memory for the northeast United States.
    Member Since: Posts: Comments:
    Looks way west. Se ct looks better it would seem.
    Member Since: Posts: Comments:
    Quoting FLdewey:


    At least he knows which way the wind is blowing.


    perhaps "shrinkage factor" is the missing variable?
    Member Since: Posts: Comments:
    Just FYI - by looking at radar, looks like an eyewall is forming with Irene. It now covers the center to the North, West and South - East is open but it looks like the storms are trying to wrap around the center on the east.

    Land seems to definitely be helping the center tighten up.
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    Quoting Tazmanian:
    this sure dos not looking like its moveing 14mph lol
    More like Drifting NE.
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    This cant be a coincidence.. but FX movie channel is playing a movie called 'Me, Myself, and Irene'
    Member Since: July 8, 2005 Posts: 259 Comments: 23565
    Quoting h0db:
    Well west and north of NHC track--COC is over eastern mainland NC, not the Outer Banks as forecast. Needs to turn NNE, but VA Beach at least is going to get more than it expected yesterday.


    Irene now a huge system.....the energy is spread over hundreds of miles. This is not an eyewall event, so looking at any single point is a mistake in my opinion.....its going to be the water that does the damage.
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    Quoting reedzone:


    Still.. his opinion.. I fully believe Irene with the pressure she has will maintain Hurricane force till landfall on Long Island. 75-85 mph.
    In this country we seem to have some confusion about the word opinion. While all citizens have equal right to hold and express an opinion, opinions are not of equal value. That's why we have the expression "Cconsider the source". Of course this is just my opinion.
    Member Since: Posts: Comments:
    Quoting zoomiami:
    All the damage that is being reported through Hampton roads, Virginia Beach etc -- and they aren't even in the worst of the weather.

    I agree with the post earlier that people are saying not so bad right now, but I think when its over it will be worse than people believed.

    Discussing this yesterday, my opinion is that people judge these storms against Andrew or Katrina, and then think its not so bad. Which it isn't, but doesn't make this storm less dangerous.


    ++++++!!!!!!!!
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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.