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*For the 3:30 Update jump down below the fold.

Irene is already onshore in North Carolina, so I suppose this morning's update - since I primarily focus on the forecast, because I'm trying to raise people's awareness and preparation, is mainly for folks off to the north, in New Jersey, New York and New England.  Folks up there (or should I say, "up here", since I'm in NY myself?) still have time for last minute preparations.  It won't be fun, as it'll be fairly rainy today.  But today is predominantly lead-up "junk" rain, lacking too much wind (maybe an occasional gust), as it's not even 100% related to Irene.  An old, dying frontal boundary is being pushed back onto us by Irene's southeasterly flow.  And her flow is strong enough to force some rain to break out along this front.  So, anything you need to do to be prepared, you still have time to wrap up today.

That said, if you prepare properly, you should be fine.  This was never going to be the collossal, once-in-a-millennium storm that the media was playing it up to be.  But now, with Irene weakening, it won't even be the "major" event that the more subjective analysts thought it would be.  I do not want to downplay things too much.  There will still be some pretty significant impacts from Irene!  You should still make sure you are amply prepared.  But, when all is said and done, you'll probably walk away from this thinking it was just a bad storm.

 First, let me just point out that in an attempt to emphasize Irene's weakening, perhaps to many I OVERemphesized her lessenning impacts.  Make no mistake, there WILL be storm surge flooding, there WILL be rainfall flooding, there WILL be wind damage - especially tree damage, which will bring with it plenty of power outages and collateral damages.  All the effects predicted from Irene will still occur.  But about 24 hours ago when the coverage of this really revved up and when I posted my last diary, Irene was forecast (by the NHC and myself) to come ashore the Northeast as a 70-75kt hurricane; and before that she was expected to come ashore at 80-85kts.  Now, the forecast is for a 60-65kt tropical storm or hurricane (and in my own personal opinion, that may be high).  There really can be no question that losing 10-20kts of intensity the damage Irene yields will be less, wind damage will be less and surge damage will be reduced (maybe only slightly, given her fetch, but it will be reduced).  But to be clear, folks should still be 100%, fully prepared for the worst.  Irene is still a large, strong storm!  Don't disregard warnings or advice just because she's a little weaker.  I'm trying to emphasize her weakening because it IS pertinent to her damage potential, and most of the media I'm seeing is acting like it doesn't matter... like Irene's the same storm she was 48 hours ago.  She's simply not.  But, that said, be smart, take all necessary preparations for a full-fledged hurricane Irene.

At any rate, I wanted to post an update on Irene's progress, as she is getting close to coming off the North Carolina/Virginia coast.  While odds of any re-intensification back over water seem small, given that she's actually weakened the past 48 hours, the dry air entrainment seems to have reduced some.  So, folks in Irene's way should contniue to keep tabs on the storm.  There is a small chance she revs up a bit here in the next six hours or so.  It is NOT expected, but it is a definite outside possibility given her improved appearance on satellite (rather remarkable that this occurred over land).  As one commenter correctly pointed out below, forecasting intensity is always the tough thing in these storms.  The forecast accuracy is not that high - and it certainly hasn't been great with Irene (which is a good thing - since, to date, she's usually been coming in on the weak side).  But a recent recon plane continued to find 90+kt winds at flight level.  So, if Irene can get a solid burst of convection, she could re-intensify some.  Again, NOT expected... but possible.  Just keep an eye on her.  It won't matter much at all for rainfall - that'll be torential no matter what.  It'll only matter a little on surge, as I mentioned above.  But it would notably increase the potential wind damage.  The force wind creates on objects is exponential.  Do the math on that... 50kts winds versus 60kt winds doesn't sound like a big difference, but theat mere 10kt difference creates a 44% increase in wind force.  So, just as Irene's weakening really IS a big deal, esp. with regard to wind damage potential... it also will be if she manages to regenerate a little here coming off of NC/VA.  So, even at this late hour in Irene's life cycle... stay tuned!

The media has really overplayed this storm.  But, frankly, it's easy to poke sticks in the eyes of the media.  Even I (and most meteorologists, I don't think I'm alone here) never saw this degree of weakening coming with Irene.  There has never been that much really extreme dry air surrounding her, and there still isn't.  Yet, Irene has made a habit of sucking in just about as much dry air as she can find.  She did it sucking in dry air off of Hispaniola's mountains.  Then right after that did it by sucking in dry air to her southwest.  And she's doing it again sucking in dry air over the U.S. off to her west.  The amazing thing is that this was not extremely dry air.  I've seen hurricanes inhale far more extreme dry air.  And, yet, she responded like someone just poured water in her gas tank.  Travelling over the extremely warm Gulf Stream, with superb upper level outflow and only some modest shear from the southwest, Irene still choked out and weakened some... almost solely due to the dry air (the weak shear may have had an impact too, but upon examining the satellite imagery, I doubt it... it was all dry air induced).  If one were to personify Irene, she'd be the big, thin-skinned bully, or the big, powerful prize fighter with the glass jaw.

She continues to struggle, and this is what she looks like this morning, as she impacts North Carolina:


...actually, that core of convection near the center looks stronger now than it has in the last 12 hours... ironically, since Irene's over land now.  But you can still see those breaks in the yellow and orange colors (which represent the convection) on the southwest side.  Those breaks are where the dry air is eroding Irene.  This dry air has been the blessing for the East Coast.  Irene was previously expected to hit North Carolina as a Category 3 and NY/New England as a Category 2 (or high end Category 1, at least).  Now, she's come ashore as a Category 1 in North Carolina and may only be a tropical storm for NJ/NY/New England - though she is officially expected to hold onto minimal hurricane strength.

At this point, the forecast is pretty well a done deal.  Here's where the National Hurricane Center's brand new advisory takes her, and I see no reason to argue with it:


So, my focus now is to point out the impacts the Northeast can expect:

Winds:  I think this'll be a mixed bag.  On the one hand, winds will probably come in far under what some have been advertising.  If New York City itself (at the official observation site at Central Park) comes in with sustained winds exceeding 50mph at any time, I'll be surprised.  On the other hand, Irene has remained pretty strong aloft.  Part of her weakening is her inability to transfer those winds down, because of weaker convection.  Normally, the winds the reconnaissance planes get (when they fly at the level they've been flying at) can be taken at 90% to estimate surface winds.  Not too long ago earlier this morning recon clocked a wind to nearly 100kts, which would've supported Irene being about 90kts.  Yet she's only at 75kts now and, frankly, that may be a little generous.  Anyway, I explain that all to point out that what it does mean is that any good squall could transport down MUCH higher gusts.  So, these winds are, as I said, a mixed bag.  Sustained winds will be modest, but there could be some impressive gusts embedded within there.

The biggest problem from winds is going to be tree damage... taking out power lines, blocking roads, falling on houses and cars, etc.  But it's going to be spotty.  I don't think the sustained winds will be enough to yield excessive, widespread tree damage.  But to my point above, anywhere where one of these heavier squalls moves through could see briefly, much higher wind gusts.  And at those locales there could be some pretty hefty tree damage.  Given the sporatic nature I expect the damage to be, this is a great case of "expect the worst, hope for the best".  Be prepared for a multi-day power outage, get all loose stuff indoors, don't park you car under a tree, etc.

Rain:  Rain is going to be pretty excessive near and a little west of the track.  This could be a pretty big deal.  Rainfall is one aspect that doesn't minimize with a weakened storm.  In fact, some of the worst rainfall totals in tropical cyclones have been in mere tropical storms.  Here's one model's rainfall prediction.


...It's just a model.  It won't be perfect, but it gives the correct idea.  Near and a little west of the track rainfall amounts of 6-10" will be the rule.  That's a lot, especially in areas where the ground is saturated by heavy rains over the past couple of weeks.  Small creeks and streams will likely flood.  Low lying areas and poor drainage urban areas will flood.  Anyone who has issues with basement flooding, roof leaks, etc is probably going to have an issue with this storm.

Storm Surge:  This has really been talked up.  From a scientific standpoint it will be interesting to see what really happens.  Irene will barely be a hurricane (and may not be) by the time she hits the Northeast tomorrow.  With that, surge heights would normally be pretty minimal... 1-3 feet.  On the other hand, she's a large storm and moving relatively slowly for an East Coast storm, allowing her to really pile up the water.  So, maybe a 4-6 foot surge could occur... and on top of the near new moon high tides.  Another case of "prepare for the worst, hope for the best".  Though I'd add, perhaps lost in all the media hype, even a worst case with Irene won't come remotely close to the "big one" that is talked about (a Category 3 hitting the city with a bit more of a NNW motion).  The surge will be, at worst, "moderate".

Tornadoes:  In the front right quadrant tornadoes can be spawned by landfalling hurricanes.  This is a pretty minor issue, as they're relatively weak tornadoes and are few and far between.  Nonetheless, they can occur and any tornado is going to have stronger winds than Irene herself.  So, folks east of the forecast track should be aware of this threat.

So, that's pretty much the story with Irene in the Northeast.  She's significantly weakened and I do not expect her to wreak any widespread havoc on the region.  But, that said, she can produce some pretty furious wind gusts, so there will definitely be some tree damage - even if somewhat scattered - resulting in power outages, transportation issues and tree-impact damages.  The rainfall with Irene is also certain to cause some local flooding issues.  The surge is a bit more of a question mark, it might be no big deal, but people in the warned area would be fools not to heed the warnings.  Tornadoes are probably the smallest threat, but people east of the center should still be alert to the possibility.

And as for the timing, Irene's biggest impact on the Northeast should be early morning Sunday to early evening Sunday.... starting and ends a little sooner than that as you move south through New Jersey.

Originally posted to millwx on Sat Aug 27, 2011 at 08:50 AM PDT.

Also republished by Hurricane Kos and _.

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