Wednesday, August 24, 2011

Irene Becoming Very Dangerous; Major Impacts Still Expected Along Much of U.S. East Coast

As of the 5pm EDT National Hurricane Center (NHC) advisory, the center of Hurricane Irene was located about 30 miles East/Southeast of Long Island, Bahamas.  This position is also about 215 miles Southeast of Nassau, Bahamas.

Maximum sustained winds were recently measured by a Hurricane Hunter Aircraft at 120 mph.  The minimum central pressure was 28.17 inches of mercury (954 millibars).

Irene was moving toward the Northwest at 12 mph, and this general motion is expected to continue overnight tonight and into Thursday.

As you can see in the above visible satellite picture (visible meaning the presentation is as if you were up in space looking down and that image is what would roughly be visible to your eyes), the eye of Irene has become obscured again.  You can still make out the eye on the infrared (measures the temperature of the clouds) and water vapor (measures the amount of moisture in the clouds) satellite images, as shown below:

The large "bubble" of higher cloud tops just to the North of the center (you can really see them the best on the visible satellite image) appears to be vigorous new thunderstorm development right along the Northern part of the eye wall.  This signals that we could be witnessing the beginning of an "eye wall replacement cycle" in Irene.  In a nutshell, as the name implies, an eye wall replacement cycle refers to the process in which the original (or a subsequent) eye wall is replaced by a newly developed one.  You can click on the link in blue in the middle of this paragraph for a more technical explanation if you're so inclined.

Some fluctuations in intensity can be expected during the eye wall replacement cycle, however, in the end... Irene will emerge at least as strong as she is presently, or more likely stronger.  Irene is continuing to move into a region favorable for strengthening, both with respect to warm water temperatures and favorable middle & upper level weather conditions.  These factors suggest that Irene will strengthen into at least a Category 4 hurricane (winds of 130+ mph) during the day Thursday.

In general, computer model forecast trends have not changed significantly since my last detailed post at about this time yesterday (with the possible exception being on the Northern end of the track, which we'll get to in a minute).  Below is the latest computer model composite image:

...and the official NHC forecast track also generally remains the same through the Mid-Atlantic Coast, with a Westward shift on the Northern end of the forecast track (which we'll discuss in more detail shortly):

What about Florida?  Yesterday I alluded to the fact that tropical storm force winds were still not to be ruled out along the far Eastern coastline late Thursday and into Friday.  We'll have to see how rapidly the Western edge of the tropical storm force wind field expands tonight and Thursday.  If Irene makes the expected more Northerly turn during the second half of the day on Thursday, indeed only the outer fringes of the extreme Eastern coastline could potentially see wind gusts to near tropical storm force.  Regardless of whether this takes place or not, steady East-Northeast winds of 30-35 mph and much higher than normal surf can be expected along the Florida East coast late Thursday into Friday.

As we started pointing out on Monday, it's from the Carolinas on Northward that will face the most significant impacts from Irene.  One thing that's absolutely driving me crazy at this point are completely irresponsible media headlines such as these:

As usual, these and other folks are completely fixated on the forecast track of the center of the storm.  The black dots that you see on the above forecast track map from the NHC, the various colored dots along the track forecasts of the computer models, etc., etc., all show where the center of Irene will be at a given point in time.  This does not mean, in any way, that strong, potentially damaging winds will only reside at those locations.  Quite to the contrary, as I've been trying to point out for the past several days, Irene is already a large hurricane and is forecast to grow even larger.  As she does that, the corresponding wind fields will also expand outward.

For example, lets take the latest image from the NAM Forecast Model, valid at 11pm EDT on Saturday, August 27th:

Sure, the model is forecasting the center of Irene to be offshore "path moves to the East; Irene to stay offshore..." as the media would say...  That's not what's important though.  If you take a closer look at the forecast wind field around the Western side of the system, and you'll see that the model is predicting sustained winds of 85-90 mph as far West as the Raleigh-Durham area (darker red colors to the West of the center).  

This is why I continue to preach that anyone living across roughly the Eastern half of North Carolina should continue to make preparations for hurricane force winds on Saturday.  Unless the center of Irene tracks 100 or more miles East of the current projection, hurricane force winds are likely in this region - not just along the outer banks!  This 100 mile envelope could also change over the next 24-36 hours, if the hurricane force wind field expands even further out from the center than currently expected.

We'll be able to fine-tune the likely wind impacts across the Carolinas as early as tomorrow as additional recon, satellite and computer model data are obtained.  In the meantime, please don't fall victim to the hype and focus solely on where the center of Irene is forecast to track, as the impacts will be felt in a much larger area on both the East and West sides of the storm.

Further North, it's continuing to look like Irene will have significant impacts on the major cities from Baltimore/Washington and New York City, on into Boston and New England.  

If the following GFS computer forecast model verifies, then sustained winds of up to 80 mph can be expected in the Baltmore/Washington area late Saturday night and early Sunday morning (image valid 5am EDT Sunday, 8-28-11):

About 12 hours later, the same model is forecasting sustained winds of around 100 mph on Cape Cod and 85-90 mph possibly as far West as Boston (image valid 5pm EDT Sunday, 8-28-11):

Aside from the potential impact from the winds, serious flooding and coastal storm surge impacts also need to be considered in these areas.  We'll be able to fine tune each of these potential impacts over the next 2 days as the future path and intensity of Irene becomes more clear.  

I strongly urge (as I have been for nearly 3 days now) all residents from the Delmarva region on Northward across New Jersey, Long Island, New York City and up into New England (definitely including the Boston area) to closely monitor the progress of Irene.  Begin making preparedness plans now that way you're not caught off guard later in the week.

Irene is likely to be the most significant hurricane to affect the Northeast since at least Hurricane Bob back in 1991.  Don't be caught off-guard!

We'll be able to be even more specific as to projected impacts from the Carolinas on Northward stay tuned, and remember not to pay attention to short-term fluctuations in intensity or computer model tracks in the meantime - it's the smoothed out average that counts!

Let me restate this one more time - If you are reading this and live from North Carolina on Northward along the East Coast of the U.S. - your preparedness plans should continue.  Please don't wait until panic sets in and it's too late to take responsible action!

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1 comment:

Anthill_Goddess said...

Thank you, Rob. I hope some heed your words (I've been "sharing" you on my FB page today in hopes!)