Irene - 8/24/2011 at 11:00 PM

I have received multiple requests for updates on Irene, and I actually started providing them on Tuesday.  I promised that I would call out Meghan as the first requester.

Obligation fulfilled.

To Meghan on Tuesday, I laid out three possible scenarios, all of which were possible at the time.  The first was a southerly course with a landfall in South Carolina.  I rated this as unlikely.  The second was a landfall in North Carolina, south of the Outer Banks.  The third was a brushing of the Outer Banks.  My prediction on Tuesday was a blend of options two and three.

Not too shabby for five days out, better than the NHC at any rate.

So far, this hurricane has been nearly textbook.  It helps that the NHC has been running about three missions a day into the eye of the hurricane, and another five to seven around it.  That provides excellent data for all of the models to do with it what they will.  Therefore, most of the one to three day forecasts have not only had very good precision, they have been remarkably accurate.

The problem is in that five day range where there can be a range of 200-300 miles difference in predicted landfall.  We know a lot about hurricanes, but not everything.

The trend for the past four days or so has been a gradual turn to the north and east from the predicted long-range tracks.  I thought there would be a limit to those changes, and it appears to have been reached.  The current three day forecast calls for Irene to clip the Outer Banks (perhaps with landfall) Saturday night as a strong category two to a moderate category three.  I think it more likely to be a weak to moderate category three.

What does this mean for a forecast?  Avoid the coast.  Seriously.  Don't go there.  If you're anywhere along the coast from Myrtle Beach to Newfoundland, stay away.  Even surfers should avoid the water.  The rip currents are nothing to mess with, and that is starting shortly.

Normally when hurricanes get above North Carolina, there's not as much warm water to work with so they quickly fall back from a hurricane to a tropical storm.  The key word today is "normally".  This year does not follow that definition.

Water temperatures along the coast are anywhere from 2-2.6 degrees Celsius above average, which means Irene can stay a hurricane until approximately Long Island.  So after its brush with the Outer Banks, Irene is going to be tracking up the coast drawing on a deep reservoir of warm water.  It's going to be big, powerful, and have a ton of moisture to work with.  Areas along the coast could easily see over six inches of rain, maybe even ten or twelve.

Depending upon the overall track, DC and Baltimore look to only be in for less than two inches.  Coastal Delaware, New Jersey, New York and New England could see hurricane force winds and perhaps require an ark to navigate the waters.  It's very likely that inland in those areas will see at least tropical storm winds.  In fact, Irene looks to make landfall close to Cape Cod as a category 1 hurricane.  Yeah, Massachusetts.

Tropical Storm force winds will extend 150 miles or so from the center, hurricane force probably 60 miles or so.  Earlier today the forecast track was still a little out to sea such that the Outer Banks were only going to get brushed, but I think there's a decent shot at landfall there (briefly).  The models have come around to support this idea.

Overall, exact timing and details are yet to be finalized, but up and down the coast, it's going to be a wet weekend.  Coastal Carolina could make up for their moderate to severe drought just this weekend alone.  No such like for Texas.  If things change, I'll probably end up posting about it.  There will be a lot more refinements made over the next couple of days, and an exact track up the coast probably won't be refined fully until Friday.

Stay tuned.