The first thing I want to do is make a clarification. Based on some comments I received I may not have been overly clear yesterday. I was favoring a more westward solution, closer to the coast, than NHC... in line with the "global models" (models which produce forecasts for the entire globe, rather than "regional" models which run on sub-domains). However, I was not (and still am not) forecasting or expecting an actual landfall. That is important, as Earl's strongest winds will be on his east side. So, if he fails to make landfall, no one is likely to see hurricane conditions. To be clear, depending on how close he comes to the shore, some folks could see tropical storm force winds. Moreover, his nearest pass is still just far enough out so that landfall cannot be written off. So... Earl remains a significant threat, but I did want to clarify that I did not and still do not think Earl makes landfall in the U.S. (I emphasize "in the U.S." because my focus is on the mainland U.S., but a Canadian Maritimes landfall is still very plausible). Anyway, on to the update...
I'm beginning typing this up early in the morning, as I will be interupted repeatedly by my "real" job, and I don't want to get this posted too late. And, in the meantime, before actually submitting this to post, there will not be too much new data coming in. But there will be a little bit of worthwhile data flowing in, so forgive me if my thinking actually evolves as I write this, as a reflection of new data and information flowing in.
First off, let me state that I'm not leaning west of the NHC track any longer. Mostly, it is because they shifted their track left (west) twice since my post yesterday morning. So, I still think Earl will pass close to the benchmark location of 40N latitude and 70W longitude. However, not all of my agreement with NHC is because they've adjusted their forecast. But I'm also leaning a bit more east today. Just a bit. I haven't really changed my thinking that Earl tracks near the benchmark. But yesterday I felt he had an excellent shot of pulling inside (NW of) that benchmark. Today, I'm less certain. He still could, but I think it's equally likely that he runs just outside the benchmark. And even my thinking close to the benchmark, though in good agreement with most of the best models, is on the western side of those models. So, all in all, things haven't changed much, but, if anything, the risk - in my view - looks slightly less than it did yesterday. However, to the general public, depending on the NHC forecast, it's actually gone the other way, as their track has shifted west. They are now just barely outside the benchmark (5AM forecast from NHC puts Earl at 40N, 69.5W early Sat AM).
Well, I'm getting ahead of myself a bit here. Let's take things in the order I usually like to. First, let's get a current look at Earl on satellite:
...needless to say, that's a pretty impressive shot. I kind of speaks for itself. So, all I'll say is, yes, I've certainly seen many more impressive Atlantic hurricanes than Earl. But all of them are amongst the most powerful ones to roam the Atlantic. Earl is quite intense. As I write this we're in a lull in aircraft recon data, so there's nothing new. However, the last pressure reading was lower, with no increase in wind. Since the pressure drives the wind, some slight uptick in wind would not be surprising in the near-term. And, officially, Earl is already right now a powerful Category 4 hurricane with 115kt (130-135mph) sustained winds.
The general thinking on Earl going forward is pretty much unchanged, but the model guidance has been a mess in the fine details. In general, they've been excellent... keeping a tight clustering, showing a track about 50-150 miles off of Cape Hatteras and then about 100 miles off of Cape Cod. The problem is, at those distances, details become incredibly critical. Shove Earl just 100 miles west and we're suddenly looking at deep trouble for Hatteras, Cape Cod and possibly Maine (depending on the sharpness of the eastward turn). But shove him 100 miles further east and impacts will be minimal across the board and all this typing and your reading will be merely an exercise in understanding. And how accurate are forecast 72 hours out (about the range Earl is from Hatteras and Cape Cod... obviously a bit further out for Cape Cod than Cape Hatteras)? Check out this image...
...the average 72hr error in the official forecast (which is, in long term averages, better than any of these models) in the best season ever (last year) was just over 100 miles. Earl may be a bit easier to forecast given the reasonable model agreement, but an error of 50-100 miles seems highly plausible, if not likely. The question is, will Earl be 50-100 miles west, east or neither (he could be right along the projected track and just get a 50-100 mile error by being slower or faster along track)? To be blunt... I'm really not sure... it is a small error distance to try to nail down three days out.
But, anyway, one reason for not pushing the "further west" them much more is better model agreement. Here's where all the model tracks lie:
...I grabbed this from Ryan Maue's excellent web site this time, because this plot contains more of the global model solutions. Remember, those solutions were running more to the west yesterday. Yet, on this plot we see only a handful of plots on or west of the "benchmark". While some of the hurricane models have trended further west (note the blue line landfalling in Cape Cod and Maine is the hurricane-specific HWRF model), some of the global models have trended east (the green line far to the east... the third easternmost track for part of the time... is the Canadian model). Now, mind you, most of the global models haven't jumped east like that. So, I'm not shifting my thinking to the east much, if at all. I'm sticking to a track near the "benchmark". But my reliance on the global models means I'm not inclined to edge things any further west.
So, if it takes a track similar to what I'm expecting, what might the impacts be? Well, it's tough to determine exactly how the wind field will establish itself. Heck, it's hard enough just trying to forecast the actual maximum sustained winds, nevermind the structure of the wind field. So, I'll use a decent hi-res model to depict this. From the same web site linked above, here's the latest HWRF wind and pressure field by Friday morning, when Earl is passing east of Cape Hatteras:
...The surface winds are in the lower right panel. Tropical storm force winds cover the Outer Banks, but do not really penetrate inland. Nor are there anything remotely close to hurricane force winds along the coast... heck, the highest is about 40kts on the coast.
Once Earl gets off of Cape Cod late Friday night or very early Saturday, it looks like this:
...Here it does show some stronger winds, but still nothing outrageous. It has winds no higher than 50kts out at Chatham and Nantucket. However, squalls can "mix down" wind gusts from higher levels of the atmosphere. note the chart on the upper left with hurricane force winds at 900mb (which is roughly a couple thousand feet above the surface) over the entire outer Cape. So, gusts could hit hurricane force there (*according to this model*).
Most models don't show landfall in Maine, they hook Earl east. Let me throw that caveat out there before showing this next plot, because this model (the HWRF) does bring Earl into Maine on Saturday. Here's what it shows for them:
...Even this keeps the hurricane force winds off the coast (lower right panel), though the plot doesn't show max winds right at landfall, so brief hurricane force winds could impact the coast from Eastport down to some point north of Bar Harbor. And the upper left plot indicates that squalls could mix down hurricane force wind gusts over much of southeastern Maine... not to mention Nova Scotia.
Now, let me be clear on one thing... I showed these plots because they are some of the nicest plots to display this information. This is not necessarily the most accurate model. It holds Earl closer to Cape Cod than most models and much closer to Maine than most models. Since I'm still leaning towards the western side of the various computer guidance, I don't think this model's solution is horrible. But I do think Earl will track a little east of this... very much in line with the National Hurricane Center's projection:
...this would yield a reduced impact on Maine and Cape Cod compared to the wind maps shown above. The bottom line then, is this:
I do not expect any hurricane force winds or destructive conditions anywhere in the U.S., though Nova Scotia could see hurricane force winds if Earl doesn't turn so hard that he even cuts southeast of them. But tropical storm force winds, at least minimally (35kt... 40mph), sustained, with higher gusts, do seem likely along the North Carolina Outer Banks, Cape Cod and maybe extreme eastern Maine. Obviously, such winds are not a huge deal for these areas. But there is one remaining caveat... keep in mind the image near the top, showing the typical errors out three days in advance; and there is almost no chance that the forecast error will be zero. So, there is a chance that Earl could move 50-100 miles closer to the coast than currently projected... possibly near the track displayed in the wind field maps above, or maybe even a shade closer. Of course, there is also a chance he'll head more to the east, or that the errors will simply be "along track". So, I'm not trying to be alarmist saying "he could come closer!"... in fact, Earl may even move further out. All I'm saying is that, given standard forecasting errors, there is room for some shifting around of the forecast. And if that shift is in the wrong direction considerably worse conditions could impact the North Carolina, southeastern New England and Maine coastlines. So, all interests in those areas should continue to keep a close eye on Earl.
As usual, I'll do my best to follow comments and answer questions below.
Just a quick note on some new data as I finish this up. New reconnaissance aircraft data indicates that Earl may have peaked... temporarily or permanently is unclear... with his pressure at 935mb. It has earlier been at 931mb (remember, the lower the pressure the stronger the storm). So, Earl is off of his deepest/lowest pressure and, therefore, a little weaker or at least not any stronger (4mb may not really be much "weaker"). Also, the HWRF plots shown above were from the newest run. The other hurricane-specific model (the GFDL) runs at about the same time... just a bit later... and has just come out. It has trended east of its previous run, is outside of the "benchmark" and is east of the HWRF. It is, however, well west of most of its previous runs (it had been one of the further east models). So, this doesn't impact my expectations much... a track near the "benchmark" late Friday. On a side note, I have no real thoughts on Fiona, except that she will likely go out to sea.