TS Sandy could have the dubious distinction of offering up the largest East coast surf of the season, not necessarily something to celebrate if you bring potentially destructive winds with you.
With no significant change in the outlook since yesterday it still looks likely (the NHC say 60-70% chance) that after a destructive path through Jamaica, Cuba and the Bahamas the then weakened storm will emerge in the Atlantic with enough power and proximity to produce significant surf for the East coast.
Passing over land will weaken the storm, deprived of the warm water fuel it needs for growth. Wind shear will also have an impact, almost certainly seeing the storm downgraded from Hurricane status – however upper atmosphere conditions are forecast to be favourable for the system maintaining Tropical Storm status on reaching the Atlantic and model outlooks suggest an increase in size on into next week.
The surf outcome, should this be the case, looks markedly different to that of recent storms. Where the best this year has been in the form of relatively well organised mid sized surf from storms kind enough to steer well clear of the coast there’s an odds on scenario in which TS Sandy brings sizeable surf for most of of the coast, accompanied by strong or very strong winds. While it’s quite usual that the swell models can be a little over enthusiastic at this stage none the less numbers like 19ft@13 seconds are cropping up for the Outer Banks and even Florida reflecting the potential power of the storm and, crucially, it’s proximity to the coast.
The GFS model is showing the storm building in size and moving slowly North and away from the coast. If this is the case we can expect a prolonged swell event covering the whole region, with the size at the start but the quality later on as we avoid landfall and see a drop in the winds. However ECMWF shows a closer path to the coast with a potential for landfall over the Outer Banks towards the middle of next week. However the NHC describe the overall outlook as ‘low confidence’ for the period beyond about the next 48hrs so, as always, we’ll have to wait and see.
Winds will be an issue for most of the coast with stronger winds extending all the way to Long Island later in the weekend or early next week on the latest predicted track. Certainly further south winds will all but rule out contestable surf except in the most sheltered locations with a 10-20% chance of N or NE winds exceeding storm force at times from the NHC guidance and a real risk of landfall beyond this looking at the longer range models.