1 October 2015
Hurricane Joaquin is now a Cat 3 storm with 115 mph winds tonight, but even if it does not turn toward the Mid-Atlantic coastline, we will see a significant coastal Nor’easter across the Mid-Atlantic from New Jersey to North Carolina including the Delaware and Maryland Beaches. This is because of a strong pressure gradient between a large Canadian high pressure over New England and a low pressure system in the Carolinas.
There seems to be two likely options for Joaquin, one which I think is the slightly more likely, is for it to turn northward into the Atlantic. The ECM model from London continues to forecast this and this is the model that outperformed all the U.S. and Canadian models with Sandy. The reason it is superior is that it has better physics, along with a better initialization scheme. If you cannot give the model an accurate starting point it will not usually do very well! The other option is a turn toward the Carolina or Virginia beaches, which would be, by far, the nightmare scenario for the Mid-Atlantic and Delmarva Peninsula. My guess as of now is that this has about a 45% chance of happening.
If Joaquin does indeed get drawn inland and merge with a strong upper low over the Southeast, there is a potential for rainfall of over 12 inches in a few spots, along with severe coastal beach erosion and inland flooding as well. NOAA has sent up extra weather balloon soundings, and also flown a Gulf stream 4 jet, in and around Joaquin, to take extra samples of the atmosphere at different levels tonight. This data will go into the model runs that are beginning to come in as I write this. The evening NAM Model from NOAA has flipped again and is bringing Joaquin into the Carolinas on Sunday.
Hopefully the extra data will narrow the uncertainty and increase the confidence in the track of Joaquin. If tonight’s run of the ECM finally flips toward the Eastern Sea-board, that would be bad news. In the meantime there remains the possibility of a historic weather event in the Mid-Atlantic. One that may very well be remembered for decades, and change the coastline permanently.