Any storm which threatens the Northeast is a worry following Sandy and the damage and exposure brought to beaches, as well as the weakness to trees, power and property.

For many days now, models have shown a Pacific disturbance crossing the country which will deepen a trough already established over the East. This feature will draw energy in as it moves offshore and is set to develop a low pressure centre off the Carolina coast.

The overall flow across the US flattening out with a more north-south thermal gradient. No arctic air will be over the US through at least the next 7 days I believe and anything cold, will be a Pacific-polar origin thanks to increased storm activity between Alaska and the Pacific Northwest.

Residual cold air remains but continues to weaken across the Great Lakes extending into the Northeast, the arctic air has now retreated back to the north thanks to a positive Arctic Oscillation. This setup over the next 7+ days will keep things fairly mild but like I say, there will be an active Pacific storm track which will increase storminess in the West with wind and rain spreading down the West Coast and affecting such areas as San Francisco in coming days.

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Although the AO has turned positive, the NAO is going negative once again and so this supports the prospects of a developing low moving north and paralleling the coast with a building high to the north of the storm.

As we saw with both Sandy and the Nor’easter named Athena, there is divergence in the models with the GFS has been trending further east and ECMWF further west, nearer the coast. That was very much the way with the previous two systems and the ECMWF won out on both occations, so one would have to expect the bias is on the ECMWF.

As you can see from the above chart 1000-850 thickness chart off the GFS, a big high builds over Eastern Canada, this should keep the system nearer the Northeast coast and it may also slow it down between Monday and Thursday. That could be a problem, especially if the low itself holds back further east but drives easterlies towards the shore. A wind blowing from a long way out will pile larger spells into the areas of coast that were devastated.

Ultimately, it’s all in how close it tracks to the coast. Pressures are expected to be down near 978 mb and could bring coastal gales if the low takes that further west track nearer the coast. Heavier, squally rains would also have greater impact onshore from DC all the way to Maine also.

A lot can and likely will change from now till next week but as it stands right now, I personally don’t see this being a major problem given the latest model output. Check out the latest ECMWF for next Wednesday.

Below is the 144 hr 1000-85 thicknesses according to the GFS. Notice the system well offshore. Also notice the action pushing into the Pacific Northwest, that’s a lot of wind energy as well as heavy rains and mountains snows.

If these charts prove correct then by far, the worst conditions remain out at sea, however, wave action may cause problems given exposure to the beaches but rains do not at this time look to be a major deal.

As for snow, well there is relatively mild air going to be in place. Yes it will be chilly across the interior and we may get a few flakes flying, particularly over the mountains but I don’t see this bringing much in the way of snow. The cold air will be well to the north.

The below chart is day-10 (240 hr) of the ECMWF. Notice intensely cold air trying to bleed south over Canada, could this be hints of the AO turning? The next 7-10 days will see cold building over Alaska and Northern Canada and bare in mind that as the AO is expected to go negative again late month, if the NAO holds in negative territory too then a major period of cold and snow is likely for particularly the East.. Stay tuned..

 

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