Nor’easter will impact New Hampshire weather

The first nor’easter of the season is brewing just to the south of New England. The pieces are fusing together as we speak and the storm will hurl itself at New England later today.

The main event looks to be late this afternoon throughout the overnight hours. There will be very slow clearing tomorrow so expect another gray and cool day.

Fall nor’easters are not uncommon and do not necessarily need to have snow as one of the principal ingredients. The only true requirement is a strong northeast wind and that certainly will be true later today.

Hurricane Sandy occurred this week 9 years ago and though classified as a hurricane it was more extratropical and nor-easter-esque once it reached our area. This week also marks the 30-year anniversary of the “Perfect Storm.” The Perfect Storm was a deadly combination of a dying hurricane, stalled cold front and other weather phenomena that created one of the most rare weather systems in U.S. history. It is classified as a nor’easter.

The graphic above was produced by the Boston/Norton, MA National Weather Service office and primarily outlines the hazards for Massachusetts (though this could also include southern New Hampshire as well). However, the timeline of rain and wind is the same for just about everyone in New England. The only thing that will differ is the intensity.

This nor’easter is forming under ideal conditions with a polar and tropical connection. The linkage between these two components equals a very strong weather system. The polar piece brings energy and “spin” within the atmosphere and the tropical piece brings heat and moisture. The combination of the polar and tropical conveyor belts will create a nasty cyclone.

The term “bomb cyclone” has been thrown around with this storm and though it will be strong, it doesn’t really fit the criteria (a certain drop in atmospheric pressure in 24 hours). Many winter nor’easters that develop rapidly are true bomb cyclones. Bomb cyclone is one of those sensationalized weather terms like “polar vortex” that someone found within a weather journal which meant one thing and put a flashy spin on it and used it for other purposes.

On and off rain will continue throughout the day and will turn into a steady, heavy and eventually driving rain by this evening. Strong northeast winds will develop by this afternoon with gusts easily reaching 40-45 mph (which is tropical storm force winds).

Southern New Hampshire and especially Massachusetts will likely experience hurricane force gusts with sustained winds in the tropical storm range. Street flooding is possible as fallen leaves clog catch basins. Rainfall rates of 2-3 inches are predicted. Power outages are also very possible with the forecasted wind speeds.

Basically, the closer to the coast you live, the worse this storm event will be for you. The storm will be retrograding (moving west) this afternoon and evening which is a major reason for the significance of this weather event. Most storms in this region move east. This one is moving west. Ocean storms are able to have stronger winds due to less friction and a long fetch with the flatter water surface below them. This is one reason why hurricanes and typhoons are so strong and deadly.

The sun will return by Thursday only to fade away as another system approaches for Saturday. Halloween looks seasonable and most important precipitation free.