Time_Zone wrote:How is the pressure falling? It's over cold water and high shear.
This storm confuses me...
These tropical cyclones transitioning to non-tropical are very confusing until you learn the dynamics. I know them a little better because I live up here where this happens all the time and because my friend Stacy Stewart taught me a lot of this. Because the thunderstorms are maintaining (for the reason I just posted) and the circulation is still very symmetric, the winds are maintaining so the pressure maintains or even drops a little bit. Also, as you go northward towards the poles the Coriolis force gets stronger, so a cyclone with a pressure of 970 mb near Cape Cod is needed to support similar winds as a 980 cyclone would further south. (These are rough numbers just for an example). Recall that Hurricane Sandy (becoming extra-tropical) had a very low pressure around 940 mb at New Jersey but top sustained winds were 70-80 mph. Hurricane Hugo at South Carolina in 1989 had a similar pressure and had sustained winds near 140 mph! There are other reasons that are pretty complex to go into here, especially the dynamic differences between tropical and extra-tropical cyclones, but the important point is that if a hurricane racing northward off the mid-Atlantic has the necessary dynamics to maintain its winds, the pressure will maintain or even drop.
This is a simplification just to give you an overall idea.