Friday 9 AM
Sandy continues to threaten the Northeast, and in the area where is comes ashore, there will be damaging winds knocking down trees and cutting power, flooding rain and, at the coast, a dangerous storm surge. Time of that is crucial, because we will be close to the time of the full moon, and range between high tide and low tide is greatest then. This map shows the track forecasts of a wide variety of computer models. Why the differences? Each one has its own way of ingesting data and handling the intricate math associated with second order nonlinear differential equations. A big problem is we simply do not have data for every place in the atmosphere.
This video discusses where the storm is heading now, what should happen next, and what some of the effects will be. Unfortunately, this kind of storm can affect millions and cost billions.
Over the Ohio Valley, rain is starting nudge northward again, prodded by one of a series of upper air disturbances embedded in the flow. It appears the rain will advance across Pennsylvania overnight, reach the area from New York City to Boston tomorrow... then head out to sea.
Farther north, the area from Chicago to Boston looks most likely to have sunshine and dry weather. Cloud cover will vary during the weekend, and I focus on that aspect of the weekend forecast in this video.
A band of heavy rain and locally violent thunderstorms moved from the New York City area at 4 a.m. to just past Boston (distance: 188 miles) by 9:30 this morning. Note the stunning contrast between where it is pouring (dark red) and where it has dried out.
On the map, showers and thunderstorms were located along and ahead of the gray line that cuts through Pennsylvania and along/ahead of the blue line. Both should be off the East coast by Thursday. Drier air from the Upper Midwest should filter into the Northeast later in the week.
The large storm that drenched the Northeast during the weekend has drifted out to sea and somewhat drier air is coming in to replace it. However, another upper air trough extending from Wisconsin to Louisiana is supporting several pockets of showers and thunderstorms.
From northern West Virginia across most of Pennsylvania and western and central New York, there could be several inches of rain with flooded streets and streams.