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.
For example, the purple line in the east marks the boundary between air coming in from the ocean and a southwesterly current of warmer air. That boundary was the scene of showers and thunderstorms when it was in the middle of Pennsylvania yesterday, and was associated with rain that moved through the Hudson Valley early this morning.
Looking ahead to late next week, some of the computer models suggest a hurricane could affect areas between the Gulf of Mexico and the Atlantic east of the Bahamas. We are entering the prime part of the Atlantic hurricane season, but at this point there is only one model I am prepared to accept:
The following map shows the individual members of the forecast for the 5,880-meter height line at 500mb. If the 500 mb height is that high, it usually means the weather at the ground in the Northeast is hot. However...
This pressure analysis was made using 9 a.m. ET data. The thin west-east black line is the boundary between hot and cool weather. A low pressure area is moving eastward along the boundary zone, causing showers and thunderstorms. The next low pressure area should send some of the rain farther north.
In the early to middle parts of next week, we expect to see a boundary zone separating hot, humid air to the south from cooler air to the north. A series of ripples or disturbances aloft moving west to east will take turns at enhancing or reducing the chance of showers and thunderstorms.
Looking beyond next week, we see signs of something that has been missing in the Great Lakes and Northeast just about all summer: hot weather. That may change. Here is a computer model prediction of the upper air flow on Sunday, Aug. 24. Note how the flow appears to run from Arizona all the way to north of New England.