Summary: The computer forecast models are beginning to converge somewhat on Hurricane Sandy. The exact track is still somewhat uncertain but most models now have landfall along the Northeast U.S. coast while Sandy is in the process of undergoing an “extratropical transition” from a tropical storm to a strong midlatitude cyclone (think Nor’easter). Landfall is most likely between the Delmarva Peninsula and the southern New England coast sometime late Monday into Tuesday. The European model (ECMWF), which has the best track record, has the storm making landfall along the southern New Jersey coast/Delmarva Peninsula region on Monday afternoon. This model has been very consistent with this track. This model generates a central pressure for the surface low in the 970-980 millibar (mb) range. This is quite deep and would be likely accompanied by gale force winds and coastal flooding and power outages. However, this scenario is unlikely to lead to a catastrophic outcome. The U.S. Global Forecast System (GFS) model generates a bit of a different scenario. It has the storm making landfall along the Long Island/southern Connecticut coast on Tuesday afternoon after it has undergone an “extratropical transition” and intensified profoundly due to its interaction with and extraction of energy from the jet stream. This model generates an enormous amount of divergence in the wind field at upper-levels of the troposphere (jet stream) above the storm on Monday and Tuesday while the storm is still out over the relatively warm waters of the Gulf Stream. Essentially, this divergence would create a vacuum at upper-levels that would suck air rapidly up and out of the atmospheric column above the surface storm causing a rapid drop in pressure. Since the storm would be over water where there is little friction so there would be little convergence at the bottom of the column to replace the air being evacuated from the top. The bottom line is that the GFS model generates a surface pressure between 940 and 950 mb. This is equivalent to the central pressure seen in a Category 3 hurricane and would create an enormous pressure gradient that could generate hurricane force winds and a very large storm surge. This scenario could, in fact, be catastrophic. However, before you think that I am engaging in hyperbole (just call me The Weather Channel), let me clarify by saying that I believe this “nightmare scenario” is not particularly likely. The situation does bear close monitoring over the next few days though. If the computer models begin to converge on this scenario than I think it would be wise to engage in enough hyperbole to get folks living along the coast, inland, and out of harms way. One scenario that does appear likely is that, as I noted yesterday, this storm should be very slow moving once it nears land and makes landfall. Therefore, there likely will be a prolonged period of rain, possibly through Thursday, and rainfall flooding would likely occur in the usual flooding prone river valleys. As of this point (4-7 days away), it appears that most areas could receive upwards of 2-3 inches of rain with upwards of 5 inches in some locations. More on all of this tomorrow……On a more boring note, our local weather is finally starting to improve with the sun poking out in most of the county this afternoon and temperatures reaching 60 in many locations. Sunshine should return with more vigor tomorrow as the warm front weakens and moves east and this will allow temperatures to reach 70 in many locations. It will remain mild on Saturday but begin to cloud up as the trough/cold front to our west inches eastward and then stalls to our west, awaiting the arrival of “Sandy”.

P.S. After writing this summary, the ECMWF run from this morning came in and the central pressure of the storm when it makes landfall is in the 950-960 mb range. Yikes! Me not liking this much. This model still has landfall near the Delmarva Peninsula sometime on Monday, even as early as Monday morning. More to come……

Thursday Night

Mostly cloudy and remaining mild.

Low temperatures will be near 50 countywide.

Winds light and variable.

Friday

Mostly cloudy early with increasing sunshine over the course of the morning. Becoming mostly sunny and unseasonably mild during the afternoon.

High temperatures in the upper 60s in Pittsfield, Williamstown, Adams and North Adams, low 70s in South County and mid 60s over elevated terrain and the hilltowns.

South-southwesterly winds at 5-10 mph.

Friday Night

Clear in the evening with an increase in clouds after midnight. Remaining unseasonably mild.

Low temperatures will again be near 50.

Calm winds.

Saturday

It will start out partly cloudy early in the morning. There will be an increase in clouds throughout the day. The cloud increase will involve high clouds at first, which will filter the sun, but these clouds will thicken and lower somewhat over the course of the afternoon. It should be mostly cloudy by late afternoon.

The cloud cover will likely keep it a few degrees cooler than Friday. High temperatures in the mid to upper 60s in lower elevations of Central and Northern Berkshire, near 70 in South County and low to mid 60s over the elevated terrain, depending on elevation.

Light north-northeasterly winds.