Summary: Results from the latest computer model run from the U.S. based Global Forecast System (GFS) form 12 UTC (8 am) are in and this model continues to generate a historically low central pressure in the surface low pressure system, of what is presently Hurricane Sandy, of near 950 mb. With each successive run that shows a similar outcome, it becomes more worrisome. Just to reiterate, this storm, which is presently a hurricane located over the Bahamas, continues to weaken as it encounters wind shear and cooler waters as it moves north. However, as mentioned in yesterdays post, the storm will begin to strengthen as it begins to draw energy from the jet stream and transitions to a midlatitude type storm. The reason that this storm is projected to become unusually strong is that it will retain much of the energy (latent heat) that it derived from the warm ocean as a tropical system while it draws additional energy (kinetic energy) from the jet stream as it transitions. It is, for the most part, irrelevant whether we call this storm a hurricane or a Nor’easter, or whatever. That only tells us about the structure of the storm and how it derives its energy. What we care about is how deep the low pressure at the center of the storm is, since the pressure “gradient” (how much the pressure changes over any given distance) determines how strong the wind will be, as well as how large the storm will be.  These two factors will combine to determine how large of a storm surge will be generated, and this is the most dangerous feature of any coastal storm. It still appears that the storm will have a very tight pressure gradient and will also be very large. As I discussed in the Introduction to Meteorology class this morning, the strongest winds and greatest surge are always to the right of the storm track. The GFS continues to bring the center of the storm onshore near eastern Long Island and the Connecticut Coast. If this were to hold true, then eastern LI, easter CT, RI, Cape Cod and the eastern Coast of New England would be in greatest danger.

The higher resolution North American Model (NAM), which only generates results out to 84 hours (due to its high resolution), now shows landfall at the end of its run. This model also shows landfall over Long Island but with central pressure of 960 mb (still very low) on Monday evening. The GFS has landfall early Tuesday morning. The results from the European model are not in yet and I will update this post when those results become available. In terms of possible impacts in Berkshire County, IF the storm does follow that track, we would likely have gale force winds with some gusts near or exceeding hurricane strength, with widespread power outages likely. Rainfall flooding would be a very big concern since we could receive 5 inches of rain, with locally heavier amounts. Fortunately, storm surge, the biggest fear in a coastal storm, is not an issue for us……

The weather timeline for Berkshire County for the following week is likely to progress as such: After the low level clouds “burn off” and it clears this afternoon, temperatures will warm into the 60s. However, with all of the low-level moisture (high dewpoints for this time of year) low clouds will likely develop again tonight. It will remain mild tomorrow but it will be very difficult to “burn off” the low clouds tomorrow as the sun becomes blocked by increasing high and mid-level clouds from the enormous cloud shield extending out from Sandy. It should be cloudy and cooler on Sunday but other than a few isolated sprinkles or light showers, we should remain rain free. Rain should begin to develop overnight Sunday or early Monday and become heavy at times Monday night into Wednesday. We will continue to have showers into Friday although the rainfall intensity will decrease markedly, starting on Wednesday as the storm stalls over the Northeast but weakens dramatically. Winds will begin to increase on Monday and will reach their peak on Tuesday but begin to die down considerably on Wednesday. Most of the rainfall, which at this point looks to be about 3-5 inches should have fallen by Wednesday morning. We will probably not see the sun again until sometime next weekend.

One note: I have been asked many times about snow with this system. Snow will not be an issue for us. There may be some snow over Ohio, western PA and West Virginia. It will become progressively cooler over the course of next week as the low becomes cut-off and the colder air from the trough mixes into the system. It will probably only be in the 40s later in the week for high temperatures.

Friday Night

Low clouds will build back in but it will remain mild.

Low temperatures will be near 50 countywide.

Southerly winds at 5-10 mph will shift to the southeast and become light after midnight.

Saturday

Mostly cloudy. Still unseasonably mild despite the cloud cover.

High temperatures near 60 in Pittsfield, Williamstown, Adams and North Adams, low 60s in South County and upper 50s over elevated terrain and the hilltowns.

Southeasterly winds at 5-10 mph.

Saturday Night

Remaining mostly cloudy and mild.

Low temperatures will again be near 50.

Easterly winds at 5-10 mph.

Sunday

Overcast and a bit cooler. It may even feel somewhat “raw” after the run of mild weather we have had. There is the chance of a few scattered sprinkles and light showers. Probability of precipitation 40%. Any precipitation totals should be under 0.05 inches.

High temperatures in the low to mid 50s in lower elevations of Central and Northern Berkshire, mid to upper 50s in South County and near 50 to low 50s over the elevated terrain, depending on elevation.

Northeasterly winds will increase to 10-20 mph in the afternoon with some gusts in the 20s.