It now appears that Irene will be downgraded to a tropical storm before it gets here.
However, it also appears that the eye will pass over, or very close to, this lake. That complicates the forecast -- a lot. Most of our effects from the storm are going to be localized, due to the many hills and mountains we have, as well as the wide-open expanse of the lake itself, which often serves as a runway for wind flow. These local effects are highly dependent on which direction the wind is blowing FROM. If wind hits one side of Gunstock or Red Hill, one thing happens. If it hits the other side, something very different happens.
With the eye of the storm -- the center of the whole storm's counter-clockwise circulation -- expected to track right over the lake, that means the margin of error is equally to either side of the lake.
--If it stays to the west of us, we'll get the strongest winds from the south and southwest.
--If it passes east of us, we'll get the strongest winds from the northeast and north.
--If it goes right over us, we'll get the strongest winds from the east AND the west -- with east winds suddenly dropping off to near calm, then coming back just as strong from the west.
All three scenarios are a good possibility. This much is for sure: We're going to get a big wind-driven rain storm. Local effects (like hills, and the lake) are definitely going to play a role. What kind of role depends totally on what direction(s) the wind blows from.
Here are some of the local effects that have decided our weather before:
* The wind-facing side of any significant hill or mountain will get a lot more rain than the opposite side. The sides of hills facing away from the wind may get much lighter rain -- for as long as the wind stays blowing from the same direction.
* A space between two mountain ranges, such as the Route 25 corridor between Red Hill and the Ossipee Range, can be a wind tunnel. When wind squeezes through there it increases in speed until it reaches the other side. This is not the only "wind tunnel" we have in the lakes region, but is just one easily-visible example. This particular wind tunnel is aligned north-south and works best with winds from those directions.
* The lake itself, aligned NW-SE, has often served as a runway for ocean wind that is strong enough to reach Alton. If any weather is blowing in from the ocean and is strong enough to reach Alton, it can then follow the lake right up to Center Harbor. Locations just a mile north or south of the lake may not experience that weather at all. Wind on the lake reaches more of its potential because there isn't much friction with land to slow it down. By the time it goes from one end of the lake to the other, it's usually a lot faster than when it started out, and the waves underneath it are worthy of the ocean.
* There are many points on the lake shore, and over 200 islands. When wind has to bend around them, it often increases dramatically in that location only.
The main theme with Irene, for the lakes region, will be flooding and wind damage. We're no strangers to either threat here in NH. It happens all the time. What is different this time is that the storm is affecting such a large area of the nation that our usual cleanup help may be busy with their own areas.
The kind of weather that Irene threatens to bring to NH is all stuff we've had recently, but not on the same day.
1. The Alstead floods and road washouts might happen again, in a different town.
2. A tornado like the Raymond-Barnstead-Effingham tornado of 2008 might happen again, on a different path. Tornadoes happen within tropical systems and their remnants.
3. Damage similar to the April 2007 Nor'easter may happen again, in different places.
The question "Where?" is not one that can be answered in advance of the storm. Humans just can't do that.
Statewide, there will probably be numerous roads closed due to flooding, downed trees and wires. Our summer thunderstorms bring that sort of thing all the time to individual locations while areas 10 miles away get nothing. Irene's damage will be over a much larger area.
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