As of 9AM, Irene is now a tropical storm with top winds near 65 MPH and is centered near Coney Island NY, starting to accelerate to the north northeast. Irene continues to have a very widespread wind field of tropical storm force winds and hurricane force gusts. The center will cross western Long Island and western to north central CT, west central to central MA (passing close to Springfield) then up across southwestern NH where it will cut across central NH and into and across Maine by tonight, weakening and beginning to lose tropical characteristics while accelerating in forward speed.
Rain: Expect the heaviest and steadiest rain west of the storm track with more showery but still at times very heavy rain to the east.The heaviest areas of rain will lift north northwest across the Boston area through 1PM. Expect rainfall amounts 1-4 inches east of the track, 4-8 inches to the west, with locally heavier amounts. River flooding most likely in the heavy rain areas to the west. Rivers east of the center will not likely flood and should handle the rainfall fairly well. Poor drainage flooding will be a bigger concern in these areas during and shortly after the heavier rain periods.
Wind: East of the storm track, winds mostly from the southeast to south, often tropical storm force, top gusts 40-60 MPH with locally stronger, except gusts around hurricane force possible along the South Coast and some of the higher elevations. Strongest winds will occur in the next few hours, but will strengthen again as southwest to west winds behind the storm late today and this evening. West of the track, expect northeast to north winds 15-35 MPH with higher gusts, but strongest winds there will be northwest to west behind the storm, 25-40 MPH with stronger gusts, likely over 50 MPH for a period of time Sunday evening. Considerable tree damage is expected from this event, because it has been a while since such a storm, and the ground is saturated from heavy rain before the storm, making the soil softer around bases of trees.
Storm Surge: 4 to potentially 7 foot storm surge flooding on the South Coast, especially in the bays, with the morning high tide. A second surge with the evening high tide and may be similar to the morning surge. East-facing coastal areas will see a storm surge of 1 to 3 feet with the morning high tide as the winds will be most onshore at that time. By the evening tide, the winds will be blowing more from the land toward the water so storm surge flooding will not be an issue, but splash-over flooding may still occur due to the very rough seas and waves.
Tornadoes: Isolated tornadoes are possible in heavier rain bands this through early afternoon, especially from the Boston area and Merrimack Valley to southeastern MA including Cape Cod and the Islands. These are usually very weak and short-lived, but still significant enough to add to wind damage. These kinds of tornadoes are spawned from low level wind sheer (change of speed and/or direction of wind with height) that is set up when friction near the ground slows the wind speed and turns it more toward the center of the hurricane and winds above the ground are fast-flowing and more parallel to the storm center.
Updated Boston Area Forecast…
TODAY: Overcast through early afternoon with numerous tropical showers including some downpours. The heaviest rain in the Boston area should occur through about 1PM. Mostly cloudy mid through late afternoon with additional tropical showers, heavy at times. Brief sun may appear between showers. Mild with tropical humidity. High 70-75. Wind SE increasing to 25-45 MPH gusting 40-60 MPH, occasionally stronger, shifting more to S and eventually SW during the day. Isolated tornadoes are possible from mid morning through early afternoon.
TONIGHT: Rain and showers ending from south to north with breaking clouds before midnight and clearing overnight. Still mild and very humid. Low 65-70. Wind W 15-35 MPH with gusts over 40 MPH, still may reach around 50 MPH over exposed higher elevations, diminishing somewhat overnight.
MONDAY: Mostly sunny. Warm and still humid. High 80-85. Wind W 15-30 MPH early, diminishing slowly.
MONDAY NIGHT: Mostly clear. Low 58-63. Wind W 5-15 MPH.
TUESDAY: Sunny. High 74-79. Wind NW 5-15 MPH.
WEDNESDAY: Sunny. Low 56. High 78.
THURSDAY: Mostly sunny. Low 62. High 83.
FRIDAY: Partly sunny. Low 63. High 82.
SATURDAY: Partly cloudy. Low 65. High 84