Sunday Sandy Update

6:12 PM, Oct 28, 2012   |    comments
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Ok now that the morning show is over I can spend a little more time on the details of Sandy and her impact on Maine.

First let's get through the 24 hour forecast: Mostly cloudy with some patchy drizzle. Clouds from the outer shield of Sandy have engulfed the state so I don't anticipate much in the way of sunshine. Temperatures stay in the 50s.

Now on to Sandy. What struck me this morning when I pulled up the satellite image of Sandy is how a BIG storm she is. Her spatial coverage is enormous, form the center through the outer bands. In fact, according to the Hurricane Hunter aircraft data from this morning, tropical storm force winds extend over 500 miles away from the center. I've never seen a wind field THAT large.

What that large wind field means for Maine is that the exact track of Sandy is no longer important. Track was king a few days ago when it meant the difference between a direct hit into Maine and a sharp left into the Carolinas, but now that most computer models have zeroed in (thanks for joining the party boys, could have used some agreement days ago) just south of New York City a shift 50-100 miles north or south will be of little consequence to our forecast.

Now that the track is pretty much decided the real key to the forecast is determining the period of strongest wind gusts here in Maine and what some of those gusts might peak at. Sure, there will be a decent amount of rain and some minor coastal flooding, but make no mistake, Sandy's biggest impact will come in the form of wind gusts.

Winds: My thinking right now is that Maine, southern Maine in particular will be most exposed to strong winds between 7 PM and 11 PM Monday evening. You will wake up to some breezy conditions already by Monday morning but those winds will steadily increase through the afternoon and early evening as Sandy moves northward towards the state. Why do I say "most exposed"? Because Maine will experience the strongest wind gusts when the "fetch" is from the northeast-east as the winds will be coming directly in from the ocean and NOT over any landmass. This wind direction looks most likely right before Sandy makes landfall to our south, so that's when I'm penciling in the strongest gusts (Monday evening). Once Sandy moves further inland over NJ, the winds will be out of the south and all of a sudden we are essentially using MA, RI and CT as a shield against the brunt of the wind field. (Winds slow over land due to friction, that's why interior Maine won't see the gusts the coast will) 

I think we will see gusts, during this peak period, of up to 65 MPH with some isolated 70 MPH readings over southern coastal Maine. Further inland it will likely stay in the 40-60 MPH range as the land slows down the incoming air. By Tuesday morning(7 AM) winds will decrease a bit to the 40 MPH range and stay in that area through the afternoon on Tuesday.

I will fully admit I'm going aggressively high with these wind gust numbers, and they might not match up with other predictions you see...but there's a method to my madness. I am concerned the computer models are having a hard time "mixing" down winds from the upper levels of the atmosphere down to the surface with Sandy because they aren't exact sure what to make of her structure. She won't be a warm core hurricane at landfall, nor will she be a cold core Nor'easter. So I'm going to err on the aggressive side in the interest of safety.

Rain: Bands of rain will spiral in from Sandy starting Monday afternoon. Some of these bands will be heavy, however, I don't see statewide flooding as a problem. Total rainfall amounts from the storm ARE high but that's over a several day period as Sandy sits and spins overhead as a weaker low pressure system on Wednesday and Thursday. Most of us will end up with between 1.5-3.0" of rain for the event with the best chance of higher amounts being the lee side of the mountains. The reason for this? Moisture screaming in off the Gulf of Maine will bank up along the ridge line and produce heavier rain there. Computer models NEVER pick up on this, but the situation looks ripe for this kind of effect. So, in short, the foothills and western Maine should be concerned about flooding more than the rest of us.

Coastal Flooding: There will be some coastal flooding but I'd characterize it as minor. Low lying areas that typically flood during a strong Nor'easter will flood during Sandy. The time of largest concern will be around midnight on Monday evening when high tide is occurring.

As I mentioned winds will SLOWLY settle down through the day on Tuesday, as the rain continues on. By Wednesday Sandy will be trapped to our southwest as a decaying low pressure system so expect periods of rain and showers with breezy conditions. The same really goes for Thursday, but the winds will slacken even further by then.

Our next chance at a totally dry day arrives on Saturday.

Bottom Line: Sandy will hit Maine hard, but nothing compared to what they will experience down towards New York City. The impact for the metro area could be historic.  Around here, take this storm seriously but don't panic. The hype train has been off the charts lately and given the facts on the table, in my opinion you simply need to be prepared for some flooding and widespread power outages...nothing more.

Twitter: @keithcarsonWCSH  



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