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Weather Wisdom

Hurricane Arthur to bring rain to all and some wind to Cape/Islands

Happy Independence Day folks. I know it's not the weather we all hoped for, but it's all we got.

Arthur, a formidable Category 2 hurricane, hit the outer banks of North Carolina, making landfall there as the earliest storm to do so on record. This morning, they will be able to assess damage. Fortunately, the storm is now going to stay off the coast before making landfall as a weaker hurricane or strong tropical storm in Canada tomorrow.

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Here in southern New England this is primarily a rain event. Winds are negligible except over Cape Cod and Nantucket where a tropical storm warning has been issued. The reason this advisory is posted is because winds can reach 39 miles per hour. Of course Cape Cod, Nantucket, and Marthaís Vineyard have all seen winds much stronger than this in a winter snowstorm, so this isnít a big deal.

If you are nervous about the storm and live in an area under the tropical storm warning, you should take in your lightweight (plastic) lawn furniture. And if you are a boat owner, secure it however you normally would for a moderate noríeaster. Anytime you get some gusts of wind near 40 miles per hour there can be scattered power outages and a tree can fall, but this would be the exception not the rule from this event.

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For the rest of the region itís a rainy afternoon and overnight. The map below shows one prediction for rain early this afternoon. Notice the rain from Arthur is south of us, but there is a feeder band of sorts running north from the storm. This is part of the cold front which is now interacting with the storm. This will help to enhance rainfall amounts through the next 20 hours when most of the rain will fall. (until about 3AM).

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I am not expecting widespread flooding from this storm. Yet, any setup like this does provide the opportunity for a lot of water in a short period of time. Therefore, we are under a flood watch. Rainfall will range from an inch to 6 inches across the region with the highest amounts likely in pockets which see thunderstorms.

The map below shows how much rain is expected from this storm. If you review it, youíll notice there are no 6 inch amounts over land. However, since the amount of water potential is so high and so close, itís prudent to put that number as the high mark for the storm. Most of us after this is over will likely see 1 to 3 inches of rain with those higher amounts being in pockets rather than widespread.

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I would check my sump pump just in case you end up as one of those towns with the extreme amounts of rainfall. Earlier this week Rumford, Maine saw over 4 inches of rain in one hour! A few towns away saw half of that. Tropical air masses can provide as interesting a pattern in rainfall as a good winter storm can do for snow.

I think itís going to be really tough to get the Red Sox game played today. Even if itís not raining at Fenway by 1:30 PM, itís very unlikely it wonít be sometime during the game. My hunch is they will postpone it before then, but check with them of course.

This next map shows rainfall increasing in coverage by 6PM. Remember, these are static maps and the precipitation moves. Focus on the widespread rain, not individual holes in the rain.

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This whole system rapidly moves east and north of the region by early Saturday. At sunrise just after 5AM there might be some clouds left, but by 7AM or 8AM the sun will be bright and the air will feel a lot drier. Dew points are going to drop by 20 degrees by mid-morning tomorrow, this mean you will no longer feel the moisture in the air. This next map shows how far east the rain will be after sunrise Saturday.

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Iíll be updating the forecast @growingwisdom on Twitter.

High temperatures will reach the upper 70s and lower 80s Saturday and be similar or a few degrees warmer for Sunday. As usual it will be coolest over Cape Cod and in the hills. Winds will be gusty in the morning over Cape Cod, not a great morning for a boat ride with the seas still a bit churned. If you are going swimming this weekend rip currents will be a factor so be cautious.

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Have a great 4th of July weekend and Happy Birthday America!


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