The Pieces to the Puzzle Called Sandy

Posted by Chris Lambert

The forecast challenge for early next week continues with the path of Sandy and any impacts that’ll have on our weather here in New England.  

The 5:00 AM update from the National Hurricane Center has Sandy as a tropical storm with winds of 70mph.  Sandy likely becomes a hurricane as it approaches Jamaica later today and maintains hurricane strength as it approaches Cuba later tonight.   Sandy then goes through the Bahamas and emerges north of the Bahamas by Friday night. 

Notice the 5-day track? There is a hard turn NE by Saturday and almost all of the time, that turn is the point of no return, where storms head out to sea and never look back.   Especially in the Fall when a fast moving, west-to-east jet stream accelerates storms across the opens waters of the Atlantic. 

Therein lies the potential problem.  The jet stream may, indeed, not be west to east this time.  There are a few computer models that insist that a massive area of high pressure builds in south of Greenland and just east of Labrador, blocking the pattern.  It’s what we meteorologist refer to as a negatively indexed North Atlantic Oscillation (-NAO).  That often coincides with the jet stream upstream (across the eastern U.S.) buckling.  If a piece of energy can rotate in around that buckling jet stream at the right time across the eastern U.S., Sandy could actually phase with that upper-level energy and move back toward the coast.  If this were to occur, Sandy, which transitions into a massive Nor’easter, would provide an expanding shield of powerful winds and rain, bring in damaging gusts, flooding rains and coastal flooding over parts of the mid-Atlantic and/or New England anywhere in the Sunday-Tuesday timeframe.  Highest impact areas would depend on track.

Obviously, the stakes are high, but unfortunately, so is the margin of error.  In the grand scheme of things, we’re trying to have a system in the Caribbean phase with upper-level energy which is currently way out in the Pacific, based on what happens to pressure patterns south of Greenland. If it sounds complicated, that’s because it is, and that is the reason why computer models are having a tough time handling it.  Climatology tells us this is a storm for the fishes, which is certainly still a strong possibility, but given the fact that the NAO is so strongly negative, a plausible argument can be made for this one heading back to the coast.   There have been October storms that haven’t curved out to sea.  Hazel in 1954 is one, and the Gale of 1878 is another.

I’m not leaning one way or the other at this point giving how far out we are.  My advice for the next couple of days is to keep checking up on this, as new model data comes out and the pieces to the puzzle get closer together in the atmosphere, the picture the puzzle leads to will become clearer. The forecast challenge for early next week continues with the path of Sandy and any impacts that’ll have on our weather here in New England.  

Come On Ride The Train

Posted by Pete Bouchard

Heavy rain is on the move! All afternoon long it was stalled over Western Massachusetts and Connecticut. Heavy pulses of rain traveled over the same towns and cities - a process meteorologists call "training" - resulting in flash flooding in some counties to our west.

Unsettling

Posted by Jeremy Reiner

Another day where we have cool, ocean air battling warmer land air leading to a clash of air. That means clouds, drizzle, fog, humidity (frizzy hair) for much of the day. It's not a washout though. The highest chance of rain is this morning--until 9:30am and then later this afternoon (after 3pm). In between, you will see a lot of clouds but also some sunshine at times. Even limited sun will be able to shove temps well into the 70s. This warm & humid air is what will lead to another round of showers & t-storms later today. Some of the storms will be intense. Like the past two days the strongest storms will be in western New England. Only isolated showers/ thunderstorms are expected along the coastline later today. Sox game will have the risk of some showers but they should be able to play that game. Welcome back Tito!

Saved by The Sea Breeze

Posted by Pete Bouchard

Although my forecast was busted today, there was one good thing that came out of it.

Stability.

That gray overcast that hung over the eastern half of the Commonwealth provided a stablizing influence to our atmosphere. The cool air blowing in from the ocean kept the temperatures in the upper 50s and low 60s all the way back to Metrowest. While that makes for lousy short-and-t-shirt weather, it is poison to thunderstorms.

Wild & Wacky

Posted by Jeremy Reiner

Wild temperatures yesterday---from the 80s down into the low 60s in just an hour AND some heavy duty thunderstorms. The reason was a cool front that dropped in from Maine. That front is in western New England this morning and it's a chameleon as it will become a warm front and try to warm things back up during the day.