Messy Evening Commute

Just in case you forgot, we have not reached 32 degrees for over 180 hours now, dating back to last Sunday! Although I am sure that most of you already knew that it has been damn cold. Well, that cold air is about to finally retreat back into Canada. But not before we get a poorly timed few inches of snow.

One look at the current surface temps in the US will show you the large divide between the cold air and the warm air. The surge of warm, moist air has overtaken much of the Midwest and is heading our way.

Some of that warm air will begin to leak into New England today. Remember, warm air is lighter than cold air. And this cold air we've had for 8 days really doesn't want to leave quietly! So that surge of warm air will ride over the surface cold air and creates this.

All of the leading precipitation is snow, which will be ours to deal with sometime after 4PM. Bad timing. We aren't talking about a blockbuster storm here, generally 1-3 inches for most. But we all know that any snowfall that starts at the same time as the commute does creates big time problems. Expect a slow go of it tonight.

Notice the pink color on the image above. That denotes mixed precipitation. Eventually, the warm air will intrude at all levels of the atmosphere, including the surface. So we should all change to a sleet/freezing rain mix after midnight tonight and early tomorrow morning. Any untreated surfaces tomorrow might be a bit slippery.

Tomorrow is a transition day but we really tap into the warm surge of air on Wednesday. Highs around the area will be in the mid to upper 50's!

Active Week Ahead

Last winter, our problem was warmth. This winter, while warm at times, I think most of you would agree that cold air hasn't been an issue! I mean, we are going on 100 hours now of our temperatures being below 32 degrees. Even for New England, that is a long cold outbreak!

But as we know in the weather world,changes are ahead. Not for tonight however. Take a look at the current afternoon temps in the area.

There is still plenty of cold air for everyone.In fact, some new guidance suggests that the while the rest of us see some moderation in the temperature department over the next few days, northern New England will hang on to that Arctic air through the weekend.

As for any snow, well the fishies are going to get a good storm, but not us. Take a look one model run from this afternoon.

We see here that the energy diving from the mid-west eventually develops into a decent storm, just too far offshore. We have seen this happen with our last 3 potential storms. There is not one exact cause for why this is happening, but one definite reason is the strength this pool of cold air has. Just look at how dry and cold the air mass is above our heads.

This weekend, the dry and cold air wins out, giving us a shot at some snow showers tonight but thats all. We went 0 for 3 this week. That is starting to look like Paul Pierces first quarter scoring line.

Next week looks like an active weather pattern. The cold ail will back off a bit and give way to a warm up by mid week. By Wednesday and Thursday, we should see temps in the mid 40's.  Wednesdays high temps are shown below.

But this comes with a price. Two storms will make a run at us as our boundary between warm and cold air becomes very sharp. Both will feature a whole mixed bag of precipitation types, including ice. Interior areas should be cautious of the Mon/Tues and Wed/Thur time frame. But of course, I will have more about that next week! Enjoy the weekend!

PS. I added a new polling feature to the blog. Answer the questions and win prizes! I am just kidding, there are no prizes, unless you consider a lunch date with me a prize.

A Tricky Snow Forecast

Lots to talk about, so I shall get right to the point.

A small and relatively weak storm is currently moving out of the Great Lakes region.  This system will slide to our south rather inconspicuously until reaching coast, transferring its energy (as these storms so often do) to a new, stronger storm center over the ocean.

Under normal circumstances, this coastal storms track would be too far east to really give SNE any significant precipitation. But a few ideal atmospheric conditions have set up for accumulating snowfall and even heavy snowfall bands in some areas.

1.) Cold air. Shortly after the Patriots waxing, some real cold air settled in over New England. Most areas are currently in the mid to low 20's, even in Cape Cod and the Islands. What this means is any moisture that does fall will be snow. It also means that the snow will be light and have a high "fluff" factor. Normally, the snow to rain ratio is 10 to 1 (1 inch of rain equals 10 inches of snow). The ratio will be closer to 20 to 1 tonight, meaning snow can pile up higher with less moisture.

2.) Atmosphere Instability. I will try to avoid too much technical stuff here. First, a physics review.  Atmospheric instability is created when warm air at the surface rises uninhibited through a cold pool of air just above the surface. This phenomenon is commonly seen in those high and towering thunder clouds we see in the summer. The approaching storm will in a sense "kick-start" the comparatively warm air we have at the surface upwards, rising swiftly through the cold air and creating more clouds and enhanced precipitation. The areas of heavy precipitation can become localized along a trough (line) in a sort of inverted manner, like a tail hanging off the main storm. This phenomenon actual has a name, Norlun trough, named after the two meteorologists who first observed the pattern. With these troughs, its all about location. Where does the tail set up! The bands of heavy precipitation are quite narrow and don't move, resulting in high snowfall variability and a big bust potential in snowfall forecasts.

Alright, you hung with me through the boring stuff, so now to what everyone wants to know. How much? Since I can't make my own maps due to a lack of talent, I chose to borrow this map from NECN meteorologist Matt Noyes.

A couple of things to note. The snow won't really start to accumulate until around midnight. The heaviest snowfall will occur overnight, with most areas picking up a fluffy 2-4 inches. Not enough to cancel school I'm afraid. Some heavy snow bands will set up along the Norlun trough, which figures to be stationed over the outer Cape, Cape Ann and Portland, ME. It is here where some areas may hit the jackpot and a foot of snow. Unfortunately, we won't know where until the storm develops.

Its worth noting that this is a type of scenario where one town may get 2 inches of snow while the next town over gets 8 inches. Quite variable and hard to predict. Not that I would expect any sympathy from you good people. Some people will wake up tomorrow disappointed, while others might be pleasantly surprised.


Here are two interesting further readings on Norlun troughs. One from Matt Noyes concerning the last Norlun trough we had in 2011 and the other the summary of that last storm from the NWS.

Matt Noyes
NWS

Nor'easter makes a very close pass tonight

Those of us who love snow storms are getting pretty frustrated. Last winter, we suffered from a lack of cold air which resulted in record low snowfall totals. This year, we finally have the cold air but we are missing the moisture!

Over the next few days, a series of cold fronts will usher in some truly Arctic air in New England. The first such front will pass through tonight, dropping most of us into the teens tonight. At the same time, a relatively strong ocean storm will pass just to the south. Some models are hinting at light accumulation over Cape Cod, with some potential for a dusting over the south shore.

The above image shows one model's thinking on total accumulation. The further south and east you go, the more likely you will wake up to some snow on the ground. I wouldn't be surprised to see some higher totals of 4 inches on Nantucket and the outer Cape.

As always, a slight shift in the track of this storm could mean more of SNE sees snow or a complete miss all together. Regardless, I wouldn't change your Friday morning plans, which probably consists of wasting time on the internet or driving to work.

The second Arctic front arrives during the middle of the Patriots game, which could make for a very COLD finish. 

Sunday Stormy Sunday

It seems like stormy patterns always like to coincide with mid-terms and finals. Its not as if I don't already have enough distractions (thanks a lot Redditt). As such, I am taking this time meant for studying to discuss the upcoming changes in our weather.

First, I must point out how dry November and early December have been. In November alone we finished the month almost 3 inches below normal for precipitation. After the onslaught of Sandy and the early November snow, things have been pretty tranquil around these parts. Not for long.

Beginning Sunday, its as if mother nature flipped a switch and said "game on". Several short waves (fancy term for storms) are going to spin up from a suddenly very active and tilted jet stream.After Sunday, there are going to be about 3-4 more storms taking aim at the region over the period of about 1 week. Now, it is worth noting at this point that the operational models that we use to make forecasts have traditionally sucked at handling big pattern swings. Like my father, they dislike change. With that said, there are a large amount of discrepancies and disagreements among the models and as such no forecaster is confident about the conditions from Sunday-Thursday of next week.

Two problems exist in my mind.

1.) What happens on Sunday? A small and weak system will start the parade of storms off by Sunday morning. It is very likely that everyone gets a little snow in the morning but at some point, there is going to be a change to a mixed precip and rain. But there is no agreement on when this happens and until there is a consensus, many questions remain. Here is a little insiders knowledge from the weather world. When there is no agreement among the major models for a period just 70-80 hours away AND there is a major pattern swing in the mix, you might be sh#@ out of luck trying to predict anything with greater than 50% confidence beyond 3-5 days.I can't even say what the conditions will be like at the Patriots game! Which brings us to...

2.) The all important cold air! It's pretty simple. No cold air means no snow. I bet you didn't know that. In order to get cold air to stick around in these early season storms (yes it is still early), we must have a strong enough source (High Pressure) that is located close enough by and is also aided by some large atmospheric blocking to keep it from escaping. Without firmly entrenched cold air and an offshore track, any ocean storm that develops close enough is likely to result in too much low level warmth in most areas. And it appears that we are going to be on the cusp of some retreating cold air.

That seemed like a mouth full. Essentially what this means is that we are in wait and see mode. I can tell you that tomorrow and Saturday will be sunny and chilly, especially Saturday. By Sunday morning, I think light snow breaks out for us all. At some point, that snow will change to rain. Snow and mixed precipitation will hold on longer for interior areas, say west of 495. Some ice can't be ruled out in spots. It should dry out by Monday morning but then the guessing game begins. A potential big storm remains a possibility next Wednesday.

That is all. Go out and see the Geminid meteor shower tonight! Clear skies for peak viewing time after 10pm!

Pattern Shifting Back to Stormy Next Week

We can all agree that the weather around here over the last month has been quite varied and even extreme. Two powerful storms have left their toll over the Northeast, with the effects of Sandy likely to be felt for many more months.

A nice reprieve was in order this past weekend, with a true "Indian Summer" occurring on both Sunday and Monday. Despite a raw day today, tranquil weather awaits us for the rest of the week. Strong high pressure will dominate our weather from Wednesday-Saturday, with very seasonable conditions but plenty of sunshine.

As we look at next week, which of course is the busiest travel week of the year, we are starting to see indications that the East coast will return to a more stormy pattern. Our main source of concern is what we call a negative NAO (North Atlantic Oscillation)

Many of you heard this referenced when Sandy was making her way up the coast. Indeed, a negative NAO correlates to more atmospheric blocking which generally results in a tilted jet stream that allows storms to travel along or close to the coast. 

The image above shows that indeed the NAO appears to be heading to a big negative phase after November 16th. And some of our long term models are picking this up and hinting at 2 possible coastal storms on the week of Thanksgiving.

There is no details to give as this is WAY to far out to try and forecast specifics. But these large scale indices like the NAO are becoming more vital and more accurate at predicting large swings in the atmosphere's flow.

Just something to keep in the back of your mind if you have travel plans next week! 

Desvestating Hurricane Sandy Was Not As Rare As You Might Think

It's been days since Hurricane Sandy began to effect the East Coast of North America. Yet some of the images and stories we continue to hear come out of the most hard hit regions, like New York City and New Jersey, still shock us to the core. Most of us, including myself, have yet to fully comprehend just how such devastation could have occurred in areas that typically don't have this type of catastrophe.

Some of the statistics and effects attributed to Sandy are hard to believe as well. 180 killed across 8 countries, including 98 in the United States. Upwards of some 50 billion dollars in estimated damage done along the East Coast. A two day shutdown of the NYSE, the first time a weather related issue has forced the closer of the Exchange since an 1888 blizzard. NYC transit service coming to a halt, half of Manhattan without power. The list goes on and on.

From a meteorlogical standpoint, Sandy set some records as well. Sandy had a record low pressure for a hurricane north of Cape Hatteras, NC. At her peak size, she had tropical force winds extending out for a total of 580 miles from her center! And several high water mark records, the most notable being the 13.88 ft record height reached at Battery Park in Manhattan. With such a record breaking storm, its easy to assume that Sandy was the first of her kind. But if we look a little closer at hurricane track history, we find that Sandy wasn't that unique at all.

Umass Lowell graduate meteorology student Lance Frank compiled a record of tropical systems, dating all the way back to 1851, that all had a storm track that traveled to the west well north of Cape Hatteras, NC and occured late in the hurricane season between the months of September and October. These are very specific guidelines, especially considering how obscure this type of behavior is for a tropical system.

What he found was quite interesting. A total of 16 storms fit the criteria, with 7 of those storms making landfall somewhere along the Eastern coast of North America. Three of those storms actually made landfall in Massachusetts in 1869, 1896 and 1923.

Whats more, Sandy was not even the strongest of the this group of storms. You will notice that both the hurricane of 1938 as well as the previously mentioned 1869 storm were both stronger in terms of maximum wind speed. Lance actually went further into the historical weather data and was able to connect large scale weather patterns for each storm. I am sure most of you have heard the term "blocking" as one of the main causes for Sandy's odd track. It turns out that with just about all of these storms, a similar sort of "blocking" pattern was present, helping to push all of these systems back to the West, when they should go out to sea.

So what does this information tell us? Well, for one, it tells us the a Sandy type of storm has clearly happened before. Not all of these storms hit land and Sandy was certainly unique in both her sheer size as well as her landfall in the most heavily populated part of the country.  It should also put the breaks on any premature talk of climate change influencing Sandy. It is incorrect and scientifically immoral to suggest that Sandy's destruction was driven by climate change. The fact is, we just don't know. There is not enough reliable information to connect the two.

With large scale events such as Sandy, we must deal with what we know to be true and not try to infer otherwise. Having analogous historical data like this helps immensely in understanding why Sandy did what she did and more importantly, it helps us to be able to recognize similar situations in the future which will lead to more accurate forecasting.

Regardless of any similarities to the past, Sandy's swath of destruction and devastation will be felt for many years to come, meaning we certainly won't be forgetting this Hurricane anytime soon.