Welcome to the weather blog - a regular Monday through Friday discussion of the weather! You'll find a quick weather synopsis and a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net. While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants. This blog is for you, so I hope you enjoy it! -Matt Noyes
For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net
Matt's Quick Weather Synopsis (New!): A blizzard is en route to parts of Southern New England for Saturday night into Sunday morning, but quiet weather prevails for our Friday. Sunshine gives way to increasing clouds late in the day, and arctic air in association with a bubble of Canadian high pressure just north of the border holds temperatures in the teens north and twenties south, with a breeze adding a bit of an extra chill to the air. Thickening clouds Friday night lead to a period of light snow that may drop a fresh dusting of snow, especially in Southern New England, associated with an upper level disturbance moving overhead and not associated with the major weekend storm. Most of Saturday will be quiet - while bands of light snow may come streaming in from the ocean to Eastern MA throughout the day, these should not affect plans through the daylight hours. Saturday night, snow moves north associated with a rapidly strengthening storm that moves southeast of Nantucket early Sunday morning. The result is snow developing from sundown (at the south coast) onward and from south to north Saturday evening, then becoming heavy at times Saturday night into Sunday morning, especially after midnight. Winds will gust frequently over 35 mph along the coastal plain of Eastern MA and the South Coast of New England, as well as the Worcester Hills, and combined with heavy snow, this will cause blizzard conditions with visibility near zero, especially after 11 PM Saturday night, lasting into Sunday morning. Scattered power outages may result in these areas and travel will be treacherous. Waves will build 15-20 feet offshore, but limited if any coastal flooding is expected. They key to this forecast will hinge upon how far north and west the heavy snow penetrates into New England - a track farther south will result in a change to the accumulation forecasts on the north side of the precipitation. Snow winds down late Sunday morning, then windy and cold with partial clearing late. Monday looks breezy and cool with a quick moving disturbance racing eastward, bringing a period of snow Monday night into Tuesday morning. Warmer air moves in for midweek before the winter pattern resumes toward the end of next week. -Matt
Accumulation Maps and Blizzard Condition Details:
General Weather Summary: The pattern you and I have been watching together in these discussions the past few weeks is finally cranking out the first of what will likely be several winter storms over the next four weeks. A month of record national warmth in January - some 8.5 degrees above normal (see end of this Summary for details) - has left an abundance of available energy in the atmosphere across the nation. As cold air piles southward out of Canada creating a clash in airmasses across the country, the natural way for the atmosphere to find equilibrium is to disperse this energy in the form of storms. We've seen these storms all winter long - though many with rain, and other with snow that melted quickly, each storm has been quite vigorous and has brought plenty of wind. This time, enough cold air is in place that we'll wring out snow across New England.
But a complete weather discussion takes this one step at a time, starting with our Friday. Sunshine abound Friday morning will continue to give way to increasing clouds moving in from the west. Arctic air is in place throughout New England, and northwest winds pushing against the Northern Green Mountains have allowed some light snow to continue in these locales. Elsewhere, winds will swing around from the west-northwest, and breezes will add an extra chill to already cold temperatures expected to top off in the teens north and 20's south. Increasing clouds through the day come in advance of an upper level energy center, racing east out of the Great Lakes and having nothing to do with the upcoming weekend spectacle. With this disturbance, light snow will fall in parts of Southern New England overnight Friday night, just north of an arctic cold front that settled south of New England Thursday night, and will serve as the boundary for a clash in airmasses as slightly warmer and more moist air attempts to rebound from the south, ahead of the incoming disturbance. Only a dusting of snow is expected in most areas overnight Friday night.
While some of this light snow may linger into Saturday morning, by and large the first half of our weekend will begin fairly quiet. Mostly cloudy skies will prevail through the day, and with a developing east wind due to clockwise airflow around a center of cold high pressure over Maine Saturday morning, ocean effect snow showers are possible in Eastern Massachusetts later Saturday afternoon. These should be fairly light in nature, and will not affect preparations that are being made for our incoming storm. Meanwhile, to our south, an area of low pressure will be strengthening along the mid-Atlantic coastline. The players in storm development are a strong energy center dropping across the Northern Plains Friday Morning, and a moist storm moving east across Texas. After bringing heavy rains to the Lower Mississippi River Valley and the Gulf Coast, these two storms will merge and combine their most volatile characteristics to create a moisture-loaded, energetic, and therefore rapidly strengthening storm along the East Coast.
Aloft, the jet stream pattern - the fast corridor of wind aloft that steers our storms and acts as a thermostat for the atmosphere, separating cold air to the north from warm to the south - will be orienting from south to north up the Eastern Seaboard. These fast jet stream winds will pick up the developing storm and carry it north-northeast, eventually taking the storm over Nantucket Island, MA, early Sunday Morning.
Well in advance of the approaching storm, warmth and moisture will be thrust northward, colliding with our arctic airmass in place across New England and resulting in snow. This snow will develop from late afternoon through sunset across Southern Connecticut, Rhode Island and Cape Cod. After sunset, expect the snow to march northward across the remainder of Southern New England, though it may take until after midnight to reach the New Hampshire border. Saturday night through Sunday morning, snow will fall heavily at times as the center of low pressure moves northeast toward New England. This strengthening area of low pressure - like so many others this year - will create plenty of wind, and this wind will combine with the heavy snowfall rates of 2"-4" per hour at times to create blinding conditions amidst frequent wind gusts over 35 mph, especially after midnight Saturday night, especially likely from Connecticut east through Southeastern MA. This combination of visibility below .25 miles and frequent gusts above 35 mph meets the criteria for a blizzard, and for this reason the National Weather Service has posted a Blizzard Watch for the South Coast of Connecticut for Saturday night into Sunday morning. Farther north and west, through the coastal plain of Massachusetts, Southeast NH, and the higher terrain of the Worcester Hills, this potential is highly dependent upon whether the heavy snow band can rotate far enough north and west late Saturday night and Sunday morning.
For the areas that fall into blizzard conditions, the typical threats associated with a blizzard apply, though it certainly is a help to one and all that this storm will be charging through on a weekend, when a relatively small number of people have critical need to be out and about. Nonetheless, travel will be treacherous through Saturday Night and into Sunday morning. If you absolutely must travel in the blizzard areas, be sure to have a winter survival kit in your vehicle, containing a shovel, warm clothes, a blanket, water and small food items should you become stranded. Power outages are likely to occur for at least some communities. Total snowfall amounts will be posted in the accumulation maps with this discussion shortly, but expect over a foot for parts of Southern New England, and I wouldn't be surprised to find localized higher amounts, especially considering that there is also likely to be a coastal front that develops - the collision between modified ocean air, and arctic air through the interior. Where this coastal front sets up - sometimes just miles inland from the coast - localized enhancement of snow will occur and some amounts may be exceptionally higher. There is certainly a marine threat with this storm, as well, and given the likelihood of storm force gusts and seas of 15-20 feet, mariners should plan on staying in port from Saturday afternoon through Sunday. As for coastal flooding, there is the potential for minor coastal flooding in Western Long Island Sound at high tide late Saturday night, otherwise the combination of an astronomically lower tide and a wind that won't kick until right around the time of high tide should limit the threat elsewhere. If winds still are out of the northeast Sunday morning, some splashover and minor coastal flooding will be possible in Eastern Massachusetts and Southeast NH.
Snow most likely snow lingers in the morning regardless of which storm scenario plays out, and as the storm draws east of New England and intensifies, winds will be gusty and cold air will spill into New England. The next upper level disturbance swings through on Monday, bringing a chance of snow showers later in the afternoon.
Obviously there's plenty to keep an eye on over the next several days, but for those of you who enjoy looking farther into the future, there are some signs coming back on how the rest of February may play out. Though I think we've shifted into what will - on average - be a wintry pattern through the end of the month, some atmospheric reshuffling appears to be in the cards around and just after Valentine's Day. As mentioned above, while we're currently in the heart of cold Canadian air, and this cold air extends west into the Northern Plains, heat is building under a strengthening high pressure center in the Western United States. Strong signs are for this high pressure center to grow very large and very warm over the next several days, and though we deal with a storm threat Saturday night into Sunday, this will mean that our replenishing supply of cold air will be temporarily cut off, since we've been feeding our cold in from Alaska. While this is likely to result in 3-4 days of somewhat warmer weather - at or somewhat above normal temperatures for this time of the year - next week, I don't think it's the end of winter, or of the new wintry pattern by any stretch. I continue to foresee a pattern shift allowing cold air to return once this Western high pressure ridge has reached its peak next week, and with an active subtropical jet stream nearby, multiple opportunities for cold and moist systems will exist in the new pattern. It's obviously not a comfortable feeling to make a prediction of a return to cold and multiple chances for snow, then see even a brief return of warmth, but indications of this being only a brief stint with milder air are fairly strong, so I remain confident that winter turns back on at the end of the month.
Updates will follow through the weekend.
Details on January Warmth: The nation checked in with an average temperature of 39.5 degrees for the month of January - the warmest January ever recorded with regard to national average. The previous record was 37.3 degrees set in 1953. Over 75% of the nation was "much above normal", which has only happened twice in history - once in March of 1910, and the other time in November of 1999. This remarkable warmth marks an abundance of energy available in the atmosphere as we enter a new, colder, stormier pattern.
Matt
Matt's Technical Meteorological Discussion: Updated Friday, February 10 at 4:45 PM
Most of the details on the overall evolution of the system have been laid out here over the past couple of days, and especially touched upon yesterday, but let's polish up the technical side of things as best we can.
Cloud field that expanded over NewEng today is evidence of warm advection setting back in aloft, and the clash between this weak warm advection and the arctic frontal boundary that settled south of NewEng and is now returning back northward, coupled with vorticity maximums being pulled into confluent flow east of NewEng, will be the impetus for tonight's periods of light snow in most of Southern NewEng. Limited amounts from this - a dusting is all that should be received in most spots - but as the 850 mb trof swings thru overnight Fri Ngt, confluent flow shifts a bit farther north and east, and 850 mb winds slacken quickly early Sat.
Low level RH that saturates overnight tonight in Central/Southern NewEng really doesn't go anywhere tomorrow and low gray clouds are likely to linger in these areas thru the day, even tho air above this level is fairly dry thru the day. Additionally an onshore flow develops as center of surface high pressure moves over Gulf of Maine, and this onshore flow of cold air is able to work a bit deeper up into the atmosphere as the 850 mb winds die down, and this should generate ocean effect snow bands in Eastern MA and esp on Cape Cod. If an onshore flow was more quickly establishing aloft, I'd say this could produce some significant bands well in advance of the storm, but given that we need to go from an offshore to onshore flow aloft thru the day on Sat, it's probably going to be more disorganized spray of snow showers that comes off the Atlantic. WRF doing a nice job of picking up on this activity (has been for the past several runs) and the NAM continues to obtain a better grasp on this with each run.
But while the mesoscale effects will produce some snow showers in these Eastern areas, there's no question the synoptics are featuring a slowing trend among the guidance. A large part of this is due to the strongly confluent flow at 700 and 500 mb just east of NewEng, and while confluent flow is necessary to lock in cold air, this strong and this close has been a concern all week long with this storm that it's not going to allow the moisture to spread northward. Admittedly, this is still a bit of a concern for me, but there comes a point when we have to examine the storm and decide which features will dominate its evolution. As mentioned yesterday, the baroclinicity and low level dynamics are impressive enough that surface cyclogenesis should overpower the progressive tendency of this flow, though if someone told me to find where the forecast might bust, certainly this close confluent flow would be the way to do it. Nonetheless, there is a decided midlevel wind shift that moves northward to the South Coast of NewEng by 00Z as the northern stream 850 mb trough pulls out, and the snow shield should follow this directional convergence zone.
Theta-e progs at all levels show a direct tap from the Gulf of Mexico up a warm SW wind conveyor belt feeding off the Eastern Seaboard. This is a huge reason to support the idea of dynamics and baroclinicity taking center stage, not to mention the cold core aloft that's rotating east with the upper low across the OH Valley, the relatively warm ocean temperatures sitting offshore, and an airmass that is DRY extending all the way down the Eastern Seaboard. Amazing that...even as the storm moves east across the Gulf Coast...dewpoints are still in the teens and 20's all the way down the Eastern Seaboard. Lots of 50's/20's in the Carolinas - yikes! This should stand out to many meteorologically inclined folks as further evidence of how well entrenched the land airmass truly is - and remember that those temperatures are going to plummet on the cold northwest side of the storm as the column saturates.
So how does this play into the evolution of our storm? First and foremost, it guarantees we'll be setting up a land/ocean contrast once the storm winds up along the Carolina coastline. Second, this should serve to increase the baroclinicity present along the coastline. Now, with the models beginning to sway from run to run after great agreement in the 00Z cycle last night, meteorologists are having heart attacks throughout NewEng. Of course, those of you who read often know how much I hate a flip-flopping forecast, so what we need to do in order to avoid such a forecast is find something worth hanging our hat on. We've already agreed together in this discussion that baroclinicity is going to be a key player, so let's think in terms of airmasses. My absolute favorite airmass indicator is theta-e, or equivalent potential temperature. A fancy term, but basically a measure of both warmth and moisture in an airmass. Theta-e values are quite high across the Gulf Coast, and moderately high SE of Florida - indicating lots of warmth and moisture. Normally this would be a "no kidding, Noyes" comment...of course there's warmth and moisture there. But the important key is that it is MUCH warmer and MUCH more moist air than the exceptionally dry and soon to be cool air all up and down the Eastern Seaboard. Additionally, buoy 44001 east of the Carolinas is reporting a water temperature of 66.2 F this afternoon with an air temp of 52 F, and 44004 which is 200 mi E of Cape May, NJ, has a water temp of 57.7 and an air temp of 42.1. The thing to focus on here is not the air temp, but water temps. Warmth surging north out of the Gulf and Bahamas is going to thrive over 66 degree water temps, and should be able to boost air temps well into the 60's even over the 57.7 degree water. Remember, this isn't model data we're looking at, this is real data - far more important in this situation. But now we can incorporate model data, and a model such as the WRF is doing a fantastic job, in my estimation, of carrying this high Theta-E air up over the Western Atlantic ahead of the storm track for no only tons of available warmth and moisture, but also a tremendous increase in baroclinicity between the Eastern Seaboard dry and soon to be evaporatively cooled air, and the downright tropical airmass that will be advecting northward off the coastline. So the key as we come into New England territory is to nail down this gradient of airmasses - the battle zone that will serve as the storm path. Then don't forget to add the retreating but very evident arctic boundary into the equation. This arctic boundary is likely going to play a more important role regarding coastal front development and heavy snow banding during the storm as it retreats across the interior, but I think the important point to make with regard to storm track here is that the natural baroclinic zone is farther north than even the GFS would indicate from its forecasted surface low track, meaning I think even the 12Z GFS is probably too far south. Again, the confluent flow aloft so close to us can make us nervous, but if we're going to agree that the extreme baroclinicity is going to be the dominant force here, than we need to follow through on that theory by finding real data, not model data, to hang our hat on. I think we've done that above.
So, the bottom line on this is that the forecast laid out in the Weather Summary and maps above stands for now. I can't say I was surprised, though I will admit I was relieved, to see the 18Z NAM come back northwest, and I expect that trend to continue at 00Z. Blizzard conditions still appear likely not only for the areas already in a blizzard watch in Srn CT, but also in at least part if not most of the coastal plain of Eastern MA.
I will spare you from the rest of the details on this storm regarding things like timing, duration and intensity, for the most part, because these are factors that I think...once we get through the hard part of not worrying so much about forecast track, like we've done above...become rather self-evident as we examine the guidance products. I will say that I see enough warm advection and cyclonic vorticity advection both in the lower and midlevels for 2"-4" per hour snows in eastern Southern NewEng during the heart of the storm, and that the most intense period certainly appears to be centered on early Sun AM.
If you're interested in the extended period beyond this storm, I'd invite you to check out yesterday's post below, or the archives at left.
That's all for today. Now we wait and see what transpires in the guidance - awaiting the northwest shift I'm anticipating - and we'll see where we are tomorrow.
Matt
