SATURDAY UPDATE: GORGEOUS SATURDAY BEFORE FIERCE AND POTENTIALLY HISTORIC STORM SUNDAY INTO EARLY WEEK
Welcome to the weather blog - a regular Monday through Friday discussion of the weather! While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants. I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible. You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is email@example.com. This blog is for you, so I hope you enjoy it! -Matt Noyes
General Weather Summary:
We enjoy a calm and pleasant day before the big storm on Saturday, with the forecast looking on track for a day in the 50s south, near 50 central and 40s north under plenty of sun and a few clouds. Clouds should increase overnight Saturday night well in advance of the approaching storm that will be strengthening off the Mid-Atlantic coastline while pulling north toward New England on Sunday. Today's discussion is meant only to build upon and supplement yesterday's mammoth discussion below, so if you're looking for a full setup, you'll want to read that one (included below) to get spun up.
The big question on this storm remains how far north it progresses before slowing/stalling/looping then migrating south and southeast and eventually departing. That uncertainty continues to hold the cards for Monday's forecast, though the trend is toward a solution that would pull the storm far enough north to at least bring it over extreme Southern New England. But before we delve into that, let's touch up what I know and what I believe to be the biggest and most immediate concerns, and that is the scenario for later Sunday through Sunday Night.
Rain: Heavy rain is still expected to spread across New England from southwest to northeast Sunday, beginning in Connecticut early to mid morning, then Central New England around midday and Northern New England during the afternoon. Rain will become torrential later Sunday through Sunday night, with total rainfall amounts indicated in the map from yesterday's discussion (below) but expected to AVERAGE near 4" in Eastern New England! That means some spots may be lower, but others will be locally higher, and this is enough rain to prompt flooding of not only streets, streams and low lying areas, but also of rivers. Though you can always check for Watches/Warnings/Advisories from the National Weather Service through the links at left, latest river observations and forecasts can be found from the Northeast River Forecast Center by clicking here. Do notice the tab at the top of their map, to be sure you're looking at either forecasted or observed conditions.
Snow: With a deep southeast wind flow, it's unlikely that we'll
find much snow in a lot of Central and Eastern New England, thanks to
modified ocean air streaming in off of the Atlantic. The farther west
and north one is, however, the more likely snow becomes thanks to dry
and cool air already in place, and a bubble of high pressure across
Eastern Canada that will be able to supply more cool air as the storm
center deepens to our south and draws air into its center, meaning that
cool reinforcing air will be tugged southward across New England. The
result will be developing snow and rain mix on Sunday afternoon
changing to mostly snow from Upstate New York through the Berkshires
and into Vermont, Central and Northern New Hampshire and Central and
Northern Maine. In the Berkshires, Southern Vermont and Central New
Hampshire, the snow should change to rain overnight Sunday night after
four to eight inches of snow. Farther north, however, through Northern
Vermont, Northern New Hampshire and Central/Northern Maine, half a foot
to a foot of heavy, wet, spring snow is likely, and coupled with
increasing winds, this will once again mean power outages. For some
areas of the North Country, due to persistent winds for a few days that
will make the job of repairing and restoring power service difficult,
outages may last a few days. Please note that my accumulations given
here are through midday Monday. Additional snow is possible Tuesday
(when snow may fall into even parts of Southern New Engalnd) and
Wind: The wind is, of course, the biggest threat to mariners, but will be a problem for us all. A corridor of fierce winds will develop on the north side of the storm circulation, and that corridor of wind, blowing from the east and east-southeast, will lift from south to north late Sunday into Monday. The first areas to see the increase in wind will be the South Coast of New England, where afternoon winds of 30-40 mph with gusts to 50 mph will arrive by later Sunday afternoon. This will only be the beginning of the wind, as the wind corridor is expected to increase in intensity as it pushes northward, resulting in gusts to over 60 mph along the South Coast of Connecticut, and Sunday night gusts to hurricane force (74 mph or greater) on Cape Cod and the Islands in especially the first half of Sunday night. These hurricane force gusts will move up the coast of Eastern Southern New England overnight Sunday night, with gusts to 60 or 65 mph possible through most of Eastern Massachusetts, and this will down some trees and power lines. By Monday morning, the corridor of fiercest wind will shift to Southeastern New Hampshire and Southern/Coastal Maine, where gusts to hurricane force would still be a possibility early Monday. Thereafter, much will depend upon where the center of this storm stalls or loops. At this point, if the storm were to stall over far Southern New England, winds would gradually come around to blow from the northeast on Monday and then last into Tuesday, with the most intense wind from Cape Ann northward along the Maine coastline.
Coastal Flooding: Latest statements and warnings should be monitored from the National Weather Service (again, warnings/watches/advisories are linked to at left of this discussion) for Coastal Flooding, as this has the potential to be a ravaging event for some of us. The National Weather Service office in Upton, New York, is comparing the magnitude of coastal flooding for Southern Connecticut at the west end of Long Island Sound Sunday night (and perhaps Monday if the storm stalls far enough south) to that witnessed during the Perfect Storm of 1991. The biggest immediate concern will certainly be for the west end of Long Island Sound, where fierce winds will coincide with an astronomically high tide in the new moon cycle Sunday night, pushing water up against these western coastal locales and resulting in perhaps a major flooding event. Farther up the coastline of Southern New England, vulnerability will center around the 10:20 PM Sunday high tide for especially east and east-southeast facing locales. With an onshore wind and waves building to 25 feet offshore, the threat for coastal flooding continues through Monday and Tuesday, though magnitude will depend upon location of the storm, and therefore the resultant wind direction and speed. This could end up being a ravaging series of high tide cycles from Monday morning through Tuesday evening for the Maine coastline and New Hampshire seacoast, and perhaps the far North Shore of MA near Newburyport and Salisbury, where winds may continue to gust to 50 or 55 mph even into Tuesday. If the storm stalls a bit farther south, these effects will be felt farther south along the Eastern Massachusetts coastline as well.
That's all for the early Saturday update. Yesterday's discussion here:
The storm I'm watching for later Sunday through Tuesday - when considered with its intensity and duration, will rank as one of the post powerful nor'easters in several years. Though this storm will not be as ferocious as the Halloween storm of 1991 (a.k.a. "The Perfect Storm"), it's likely to be located closer, and the duration will result in significant damage to New England's coastlines. Over the course of this discussion, I will outline what is known and what has yet to be determined with this major storm. Through the weekend, I will update this website as necessary if any information changes my view of how the storm will transpire.
Check out Coast Guard preparations from their site: http://www.uscgnewengland.com/go/site/778/
In the meantime, Friday morning dawned with heavy snow producing white out conditions at times across Northern Maine as the storm that swept across New England Thursday and Thursday night exits to our east. The bands of heavy snow in Northern Maine will taper through Friday, with scattered snow showers continuing through the mountainous terrain, and a few sprinkles and flurries floating across the remainder of New England at times Friday afternoon. Though plenty of lingering moisture in the lower and middle levels of the atmosphere is allowing a wide variety of clouds to linger over New England on Friday, winds blowing from the west are sloping down the mountains and hills, and in many downwind communities of Central and Eastern New England, this can assist in bringing breaks of sun through the clouds. The storm responsible for up to a foot of heavy, wet spring snow and over 10,000 power outages in Maine continues to move out across Nova Scotia, but wraparound snow has been sluggish to depart from Northern Maine. Gradually, this snow will move across the Canadian border and out of the United States entirely.
Diminishing rain and snow showers and diminishing clouds will yield a partly cloudy and cool night Friday night with breezes slackening a bit, as well. Saturday's sunny start will blend with a few puffy cumulus clouds during the afternoon, but will yield milder temperatures as a small wedge of high pressure, or fair weather, moves over New England. Meanwhile, all eyes will turn to the approaching major storm, which will already have left a path of destruction in its wake. After damaging thunderstorms and tornadoes through the Southern Plains, including the Dallas/Fort Worth area, Friday afternoon and evening, and another severe weather outbreak with numerous tornadoes in the Gulf Coast and Southeast states Saturday, a ball of intense energy will roll to the Mid-Atlantic coastline. This energetic disturbance will be the driving force of our upcoming storm as it absorbs Gulf Moisture, Atlantic moisture, and encounters a clash of airmasses from warm and humid southern air with cooler and drier northern air. These factors will combine to produce what's referred to as a "bomb" in the world of meteorology - a storm that will strengthen rapidly off the Mid-Atlantic coastline. Caught in a volatile jet stream pattern flowing quickly from Georgia to Vermont, this storm will be pushed northward by this corridor of storm-steering wind, drawing closer to New England as we head into Sunday.
The first evidence of the impending storm will be quickly increasing and lowering clouds Sunday morning, after a cool Saturday night thanks to dry air still in place for most of New England. In fact, an important player in the upcoming forecast is the center of cold and dry air over Eastern Canada this weekend, that will be available to bleed cold air southward across New England, and will do so through Saturday night. It won't take long after the increasing Sunday morning clouds for rain to follow suit, as it races up the Eastern Seaboard, with heavy precipitation developing in Southern New England perhaps as early as Sunday morning, then spreading north into the Northern half of New England Sunday afternoon. Precipitation type will be mostly rain in Southern New England, though the presence of cool and dry air may allow for a brief burst of snow in many Southern New England communities, but especially in higher terrain. Meanwhile, most of Northern New England and even North-Central New England should be cold enough to start as a period of snow, and perhaps accumulating snow through the interior. Within about 50 miles of the coastline, any chance for accumulating snow would be brief, given a deep developing southeast flow off the milder ocean water.
It's at this point that all of the ingredients begin coming together to rapidly strengthen the coastal beast, with its minimum central barometric pressure dropping to around 29.10" and still falling overnight Sunday night. This rapid strengthening will allow a fast corridor of wind to begin feeding into the storm, and pushing through the counter-clockwise flow around the storm center. On the north side of the circulation, this will mean an east-southeast wind approaching the South Coast of New England Sunday afternoon, blowing at as much as 30-40 mph by the end of the day from the South Coast of Connecticut to Cape Cod, with gusts to 50 mph possible. Across the remainder of New England, winds will also increase sharply as the wind field associated with the storm expands markedly, with Sunday afternoon and evening winds of 15-30 mph reaching through most of the six-state region. But that's not the whole story for winds - they will continue to increase Sunday night.
All the while, tropical Gulf moisture will be feeding north, and the approaching storm will team with favorable jet stream winds aloft to churn out plenty of precipitation. In Sotuhern and coastal areas where a change to rain happens fairly quickly, rain will fall in torrents, and the development of a weak coastal front - the difference between ocean air and land air - may develop Sunday night, cranking out even higher amounts near the front. In most of eastern Central and Southern New England, in excess of 3 inches of rain is expected Sunday evening and night, though near the coastal front, even higher amounts are likely. Meanwhile, there's a good chance this will crank out as heavy snow from Upstate New York east across Northern New England. At this juncture, just how much snow would fall is still up for grabs, largely because the path and timing of the storm is still uncertain...more on this below.
The heavy precipitation that falls Sunday night is sure to be windswept, as the corridor of wind moving north continues to crank, bringing winds of 45-60 mph from the east-southeast to coastal Southern New England, with gusts to hurricane force possible. The question regarding wind is how quickly these damaging winds march northward up the coast of Southern New England. Both this question, and the question of precipitation, revolve around the interaction of the surface storm with its energetic upper level counterpart. That is, while the storm is propelled northward by the jet stream winds Sunday, at some point it will strengthen so much that the jet stream winds will bend to flow around the storm, and while this will allow it to maximize its strength, it also will result in a stall of the storm. At this point, the question is where the storm stalls, and that's a matter of fine tuning that will come as we near the event a bit more. For example, a storm that continues moving north until stalling over Southern New England on Monday would deliver the strong winds and hurricane force gusts in a progressive blow to the coastline, progressing up the coast from south to north overnight Sunday night, and stalling as continuous damaging wind from the New Hampshire Seacost to the southern coast of Maine. A stall just south of New England would mean continuous battering of Southern New England with both heavy rain and damaging wind. This detail is obviously an important one, but it seems that either way - progressive or slower - all of New England is in for gusty wind and heavy precipitation, and Southern New England will be hit hard with wind Sunday late afternoon through Sunday night. At this point, I actually favor a solution closer to the southern scenario, with the low pressure center still south of the Islands of Massachusetts as late as Monday evening after stalling south of us. If my hunch on this is right, we're going to be looking at a very dangerous and prolonged storm for Central and Southern New England, especially, where the coastlines would be hit extremely hard.
This storm progression also will make a big difference on precipitation amounts by Monday morning, as a faster progression will spread more snow across Northern New England quicker, dropping a foot to a foot and a half of snow on Northern New England by Monday morning while a slower progression would shave about half a foot off of those amounts, and bring little to the immediate Canadian border by Monday morning! Again, at this point, a slower progression seems most probable to me, though we still would see heavy precipitation spreading across New England during the day Monday.
Regardless, this storm should not be underestimated for its effects on the marine community. Storm force winds and hurricane force gusts mean all mariners must be in port by Sunday afternoon to avoid life-threatening conditions. Waves will build to over 20 feet Sunday night into Monday. Coastal residents couldn't have worse timing, as we enter some of our highest tides of the year with a New Moon Spring Tide cycle producing 11 to 12 foot tides. This, coupled with persistent onshore flow through Tuesday, makes coastal flooding a virtual certainty at almost every high tide cycle from Sunday evening through Tuesday night. Exactly what communities get hit, and whether this is a moderate or major coastal flooding event, will depend heavily upon wind direction, and that, as alluded to above, depends heavily on where this storm stalls out. For now, coastal residents who are prone to coastal flooding, even if only during significant events, should prepare for flooding. If a major event shapes up, and especially if the slower solution verifies, evacuations may be needed on Monday. Mariners in particular may wonder why I'm calling this a northeaster if winds are east-southeast. Though winds begin with a great blow from the east-southeast Sunday night, if the storm center stays south of us, winds will shift to blow from the northeast during the day Monday, and remain from the northeast Tuesday. Two of the three days are spent with northeast winds - and truly the winds will probably remain northeast through most of the week - and that's the reason for the nomenclature.
Marathon Monday depends heavily upon where this storm stalls, too. A stall south of New England, as mentioned above, would keep heavy rain and heavy wind across the entire race course. A stall overhead would allow winds to relax in Southern New England and rains to shift north as rain and snow to Northern and Central New England. I suppose optimists should hope for this farther north progression to verify, though that would mean south coastal Maine and New Hampshire would be under the gun for heavy precipitation and coastal flooding.
The effects of this major and slow moving storm will linger through most of the week. Tuesday will bring heavy bands of precipitation to New England again, focused especially across Northern and Central New England, with colder air gradually draining south from the Eastern Canada high pressure cell, changing many areas to snow, though accumulating snow would likely be contained to Northern and Central areas thanks to above-freezing temperatures in Southern New England Tuesday afternoon. I wouldn't expect nice weather to return in any big way at all next week, as the big storm leaves behind a very big "trough," or dip in the jet stream, that will favor new energy and cool air continuing to drop over the Eastern Seaboard. In fact, another much weaker storm will develop in this trough later in the week (Thursday into Friday) though will probably stay south of us. Nonetheless, with energetic disturbances still dropping in aloft, the chance for precipitation remains, along with plenty of clouds, through the end of the week.
I will issue updates as needed this weekend for this storm, but I hope I've conveyed clearly above that we're dealing with a major storm with major negative effects. The combination of its duration and intensity, precipitation types and prolonged onshore flow with propensity for coastal flooding and the impact on the marine community - keeping many in port through a good part of the week - along with beach erosion that may compromise houses if the slower, southern solution verifies, all are my reasoning for saying this storm has the potential to rank among the top 5 storms in the past several decades.
Technical Discussion: I plan on updating the technical discussion in snippets over the weekend to give an idea of my thoughts.
Matt's Technical Meteorological Discussion: Updated Saturday, April 14 at 11:30 AM
12Z Sat NMM just coming in and now shifting much farther south than previous runs. This is a significant trend toward the ECMWF/GGEM/Canadian Ensemble Guidance and tho the 12Z GFS is not in yet, I expect it will likely follow suit. If you've read the General Wx Summary yesterday or this AM you know my preference is to keep this storm farther south, which keeps east coastal MA under the gun - at least the NShore - thru the NH Seacoast and Srn ME thru Monday. This also will have huge implications on closing the window of optimism for a dry slot in Ern MA for the Marathon. Wouldn't rule out that possibility yet, but if the Srn solution does indeed verify - even with the low as far north as the SCoast of NewEng we'd still find well developed onshore flow to saturate the lowest several thousand feet of the atmosphere with bands of ocean enhanced rainfall. Will be interested to see how the 12Z GFS comes in, but to find such a shift in the NMM to the very consistent foreign models certainly is a huge sign that should not be ignored. Those following a northern solution for the low need to reopen the southern solution window and allow room in forecasts for the implications of such a track. Those believing in a more southern stall of the storm (myself included) this is a step in the right direction for the forecast (the wrong direction for the public) but of course there is a lot of time to go.
1:10 PM: After two days of plenty of diurnal Cu and cool temps, sunshine is more abundant than expected early this AM and temps responding, so had to bump numbers up a few degrees for this afternoon. Winds slacken a bit overnight but even 5-15 mph sufficient to produce chills in the teens with dry air allowing falling temps into the 20s most areas. Tuesday's llvl temps are actually progged to be colder than Mon, so may see numbers coming back just a shade cooler, tho less wind shud produce a comparable feel. Sfc rdige axis crests overhead on Wednesday, and this brings nearly neutral horizontal thermal advection along with a light wind. Aloft, the persistent upper low over extreme Eastern Canada pulls northeast and well east of Newfoundland.
The shift in this pattern aloft allows for a more progressive upper air pattern. This effectively cuts off our protective northwest flow, and with a pinched off ridge over Central Canada as part of a highly amplified omega block, troffing locks over Nrn NewEng and Ern Quebec, meaning cold air keeps coming south in the lower several thousand feet of the atmosphere, locked in by confluent flow east of ME. Warmer air will try to spread NE out of the Ohio Valley later Wed, resulting in increasing clouds. Of more importance, of course, is the strong Pacific energy coming into the NW US early this week, traversing the country quickly in fast westerlies midweek, and amplifying as it approaches the NE US trof by later Wed and Thu. This system comes not only with moderate vorticity, but also carries a moist and warmer airmass owing to its Pacific origins. Additionally, an active subtropical jet will offer at least modest input to this storm on its southern flank. This additional warm and moist advection will aid in shifting focus from primary low in Great Lakes to new developing secondary low off Mid-Atlantic coastline. With cold air wedged in NewEng, sfc low is likely to favor a track S of NewEng, and the airmass will be dry enuf to stay cold upon saturation, and most certainly looks cold enuf for snow. Of course, one critical component is storm track in this scenario. With such dramatically conflicting airmasses, there's likely to be a rather sharp rain/snow line on the NW side of the circulation, tho the NE side may have a small mix area where midlvl warmth rides farther north but northeast wind holds in ageostrophic wind component. Still, for the interior of even Southern NewEng this has the potential to be a 6"+ snowstorm of heavy wet snow, that may produce power outages this time in Srn NewEng. Tough to accept that possibility logically, knowing we're a week deeper into spring and yet contemplating a storm producing a swath of heavy snow farther SOUTH than the last one, but the cold in place now is deep and thanks to the combination of the persistent upper low aloft, and the building anticylcone at the surface, is stubborn. Also of importance will be the timing of the onset of precip. While last week proved full well that this was not important for areas deep enuf into the cold air, diurnal effects certainly did make a difference in Srn NewEng last week, and will again this week, tho perhaps more of Srn NewEng will be more squarely into the cold air this time around, making it more of a factor farther S. What I mean by this is that a strong April sun angle can have a big effect on temps - especially in lower elevations - and this would influence ptype right from the start. An early start means less diurnal effects before dynamic and evaporational cooling takes over, while a delayed start increases boundary layer temp and makes pure snow at least a bit more of an effort, creating elevation AND north/south dimensions to the rain/snow line. Again, deeper into the cold air - which may even simply mean interior Srn NewEng this time around - this will be less of a factor.
The storm should be out by later Thu ngt, and Fri looks like a windy and cool day. But for the weekend comes a very impressive upper level low, barrelling E in the jet stream flow with a well amplified trof that has shown very strong indications of being an efficient precip producer in the Ensemble guidance for two weeks! This disturbance will amplify sufficiently to tap the gulf of mexico full bore, meaning inches of rain will be possible Sat Ngt/Sun, and on top of snow, this would result in flooding for Srn NewEng on Sunday. Of course, that comes just a day before the Boston Marathon, meaning conditions could be sloppy, especially in the fields of Hopkinton where preparation for the race takes place.
Farther down the road, troffing persists into the last week of April! This will keep temps below to much below normal for the week of the 16th to 20th of April, then near or slightly below normal on average (a day or two may exceed normal) the final week of April.
Plenty to watch carefully - an amazing winter pattern continues in the middle of spring!