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 contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
General Weather Summary:
Don't forget the Southern New England Weather Conference, slated for this Saturday, October 28 in Brookline, MA! Open to ameteurs and professionals, alike, this conference is a great way to stay on top of the latest weather information for New England forecasters. For more information, click here!
Weatherwise, New England is enjoying a calm and mostly sunny Friday ahead of what will be a powerhouse storm on Saturday. This storm will bring heavy rain, damaging wind, a period of snow, and large waves to New England this weekend.
We're watching the merger of two strong storms over the Southeastern United States for our Friday, which will merge into a powerhouse storm for New England on Saturday as a third piece of energy becomes involved. Each of these disturbances have been examined in this discussion over the course of the week - the moisture-packed remnants of what was once Hurricane Paul, the Alaskan energy that brought a blizzard to Colorado on Thursday, and additional energy diving southeast across the Northern Plains. As of this writing, morning tornadoes have already been reported in the Gulf Coast states as deep tropical moisture funnels northward into the developing storm center. Closer to home, high pressure (fair weather) has been gradually letting go of the region, but is holding on with enough dry and cool air to bring sunshine, much needed after a morning start in the 20s and 30s! With a light wind, the chill of the past few days has been significantly muted, and even though actual temperatures will be somewhat cooler than midweek, the presence of sunshine and lack of wind will make a big difference.
Increasing clouds Friday night will come in advance of the approaching major storm, and rains will develop from southwest to northeast - first in Connecticut around midnight, then farther northeast thereafter. While this storm won't reach peak intensity until over Eastern Canada, it will be undergoing a rapid strengthening phase as it moves over New England on Saturday, which means we'll experience a variety of dynamic weather.
Steady rains will be falling by Saturday at 8 AM through the southwestern half of New England, or a bit more than that, all the way into Western Maine. This moisture surges north as we're still trying to let go of a stubborn cold airmass and importing a lot of deep tropical warmth and moisture. The tropical nature of this air will mean it will be quick to erode cold air in most locales, and it will find additional and crucial help from a strengthening southeast flow that comes off Atlantic waters still running well into the 50s. This marine influenced airmass will penetrate the lower few thousand feet of the atmosphere, and even though temperatures above about 5000 feet will be below freezing at the beginning of the event Saturday morning, the warmth near ground level will be sufficient to melt any ice crystals (snowflakes). The exception to this early Saturday morning may be in the Northeast Kingdom of Vermont and the higher terrain of the Green Mountains, where snow may begin the event on Saturday morning for an hour or so before changing to rain, and after only a dusting to an inch. Farther north and east, through the Northern White Mountains and Mountains of Maine, it will be harder to dislodge the cool air, as southeast winds struggle to displace cold air more in these locales, meaning a few hours of snow would be possible in these locales, too, with some accumulation in the higher terrain (especially of Northwest Maine) of anywhere between one and four inches (see map) before a brief change to sleet, then to all rain. Even farther north, the precipitation won't arrive until later in the day Saturday but cold air will likely hold on long enough for a period of snow here, too, in Northern Maine.
So where does that leave us farther south? Most of New England will rain quite hard with this Saturday storm, as the primary storm cuts west of New England, but a slight reflection develops as a secondary storm from Virginia in the morning to Eastern New England in the afternoon. Winds will ramp up along coastal locales where gusts to or over 50 mph will be possible Saturday afternoon, and gusts to 70 mph will be possible Saturday evening along the middle and Downeast coasts of Maine! Winds of this velocity would be sufficient to cause damage to trees and powerlines, as well as blow around lightweight objects and destroy Halloween decorations through the day Saturday, especially within 30 miles of all New England coastlines, and the risk of power outages would be heightened in these areas. With the exceptionally intense gusts along the Maine coast, shingle damage may be done to some immediate coastal residences.
Additionally, the infusion of tropical moisture to a lingering cool fall airmass will mean a strong clash of different airmasses that will crank out heavy rain across all of New England with at least one to two inches in most areas, though more along the lines of two to three inches of rain through the interior of Central and Southern New England! This much rain will fall in roughly a 12 hour period on Saturday, timed right in the heart of the day, and would be enough to prompt at least minor flooding of streams, along with ponding of water in poor drainage areas, including areas where catch basins are clogged with leaves. Runoff may even result in some small rivers experiencing minor flooding by Sunday morning.
This major storm will churn the ocean waters, as well, and mariners will not want to be caught out in this storm on Saturday, with large swell lingering into Sunday as seas build 15-20 feet on Saturday, and linger at 10-15 feet on Sunday.
As for the weather across New England on Sunday, our powerful storm will have pulled over the border into Eastern Canada, but will grow quite large. This will mean an expanding wind field under the belly of the storm, with brisk winds for all of New England gusting to 45 miles per hour (stronger in the mountains and hills where damage will still be possible) and snow showers across the mountains of the North where moisture and cold air will both wrap underneath the storm and cross the Canadian border. Elsewhere in New England, the chill of the cool breeze will at least be muted somewhat by sunshine mixed with plenty of puffy cumulus clouds. Nonetheless, the day should be redeemable in many areas after a virtual loss on Saturday.
Cold air will already be battled aloft by incoming warmth on Monday, and this is likely to bring a few clouds through the day, possibly producing a few isolated showers. Milder air will make a surge north for Tuesday before another shot of chill sends the remainder of the week back to below normal temperatures.
Technical Discussion: None today, believe it or not...but I think we've sufficiently addressed the storm thru prior techie discussions (below) and the maps/discussion above. Enjoy the storm, techies!
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, October 26 at 2:45 PM
Plenty put down here yesterday (see below) and crunched for time today so will keep this rather brief. Decoupling tonight with winds slackening and high building in. Dewpoints have been lowering thru the day and this dry air will allow temps to fall quickly after dark with widespread frost. Cold start Fri AM will be moderated by sunshine tho sfc ridge is overhead which means axis of chilly air overhead and mixing limited thanks to subsidence inversion, which will limit temp rise and keep max temps around or perhaps even a degree or two cooler than Thu, even tho drier ambient air will increase amount of insolation. Reports from Nrn VT indicate no sun all week...will try to get some peeks of sun out with mixing on Fri.
Weekend storm will be a doozie...remains to be seen just how fast it strengthens but looking at minimum of a 12-14 mb drop from Ern VA 12Z Sat to Ern MA 00Z Sun, and perhaps more strengthening than that, which will both crank winds ahead of the circulation, cause banding of precip, and result in ageostrophic wind N of the storm. Winds fcstd to crank to 70 kts over Srn Gulf of ME at 925 mb...and gusts over 60 will be likely from Nrn MA coast thru ME coast Sat afternoon. Seas churn to 15-20 feet as a result. Baroclinic zone discussed yesterday still looks like important player in focusing rainfall which will be heaviest thru interior and 2"-3" likely in large swath with closer to 2" elsewhere and lesser amounts NW. As for the ageostrophic flow, that is the toughest part of the fcst wtih regard to ptype and tho it is not modeled by guidance, a rapidly strengthening storm would turn a fcstd E/ESE wind to a NE wind over Aroostook Cty ME and that's my concern for extended wintry precip there. Elsewhere, Greens and Whites both shud have enuf cold air in place on commencement of precip for wintry burst, with Whites thru ME Mountains seeing slowest erosion of cold dome that historically would lead to some accum before a mix and change to sleet, then eventually rain as the cold is overwhelmed.
3" in 12 hrs enuf to aggravate streams and drains clogged with leaves will make many areas of poor drainage on Sat. Cold air to wrap around belly of storm Sat Ngt/Sun with snow showers in Nrn NewEng and upslope heavier snows Nrn Greens/Whites/NW ME mountains. Below normal pattern holds thru next week.
More detail for public consumption above in General Wx Summary.
Matt
Wednesday's Discussion:
2:20 PM: Winds kicking up on cue across NewEng this afternoon and with gusts to over 30 mph at times, this is especially raw across Nrn VT where rain showers have been lingering beneath cold pool and with assistance of upslope flow. Remainder of north seeing sct rain and snow showers with multiple weak vorts and localized upslope flow, along with lingering instability thanks to cold air aloft. Conditions stay similar overnight but without diurnal disruption due to thermally induced mixing, and this will allow revitalization of upslope areas of snow showers, where some light accumulation is possible on the order of 1-3" for higher terrain - esp above 1200-1400 feet from VT to NH/ME as profile is colder over VT. In fact, below freezing profile reaches 900-1000 feet in Nrn Greens by predawn Thu.
Overall trend for slower progression of weather pattern offsets a few parts of the forecast for us, starting with Thu when more clouds will linger below sluggish cold pool, then for Fri when we can extend dry weather thru the day with increasing clouds late.
Yesterday's thoughts on the weekend storm focused upon Dr. Colucci's "always beware the col" and the belief that this upcoming storm would take a track southeast of NewEng toward the well-defined col. 00Z GFS and Canadian Ensembles have both come back with eastward leaning solutions, but there are plenty of factors that need to be considered in this forecast for NewEng. First of all, let's understand what's going on in the longwave pattern, and that is the combination of two big factors: 1) The continued and, in fact, accelerated breakdown of the Greenland block that has been in place, and 2) a large amount of Alaskan energy ejecting from the Aleutian low (which has shifted N recently in response to Siberian input) and diving into the mean trof position which begins W of NewEng but comes directly overhead given these two major factors at play. What's to be truly amazing come Friday is the interaction of systems that take part in this longwave redefinition, which includes 1) Pacific energy sliding into the Pac NW currently that will carry a primary low well to our west, 2) the remnants of what was Hurricane Paul, coming across TX and tapping the Gulf for copious amounts of moisture and a storm center chock full of latent heat expenditure, and 3) the aforementioned Siberian/Alaskan energy combo that slides quickly SE in the fast Westerlies and is the final addition to prompt a negative tilt of a wildly amplifying trough. Diffluence ahead of this system will be quite impressive aloft on Saturday over the waters south of NewEng, and this, coupled with tight baroclinic zone and aforementioned col will aid in steering quickly strengthening storm over the waters S and SE of NewEng on Sat, to a position N of NewEng where the low will become vertically stacked and bomb over Ern Canada, ensuring very windy conditions across the Northeast on Sun/Mon, though without much available deep cold (we've expended a large chunk of it already and there is currently no well of deep cold available in the Northern Hemisphere) it's unlikely we'll find more than a shallow surface dome of cold moving in, which will mix enough diurnally to warm on Sun and Mon, esp in Srn NewEng where strong wind is also downsloping wind.
We'll pick that thought up again in a moment, but before we get too far ahead of ourselves it's important to cover more details on the events that will transpire with the weekend storm itself. We left off with storm track, likely to be S and SE of NewEng before hooking N as the surface center is pulled beneath the upper low and bombs as a result. The question of the last few days has been just how much cold air holds on with the approach of the storm, and what ptype we're looking at for whom. There remains little doubt that this event will be a liquid event for Central and Southern New England, where 850 temp anomalies of +2 to +6 C move in ahead of storm thanks to tropical input from remnants of Paul. This is where it's important to keep in mind the origins of a storm, which I often will refer to in these technical discussions, as airmass origin can and does make a difference later down the line. With so much tropical air available, it's quite likely there will be a slug of midlvl warmth that will be nearly impossible to stop without deep cold, of which we'll be out of when the moisture arrives. The warm advection will be so intense that it's likely to overtake most of NewEng with warm air as the storm pushes N on Sat. That's not the end of the story, however, as warm and moist advection means the influx of higher potential temperature air, which will create isentropic lift. Strong enough isentropic lift will aid in dynamic (adiabatic) cooling, which will in turn hold a colder atmospheric profile. Yesterday I noted the presence of a surface anticyclone in Eastern Canada that would serve to hold the low level cold into Nrn NewEng for me to consider significant snows in the mountains of the North, though the slowing of the pattern has allowed this high to weaken as upper level diffluence lifts north Fri night into Sat, which means we've lost the mechanism originally in place to hold the cold, and all we can count on for wintry precip is old, diminishing low level cold and dynamic cooling. The end result of this should be a burst of snow in the mountains of Maine, especially, and perhaps in Northern Maine to begin the storm. With a northeast surface wind ahead of the storm center thru most of Sat, until the passage of the occluded front connecting the primary low over Ontario with the secondary low swinging northward, east of NewEng, we are likely to hold the surface cold into esp mountain valleys in Maine, but the warm surge aloft in the midlvls (750-600 mb) assoc with the tropical moisture should be too strong to hold off, and ptype will swing to rain even thru most of ME later Sat, tho perhaps could hold as sleet for a time in the mountain valleys.
Elsewhere, heavy rain and strong wind will be the features of the strengthening low, with a well-established tropical moisture tap loading the system and intense dynamics assisting in wringing this moisture out, esp along low and midlvl baroclinic zone that lifts across interior NewEng where banded heavy precip is most likely. Given high precipitable water values, should be able to exceed current guidance and crank out 2"-3" liquid QPF for these interior locales - even though most of the QPF comes with the slug of warm advection, this still lasts a good 12 hours during Sat. Potent low level jet will crank ahead of this storm and this will translate to strong sfc winds near the storm center along Eastern Coastlines from the E on Sat...perhaps beginning NE but then will have to come E or even SE as this low pressure center is developing as secondary/triple point along occluded front.
As the storm pulls away Sat Ngt/Sun, mentioned above that storm deepens rapidly and winds kick, but lack of deep cold thanks to lack of strong anticyclone means no rapid surge of cold for all of NewEng, though low level cold will be intense enuf in Nrn NewEng to turn ptype to snow and snow may come down hard in Nrn ME during this period as wraparound comma head will come all the way under belly of circulation...biggest question here is whether it misses just north of ME or delivers a windswept snow to Nrn Aroostook County, which is possible on Sun. Farther southwest, upslope flow will be maximized in mountains of ME on Sun, but lots of instability Cu will layer the skies of NewEng with snow showers in most of the mountainous terrain. As the upper low churns over Ern Canada, it essentially creates its own pool of cold air courtesy of dynamic cooling, and this cool pool settles over NewEng middle to end of next week, and though it is progged to be at least 8 C anomalously cold at 850, the shallow nature of the cold is likely to allow mixing and therefore modify the impact somewhat, though clearly below to much below normal temp regime will continue.
Matt
Tuesday Discussion:
1:10 PM: No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts. Let me get them out as quickly as possible:
Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM. The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight. Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see. Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow. To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably. Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well. Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing. Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly. Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels. Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue. Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.
Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool. Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US. This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE. 1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng. At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col". As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking. A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.
Enjoy your day.
Matt
