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:
A band of rain shifting east across New England on Friday will remain progressive, meaning drier air will move in quickly behind it. Nonetheless, while this quick-moving weather pattern quickly brings dry air into New England, it also will mean a quick return of showers to the forecast by Sunday.
In the meantime, you can monitor rainfall through the radar links at right as the band of rain, downpours and embedded thunder swings east across all six states. This rain band is driven east by an energetic disturbance aloft, and the strong cold front associated with it at the surface that will quickly usher in a new, cool Canadian airmass. The clash of airmasses has been accentuated today by an influx of tropical warmth and moisture from the south, evident by the bursts of rain that eminated northward from the Atlantic Ocean and over Eastern New England, first in the predawn hours of Friday, then again during the mid to late morning. This influx of moisture will help to fill in the rainfall across Eastern New England for a time, though the quick shift of winds to the west from mid-afternoon onward will usher in enough dry air to dry up the rain for most of Southern and Western New England, and by evening for most areas except Central and Eastern Maine, where showers will linger. Elsewhere, it won't be a bad evening to head out on the town or to kick off many of our fall fairs and festivals - just be sure to grab a jacket as the incoming dry air will also be quite cool and temperatures will fall quickly after sunset.
A chilly night Friday night will be made even more brisk by a fresh west wind that will persist through the overnight, but should preclude frost development in most areas. A chilly start will yield a cool day on Saturday, as Canadian air ensures plenty of sunshine but also means temperatures will straddle the 60 degree mark in many areas, though with the center of a high pressure center moving overhead, winds will be fairly light. With a fast-moving weather pattern taking hold, no sooner do we enjoy a gorgeous fall day on Saturday that clouds and showers return on Sunday. Another strong jet stream disturbance will race eastward, dragging increasingly warm and moist air northward ahead of it, thanks to southerly winds in a counter-clockwise flow of air around the incoming associated surface storm center. Showers will develop during the morning for Central and Southern New England on Sunday, where afternoon rains will fall - heaviest in localized bands of rainfall that will develop on the north side of the storm system as it passes over the waters south of New England. With the same area of high pressure that locked in a good day on Saturday not far away as it shifts over the Canadian Maritimes, the clash between that fair weather center and the incoming storm center will allow winds to pick up, especially across Cape Cod where a downright raw feel will accompany a sustained northeast wind of 20-25 mph! Farther north across the North Country, Sunday *may* end up a bit drier, though still is like to be cloudy and, of course, a northeast wind is also a cool wind this time of the year, and Sunday's temperatures will remain chilly under clouds for one and all.
Though showers and lots of clouds will likely linger into early Monday, meaning another cool day, conditions will improve late in the day and especially for Tuesday.
In the tropics, Tropical Storm Isaac remains over open waters of the Central Atlantic. While the storm will remain east of Bermuda, it will send swell north and west of its path, and the storm's track will take it over the Laurentian Fan and the Southwestern Grand Banks next Tuesday and Wednesday with swell well in advance of the system. Check out the latest from the National Hurricane Center by clicking here.
Technical Discussion: None today, see you Monday.
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, September 28 at 1:45 PM
Clouds popping up most heartily in Nrn/Wrn NewEng today thanks to areas of warm and moist advection strongest in these locales, though cloud streets of cumulus indicate warm and moist flow is strengthening most areas and clouds will continue to expand both horizontally and with regard to vertical structure. A few sprinkles or light showers are therefore still possible just about anywhere in NewEng Thu afternoon.
Feed of moisture into NewEng coming from two areas - one is the circulation evident east of Delmarva on VIS satellite imagery, feeding tropical moisture northward, and the other is the cool area of stratus and fog drifting westward to the east of Nantucket as of this writing, with buoy reports showing very slight dewpoint depressions (difference between temp and dewpoint) and a steady east wind. The bottom line here is that convergence is occurring in the lower levels over NewEng - both air and mositure convergence - and with a piece of the circulation to our south breaking northward tonight, we're likely to find at least some showers moving northward off the Atlantic. These are already evident on OKX radar moving due north, though as the upper level trough to our west begins to kick in our direction, this feed of showers is likely to move east, as well, so I've included showers in Eastern NewEng for overnight tonight into Fri AM, in concert with the NMM RH progs.
Still quite concerned on wind event for spine of and western slopes of Greens in VT tonight, where 60 kt llvl jet from the SE is in a synoptically favorable setup to translate similar gusts to the sfc overnight Thu Ngt into early Fri. With Green Mountain wind events, heavy rains typically quell the winds rather than enhance them, opposite from what normal meteorological logic would dictate, so I expect windy but not damaging conditions once the rain arrives. Nonetheless, some tree and power line damage should be done late Thu Ngt into early Fri AM. As for timing of the rain, morning west and either side of midday thru afternoon Central and East looks good, as does a realtively short duration of 4-6 hours, tho perhaps less in Ern Southern NewEng. 1-2" QPF looks good for HFD-PSM points north where rather channelled cyclonic vorticity advection moves thru, tho the limited scope of this strong CVA suggests that farther south we're unlikely to see similar amounts. The guidance is overdoing the nature of this limited precip in Ern MA, as the line of downpours and embedded thunder will probably drop half an inch fairly quickly with locally higher amounts, tho certainly these areas should see less than counterparts farther N and W.
Thereafter, Sat is rather straight-forward. Sunday, on the other hand, is a bit trickier. I'd imagine the fact that the GFS holds off precip until very late Sunday will give optimism on the forecast for some, but I also think that's way too optimistic given the deep upper trof approaching - trending a bit more amplified in each run - and this makes sense given the pattern evolution we've discussed here the past few days about each storm developing a bit farther east...it's our turn this Sunday. The vort max digs enough that the surface low should end up going south of NewEng which keeps us on the cool side and also puts Srn and Central NewEng in a favorable spot on the N side of the upper low for deformation banding of heavier precip on Sun, so if anything, while the QPF may look more promising the synoptics just look wetter and bleaker, esp when considering that the 1028 mb high over Funk Island Bank (north of the Grand Banks in the Canadian Maritimes) will provide a pressure gradient that should create a rather stiff NE wind over especially Cape Cod. Looks like precip would linger into at least early Mon with a rather expansive upper low - likely longer the farther NE one is.
Have a good day and hang onto your hat in the Greens!
-Matt
Wednesday's Discussion:
2:05 PM: Just finishing up with live updates for waterspouts over Long Island Sound. These spouts have developed ahead of warm front described in discussion below from earlier in the day. Expect these to remain mostly over the waters thanks to lessening low level convergence, and a diminishment of low level thermal ribbon gradient. Must be a wonderful show on the south coast of CT, though...
1:10 PM: After yesterday's enclopedic entry, today's will be somewhat shorter. There are, however, still some interesting and subtle features showing up in the weather around the Northeast today. One patch of clouds that popped up "out of nowhere" over CT and RI moved north into Central and Eastern MA before breaking up and dissipating. Meanwhile, much thicker and more significant pockets of clouds have been popping up over Long Island and over the Philadelphia area. 15Z surface analysis of the Eastern US shows warm fronts in each of these locations - one draped from a 1003 mb low moving across provincial lines from Ontario to Quebec that extends over UCA and to Long Island, and the second extending from a 1000 mb low over Nrn MI east to BUF and then south below a bit of cool air damming and into the PHL area. The former is progged to lay from NCentral VT to Central NH to extreme Srn ME on Thu, while the latter moves into Wrn NewEng. Along and north of these two locales are likely to be the areas to see the most clouds popping up on Thu, tho positive theta-e advection will be occuring over most of NewEng except Central and Ern ME during Thu, so believe the opportunity is there to mix in plenty of clouds in most other areas, as well, though in the areas not near a sfc front we'd be quite likely to see breaks of sun. I shud note, however, that while the positive theta-e advection is underway at the sfc and 850 mb in Srn NewEng early, almost all of Nrn NewEng is devoid of this and will likely start with plenty of sun early even tho we may end up with the most clouds there later. As for QPF, the wetter NMM and SUNYSB MM5 have throttled back, and given a lack of upstream activity even under the impressive areas of clouds this is certainly something to consider, tho there will be greater conflict of airmass over NewEng Thu than there has been farther S, enhancing isentropic lift. Additionally, guidance is spitting out a few hundredths across many areas west of Western ME, so this adds credence to the thought of at least a few showers popping up at almost any time during the day in Srn NewEng and esp afternoon into eve across the north when warm and moist advection is maximized.
NMM has sped up its timing for fropa on Fri while ECMWF and GFS have slowed a bit and we end up with relatively good agreement on a Fri midday/afternoon passage. CAPE values climb ahead of this frontal boundary and prefrontal SSE winds are cranking up to 55 kts from 850 to 700 mb, and greater speeds from the S/SSW at 500 mb. The result will be plenty of support for convection with lightning and heavy rain. Severe potential will be somewhat mitigated in Eastern and far Southern NewEng thanks to ocean modification on a SE surface wind, tho interior locales will have to be watched and higher terrain especially will see strong wind gusts. Additionally and more importantly with regard to synoptic setup, this is a very favorable pattern for a widespread damaging wind event on the Western slopes of the Green Mountains in Vermont where winds may gust up to and in a few spots in excess of 60 mph on Friday with downsloping winds off the mountain chain.
Very dry air progged by all guidance to punch in behind the rain later Fri. This dry air settles into Central and Srn NewEng on Sat, and trend has been to get the storm kicking northeast quicker and therefore can drop mention of showers in far Nrn NewEng scattered into Sat, as dry air takes hold for all.
As for later in the weekend, I mentioned in yesterday's discussion that we're transitioning from a pattern where it paid to trend slow to one where we should trend quicker, and lo and behold the latest guidance continues to speed up the timing of Sun rainfall. If clouds and showers come in early - and it looks like they will - many areas will struggle to get much above 60 on Sunday.
Have a great day.
Matt
Tuesday's Discussions:
3:05 PM: FYI: Developing news here this afternoon in NECN newsroom that Hood Blimp went down in wooded area of Beverly, MA. Nothing the pilots haven't seen before weatherwise - winds gusted to 21 kts at Beverly airport 2 hours prior to the downing but were only at 11-14 knots from the west at the time the blimp went down. Winds aloft show nothing above 20-25 kts in the lower few thousand feet of the atmosphere.
Showers found new life in Nrn ME with trailing vort lobe but as anticyclonic vorticity advection takes hold, these will diminish and breaks of sun will emerge.
Most of NewEng sees a clear night with winds slackening from gusts of 25 mph in spots this afternoon to near calm overnight and this combined with clear skies and dry air will allow temps to fall and valleys to decouple. Deeper valleys of far North Country will see a hard freeze while deeper valleys from Route 2 corridor of Nrn MA points N will see frost tho most NewEng communities will avoid frost again. Interesting that some are now hoping for frost in areas of MA and CT where West Nile and EEE are on the minds of residents, tho I see no frost for the short-range thru the weekend in these areas.
Quick rebound with good mixing and insolation on Wed, and with moderating low level thermal profile we shud see temps rebound to a couple of degrees above normal by afternoon. The forecast gets a bit tricky thereafter as the NMM is carrying moisture up the Mid-Atlantic coast into NewEng with low level high RH progged to transport north in pockets on strengthening southerly wind by Thu AM. My thoughts here revolve around the synoptic situation, which is different from this past weekend. Remember that my instinct for Sat was to keep plenty of clouds and some showers around in my discussions last week - tho it turned out to rain longer and more widespread than even I'd anticipated...we'd have been smoked if we'd followed the guidance - because of such significant warm advection at 850 mb. This time around we have much less advection occurring - minor temp changes at 850 and 700 mb which makes this a different setup, for sure. Nonetheless, we are still looking at a situation that brings continued upglide on gentler and broader but still-present warm and moist advection, and I think the atmosphere will behave in a tamer fashion as a result of weaker factors at play on Thu, tho the same basic principles should apply. I find even more support in the forecast of a strengthening southeast wind at the surface which tells me we're not going to easily slide a warm front thru even Srn NewEng unless we're advecting in a deep tropical airmass off the ocean, which we're not. Therefore, the wisest move at this point is to follow the areas of greatest warm advection and isentropic lift when making this forecast - acknowledging also that a series of weak vorts will slide from the Mid-Atlantic to the waters S of NewEng, which doesn't favor blasting warmth in here. Therefore, have to believe that clouds will thicken on Thu and areas of showers will exist - moving from S to N. The timing here is tricky considering there is no strong surge of warmth and moisture like we had this past weekend. Instead, the new air comes in pulses and this is likely to create difficult-to-time pulses of clouds and chances for showers, tho at this point it looks like one pulse into Srn NewEng Thu AM, moving into Nrn NewEng, then perhaps another pulse Thu eve or ngt. In between these times, tho SE flow is strengthening in the boundary layer we do have relatively dry air aloft and good mixing thru much of the atmosphere which should allow for some sunshine. The only thing I think we have to be careful for here is where low level warm advection will maximize as the new warmer air clashes with our old cool air, and that will set up across Nrn NewEng on Thu, where low level clouds are likely to develop and linger. The end result is for a band of clouds and perhaps showers to traverse Srn NewEng early Thu while any filtered sun fades N giving way to increasing low level clouds with scattered showers developing under these clouds later in the day as sun breaks out in Srn NewEng.
Thereafter, we come more under the influence of the large approaching cyclone. It's probably best to take a look at the big picture first, which is that each of these large upper lows over the past week and a half have come just a bit farther E each time, producing a strip of severe weather and heavy rains ahead of the cold front and a stripe of accumulating snow in the higher terrain behind the circulation. This upcoming storm will focus severe weather on the Ohio Valley and Appalachian Mountain chain on Thu and tho it's tough to find evidence of it on the guidance at this point some snow showers are likely to fall in the cold air that streams in behind the storm center across the Upper Midwest and Upper Great Lakes late Thu or Thu Ngt. So, the trend has been for each system to come farther east, tugging the longwave trough a bit farther east with each vortex, and each producing severe weather southeast of the storm center and wraparound snow or snow showers with anomalously cold air behind it. I don't expect the storm over the next 96 hours to be any different, though I do see this storm as marking a change in the weather pattern. That is, to this point a slow moving progression of the longwave pattern has kept slow-moving storms with the tendency to delay their arrival here in the Northeast. The passage of this next upper low is followed by strengthening westerlies and continued flow of disturbances off the Pacific. Meanwhile, the ridge over Northeastern Canada morphs into a Greenland block while the monster negative anomalies over the Eastern US break down and this allows for deamplification of the pattern. The net result here will be a less amplified disturbance when the next vigorous upper low slides thru Sun/Mon, tho enuf cool air may linger to make it interesting. But more on that later, as our large scale discussion has brought us away from the task at hand for the end of this week.
The subtropical jet continues to be evident on satellite imagery and is available for moisture input when tapped, and as the flow goes meridional ahead of the trof on Thu digging until it takes on a negative tilt. It's this negative tilt that will help to pull the subtropical moisture into the equation, tho not until late in the game on Fri. The result here will be for a few convective bands of precip assoc with the intense vorticity advection ahead of the upper low on Fri - with low level convergence focused on the frontal boundary. Canadian Ensembles strongly agree on a wave of low pressure developing along this front and rippling north out of the Mid-Atlantic. The GFS Ensemble members are faster with the frontal passage - Fri AM instead of PM - which makes a difference diurnally and also with regard to how potent this wave will become. The NMM has come in line with the Canadian Ensembles, tho the ECMWF is faster with its ensemble members showing large spread. Timing of this scenario will be critical for QPF amounts - esp in ME where feed of subtropical moisture would establish - and for severe wx potential in Srn NewEng. At this point, think NMM may be overdone on instability and prefer Canadian solution of developing a secondary low on the front, tho shortwave trof axis whips from VA Beach to Eastport ME at 500 mb from 12 Z Fri to 00Z Sat, which would keep any sfc system moving quickly. The result of a scenario like this would be to tap some but not all of the subtropical moisture - feeding off of the moisture rather than redirecting it - and deliver it as focused rains on Fri thru most of especially Ern NewEng. Given the slower nature of this system thus far, and the fact that it just starts to pick up speed as the aforementioned longwave pattern breaks down, this gives me some but admitedly little confidence in my selection of scenario.
While there are varied solutions on the evolution of the Fri scenario, there is much better agreement on the weekend, which leaves clouds in many areas early Sat that should be eager to dissipate given well agreed upon chunk of very dry air that moves into the mid levels Fri Ngt and Sat. Nrn and Central ME remain unstable aloft, esp early Sat, and this will prolong showers in these locales. Given fast weather pattern that takes over thereafter, clouds thicken Sun with rain moving in from W to E second half of the day. This system will also amplify - this time over far Nrn NewEng - as it follows in a similar fashion to its predecessors, tho continuing the northeast trend of the longwave trof. Precip will wrap around the back of this low on Mon into Quebec and Ontario as well as Nrn ME on Mon AM, and the question is how much cool air will linger to work with. Most guidance is shifting high over Ern Canada farther E, allowing a SE flow to move in for NewEng. The ECMWF has been farther west and stronger with the high center, but not enuf to continue feeding significant cold into Nrn ME. To the northwest, strong low will be found on SW coast of Hudson Bay and this will mean no direct shot to cold air pouring in, so what we're dealing with is a lingering pool of old cold that will get no reinforcements, meaning the deep surge of low level cold seen with the preceding lows, meaning it will be difficult to see wintry precip wrapping around in Nrn ME - not impossible, but not a synoptically favorable situation.
Have a great day.
Matt
Monday's Discussions:
2:35 PM: As it turns out I'm more crunched for time today that I initially thought I'd be so I'll keep this rather succinct. Diurnal Cu field has been stubborn given cold advection just a few thousand feet off of ground level and as it diminishes this afternoon and evening the next vigorous shortwave moves in. Should be decent convective bands with the cyclonic vorticity advection assoc with the next shortwave overnight largely owing to -24 to -27 C temps at 500 mb with the cold core aloft. With cold air in the lower levels, mountain summits of North Country will see snow in the heavier precip bursts - esp above 4500 ft. Some deeper valleys will cool into the 30s prior to arrival of precip, and while it will be a frigid rain in those locales, dewpoints aren't quite cold enuf to worry about freezing rain.
Clouds are likely to linger Tue AM, esp in Central and Nrn NewEng where sct shra blow thru overnight and predawn, and given another shot of llvl chill behind the shortwave, but this cold advection is brief, and most of Central/Southern NewEng will actually see slight airmass modification. The wx pattern remains rather stagnant over us Wed into Thu but that's only because of the tremendous digging energy into the Northern Plains and Midwest. Good Gulf tap will load the atmosphere ahead of the disturbance and when this ejects east at the end of the week it should be an efficient precip producer here in NewEng Thu Eve and esp on Fri. As has been the case with the last few disturbances, it likely won't be a clean transition out of this disturbance once it goes by - lots of CAA clouds like today have been the result the past few intense trofs that have swung thru, but significant moisture feed should shift off by the weekend.
Again, unfortunatley limited on time today - will hope for more tomorrow.
Matt
