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:
Numerous disturbances continue to drop over the Northeastern United States, bringing rounds of strong summertime thunderstorms to some while bypassing others. There have been two paths for these disturbances - one from Southeastern Canada tracking southeast over the Northeastern United States, and the other pathway running along the border with deep tropical moisture through the Mid-Atlantic and just south of New England.
Meanwhile, the increase in dewpoints, meaning a gradual increase in the amount of moisture packed into the lower levels of the atmosphere, continues and therefore each day we find increased fuel for thunderstorms to feed off of. The passage of yet another upper level disturbance on Thursday will mean another round of thunderstorms for New England. After finding significant damage in Simsbury, CT, associated with Wednesday's storms, and additional damage scattered through Western MA, VT, NH and ME, new damaging storms will be possible Thursday afternoon. Like Wednesday's action, though - and like most summertime thunderstorms - coverage will be scattered, meaning some communities will be hit hard while others don't see a drop of rain. The bottom line here is not to cancel plans, but certainly to keep an eye to the sky as threatening skies will move into most communities from the Western horizon. As was the case yesterday, south-facing coastlines and areas within 20-30 miles of those coastlines will likely see quieter conditions thanks to a cooling flow off of the ocean, limiting the potential for thunderstorm growth, though one exception will be along the southwest coast of Connecticut where Long Island Sound waters are now fairly warm.
A few showers and thunderstorms may continue to feed off of the increasing moisture near ground level, and therefore continue to float around New England during the first part of Thursday night, while most of New England sees a warm, muggy, and downright uncomfortable sleeping night. Late Thursday night into Friday, another in the parade of disturbances racing southeast from Canada will move toward New England, crossing overhead Friday afternoon.
These Friday afternoon storms are likely to take on a bit more vigor, as the strongest of the week's disturbances moves through Northern New England - likely spawning storms for most of the six-state region - and interacts with the hottest and most humid of our week's air. In other words, the greatest amount of energy comes at the time of our greatest heat and humidity, and these are the ingredients necessary for a severe weather event, so damaging thunderstorms appear possible for many areas.
One may conjecture that the passage of this disturbance on Friday would mean the passage of a surface cold front or some airmass change. With the jet stream winds aloft riding right over New England, though, the thermostat feature of these fast winds aloft will mean deep summer air can't be surpressed very far south. The result will be for a quick rebound of deep summer air on Saturday, with an isolated thunderstorm possible later Saturday afternoon, though the more likely scenario will feature a break between disturbances on Saturday with advancing thunderstorms overnight Saturday night, as another in the series of upper level disturbances moves across New England in fast flow aloft coming from the northwest. Storms would again be possible on Sunday throughout the day as a parade of disturbances marches through, though not for the entirety of the day - more like lingering storms in the morning, then new storms developing in scattered to widespread form during the afternoon.
One wild card in the weekend forecast is the tropical wave that brought heavy rains to Southern Texas and Northern Mexico over the last few days. Though this area of disturbed weather never developed a tropical storm center, it did carry plenty of moisture with it, and a piece of this energy will break off, and ride north, then east, around an area of Southeastern U.S. high pressure. As this moisture-loaded disturbance passes south of New England, it very well may provide additional moisture input to be reckoned with. The toughest part about this is determining the timing of its passage - afterall, it has a long way to travel - as the timing will be critical to whether it interacts with a northern stream disturbance riding overhead at the same time, which would ring out heavier rainfall. At this point, the most likely time for an interaction would be Saturday night or perhaps into Sunday, but this is subject to change and will become more accurate each day as the fate of this tropical chunk of energy becomes more apparent.
Also in the tropics is a swirl located east of the Windward Islands. This tropical wave has plenty of energy associated with it, but has been in an area of unfavorable winds aloft, and dry air has surrounded it, which makes development nearly impossible. The next few days, however, this tropical wave will move west across the Bahamas and as it enters an area more favorable for development, we may see it become better defined. Regardless, even if this thing does take off and head toward the Southeastern U.S., a continued flow of northwest winds aloft (the same jet stream flow delivering our parade of disturbances out of Canada) would be very likely to curl this disturbance back out to sea before it could come anywhere close to New England.
Have a great Thursday!
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, July 27 at 2:10 PM
Today's shortwave only the next in a parade of vorticity maximums to move thru NewEng over the next several days. The combination of southwest surface flow and northwest flow aloft almost always provides convective excitement and the next several days will live up to that billing, with the most significant action possible early next week when we introduce baroclinicity into the mix.
In the meantime, thunderstorms already popping in NY and carrying into VT - also orographically induced storms in the mountains of ME and both of these trends will continue thru the afternoon as cyclonic vorticiity advection sets in ahead of the shortwave moving out of Southern Ontario. Mean flow is fastest over Northern half of NewEng where generally 35-40 kts most levels, tho 25-30 kt flow over Srn NewEng not too shabby either, esp when considered with LIs to -5, CAPE soaring to 2000 J/kg thru most of interior NewEng and decent dynamic forcing assoc with the shortwave and falling mid-level temps. Severe tstorm threat exists with all stronger cells but is more defined over Northern half of NewEng, tho instability wanes in VT after mid-afternoon given passage of shortwave trof axis.
Behind this vort max, anticyclonic vorticity advection assures things will quiet down the first half of the night across NewEng as diurnally driven convection gradually wanes. In this quiet interim, fog will develop in valleys and in areas where rain has fallen and increased boundary layer moisture results. I don't expect dry conditions to persist thru the entirety of the night, however, because after midnight - likely from pre-dawn into early morning - the vort currently producing nasty storms along the lake breeze boundary of Nrn OH and NW PA will move east and directly over NewEng - likely carrying at least some lingering convection with it in a relatively narrow band, but track favors carrying this precip across much of MA, Srn VT and Srn NH.
Of course, the real show appears to be Fri afternoon and evening, when we'll take an already very strong shortwave and amplify it more as it drops into the Hudson Valley, bringing widespread PVA across most of NewEng during the afternoon and evening. Dynamic forcing will be intense and widespread in this CVA and winds will be ripping deep layered from 500 mb winds out of the west at 40-45 kts, 700 mb flow at 40-50 kts, 850 flow at 30-40 kts from the WSW. Helicity values will soar to between 150 and 250 m2/s2 in Southern NewEng. The only marginal component will be CAPE given plenty of cloud debris thru the day limiting diurnal htg, tho I do think the guidance is underestimating the effects of the limited sun we see, as even late morning to early afternoon breaks should boost temps into the 80s for most areas, which would also make progs of 250-1000 J/kg underdone. Tremendous lift and wind field should be able to make the most of what instability does develop - probably closer to 1000-1500 J/kg CAPE and LIs to below -4 - and this means widespread severe event looks like a good bet. Given backed sfc and low level flow, rotating storms certainly a possibility during the early eve in Southern NewEng, but will want to reassess Fri.
I like a break in the action for Sat with a break between shortwaves, tho a weak vort max rides across Nrn NewEng Sat afternoon and may fire isolated to sct convection in mountains. Elsewhere, will wait for next shortwave Sat ngt under warm advection that should spell noctural thunderstorms lingering into early Sun AM before yet another in the parade of shortwaves brings numerous afternoon showers and storms Sun - won't be wet all day but expecting plenty of action given tropical airmass and shortwaves racing thru.
Backdoor front will be ready to surge southwest early next week with upper low over extreme Eastern Canada swinging a monster vort max thru Quebec and across the St. Lawrence River Valley Mon ngt. Heights are rising on Mon so I am not in favor of carrying this front very far into NewEng tho Nrn ME may see tstorms induced by front. Elsewhere - still a parade of shortwaves moving thru with strong NW flow, and given the warm air that will be in place, additional thunderstorms will develop in the warm sector Mon PM. By Tue, the monster shortwave has passed and cold advection should thrust the back door front into Srn NewEng, tho heights fall only thru Tue AM before reversing and warm advection will follow suit. This will put at least CT/Wrn MA into the warm sector again by Tue afternoon and perhaps much of MA, as well, and with warm advection along this returning warm front, flow will be conducive for organized thunderstorm clusters near the warm advection boundary.
Midweek pattern for next week intersects a SW to NE oriented low level frontal boundary from the Western Gulf of Mexico to Nova Scotia with an active northerly flow and broad mean trof over the Eastern Great Lakes, all of which should help to crank out significant rains before a broad area of high pressure builds in at the end of the week and next weekend.
In the tropics, the wave moving over the Bahamas has failed to materialize, though it does contain significantly more convection than previously as it's emerged into an area of weaker shear and increased ambient moisture. Nonetheless, this wave is fighting an uphill battle as more dry air lay ahead of it, and development is looking much less likely. Meanwhile, the piece of tropical energy from the Gulf of Mexico is likely to pass off the Mid-Atlantic coast after moving thru the Southern OH Valley, but will stay just far enough south to avoid interaction with the northern stream Sat night. Still watching the strong wave pushing across Central Africa for early next week, but there's weeks to go with that one as it crosses the Atlantic. So, in all...no immediate or near-term development is foreseen.
Enjoy your Thursday.
Matt
