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 complex weather scenario will unfold over the next 24 hours as a gale center rapidly develops south of New England, moves through, then rapidly decays.
Here is expected rain and wind:
Morning surface analysis places one area of low pressure over northern Lake Superior, and another off the Outer Banks of North Carolina. The former is associated with a deep trough, or dip in the jet stream, that is carving through the Midwestern United States. Remember that the jet stream not only acts as a thermostat for the atmosphere, separating cold to the north from warm to the south, but also steers our storm systems, and as the jet stream dips farther south across the Ohio and Tennessee river valleys, the flow aloft blows from south to north along the Eastern Seaboard. This will favor a northward progression of the storm center by North Carolina, steering it into New England Wednesday night.
In the meantime, any breaks of early sun on Wednesday have continued to be covered by a veil of thickening clouds, indicative of increasing moisture heading northeast ahead of the primary storm center well to our west. The collision of warm and moist air flowing ahead of this storm system, and the cool air in place here in New England, has resulted in a clash of airmasses several thousand feet above our heads, and condensation of clouds has been the result. While dry air near the surface has kept any showers from developing through the first part of the day Wednesday, an increasingly moist airmass will allow showers to develop first in the hilly and mountainous terrain of Northern New England, then spreading in areal coverage with a few light scattered showers across New England from about 2 PM Wednesday afternoon onward. Meanwhile, the approach of the coastal low pressure center - energized by a disturbance riding aloft in the jet stream winds - will mean a squeeze play between this low pressure center, and a high pressure cell northeast of New England. The result will be a noticeably freshening wind Wednesday afternoon along the south coast.
By about 7 PM Wednesday evening, more formidable showers will spread to the South Coast of New England, filling in across most of New England by midnight. The heaviest rains will fall near the path of the approaching coastal low pressure center, and at this point it appears as though there may be a few bands of heavy rain - one to the west and northwest of the storm track, from Central Connecticut into Central Massachusetts, and another from Northeastern MA through the mid-coast of Maine, and in bands of heaver rain, over two inches may be recorded. Outside of heavier rain bands, closer to half an inch will fall. Along with the rain will come plenty of wind, as the squeeze between a fair weather center and the storm center will continue to crank an east or east-northeast wind early in the night Wednesday night, shifting to southeast as the storm center approaches the South Coast around midnight and gusting to 30 knots at the South Coast, then increasing in intensity while moving northward through Eastern New England, bringing wind gusts of up to 50 knots (58 mph) to the Southern and Central Maine coastline late Wednesday night and Thursday morning. Wind of this magnitude would be enough to cause at least scattered damage to tree limbs and an isolated power outage, blow our garbage cans around, and boat owners from Merrimack River northward will want to check fenders if the boat is still in the water.
While the morning begins on a rather nasty note for especially the State of Maine on Thursday morning, most of Southern New England will already have seen the heaviest of the rainfall move through, while Northern New England west of Maine will have seen lesser rainfall amounts through the overnight. In fact, during the day Thursday, drier air will move into Southern New England, and at this point the dry air looks substantial enough to evaporate many of the clouds that will begin the day, allowing sunshine to emerge during the afternoon. With somewhat more tropical air in place, carried northward by Wednesday night's storm center, temperatures will respond well to any sunshine, and would be able to rise into the 70s with somewhat of a humid feel! With moisture and warmth the result, a few thunderstorms will be possible in Southern New England Thursday afternoon, while areas farther north see continued clouds and a few showers from time to time through the day.
A cold front associated with the primary storm over the Great Lakes will eventually move east, crossing New England late Thursday night into Friday morning with another line of downpours and possible thunder, and serving as the leading edge to cool Canadian air that will have produced record cold across the Plains States and snow in the Upper Great Lakes. This chilly air will certainly be modified somewhat by the time it arrives, but still will allow temperatures to struggle to rise much past the lower 50s in Southern New England Friday afternoon, and much past 50 in the north. With a few upper level disturbances still upstream, ready to swing through New England, a few scattered showers will still be found Friday afternoon amidst breaks of sunshine, though most of the showers would be found in the higher terrain of Northern and Western New England.
By Friday night, enough cold air will be spilling into New England that snowflakes will mix in at higher elevations. This comes as drier air moves into most of New England, which means many areas will escape from any snow showers, though moisture input from a steady westerly flow off of Lake Ontario may contribute to snow showers along the spine of the Green Mountains overnight Friday night. Additionally, a new upper level disturbance will move across Northern New England late Saturday and Saturday night, bringing another chance for mountain snow showers, this time carrying into the White Mountains and Mountains of Maine overnight Saturday night, though it's likely these would only be found in the higher elevations of above 2000 feet, with either a mix of rain and snowflakes or simply rain showers falling in the valleys. For the remainder of New England, Saturday will be a very brisk blend of sun and clouds, leading into what will be a cool but less windy and still pleasant Sunday.
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, October 11 at 1:35 PM
Developing circulation evident in sfc analysis and in radar imagery off Mid-Atlantic coast with bands of tropically infused convection spreading north and west away from the center. This, as 70+ kt jet streak at 250 mb rides up the Eastern Seaboard with right rear quadrant ready to assist low development with diffluence aloft. Assoc with this jet streak are two moderate strength shortwaves riding over the SE US and creating parallel swaths of precip as they race to the coastline. These upper level dynamics will combine with low-level thermodynamics and tropically infused air leftover from the persistent circulation that had been off the Carolinas to create a strengthening low. Not sure it will officially qualify as a "gale center" as the center will not be gale, but the pressure gradient force between the storm and the departing sfc ridging will bring wind gusts to gale force Wed ngt into Thu AM from S to N. Looks as tho there may not be enuf PGF to get gusts much over 35-40 mph on Cape Cod overnight, but wind corridor forecasted to strengthen, blowing from the SE, as low level winds crank to over 60 kts late Wed Ngt and early Thu along the coast of ME. Have applied gusts of greater than 60 at the coastline on ME...dropping as one moves south. Please see map in General Wx Summary. As for rainfall totals, good agreement that amounts increase as one moves E, and it makes sense that greatest llvl jet should crank out greatest precip amounts in coastal ME where amounts will exceed 2"...again, reference map in General Wx Summary.
I doubt much of Nrn NewEng will break out on Thu - staying clouded over as baroclinic zone does not lift much north of Canadian border, but deep dry air wrapping ahead of main upper low will mov across Srn NewEng and likely will mix enuf in tropical and therefore well mixed atmosphere to bring sun out. Naturally, warm airmass will respond nicely to insolation and temps should climb quickly in Srn NewEng. In fact, enuf moisture and with insolation enuf warmth that LIs drop to 0 and SBCAPE rises to near 500 J/kg in some spots which will be enuf to warrant chc thunder in Srn NewEng Thu afternoon with passage of prefrontal trof.
Winds should increase with and behind passage of this trof, and stay active Thu Ngt ahead of approaching front, progged to cross NewEng from W to E during the overnight. Good news here is that the lack of pressure gradient with no strong sfc high has completely mitigated the threat for damaging wind along and behind the frontal boundary. The not-so-good news here is that this actually means wetter weather will be the result on Fri, as the surface front quite literally outruns the upper level support. It appeared all along as though the upper level flow certainly becomes more parallel to the front as it runs farther east, but now this should keep NewEng squarely on the cool side of the surface front Fri, but directly beneath the midlevel front that will interact with a number of upper level disturbances to keep precip going across NewEng on Fri. Kudos to the GFS if this evolves as such, as that model lead the way on this potential by picking up on it yesterday, and now is joined by the NMM, Operational Canadian, and some support from the GFS Ensembles. This also delays the timing for getting good trajectory developed off Lake Ontario to enhance snow shower potential in Green Mountains on Fri Ngt - esp when looking at sfc wind component - but winds at 850 come in line and have kept chc in given moisture input and upslope flow off the surface.
Another shortwave to swing thru NewEng on Sat in the nrn stream and this will likely promote convection in the mountains of the North where rain and snow showers will fall later Sat. Quiet weather sets in into Mon, while a huge rainmaker charges thru the SE quarter of the US, likely en route to NewEng on the backside of departing high to deliver a shot of heavy rain to NewEng. This system will be what is currently Tropical Depression Norman, who will cross Mexico, drag Tropical Pacific moisture across the Gulf of Mexico, then bring the consolidated slug north while NewEng would likely see low level Atlantic input, as well! Yikes! Could make tonight into tomorrow look easy, but let's keep an eye on the trends for now.
Have a great day.
Matt
Monday's Discussion:
1:35 PM: Nary a cloud in the sky today with deep dry air and split energy on the Eastern Seaboard as upper low stays south and westerlies ride north. WSW flow has advected both warmer and more moist airmass into NewEng and this will be reflected in overnight temps esp prior to cold fropa tho that fropa takes place by around midnight most areas...a bit later far Srn NewEng. This leaves a NE wind for most areas on Tue which will bring a dramatic airmass difference.
Strong cyclogenesis is set to take place Tue into Wed as potent Nrn and Srn stream shortwaves merge for deep upper low over Great Lakes. I think it's a bit early to try and get too specific and too fancy here in NewEng but a lot can be garnered from a synoptic thought process. First, the large storm surface and aloft S of Hudson Bay at the start of this week is yanking down a chunk of Canadian cool that will sit in waiting just over the border, north of the Grt Lakes, waiting to be tapped. Meanwhile, it will drag a cold front across the Plains and Srn stream wave will induce cyclogenesis along the frontal boundary. A combo of PG flow and ageostrophic flow will tug this well of cold air south, which will in turn greatly increase baroclinicity as it plows into well-established tropical feed from Pacific and Gulf. The result will be the intense cyclogenesis progged for several days now as the surface low pulls into the Great Lakes. Last week I discussed the likelihood of record cold through the Plains and early season snow in the Upper Midwest and that still appears to be the case even thru the Upper Great Lakes, with the potent cold penetrating far south into the TN valley where record cold is likely on Fri.
Of course, NewEng is ahead of the system which in this case doesn't start out quite as exciting but proves to be equally if not more challenging for a longer duration. That is, our first chore is determining when to bring precip in and to what intensity. The bottom line here is that if we maintain a SE sfc flow on Wed, which we should do with a nose of sfc ridging holding on over NewEng, the warm front gets squashed by NYC and we can forget about any warming. In fact, have gone rather significantly below statistical guidance for Wed given warm advection aloft but combo of sfc ridging and onshore flow holding cool dome at the sfc and this will create plenty of clouds along with sct showers in isentropic lift over shallow dome. Well ahead of the cyclonic vorticity advection and deep tropical warmth or moisture, it is unlikely we'll see any heavy precip, but the clouds and scattered showers we do see will hold temps down significantly, esp when coupled with the onshore component of the wind. Early Thu is when our greatest warm and moist advection arrives, and therefore should be when our heaviest precip arrives. Tho the guidance will continue to put out timing diffs, synoptic thought must prevail and that highlights late Wed Ngt thru the first half of Thu. There is likely to be a break after this initial slug of WAA precip, though expanding wind field from intense low pressure well to our west will develop, esp thanks to PGF between departing high and incoming low. Fropa timing looks to be Thu Ngt when intense winds are possible across the Northeast ahead of front with strong llvl and midlvl jet overhead - this certainly has the potential to be a damaging event for higher terrain. Fri has the potential for damage as well, tho what may save us is that there is no well-developed high building in, and the tightest gradient is found under the belly of the primary low, still over the Upper Great Lakes. Thus, while cold air spills in and the winds howl a plenty, we may avoid damage on Fri, tho there is a core of intense wind rotating around the belly of the primary low that meteorologists should continue to pay heed to. There is enuf cold air moving in on Fri that I have no problem putting Green Mountain snow showers in the forecast. The remainder of the mountains will probably see a brief period of flurries or snow showers as moisture departs late Thu Ngt or early Fri, then there will be lingering instability showers on Fri esp in Nrn NewEng when most of the mountains are likely to see at least rain/snow mix showers in convective clusters tho insolation between cumulus will mean not totally a winter scene. By Fri Night, however, lake effect streamer should be cranking off Lake Ontario and given instability and moderately fast wind flow this will carry into the Greens where upslope flow will enhance them and large area of snow showers should result, getting skiers awfully excited. This setup should continue thru Sat.
Enjoy your day!
Matt
