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:
Quick note: Today, Thursday, is our NECN/American Red Cross
"Celebrate the Gift of Life" Blood Drive. I'm honored that the
American Red Cross has asked me to be their spokesman for this event
for the third year in a row, and I've donated my unit of blood! Anyone
interested in donating tomorrow should call 800-GIVE-LIFE to either
make an appointment, or to find a Donor Center near to you. Thanks to
all who do come out and make a give the gift of life to patients in
need across New England! I'm heading out to report live from one of
our donor centers, so today's weather update is below, issued early.
Thursday morning sunshine and frigid conditions will give way to increasing clouds, but moderating temperatures, with the approach of another energetic disturbance. Ahead of this disturbance, the milder air streaming northward will quickly modify our brief shot of intense cold. Meanwhile, the storm that dropped a wintry mess across Dallas on Wednesday will be racing to the Carolina coastline. Here, this already Pacific moisture-laden storm will interact with a steady supply of Gulf moisture, and the storm will grow legs as it heads northward. Aloft, the jet stream pattern will favor quick development of the storm, and the key to the forecast right now is twofold: 1) How quickly does the storm strengthen, and 2) How much warm is is brought it off of the Atlantic? The answer to the first question comes from the knowledge that atmospheric conditions are ripe for rapid storm strengthening, but only once the southern moisture and northern energy dropping east out of the Great Lakes merge sufficiently. At this point, it appears to me as though this merger won't be complete until the storm center is moving into the Gulf of Maine, which implies a shot of precipitation for Southern New England Thursday night into early Friday, then tapering as winds turn fierce later in the day. Farther north, a more prolonged period of precipitation would result, especially across interior Maine as the storm strengthens quickly while pushing north out of the Gulf of Maine. This leaves the door open for a significant winter storm through much of Maine that would last through a good chunk of Friday, while farther south, the initial surge of precipitation will be highly dependent upon temperatures. Right now, it appears as though precipitation would develop across Southern New England overnight Thursday night - especially after midnight. With a southeast wind near the surface, and ocean temperatures to our southeast running well into the 40s, warm air will flood the coastal plain, allowing almost all rain on Cape Cod, Southeast MA, Rhode Island and a lot of Connecticut. Farther north and west, cold air will hold on longer, and a period of snow is likely in most areas Thursday night - beginning as a mix after 8 PM (follow the precipitation on radar links at right), then chaning to interior snow that would drop 2"-4" of quick snow before tapering Friday morning. Just on the cold side of this rain/snow line - a coastal front - will be where the heaviest snow falls, and this is likely to stretch from just east of the Pioneer Valley to central Worcester County to interior New Hampshire, then into the mountains of Maine. In the mountains of Maine, at least a half foot of snow would be possible, and we may approach those amounts in the mountains of NH and the Lakes Region, but farther south along the axis we'd fall closer to the 2"-4" range. Contrary to the previous storm, I don't see this as a mix event - it should be either rain or snow, with a clear-cut transition from one type to the other.
This storm will strengthen quickly on Friday while pulling into Eastern Canada, and will bring very strong northerly, then westerly, winds behind it, meaning another southward surge of Canadian cold behind the storm, arriving in time for the weekend, when temperatures will plunge back below normal by several degrees. In the longer range, we'll remain in a pattern of East Coast "troughing" for awhile. Remember that the term "trough" is used to describe a dip in the jet stream winds aloft - the fast corridor of air that flows high in the sky and steers storm systems along it, also acting as a thermostat for the atmosphere, separating cold to the north from warm to the south. With a trough over the Eastern United States, this keep us on the north side of the jet stream, with a tendency for cold air to remain locked in place and storms to move south of us, meaning we'd be on the cold northern side of precipitation shields. This may evidence itself as the deeper weekend cold begins to pull gradually away from New England, with a storm ready to ride near the Eastern Seaboard, and a chance of snow by the beginning of next week.
In the meantime, winter-lovers can continue to rejoice at the presence of a pattern that will bring an average period of below - with intervals of much below - normal temperatures through the start of February, and a pattern that at least puts New England in a spot where big snows are a distinct possibility with Pacific and Gulf moisture close to us, and repeated spurts of deep cold and northern energy.
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, January 17 at 1:50 PM
Focus today will be on the end-of-week storm. Let's review what we know before we confuse ourselves with what we don't know: Northern stream shortwave will dive southeast thru the Upper Ohio Valley and will dig at base of Great Lakes trof. Meanwhile, Srn stream wave responsible for TX winter wx today will push off the Carolina coast where it will induce sfc cyclone development. Steering flow will back in the mid-lvls and this will assist in carrying sfc wave and assoc Gulf moisture northward along the coast, and along inverted trof well modeled by guidance that develops in advance of eastward shifting longwave trof. When the two vort maxes merge, intense and rapid cyclogenesis will result. The question, of course, revolves around when the happens, not to mention the question of thermal profile. But let's focus on the merger and resultant intensification first. The NMM continues to ring the bell of a major merger that will occur earlier in the game, bottoming the low into the 970-980 mb range as it moves E of MA. The implications of such a quick development would be a better developed and more rapid wraparound precip shield, and a 0 C isotherm crashing toward the coast. The other result would be a more intense and expansive wind field, capable of delivering damaging winds to much of New England. While this is an ominous (or fun, depending on your outlook) portrayal of the storm development, at this point it is the lone guidance product on this course. We have certainly seen the NMM pull out some biggies in the past - and, in fact, those of you who read regularly know that I have gone with the NMM in the past even when it's been the "sole provider" of what I'd expected to see. In this case, however, I'm a bit skeptical of buying the NMM lock, stock and barrel, largely because there has been good agreement on a relatively progressive system from the start, at least until the storm reaches the northern Gulf of ME and moves E of ME, when it will slow and bomb. Until that point, though, it is being carried by 50-70 kt midlvl flow, and I still like a progressive scenario. This would mean a shot of warm advection precip to most of NewEng Thu Ngt into Fri AM, spreading from S to N and focused along the inverted trof where it will probably progress even a bit faster than currently progged. This inverted trof will become the coastal front in time, and will focus the QPF production through interior NewEng. Favoring a broad shield of precip, and also favoring the NMM's idea of quicker intensification if the storm center can slow down enough, is a tremendously diffluent upper level flow. Though right now I don't see that resulting in the quick bombing shown on the NMM, I do see that as helping precip production significantly across much of Southern NewEng. Of course, another major question is the thermal profile. With a developing SE flow on Cape Cod as soon as Thu eve, I don't see much hope for anything but rain there. Elsewhere, however, a burst of snow is likely with the warm advection as the incoming moisture collides with our cold and dry air in place. It's the same cold and dry nature of the antecedent airmass that was my reasoning yesterday for placing the coastal front a bit farther east than the guidance would suggest. While the Canadian global and regional are both insistent upon a rain/snow line not far from the coast, this is likely a bit too far *east*, while the NMM is likely penetrating the ocean warmth a bit too far *west*. The end result will likely be a rain/snow line that sets up as a removed coastal front from somewhere near HFD to ORH to ASH to PWM. This is subject to tweaking, of course, but is a preliminary estimate with heavist QPF amounts just on the cold side of this front. I do believe this storm will ramp up quickly to deliver a strong blow to ME, where over a foot of snow is a strong possibility in the mountains Friday. Strong winds settle in behind the storm and usher in next arctic airmass.
Matt
Tuesday's Discussion:
1:10 PM: Cold air is obviously taking hold with rapid temp drops across SCoastal locales. Most of these areas saw drying of road moisture before the rapid temp drop but some areas of black ice possible. Bigger concern, of course, is the falling ice and falling limbs/lines of Srn NH and Nrn MA that will continue to cause power outages and stiff wind driving chills below zero will make for difficult utility work this eve.
While this is the concern from a public perspective, there is little from a forecasting perspective left with this storm and attn now turns to the cold and then Fri storm. Regarding the cold, the air pouring south from Quebec - when compared with low-level thickness values and boundary layer temps - has been producing daily highs of 5 degrees or less, at least for the air that will be in place to the MA Turnpike. So, if we were dealing with snow cover that would be the rule I would follow, but that cold will moderate as it moves south over unfrozen ground and displaces the mild antecendent air in Southern New England, while even Central New Eng - though encased in ice for some areas - will see downsloping flow assisting in airmass modification, as well. With Richardson Numbers high enough for deep mixing, there will also be some adiabatic warming of the airmass, and we should be able to rise into the teens for Southern NewEng on Wed. Farther north - and esp near the Canadian border - the airmass will be more true to its original form and therefore temps will struggle to rise above 0. Pressure gradient will mean winds stay up Tue Ngt and Wed, and this wind/cold combo will be a brutal delivery of -20 to -30 chill to Nrn NewEng Tue Ngt and still close to -20 Wed, while Srn areas will hover at -5 to -15.
Cold air well entrenched enuf to prohibit quick warmup Thu tho significant moderation will take place. Clouds will incr at high and mid altitudes with upper level WAA later in the day, and this will further limit pot'l for temp rise. Nrn and srn stream interaction looks quite likely Thu Ngt and Fri to create a quickly strengthening wave up the Ern seaboard that will bring snow to the interior. Along coastline and far Srn NewEng, SE component of boundary layer wind will bring in anomalously warm SST altered air to allow for rain at coastal plain. That said, believe NMM is probably too far W in its 12Z run and over-amplifying the effects of ocean warmth, which means its progged rn/sn line also penetrates too far inland. Could see much of Srn CT/RI/SE MA and even coastal plain of MA warming, but also would expect to see development of coastal front that will result in farther E ptype line, and also would shift llvl deformation band closer to coast for max QPF amounts. Next arctic blast follows and am going some 15-20 degrees below MOS guidance for Sat!
That's the gist of my thinking right now - off to a public appearance so will have to stop here for today.
Matt
