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:
As New England enjoys continued mild conditions after record warmth in Portland, ME, with a high of 69 degrees yesterday, cold air remains locked in Canada, where daily high temperatures were held in the single digits across the Northwest and Western Provinces at the end of this week. Cooler air - though not deep cold - has been seeping southeast across Central Canada, and though that air has lowered temperatures Friday from where they were Thursday.
The new airmass in place on Friday is dry, and though it's somewhat cooler, we'll still find maximum temperatures above normal for the date with an active westerly breeze sloping down off the hilly terrain of Western New England, helping to nudge most temperatures in Central and Eastern New England to near 60 degrees. Though this bubble of cool and dry air will allow for temperatures to fall Friday night, yielding a cool start Saturday morning, sunshine should be able to assist in a rebound to start the weekend. This comes as a new, very strong disturbance dives into the Ohio Valley on Saturday, spawning a storm center to our west. The counter-clockwise flow of air around this storm will mean a strengthening south and southeast flow of air through the day Saturday, and after sunshine early, clouds will increase well in advance of this storm with a white or even gray sky to end the day, with intervals of clouds and sun through most of the day. By Saturday night, the approach of the strong disturbance aloft will result in the strengthening of a low pressure center southwest of New England that will move south of Long Island.
This is where there are changes to the forecast from yesterday, as the trend has been for a bit more southward suppression and slower progression of the storm center. So, whereas yesterday I was thinking we'd have windswept showers scattered about with a west wind, the new slower trend changes this dramatically. Instead, we're looking at a system now that will creep parallel to the coastline and maintain an EASTERLY wind deep through the atmosphere from surface to 20-25,000 feet in altitude! This seems like a dramatic change to the non-weather savvy, but in reality it is a shift of couple of hundred miles south in this low - a relatively short distance in the scope of the global weather pattern, but important here in New England. This deep easterly flow will mean a consistent supply of Atlantic moisture - also tapping the Tropical Atlantic - that will light up a swath of heavy rain to sweep from New Jersey into Southern New England on Sunday. With a strong high pressure cell to the north of New England - but limited cold air available - winds will increase Sunday along coastal locales, especially, though most of New England will find the winds kicking out of the east. Rains will be quite heavy with this slow moving band, and the slow speed of it will mean flooding will be a concern later Sunday and Sunday night in Central and Southern New England.
We've already seen a major shift in the timing of this storm once, so naturally the timing later in the period is still uncertain heading into Monday, though right now I would assume this slow moving band of rainfall will still be pestering Central and Northern New England, when flooding concerns will spread north with the rainfall. This delays improving weather conditions for most locales until Tuesday, when showers are still likely to linger in the North Country, though enough cold air may bleed southward by that point for a few snow showers in the North.
At least some return of milder air still is likely in the cards for midweek before another developing storm seems destined to deliver another shot of intense tropical moisture toward the end of the week, and that may once again raise concerns for flooding. It does appear as though that storm may be the one to break the back of the mild streak - at least for nearly a week - as temperatures will return to below or near normal values.
Matt
Matt's Technical Meteorological Discussion: Updated Friday, November 10 at 11:55 AM
Obvious trend is for slower and farther south and that trend has continued in the 12Z runs this morning. Have reviewed both the slower NMM and GFS today, tho at this point would like to see additional runs before backing off Sunday precip, as I have to assume both are underdone here in NewEng. Reasoning is a deep S/SE flow thru most of the atmosphere and a low level baroclinic zone settling S on Srn edge of strong anticyclone over Ern Canada that should result in blossoming precip Sun across at least Srn NewEng. Even if upper low does take farther S track 12Z guidance suggests, deep S flow would still usher deep moisture into NewEng.
In the meantime, near calm winds and only a few high altitude clouds Fri Ngt will mean cool but not cold conditions, and sunshine to start Sat will provide good mixing, and haven't changed thoughts on a mild Sat for most of NewEng, tho not near Canadian border where clouds thicken quickly assoc with frontal boundary producing snow thru upper great lakes this morning and that will extend across North Country Sat eventually producing showers by late in the day. Farther S, most moisture will be above 500 mb, but will thicken enuf for OVC conditions by later Sat afternoon. Still, mild increasing sfc wind and early insolation will bring temps up.
Am holding the line of steady but slow progression of upper low Sun/Mon and bringing some improvement for Tue, but as mentioned above, if 12Z trend is correct, the entire system will have to be slowed down. If my thoughts hold, however, we're looking at flooding concerns for Srn NewEng Sun Ngt and then those same concerns translate N on Mon thru at least ME where ground is already saturated.
This weekend's storm - regardless of what it delivers for precip - still does not deliver a shot of cold air, and instead allows more tropical origin air to move in for a milder midweek. The next strong Pacific shortwave, however, will bring another round of tropical moisture toward next week's end, and by that point enough low level and surface cold will be build far enough south in Canada to be tapped for a stretch of about 5 days. Thereafter, the trend may be to a few moderate overrunning events with sfc cold but rebounding warmth aloft.
Enjoy the weekend - I guess we'll all see how this plays out together!
Matt
Wednesday's Discussion:
3:05 PM: Well defined packet of tropical moisture streaming N up seaboard today is focused N of sfc low center and upper low. Still a surface/llvl thermal and isodrosothermal (dewpoint) boundary stretched across Central NewEng to the coastal plain of ME and this will continue to focus heavy rains from Hudson Valley thru Wrn MA to ME coast with heavy rains SE of that boundary, as well, and sharply lesser amounts farther northwest. FFG values 2-3" and this may cause a problem in Srn CT where flood watch is up, as well as Southern to Midcoast ME. SE wind will freshen ahead of sfc low pressure passage as it moves SE of NewEng and brief gusts 30-40 mph are possible Cape Cod this eve.
Behind this storm, wind shifts to NW, but no immediate cold air source is present, so this leaves a weakly downsloping flow with mild air to the tune of +10 C at 850 mb and +12 to +14 C at 925 mb. Subsidence sets in during the heart of the day, and this should be sufficient to poke holes in the OVC that will allow for rather rapid temp rises in warm airmass, climbing into the 60s many areas. Pioneer Valley and perhaps Boston area both stand a shot at 70 with downsloping/sun combo, depending on how much insolation we see. Have held chc thunder only for Wrn NewEng, as best chance is across NY State where strong diffluence and PVA comes thru during diurnal htg, not arriving into Wrn NewEng until eve, but strong enuf diffluence above warm enuf air to warrant downpour/thunder in the fcst.
This sfc cold front will be progressive, but while air behind it is noteably colder, that's not saying much when you're starting out so anomalously warm, and thermal profile with good mixing and downsloping flow Fri still supports an average high just over 60 with favored downslope areas warmer still. Have continued to hedge way above MOS for Sat as operational guidance suggests a relatively clean warm sector with possible contamination above 400 mb, but strong thermal advection on Sat. There are two concerns with this gamble: 1) Southeast sfc flow as low strengthens and doesn't track quite far enuf north to guarantee S or SW flow, meaning tendency is there for an onshore component, and that's frankly why I've gone mid 60s and not closer to 70. 2) Increased llvl moisture thanks to this onshore component. If that happens, going to have to slice and dice my temps.
Looks like cyclogenesis will occur overhead on Sun as anafront becomes active with wave, and wave will intensify over Ern NewEng. Still timing diffs on this, but GFS Ensemble is progressive, Canadian and its Ensembles quite slow, and ECMWF seems a good compromise, but leaves Neweng quite windy, chilly and showery on Sun...tho not cold enuf for wintry precip. Quick shot of cold behind this system for early in the week gives way to more mild anomaly before a rainstorm Thu with good tropical moisture tap again gives way to slug of anomalous cold for a few days. The warmer than normal pattern returns thereafter, however, with little available deep cold making it into the lower latitudes...for now.
Matt
Monday's Discussion:
1:35 PM: Early AM shortwave brought new snow to Nrn and Central ME while freezing rain fell in valleys of interior Ern ME. Behind this shortwave, weak backdoor front dropping S thru Ern ME with renewed clouds and temp plateau. Elsewhere, SW surface flow and assoc mixing doing a good job of breaking up the sky cover, tho where warm and moist advection continue near baroclinic zone aloft I expect clouds to fill back in for most of Nrn NewEng overnight Mon Ngt.
Weak vort lobes ride northeast ahead of strong upper low that is well evidenced on satellite imagery today. This upper low is largely removed from the westerlies and will be quite slow to progress east. Though it is packed with tropical moisture, there is no cold air assoc with it. In fact, there is barely cold left in the lower 48 at all - the coldest of whcih is most certainly over Nrn ME, as Tropical Pacific air floods the Pacific NW. Water vapor imagery confirms the origin of today's Pacific NW storm, but what is truly remarkable is that surface equivalent potential temperature values of the air in OR, WA and Western MT exceed the warmth and moisture assoc with the sfc reflection of the upper low over Arkansas! The bottom line is that the lower 48 are being flooded with warm air from all directions today, not to mention moisture input from both the Gulf and the Tropical Pacific. The leading vort from this Pacific energy arrives on Wed, and have brought in steady precip as a result, esp given that NewEng will remain under low level warm and moist advective regime. More intense Pacific energy set to arrive on Thu, and this time there is interaction in the midlevels with the upper low off the Carolina coast inputting its Gulf moisture - which more accurately will be a combo of Gulf and Pacific-entrained moisture by that point. At the surface, large anticyclone shifting off the coast this week remains quite expansive and this cranks up the pressure gradient for a long-fetched SE flow into NewEng on Thu that actually finds its roots at the base of the high - in the Bahamas! Thus, plenty of moisture to crank out heavy rains both later Wed but moreover Thu as frontal boundary assoc with Pacific short moves sluggishly thru. Keep in mind the origin of this disturbance from the Tropical Pacific, and there will not be a hearty shot of cold behind it - cool, perhaps, drawn south from the Nrn surface reflection in SE Canada, but not cold, and not long-lasting. In fact, a heartier shot of cool air would be more likely on Sunday after the passage of a colder shortwave ejected from the Aleutian low, that will carry a pool of shallow cool from Wrn Canada on its trek east.
Thereafter, mild air rules the roost again next week until Aleutian low and Greenland ridge both re-establish, allowing cooler than normal pattern to return with longwave trof eastward migration around the 18th.
Have a great Monday.
Matt