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:
The active jet stream - the fast river of air aloft that steers our storm systems and acts as a thermostat for the atmosphere separating deep summer warmth to the south from more comfortable air to the north - is flowing near New England this week, and this will continue to mean a series of disturbances move over New England through the next few days, bringing rapid changes in weather to New England through the end of the week.
With one of these energetic disturbances moving over New England on Tuesday, thunderstorm coverage amidst a blend of clouds and sun will increase through the day, and given the combination of modest approaching energy and favorable conditions for thunderstorm development given so much warmth and humidity, some of these thunderstorms will become quite strong during Tuesday afternoon, producing hailstones and damaging wind gusts for some communities as winds aloft increase over Southern New England, especially. The surface cold front driven east by the associated upper level disturbance will weaken and stall across New England during the day on Tuesday, and this will prove important in the midweek forecast.
The importance of this lingering "trough" or disturbance in the lower atmosphere left behind by the dying front is that it will lay a temperature and moisture difference across New England, meaning that as the next energetic system is pushed east toward New England by the jet stream winds aloft, the surface storm center associated with it is likely to travel along or near this dying frontal boundary, steering rain, heavy at times, into New England later Wednesday into Thursday. With an ample supply of tropical moisture streaming northward and an active jet stream continuing to steer energetic disturbances along the northern fringe of this tropical feed, heavy rains will fall in the path of this midweek disturbance. With the frontal boundary forecasted to stall over New England, at this point it appears to me the heaviest rainfall would focus on the Southern half of Vermont and New Hampshire, as well as extreme Southern Maine and Northern MA. While the placement of the front will be critical in this precipitation forecast, as just a slight nudge north or south would shift the focus of heaviest rainfall, I do expect the heaviest rain band to produce in excess of four inches of rain between thunderstorms later Wednesday and the rain band Wednesday night, with some localized amounts even higher.
While steady and locally heavy rains may continue into early Thursday, the heaviest of the rain fall should gradually shift south of New England, though plenty of clouds and scattered showers will linger in Southern New England through most of the day and as winds turn from the northeast and later from the north on Thursday, cool conditions will prevail under these clouds. Farther to the north, the North Country will see gradual improvement with emerging sunshine and warmer temperatures.
On a brighter note, drier air is expected to move into New England for the end of the workweek, likely accompanied by summer warmth, and this will lead us into a weekend that - at this point - isn't looking all that bad. My concerns for tapping a tropical Atlantic wave later in the week may end up falling by the wayside if the Atlantic high pressure ridge can bridge with another high pressure center over the Southeastern United States, but it's still early in the game, so while I'm excited about a nice looking weekend, let's take the next couple of days to iron out the details.
Have a great Tuesday.
Technical Discussion: Yesterday's was quite lengthy and posted below. If I can squeeze out additional thoughts, will do so today.
Matt
Matt's Technical Meteorological Discussion: Updated Monday, July 10 at 2:05 PM
Impressive "little vort max that could" crossing ME with severe thunder this afternoon as it's aided by orographic lift and instability in excess of 1500 J/kg of CAPE and LIs to -4. Large hail to be the biggest threat thanks to steep lapse rates, tho this also will encourage damaging winds in stronger cells. A few cells have popped in Nrn NH and VT, tho these have a limited growth potential as responsible vort max ripples along the ME coastline and puts these areas into NVA and strong subsidence that will squash active cells. The same phenomenon will spread over ME later this afternoon - an odd diurnal htg max/cnvctv decrease combo. Farther SW across the rest of NewEng, instability builds to comparable levels of 1500+ J/kg and LIs to -5 across Nrn CT, and Cu field has been building steadily as soon as NVA induced subsidence passed, but we need a forcing mechanism to get things going, especially without a well defined vort. Nonetheless, weak CVA/PVA does take place later Mon afternoon well ahead of next vort moving E across the Ern Great Lakes and an isolated thunderstorm or convective shower not impossible with initiation near CT River Valley where SW mean sfc flow intersect valley-forced south wind.
Have left a few floating showers/thunder in the forecast for Mon Ngt given lingering instability - esp in Western NewEng where CAPE remains above 1500 J/kg and PVA/CVA increases thru the night. Approaching cold front will lose frontal characteristics on Tue as it moves into NewEng and transitions to a sfc trough, but given moisture-loaded atmosphere and assoc instability, this will be plenty in concert with cooling mid levels to produce widespread thunder and some of this will likely be severe, especially in Southern NewEng where strongest vorticity advection intersects greatest instability tongue. Midlvl and low level flow are 25-35 kts which will be sufficient when coupled with updraft/downdrafts and downward momentum to produce damaging wind gusts. While CAPE values of 1500-2000 J/kg coupled with LIs to -5 are impressive, more impressive here is the synoptic setup, which put very plainly and simply features a strong remnant upper low, positive vorticity advection (PVA) normal to the instability, a well-defined cool pool aloft, and a surface convergence zone along the trough. This all should add up to a very active day.
But if you think that's something, just hang on for Wednesday! I came in this morning and had no doubt about going all out on a forecast for thunder, rain and flooding for NewEng later Wednesday thru Wednesday night - well, at least as *little* doubt as a *forecaster* could have! :) Seriously, though, I saw a NMM that was touting a terrific sunny day for Wed, but GFS/ECMWF/GGEM/RGEM/GFS Ensembles/Canadian Ensembles all were cranking rain, and this made sense synoptically. 12Z NMM run has brought it in line. The synoptics make sense as an active jet runs just south of NewEng carrying the next strong upper level low while tropical input feeds in from the Gulf of Mexico on 30-40 kt llvl jet. At the sfc, dead cold front/sfc trof will be draped across NewEng and serve as focus not only for storm path, but also for severe thunderstorm development later Wed in Southern/Central NewEng as instability should soar in this synoptic setup - progged to be over 2500 J/kg by NMM with LIs to -8 - and helicity values would also soar just south of the trough-turning-warm-front later in the day, and while guidance pins this area over Wrn CT, would expect it to center closer to the pseudo-warm front in Southern New Eng as we near the event. Convective clusters and discrete supercells both would be possible in this environment later Wed for what may be a very damaging day.
From damage to flooding as we transition to Wed Ngt as solid feed of tropical moisture on aforementioned jet intersects with incoming vort max and trof axis. Though trof axis is positively tilted it is slow moving (like its predecessors today and tomorrow) as it is removed from the main belt of westerlies that have pushed into Canada. Tho NMM/Canadian Ensembles and ECMWF would suggest Nrn NewEng to pick up the bulk of the precip here...GFS Ensembles focus around Central NewEng and this appears most likely given bubble of high pressure building southeast across Eastern Canada...with heaviest precip perhaps focused from Central VT/NH southward to Nrn tier of MA, but this is obviously highly dependent upon placement of frontal boundary.
Thursday's forecast will be highly dependent on position of frontal boundary which...as of now...I'm favoring the GFS solution of strengthening the surface low as it moves E of NewEng Wed Ngt and allowing NE sfc wind to push into Ern NewEng which will keep coastlines and Eastern areas cool while Nrn/Western NewEng warm. Obviously NMM solution is farther north and therefore keeps most of NewEng on southern side of front which depends on speed of trof axis swinging south across NewEng. Given consistency of GFS and the number of shortwaves racing overhead in progressive flow, and the consistent GFS portrayal of sliding the trof axis thru during the day, I like the cooler idea for now, which also will be a cloudy idea for most of the day in the Southern half of NewEng. Additionally, tho heaviest rainfall may end up south of NewEng with sfc front shifting S, I've seen many situations like this before where enough moisture lingers behind the sfc front that more rain can wring out ahead of the mid/upper trof, and Thu certainly is a contender to fall into this category.
While Fri and Sat both look good with building heat, Sun remains a bit more uncertain as Ensemble members are split on whether to re-establish tropical connection up the Eastern Seaboard, with positive height anomaly decreasing from Ern Canada to the East Coast, and mean SLP plots indicating sfc weakness along the East Coast. With NW/WNW flow aloft, I'd like to think the tropical moisture feed snakes up the eastern seaboard but is cut off at the pass before making it to NewEng.
Tropics: Finally, the wave we examined in this discussion last week in the tropics continues to stir up plenty of convection near Haiti. Shear is quite evident on satellite imagery from south to north and midlvl center has outrun the sfc based convection, but as flow weakens aloft and moisture west of the midlvl center is entrained into the system, this circulation still maintains potential for growth. What has changed, however, is that we're now looking at a system that will encounter a bridged and strengthened ridge on its north side, which shuts off a northern track and means the system draws near to the Florida east coast while organizing Wednesday into Wednesday night and while it will likely have enough fortitude to be either a depression or minimal storm by Thu AM as it nears the Florida east coast, the cold core nature of the mid level center may preclude its chances of being officially classified unless the convection can really dominate the center. The wave farther out over the Central Atlantic is interacting with the ITCZ which will limit its ability to grow in the immediate term, but does hold plenty of potential if it can survive the shear south of the islands over the next 3-4 days. It would then emerge into a low-shear, high oceanic heat content environment of the Western Caribbean en route to the Gulf of Mexico. Plenty to keep an eye on in the tropics.
'Til later...
Matt
