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:
Heat that's been building across the heart of the nation will expand northeast and into New England over the next 72 hours, bringing temperatures of over 100 degrees for some parts of Southern New England by midweek if all evolves as expected. In the interim, an active jet stream pattern continues overhead, and this means thunderstorms remain in the forecast.
Remember that the jet stream winds are the fast corridor of air aloft that steer our storms and act as a thermostat for the atmosphere, separating deep summer warmth to the south from more comfortable air to the north. After numerous thunderstorms on Friday, most of New England transitioned to this more comfortable air for the weekend, which was further accented in the Eastern half of the six-state region on Sunday as winds shifted off the ocean, carrying a cooler airmass far inland. Fog and low-altitude clouds that began the day on Monday in the Boston Metropolitan area and much of Eastern Massachusetts defined the edge of very cool and dry air with slightly more humid air. This boundary will only become more enhanced through the day Monday and into Monday night, as another stronger push of warmth and moisture advances northeast out of the Ohio Valley and Appalachians. Though New England will remain between jet stream disturbances through the day on Monday for a relatively pleasant and warm summer day, another jet stream disturbance will ride overhead Monday night, and this will bring a return of active weather to New England.
The jet stream disturbance riding over New England Monday night has a history of producing thunderstorms, as it produced a large thunderstorm complex over the Upper Great Lakes Sunday night, traveling along the cusp of the deep summer warmth bubbling across the Central United States. With the airmass boundary running directly through New England, and the disturbance aloft heading for New England, thunderstorms should develop from northwest to southeast overnight Monday night - after 10 PM in northwestern New England and after midnight for most areas. At this point, it appears as though Vermont, New Hampshire, Southern Maine and perhaps extreme Northeastern Massachusetts hold the highest chance of thunder, though most of New England will be subject to a few thunderstorms floating through. With fast winds aloft, it's not impossible that a few of these storms may deliver damaging winds to the surface late Monday night or early Tuesday morning. You can always follow the radar imagery through the links at right, and if there are thunderstorms, you can bet I'll have them covered in Wakeup News and Weather on NECN starting at 5 AM.
As these scattered showers and storms progress, sun will emerge on Tuesday. Remember that the storms mark the leading edge to deeper summer air, and the new airmass will be packed with moisture and heat, making for a muggy and hot afternoon. With so much moisture and heat - and yet another weak disturbance riding overhead later Tuesday - an afternoon thunderstorm is a possibility in a few locales. The big weather story, however, will of course be the heat building across New England, wrapping into the area on westerly winds - ideal for warming air. These westerly winds are so important to warming the atmosphere because in addition to carrying the heat directly into New England, air slopes over and then down the eastern side of the hilly and mountainous terrain of New England. This is referred to as "downsloping flow" and as air slopes down the mountain and hill sides, it has a tendency to warm, and this will further boost temperatures.
The westerly winds will continue on Wednesday and this will continue the flow of warm air. Once again, temperatures will soar with the wind sloping down off the hills and mountains, and by Wednesday afternoon, temperatures aloft will be warm enough to support surface temperatures exceeding 100 degrees in some Southern New England communities, with 90s widespread across the remainder of New England. Boston's Logan International Airport is one of the contenders to cross 100 degrees, which hasn't been done since August 14, 2002, when the temperature hit 101 degrees. The record for the date is 102 degrees, set back in 1975, and that does appear to be in jeopardy right now. Hartford also will take a crack at the record of 101 from 1975, and Worcester at 96 from 1975.
With the approach of a cold front on Thursday but a strong fight back by the bubble of Eastern U.S. heat, an airmass clash will set up directly over New England and with the active jet stream racing overhead, rain will crank out in the form of numerous thunderstorms and downpours through the day on Thursday. By Friday, the transition to a drier and more uncomfortable airmass will be underway, though it's likely to be a gradual one, which means at least some showers and thunder may linger across Southern New England Friday, before drier air moves in for a great start to the weekend.
Enjoy your Monday and watch for thunderstorms tonight!
Matt
Matt's Technical Meteorological Discussion: Updated Monday, July 31 at 2:45 PM
Shortwave crossing NewEng tonight with good jet max induced diffluence aloft and moderate positive theta-e advection in the low levels along with moderate speed and directional convergence. Shortwave has a history of noctural convection and expect the same tonight as the wave moves over NewEng. VT/NH/Central & Srn ME are focal point for greatest convection tonight but also will experience shallow stable layer which diminishes severe potential in this region. Farther south into Srn NH/Ern MA, the airmass is more unstable and sfc based, and this coincides with 850 mb llvl jet at 40 kts. Thus, tstorm threat is present across most of NewEng with highest QPF found north and greatest predawn/early AM severe threat found south.
Warming midlvls behind this mesoscale convective system will stabilize the atmosphere for a time on Tue, and this will allow several hours of insolation with hazy sun ahead of next shortwave which will be weaker, but following a nearly identical path from NW to SE across Central NewEng and working with the diurnally favorable instability of 3000+ J/kg and LIs of -2 to -4. Clusters of severe thunderstorms are likely given 20-30 kt flow and veering winds to 500 mb, then unidirectional. Heat and humidity both build tho abundant moisture limits mixing ratio and thereby temps won't translate as warm to 850s as they did on Mon. Downsloping areas of the coastal plain will have some negating effect to the humid temperance of thermal rebounding.
Expect nocturnal convection to shift farther north Tue ngt but still will be present. Heat unloads on Wed with optimized downsloping and chunk of deep warmth advecting in. Llvl temps support upper 90s and downslope enhancement should produce 100+ temps for the coastal plain and CT river valley...able to overcome the aforementioned effects of limited mixing ratio. Mid level temps are warm and therefore marginal for convection - therefore, in downsloped areas I do not expect afternoon convection, tho orographically favored upslope terrain and areas away from downslope flow certainly will be vulnerable given relatively fast flow at mountaintop level and plenty of instability to feed off of. Any of these storms that develop would have the ability to survive a decent trip out of the mountains as long as they don't encounter a strong downsloping area.
While I'm certainly a believer in the presence of plenty of warm air for Thu, I'm not sold on going gung ho on continued searing warmth given the slow southward sag of the approaching frontal boundary, and a small nearly-meso high parked off the coastline. The combo of these two factors will: 1) allow a propensity for a sea breeze, 2) bring cooler temps into Northern NewEng, 3) Make conditions extremely favorable for convective development in Southern NewEng where numerous thunderstorms and downpours will be likely.
I'm sure this front like every other one thus far is going to have trouble pushing thru into a pulsing very warm ridge and therefore I'm keeping the front lingering in Southern NewEng thru Fri before finally clearing S of NewEng with the passage of a shortwave later Fri and bringing in drying conditions for Sat.
That's all for today. Stay cool.
Matt
