A deamplifying mid level shortwave with dewpoints in the 70s and decent instability brought scattered thunderstorms and widespread flash flooding to Rhode Island and Massachusetts. There were many streets closed, many cars stranded in flood waters, and several houses with flooded basements or first floors.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BOX wrote it up.
A deamplifying mid level shortwave with dewpoints in the 70s and decent instability brought scattered thunderstorms and widespread flash flooding to Rhode Island and Massachusetts. There were many streets closed, many cars stranded in flood waters, and several houses with flooded basements or first floors.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Boston/Norton, MA wrote its last area forecast discussion before the first event at Sep 11, 12:38 PM EST, 52 minutes earlier.
Area Forecast Discussion National Weather Service Boston/Norton MA 138 PM EDT Mon Sep 11 2023 .SYNOPSIS... Flood Watch in effect beginning 11 am today. Showers and thunderstorms this afternoon with heavy rainfall possible. Cloudy tomorrow with a few isolated showers. A frontal system interacting with subtropical moisture will bring soaking rains to parts of southern New England Wednesday. Much drier and more seasonable weather then arrives for Thursday into at least Friday, although Hurricane Lee still could make a closer pass late this week or next weekend. Increasing surf and rip currents are likely to begin around Tuesday and continue into the weekend, although there is low confidence in any other impacts. Refer to the latest forecasts on Hurricane Lee from the National Hurricane Center. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1115 AM Update: Key Points: * While not everywhere will see heavy rain, growing risk for heavy rain capable of street flooding coinciding with the PM commute in the Greater Boston, Worcester, Providence and Hartford metro areas. Localized rapid-onset flooding is possible. * Flood Watch expanded into Hartford and Tolland Counties. Made several changes with this update, although the main message is still on track. The most significant of these changes include the expansion of the Flood Watch into Hartford and Tolland Counties, after coordination with WFOs OKX/ALY. Have also raised PoP to Categorical for the mid-aftn to early evening hrs bounded within a few miles between the Hartford, Worcester, Providence, Metrowest and Greater Boston corridors. There is a growing level of concern for heavy rain capable of flooding coinciding with the Monday afternoon commute either somewhere close to or encompassing a large part of these metro areas, being focused along a wavy frontal boundary lying near or just southeast of the I-84/I-290/I-495. Uncertainty exists in which specific location(s) may experience heavy rains, but there is pretty convincing evidence in the incoming 12z guidance in focusing rounds of rains in this general corridor. There may be embedded t-storms in this more focused area as well, and while we can't discount the potential for trees to fall at relatively lower wind speeds given the saturated soil moisture conditions, the risk for severe weather is very low to essentially nil. Expect this activity to drift E/ESE with time into southeast MA and southern RI for the late-afternoon to mid-evening period. Previous Discussion... More unsettled weather today as a deamplifying 500 hPa short-wave progresses over southern New England. Temps in the upper 70s/low 80s and dewpoints in the low 70s will continue to support modest diurnal instability ranging from 500 to 1000 J/kg of CAPE across the region. 25 knots of shear and modest low/mid level lapse rates should help to support scattered showers and thunderstorms this afternoon. Strong to severe storm threat is low, but one or two overachieving storms can't be ruled out. As was the case yesterday, the bigger concern today will be the potential for flooding. Warm cloud layer depths nearly 15000 feet, PWATs up to 1.8 inches, and very weak boundary later winds will support slow moving showers and storms with efficient rainfall processes. 00Z HREF ensemble probability match mean QPF amounts paint a large swath of 1.5 to 3 inches of rainfall across southern New England with the highest amounts over eastern MA. HREF also indicating 10 to 20 percent chance for 6 hour rainfall to exceed 100 year ARI. Given this signal, a flood watch has been put into effect through tonight. Expect most of the action to take place after 2PM, but we could see some showers and storms star to pop up as early as late morning (10 - noon). && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Tonight Showers and storms continue into the even hours before slowly dying down after midnight. Thereafter, just expect a few isolated to scattered showers. More mild weather expected tonight with lows in the mid to upper 60s and more fog/low stratus developing prior to day-break. Light east/northeast winds. Tuesday Little change in the synoptic pattern tomorrow. Thus, more mild/muggy weather with highs in the upper 70s/low 80s and dewpoints in the upper 60s/low 70s. Abundant moisture and low-level warm advection will support mostly cloudy skies and a few showers tomorrow as well. No big risk for thunder given weak low/mid-level lapse rates and overall synoptic forcing. Thus, many people may sneak away with no rain on Tuesday, and some locations to the south and east near the coast may even see some breaks of sun by the afternoon. Shower chances will be greatest across the interior. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Wet weather returns with soaking rain and t-storms on Wednesday. * Dry weather and seasonable temperatures return on Thursday and Friday, but we continue to monitor Hurricane Lee into next weekend. It remains unknown whether it will directly impact New England. * Increasing rip current risk and high surf continues into part of next weekend on beaches with southern and southeast exposures. Details... Tuesday night through Wednesday night... Shower and thunderstorm chances stick around Tuesday night, increasing as we go into Wednesday which looks like the wettest day of the extended forecast at this point. This, as we see a positively tilted mid level trough over the western Great Lakes on Tuesday night becoming neutrally tilted as it crosses New England late Wed/Wed night. This will provide plenty of large scale lift as areas of PVA cross the region and we are places beneath the right rear quadrant of an 85kt jet at 300mb. At the surface lift from WAA continues Tuesday night as SW flow ahead of the incoming trough continues to advect warm and moist air into the region ahead of a cold front. This front then crosses SNE sometime late Wednesday into Wednesday night. All this forcing will have ample moisture to work with as dewpoints remain in the upper 60s/low 70s and PWATs rise into 1.75 inch range. Instability is there with CAPE of 1000-2000 J/kg so expect some locations in SNE to see another soaking with an inch or more. At this time ensemble guidance suggests a 20-50% chance of 1 inch or more over western MA/CT; drier further east but confidence in the exact locations of the heaviest rain at this time is low. Given the instability and bulk shear values 30-35 kts some of the storms may be severe. Thursday through Sunday... Following Wednesday night's cold front will be a much drier and more seasonable airmass for Thursday, likely into Friday. 850 temperatures drop from 13C on Wednesday to 7C by Thursday afternoon. This results in highs in the 70s each day while dewpoints drop into the 40s and 50s. Dry and cooler northerly flow continues around a building high pressure over the Great Lakes and eventually the low pressure center that is now Hurricane Lee. This is where confidence in the forecast drops drastically as we continue to try and hone in on Lee's path. This will depend on many factors including how quickly Lee moves north and how it interacts with ridging over the North Atlantic and high pressure over the Great Lakes. Global ensemble guidance continues to show the mean solutions taking Lee into Nova Scotia, but all outcomes remain on the table. For the latest information on Hurricane Lee, see the latest forecast, advisories and Key Messages from the National Hurricane Center. Regardless, we will see impacts in the form of high surf and high rip current risk as soon as Tuesday when energy out ahead of Lee reaches our south/southeast facing shores. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18Z TAF Update: Through 00z Tue: Moderate confidence. Generally lower (MVFR-LIFR categories) from ORH east with MVFR- VFR conditions BAF-BDL initially; however increasing coverage of SHRA/+SHRA into a SW to NE linear-oriented fashion, mainly in the BOS, ORH, PVD, BDL and perhaps BED areas through 00z. Embedded TS possible although would be the exception vs rule but included as a TEMPO mention. E to NE winds 4-6 kt, although ESE/SE winds 4-8 kt PVD and SE MA airports. Tonight: Moderate confidence. MVFR-LIFR early with likely ongoing SHRA/embedded TS moving ESE 00-03z while weakening as it does so. While rain generally diminishes in covg/intensity, with it will be the return of stratus and fog at IFR to LIFR levels settling in; expanding soonest eastern areas and a few hrs later toward western airports. Reduced confidence in the exact timing. NE winds 3-6 kt, calm at times. Tuesday and Tuesday Night: Moderate confidence. While fog dissipates, IFR to LIFR ceilings likely central and eastern airports for most of the time. May see some 1-category improvement in categories for BAF-BDL but not likely any higher than MVFR. Spotty, light SHRA during the day. Period of steadier rains arrives late overnight to early Wed AM. NE to E winds 4-8 kt. KBOS TAF...Moderate confidence in TAF. MVFR/IFR thru about 19z, with increasing coverage and intensity of rain showers during the 19-23z period which should bring lowering ceilings to IFR levels and steady/heavy rain with visbys 1-3 SM. TS possible in same timeframe. Rain gradually shifts southeast ~00-03z Tue although NE winds will draw LIFR stratus and fog back in. Light NE winds. KBDL TAF...Moderate confidence in TAF. OVC VFR/MVFR with increasing coverage and intensity of rain showers during the 19-23z period, bringing lowering ceilings and steady/heavy rain with visbys 1-3 SM. Rain gradually shifts SE 23-00z although w/ fog and stratus at IFR/LIFR levels. Light north winds. Outlook /Tuesday Night through Friday/... Tuesday Night: Mainly VFR, with local IFR possible. Slight chance SHRA, isolated TSRA. Wednesday: MVFR/IFR conditions possible. Chance SHRA, isolated TSRA, patchy BR. Wednesday Night: Mainly VFR, with local IFR possible. SHRA likely, isolated TSRA, patchy BR. Thursday: VFR. Breezy. Slight chance SHRA. Thursday Night: VFR. Breezy. Friday: VFR. Windy with local gusts up to 30 kt. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Marine Coastal waters continue to remain fairly quiet through Tuesday. Seas do build a bit to 4 feet over the outer marine zones, but still remain in the 1 to 3 foot range closer to shore. Winds continue to be modest out of the east/southeast and become more east/northeast by tomorrow afternoon. Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Rain showers likely, isolated thunderstorms, patchy fog. Visibility 1 to 3 nm. Thursday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Thursday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain showers. Friday: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 12 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Flood Watch through late tonight for CTZ002>004. MA...Flood Watch through late tonight for MAZ004>007-012>021-026. RI...Flood Watch through late tonight for RIZ001>007. MARINE...None. && SYNOPSIS...BW/RM NEAR TERM...Loconto/BW/RM SHORT TERM...RM LONG TERM...BW AVIATION...Belk/Loconto MARINE...Belk/Loconto
Special Weather Statement
National Weather Service Boston/Norton MA
151 PM EDT Mon Sep 11 2023
CTZ002>004-MAZ005-012-013-016>021-RIZ001>007-111845-
Windham CT-Hartford CT-Tolland CT-Southern Worcester MA-
Southern Plymouth MA-Central Middlesex County MA-Eastern Norfolk MA-
Western Plymouth MA-Eastern Plymouth MA-Western Norfolk MA-
Northern Bristol MA-Southern Bristol MA-Eastern Kent RI-Newport RI-
Northwest Providence RI-Bristol RI-Washington RI-Western Kent RI-
Southeast Providence RI-
151 PM EDT Mon Sep 11 2023
...Thunderstorms will bring heavy rainfall to portions of southern
New England through 245 PM EDT...
At 149 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from Marlborough to North Smithfield to Duxbury.
Movement was northwest at 10 mph.
HAZARD...Minor flooding.
SOURCE...Radar indicated.
IMPACT...Minor nuisance flooding of typically flood prone areas.
Locations impacted include...
Providence, Hartford, New Bedford, Brockton, Quincy, Fall River,
Warwick, Cranston, Pawtucket, West Hartford, Manchester, Plymouth,
Taunton, Weymouth, East Hartford, East Providence, Woonsocket,
Braintree, Glastonbury, and Cumberland.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.
Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.
Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. For your
safety, go indoors or to your vehicle.
These storms may intensify and become severe. Stay tuned to your
local media for updates and possible warnings.
&&
LAT...LON 4212 7189 4226 7084 4204 7058 4198 7059
4193 7050 4187 7050 4149 7179 4164 7179
4166 7216 4171 7224 4164 7233 4160 7234
4159 7244 4178 7274
TIME...MOT...LOC 1749Z 116DEG 9KT 4165 7245 4197 7155 4206 7073
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH
DooleySpecial Weather Statement
National Weather Service Boston/Norton MA
211 PM EDT Mon Sep 11 2023
MAZ004-026-111915-
Northwest Middlesex County MA-Northern Worcester MA-
211 PM EDT Mon Sep 11 2023
...A strong thunderstorm will bring heavy rainfall to portions of
north central Worcester and northwestern Middlesex Counties through
315 PM EDT...
At 209 PM EDT, Doppler radar was tracking a strong thunderstorm over
Fitchburg, moving northeast at 10 mph.
HAZARD...Minor flooding.
SOURCE...Radar indicated.
IMPACT...Minor nuisance flooding of typically flood prone areas.
Locations impacted include...
Leominster, Fitchburg, Pepperell, Groton, Lunenburg, Townsend,
Westminster, Shirley, Ashburnham, and Ashby.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Get indoors when you hear thunder. Do not resume outdoor activities
until at least 30 minutes after the storm has passed.
Do not drive through flooded roads or underpasses. Avoid low lying
areas near small streams.
&&
LAT...LON 4271 7163 4262 7159 4251 7186 4261 7193
4271 7180
TIME...MOT...LOC 1809Z 239DEG 7KT 4258 7184
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH
DooleyPreliminary Local Storm Report
National Weather Service Boston/Norton MA
230 PM EDT Mon Sep 11 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0205 PM Flood 1 ESE Somerset 41.73N 71.13W
09/11/2023 Bristol MA Law Enforcement
Route 79 North at Duval Street is flooded
and impassable. Relayed by amateur radio.
&&The Boston radar (KBOX), 21 km away, was scanning. The volume nearest the first event began at 18:27 UTC.
7 flash flood, 3 flood. Local standard time, as filed.
In Pawtucket, Newport Ave at Ferris Ave was flooded.
In Lincoln, Breakneck Hill Rd was flooded.
In Pawtucket, Newport Ave was flooded.
In Pawtucket, cars were stuck in flood waters near Armisticle Blvd.
In North Providence, there was a flooded basement on Brown Ave.
In North Providence, there was a flooded basement on Brown Ave.
In North Providence, Branch Ave was closed with cars stranded.
In Cumberland, there was an inch of basement flooding along Pennsylvania Ave.
In Cumberland, there was an inch of basement flooding along Pennsylvania Ave.
In Cumberland, water entered homes on Fairhaven Rd. Marshall Ave was flooded and water came into a home through the basement window on Mowry Ave.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Rhode Island in 2023Every state in 2023This day in weather historyWarnings in Rhode Island, September 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1121806, 1121807, 1121808, 1121809, 1121810, 1121811, 1121812, 1121813, 1121814, 1121815.