With a frontal boundary stalled well south of the area, a combination of onshore flow and sea breeze boundaries resulted in the development of isolated convection across portions of southern Connecticut. Several showers and thunderstorms developed and moved across far southeastern New London county, resulting in isolated flash flooding.
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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 OKX wrote it up.
With a frontal boundary stalled well south of the area, a combination of onshore flow and sea breeze boundaries resulted in the development of isolated convection across portions of southern Connecticut. Several showers and thunderstorms developed and moved across far southeastern New London county, resulting in isolated flash flooding.
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 New York, NY wrote its last area forecast discussion before the first event at Aug 17, 1:12 PM EST, 34 minutes earlier.
Area Forecast Discussion National Weather Service New York NY 212 PM EDT Sat Aug 17 2019 .SYNOPSIS... A frontal boundary remains stalled to the south of the region with high pressure to the northeast. A trough of low pressure will develop to the west on Sunday followed by a weak cold front Monday night. This boundary dissipates over the area on Tuesday, although another cold front approaches Wednesday and moves through Wednesday night. High pressure then builds in for the remainder of the week. && .NEAR TERM /THROUGH TONIGHT/... Highest coverage of showers remains over eastern locations. A shower or thunderstorm could develop at anytime this afternoon across the region. Much of the area now observing sunshine. Any lingering low clouds across the region are expected to lift and dissipate as the afternoon progresses given time of year. A slight increase in coverage of showers and thunderstorms is expected, especially NW locations, late this afternoon and evening closer to upper shortwave, increased lift. As instability wanes, thunder chances will lower overnight. Temperatures, except eastern LI and SE CT under ovc skies, have risen to the upper 70s/lower 80s. With plenty of clouds tonight and continued light onshore flow, temps will not vary much, upper 60s to lower/mid 70s. There is a moderate risk for the development of rip currents at Atlantic Ocean beaches this afternoon and into this evening. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... A stationary front will remain just to the south of the region for the second half of the weekend with high pressure building to the south and west. This will result in a hot and humid air mass building into the start of next week, as southwest flow returns. On Sunday, temperatures across northeast NJ will touch 90 with highs across NYC metro in the upper 80s, with cooler temps along the coast. Max heat index values will be in the a few degrees higher than the air temperature. Scattered showers and thunderstorms may develop once again Sunday afternoon as a trough sets up west of NYC. Overnight low temperatures will be in the in the low to mid 70s, which is about 5 to 7 degrees above normal. There is a low risk for the development of rip currents at Atlantic Ocean beaches Sunday. && .LONG TERM /MONDAY THROUGH FRIDAY/... Hot, humid and somewhat unsettled weather will continue for the first half of next week. NWP is in good agreement with the overall upper pattern across North America during the long term period, with Bermuda high pressure remaining in place resulting in gradually rising heights rising across the Northeast into early next week. Currently, the hottest day appears to be Monday with widespread upper 80s to lower 90s, mid 90s in urban NE NJ. Dewpoints in the 70s will yield heat index values in the mid to upper 90s, possibly reaching 100 in NE NJ. With heat index values forecast to remain below 95 both Sunday and Tuesday, it looks that we will remain below Heat Advisory criteria, but it will be something to watch with subsequent updates. A weak cold front approaching on Mon could then trigger isolated showers/storms Mon aftn/eve. This boundary moves into the area Mon night so have kept the low chc during this time although tstms may be nil. It dissipates over the area on Tue although a shortwave lifting up the east coast and a digging trough to the west is expected to trigger additional showers and tstms on Wed. The former piece of energy may pass far enough east to keep that activity offshore, but pre-frontal convection is possible during the aftn/eve. This stronger front moves through Wed night bringing and end to the showers/tstms and a more comfortable airmass as high pres builds from the Great Lakes through Fri. Temps are expected to be near to slightly below normal levels Thu and Fri. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... High pressure east of the New England coast will remain in control through the weekend. Mostly VFR, lowering to MVFR this evening with some IFR east of the city terminals. Showers forming along sea breeze boundary may reach KISP this afternoon with a lower chance at KJFK and KLGA. TSTM could get close to KSWF late day/early evening. Winds mostly SE 5-10 kt away from any shower outflow. .OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... .Sunday...Chance of mainly afternoon and evening showers and thunderstorms. Best chance north and west of the NYC terminals. MVFR/IFR ceilings improving through the morning. .Monday...Mainly VFR. Slight chance shower or thunderstorm. .Tuesday-Thursday...Mainly VFR. Chance showers or thunderstorms. && .MARINE... A generally weak pressure gradient will keep seas below 5 ft into the early week. Winds and ocean seas then begin to increase by Wednesday in advance of a cold front, with seas reaching SCA levels by Wednesday night. && .HYDROLOGY... No hydrologic impacts are expected at this time through the forecast period. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off the air. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && SYNOPSIS...CB/24 NEAR TERM...PW SHORT TERM...CB LONG TERM...CB/24 AVIATION...JC MARINE...CB/24/PW HYDROLOGY...CB/24 EQUIPMENT...
Hazardous Weather Outlook National Weather Service New York NY 321 AM EDT Sat Aug 17 2019 CTZ005>012-NJZ002-004-006-103>108-NYZ067>075-078>081-176>179-180730- Northern Fairfield-Northern New Haven-Northern Middlesex- Northern New London-Southern Fairfield-Southern New Haven- Southern Middlesex-Southern New London-Western Passaic- Eastern Passaic-Hudson-Western Bergen-Eastern Bergen-Western Essex- Eastern Essex-Western Union-Eastern Union-Orange-Putnam-Rockland- Northern Westchester-Southern Westchester-New York (Manhattan)-Bronx- Richmond (Staten Island)-Kings (Brooklyn)-Northwestern Suffolk- Northeastern Suffolk-Southwestern Suffolk-Southeastern Suffolk- Northern Queens-Northern Nassau-Southern Queens-Southern Nassau- 321 AM EDT Sat Aug 17 2019 This Hazardous Weather Outlook is for southern Connecticut, northeast New Jersey and southeast New York. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. ANZ330-335-338-340-345-350-353-355-180730- Long Island Sound East of New Haven CT/Port Jefferson NY- Long Island Sound West of New Haven CT/Port Jefferson NY- New York Harbor-Peconic and Gardiners Bays- South Shore Bays from Jones Inlet through Shinnecock Bay- Moriches Inlet NY to Montauk Point NY out 20 nm- Fire Island Inlet NY to Moriches Inlet NY out 20 nm- Sandy Hook NJ to Fire Island Inlet NY out 20 nm- 321 AM EDT Sat Aug 17 2019 This Hazardous Weather Outlook is for Atlantic coastal waters. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement
National Weather Service New York NY
145 PM EDT Sat Aug 17 2019
CTZ008-012-171830-
Southern New London-Northern New London-
145 PM EDT Sat Aug 17 2019
...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN NEW LONDON
COUNTY...
At 145 PM EDT, a strong thunderstorm was located near Mystic, moving
northeast at 5 mph.
Winds in excess of 30 mph are possible with this storm.
Locations impacted include...
Groton, Ledyard, Griswold, Preston, Voluntown, North Stonington and
Pawcatuck.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
LAT...LON 4142 7180 4142 7182 4141 7184 4137 7183
4132 7193 4144 7205 4161 7179
TIME...MOT...LOC 1745Z 239DEG 6KT 4141 7191
PWThe Boston radar (KBOX), 94 km away, was scanning. The volume nearest the first event began at 18:46 UTC.
2 flash flood. Local standard time, as filed.
The parking lot at the Mystic Aquarium was flooded in Mystic.
Neighborhood street flooding in North Stonington with water over the top of car tires.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Connecticut in 2019Every state in 2019This day in weather historyWarnings in Connecticut, August 2019
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: 855261, 855265.