Both sea breezes moved inland under fairly light steering flow with a merger across inland areas during the late afternoon and evening. A mid level low overhead with 500 mb temperatures near -9 deg C increased diurnal instability, which aided a severe storm to develop over Suwannee County.
Every event with a place to put it. Tap one for its entry below.
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 JAX wrote it up.
Both sea breezes moved inland under fairly light steering flow with a merger across inland areas during the late afternoon and evening. A mid level low overhead with 500 mb temperatures near -9 deg C increased diurnal instability, which aided a severe storm to develop over Suwannee County.
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 Jacksonville, FL wrote its last area forecast discussion before the first event at Jul 21, 3:30 PM EST, 1 hour 27 minutes earlier.
Area Forecast Discussion National Weather Service Jacksonville FL 430 PM EDT Fri Jul 21 2017 .NEAR TERM /TONIGHT AND SATURDAY/... Convection will very slowly build on both seabreezes as they press inland this afternoon, more so on the gulf breeze. Activity will become enhanced around the time of sunset as the seabreezes and outflow boundaries all come together across the interior. Coastal areas will remain mostly dry as the seabreeze stabilizes the airmass. Storms across the interior this evening will tend to have a slow and erratic storm movement but most of the activity should tend to slowly drift back off towards our western zones this evening due to the easterly flow aloft. Instability not expected to be quite as high as yesterday but still high enough to support an isolated severe storm or two. The main threats with the strongest storms will be localized damaging wind gusts and locally heavy rainfall. Very localized potential for large hail as well given 500 mb temps of -9C with mid level low directly overhead. Diurnal storms should wrap up by late evening but additional late night showers will be possible across our southern zones as deeper moisture lifts up from the south. Prevailing flow will become southwesterly on Saturday. Showers/storms will get off to an earlier start across our western zones as moist southwest flow pushes the gulf seabreeze in early. Storms across northeast florida will build toward the Atlantic coast Saturday afternoon with an increase in intensity and coverage expected late in the day near the I-95 corridor as the dominant Gulf seabreeze slams into a slow moving Atlantic seabreeze. Scattered to numerous storms will be possible across northeast Florida in the afternoon with the highest chances south of a line from Gainesville to St Augustine. Drier air across southeast Georgia will keep convection more isolated there on Saturday with max temps several degrees above normal with heat indices topping out around 105 degrees. Max temps will be near normal across our southern zones due to increased cloud cover with early start to showers/storms off the Gulf. Temps will also be hotter at the beaches due to a much later start to the seabreeze. .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... Deep-layered Atlantic ridging will build westward across south Florida, creating a deepening southwesterly flow pattern. Convection will initiate during the morning hours along an active Gulf coast sea breeze, and this convection will progress eastward during the afternoon. Convection will likely pulse as it encounters a pinned Atlantic sea breeze along or just east of Interstate 95 during the mid to late afternoon hours, with strong to isolated severe thunderstorms possible in coastal locations. Wet microbursts and excessive lightning strikes will be the primary threats from this activity along and east of I-95 during the late afternoon hours on Sunday and Monday. Convection should push into the Atlantic coastal waters by sunset each day, with the evening hours remaining mostly dry inland from Saturday through early next week. Highs will generally climb into the lower 90s, with southwest winds delaying the development of the Atlantic sea breeze until the early to mid afternoon hours, resulting in highs at or above 90 at area beaches on Sunday and Monday. An earlier start to convection should keep heat index values in check at inland locations, with daily maxes generally around 100. Lows will generally range from the mid 70s inland to near 80 at the beaches. .LONG TERM /TUESDAY THROUGH FRIDAY/... Deep-layered Atlantic ridging will extend across the Florida peninsula on Tuesday, keeping a similar weather pattern from the weekend and Monday in place, featuring a dominant Gulf coast sea breeze pattern with scattered to numerous thunderstorms progressing eastward across our region, mainly during the afternoon hours. Highs will again climb into the lower 90s for most locations, including the coast, as a deep southwesterly flow pattern remains in place which will delay the development of the Atlantic sea breeze until early to mid afternoon. Ridging aloft will then build over the southern Plains states, which will drive a deepening trough into Alabama, Georgia, and the Florida panhandle by late Wednesday. This weather pattern will promote scattered to numerous showers and thunderstorms developing at any time, with temperatures generally near late July climo. Long-term models currently disagree on how far south this trough will move before weakening by late next week, with model blends yielding near climo rain chances and temperatures for next Friday at this time. There are indications that ridging over the Plains will begin to expand eastward into the southeastern states towards the end of next week, which could advect some drier air aloft into southeast Georgia by late Friday. && .AVIATION... Mainly VFR conditions to prevail through the next 24 hours. Storms this afternoon are expected to concentrate late in the day across the interior. GNV could see another round of very heavy rain with this activity, depending on exactly where it comes together. Have shown a 2 hour TEMPO group for thunderstorms at GNV around the time of sunset today. More specific details (LIFR, gusty winds) may need to be added as we go through the afternoon and the situation begins to unfold. && .MARINE... Surface high pressure will be East Southeast of the region through the early part of next week. A trough of low pressure will sink Southeast across the region and dissipate toward the middle of next week. Rip Currents: Moderate risk through Saturday. && .CLIMATE... Fifty days into meteorological summer, a whopping 28.26 inches of rainfall has been measured at the Gainesville Regional Airport. 14.08 of this has fallen in July, placing the monthly record of 16.65 (set in 2013) in jeopardy. The wettest meteorological summer on record at Gainesville occurred in 1965, when 32.55 inches of rainfall was measured. Rainfall records at Gainesville date back to July of 1890. && .PRELIMINARY POINT TEMPS/POPS... AMG 73 94 74 93 / 30 20 20 60 SSI 75 92 81 90 / 10 20 20 60 JAX 72 93 75 91 / 10 40 20 70 SGJ 75 91 77 91 / 10 40 20 50 GNV 71 91 73 89 / 40 50 20 60 OCF 72 90 74 88 / 30 60 30 50 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && Nelson/Shuler/McGinnis
Hazardous Weather Outlook National Weather Service Jacksonville FL 412 PM EDT Fri Jul 21 2017 AMZ450-452-454-470-472-474-FLZ020>025-030>033-035>038-040-124-125- GAZ132>136-149>154-162>166-220815- Coastal waters from Altamaha Sound to Fernandina Beach FL out 20 NM- Coastal waters from Fernandina Beach to St. Augustine FL out 20 NM- Coastal waters from St. Augustine to Flagler Beach FL out 20 NM- Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM- Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM- Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM- Hamilton-Suwannee-Columbia-Baker-Inland Nassau-Inland Duval-Union- Bradford-Clay-St. Johns-Gilchrist-Alachua-Putnam-Flagler-Marion- Coastal Nassau-Coastal Duval-Coffee-Jeff Davis-Bacon-Appling- Wayne-Atkinson-Ware-Pierce-Brantley-Inland Glynn-Coastal Glynn- Echols-Clinch-Charlton-Inland Camden-Coastal Camden- 412 PM EDT Fri Jul 21 2017 This Hazardous Weather Outlook is for Northeast Florida, Southeast Georgia and the Adjacent Coastal Waters. .DAY ONE...Rest of Today and Tonight... Isolated to scattered thunderstorms are expected through this evening mainly over inland areas. Frequent lightning, heavy rainfall and localized flooding are the primary hazards. A few storms could produce strong wind gusts. Storm motion will be erratic, or with a slow drift to the north. .DAYS TWO THROUGH SEVEN...Saturday through Thursday... Isolated to scattered thunderstorms are expected each day through mid-week next week. Frequent lightning, heavy rainfall and localized flooding are the primary hazards. A few storms could produce strong wind gusts. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. For additional information, visit the National Weather Service in Jacksonville website on the internet at weather.gov/jax.
Special Weather Statement
National Weather Service Jacksonville FL
457 PM EDT FRI JUL 21 2017
GAZ149-163-212130-
Atkinson GA-Clinch GA-
457 PM EDT FRI JUL 21 2017
...SIGNIFICANT WEATHER ADVISORY FOR ATKINSON AND NORTHWESTERN CLINCH
COUNTIES UNTIL 530 PM EDT...
At 457 PM EDT, Doppler radar was tracking a strong thunderstorm near
Pearson, moving northwest at 10 mph.
Wind gusts of 40 to 50 mph can be expected along with possible minor
wind damage. Small hail is also possible.
Locations impacted include...
Pearson and Axson.
LAT...LON 3139 8293 3137 8282 3136 8282 3137 8280
3134 8267 3110 8280 3113 8297 3119 8297
3118 8304
TIME...MOT...LOC 2057Z 112DEG 7KT 3122 8284
SHASHYSpecial Weather Statement
National Weather Service Jacksonville FL
533 PM EDT FRI JUL 21 2017
GAZ163-212215-
Clinch GA-
533 PM EDT FRI JUL 21 2017
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN CLINCH COUNTY UNTIL
615 PM EDT...
At 532 PM EDT, Doppler radar was tracking a cluster of strong
thunderstorms near Du Pont, or 8 miles west of Homerville. These
storms were nearly stationary.
Wind gusts of 40 to 50 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Homerville and Du Pont.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 3111 8297 3118 8291 3104 8271 3087 8289
3092 8297
TIME...MOT...LOC 2132Z 133DEG 3KT 3099 8288
SHASHYSpecial Weather Statement
National Weather Service Jacksonville FL
547 PM EDT FRI JUL 21 2017
FLZ021-212230-
Suwannee FL-
547 PM EDT FRI JUL 21 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SUWANNEE COUNTY
UNTIL 630 PM EDT...
At 546 PM EDT, Doppler radar was tracking a strong thunderstorm near
Obrien, or 8 miles northwest of Ichetucknee Spring, moving north at
10 mph.
Wind gusts of 45 to 55 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Wellborn, Obrien, Mcalpin and Branford.
LAT...LON 3022 8305 3024 8279 2998 8280 2996 8295
2998 8296 2999 8296 3000 8297
TIME...MOT...LOC 2146Z 172DEG 8KT 3005 8287
SHASHYSpecial Weather Statement
National Weather Service Jacksonville FL
548 PM EDT FRI JUL 21 2017
FLZ036-212230-
Alachua FL-
548 PM EDT FRI JUL 21 2017
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN ALACHUA COUNTY UNTIL
630 PM EDT...
At 548 PM EDT, Doppler radar was tracking a strong thunderstorm near
Alachua, or 7 miles south of Worthington Spring, moving north at 10
mph.
Wind gusts of 45 to 55 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Alachua and La Crosse.
LAT...LON 2994 8252 2993 8248 2993 8246 2992 8241
2989 8240 2988 8239 2982 8235 2975 8250
2987 8259
TIME...MOT...LOC 2148Z 158DEG 7KT 2983 8245
SHASHYThe Moody AFB radar (KVAX), 94 km away, was scanning. The volume nearest the first event began at 21:57 UTC.
2 thunderstorm wind. Local standard time, as filed.
Several trees were blown down on 45th Drive. The cost of damage was estimated so that this event could be included in Storm Data.
Trees and power lines were blown down on 77th Drive and County Road 252.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2017Every state in 2017This day in weather historyWarnings in Florida, July 2017
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: 708035, 708036.