An outflow boundary from a squall line of storms triggered severe storm development across SE Georgia during by midday across SE GA over an unstable and unseasonably high wind shear environment. SPC had a marginal risk of severe storms.
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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 JAX wrote it up.
An outflow boundary from a squall line of storms triggered severe storm development across SE Georgia during by midday across SE GA over an unstable and unseasonably high wind shear environment. SPC had a marginal risk of severe storms.
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, 8:12 AM EST, 6 hours 33 minutes earlier.
Area Forecast Discussion National Weather Service Jacksonville FL 912 AM EDT Sat Jul 21 2018 ...SQUALL LINE APPROACHING FROM CENTRAL GEORGIA... .UPDATE... Fog and low clouds will continue to clear throughout the late morning hours as heating occurs. Attention will then shift to the approaching squall line moving southward through central Georgia at 40-45 mph. The area of storms is currently associated with a region of sfc-6km wind shear of 40-45 mph. This has allowed the complex to maintain organization despite the lack of surface instability. While surface instability will increase throughout the late morning hours ahead of the storm complex, atmospheric wind shear will gradually decrease to around 20-25 mph. With this in mind, the current expectation is that the storm complex will remain below severe limits as the storms fall behind the outflow boundary due to the weakening wind shear. Based on the current radar imagery, strong storms could still reach the Altamaha River area with gusty winds (25-40 mph) and heavy rain between 11:30 am and noon. Later in the day, new storm development is expected, and the location of the new development will likely be dependent on the outflow boundary associated with the ongoing squall line. The atmosphere this afternoon is forecast to be unstable with 3000-4000 J/kg of CAPE along with modest wind shear of 25-40 mph. Also, although drier (1.6" PWAT) air currently exists in the mid- levels as seen by JAX 12Z sounding, deeper moisture (1.9-2.1" PWAT) will move southeast into the area by early afternoon and evening. Mid- level lapse rates will also slowly steepen throughout the day as the trough brings in cooler temperatures aloft. This environment will support strong to severe storms throughout the afternoon and evening hours. The environment is a little different from the normal summer time thunderstorms. Anyone with outdoor plans should be prepared for quick changes in the weather if a strong to severe storm were to occur. && .AVIATION... Fog and stratus are gradually clearing/lifting during the morning hours. This will continue into the early afternoon with a cumulus deck developing around around 3,000 feet. Showers and thunderstorms are once again possible today, but not like the last few days. A squall line is currently moving through central Georgia and will eventually move into an area void of local TAF sites. Additional thunderstorms development is expected this afternoon with strong to severe storms possible, although coverage is not expected to be widespread. This is observed in the 12Z TAF package, but trends will be monitored closely for potential changes for the 18Z package. && .MARINE... Southwest winds decrease some today as the surface low across the Carolinas lifts northeast ..but increase again to cautionary levels Sunday into early next week as another surface low develops across the Carolinas and drops south which will tighten the gradient. Fast moving showers and storms will be moving offshore with bulk of activity in the afternoon and evening. Some storms may be strong or severe. Rip Currents: Low risk of rip currents for area beaches due to off shore flow. && .PRELIMINARY POINT TEMPS/POPS... AMG 92 75 92 73 / 40 40 40 30 SSI 90 78 93 77 / 30 40 50 40 JAX 92 75 94 74 / 30 30 50 40 SGJ 92 77 94 75 / 20 20 40 40 GNV 92 76 92 75 / 30 30 40 40 OCF 90 76 91 75 / 40 30 30 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && McGinnis/Sandrik/
PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
231 PM EDT SAT JUL 21 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0222 PM TSTM WND GST 5 NNE ORANGE PARK 30.23N 81.67W
07/21/2018 M52 MPH Duval FL AWOS
KNIP ASOS MEASURED SUSTAINED WIND SPEED OF 41 MPH AND A
WIND GUST OF 52 MPH.
&&
NMCGINNPRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
234 PM EDT SAT JUL 21 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0230 PM TSTM WND GST 1 N JACKSONVILLE BEACH 30.29N 81.39W
07/21/2018 M48 MPH AMZ452 FL MESONET
WEATHERFLOW MESONET STATION MEASURED THUNDERSTORM WIND
GUST OF 48 MPH.
&&
NMCGINNSpecial Weather Statement
National Weather Service Jacksonville FL
259 PM EDT SAT JUL 21 2018
FLZ030-031-036-037-040-211945-
Putnam FL-Union FL-Alachua FL-Bradford FL-Marion FL-
259 PM EDT SAT JUL 21 2018
...SIGNIFICANT WEATHER ADVISORY FOR ALACHUA...SOUTHERN BRADFORD...
NORTHWESTERN MARION...WEST CENTRAL PUTNAM AND SOUTHWESTERN UNION
COUNTIES UNTIL 345 PM EDT...
At 258 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Upland Pines to near Keystone Heights.
Movement was south at 35 mph.
Wind gusts of 45 to 55 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Gainesville, Keystone Heights, Melrose, Worthington Spring, Alachua,
Hawthorne, Archer, Worthington Springs, University Of Florida and
Rochelle.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
northern Florida.
LAT...LON 2943 8241 2948 8241 2948 8255 2997 8251
2987 8205 2941 8204
TIME...MOT...LOC 1858Z 358DEG 28KT 2990 8253 2982 8210
23Special Weather Statement
National Weather Service Jacksonville FL
304 PM EDT SAT JUL 21 2018
FLZ033-037-038-040-133-138-212000-
Coastal Flagler FL-Coastal St. Johns FL-Putnam FL-Inland Flagler FL-
Marion FL-Inland St. Johns FL-
304 PM EDT SAT JUL 21 2018
...SIGNIFICANT WEATHER ADVISORY FOR FLAGLER...SOUTHERN ST. JOHNS...
EASTERN MARION AND PUTNAM COUNTIES UNTIL 400 PM EDT...
At 303 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from Vilano Beach to Melrose. Movement was south at
35 mph.
Wind gusts of 40 to 50 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Palm Coast, Saint Augustine, Palatka, Flagler Beach, Bunnell,
Crescent City, Interlachen, Pomona Park, Hastings and East Palatka.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If on or near inland waterways or lakes, get out of the water and
move indoors or inside a vehicle. Remember, lightning can strike out
to 10 miles from the parent thunderstorm. If you can hear thunder,
you are close enough to be struck by lightning. Move to safe shelter
now! Do not be caught on the water in a thunderstorm.
&&
LAT...LON 2947 8108 2946 8112 2943 8110 2941 8115
2927 8115 2926 8141 2940 8142 2933 8168
2928 8164 2896 8166 2896 8204 2972 8205
2984 8169 2984 8158 2987 8159 2996 8125
TIME...MOT...LOC 1903Z 352DEG 31KT 2994 8128 2971 8202
HESSSpecial Weather Statement
National Weather Service Jacksonville FL
329 PM EDT SAT JUL 21 2018
FLZ035>037-040-212015-
Putnam FL-Alachua FL-Marion FL-Gilchrist FL-
329 PM EDT SAT JUL 21 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN GILCHRIST...SOUTHERN
ALACHUA...WESTERN MARION AND WEST CENTRAL PUTNAM COUNTIES UNTIL 415
PM EDT...
At 328 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Bell to near Hawthorne. Movement was south
at 40 mph.
Wind gusts of 45 to 55 mph can be expected along with possible minor
wind damage.
Locations impacted include...
Gainesville, Ocala, Rainbow Lakes Estates, Trenton, Citra, Hawthorne,
Archer, University Of Florida, Sparr and Cross Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
northern Florida.
LAT...LON 2905 8247 2904 8253 2921 8254 2922 8240
2948 8241 2948 8255 2954 8256 2953 8265
2956 8266 2956 8275 2958 8278 2959 8286
2958 8295 2962 8297 2976 8295 2962 8203
2896 8205 2896 8231
TIME...MOT...LOC 1928Z 342DEG 33KT 2976 8295 2962 8204
23PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
340 PM EDT SAT JUL 21 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0322 PM TSTM WND GST GAINESVILLE AIRPORT 29.69N 82.28W
07/21/2018 M40 MPH ALACHUA FL ASOS
GAINESVILLE AIRPORT ASOS REPORTED WIND GUST TO 40 MPH
FROM THE NORTH AT 322 PM. THIS IS A RECORD HIGH WIND GUST
FOR THE DATE, JULY 21ST.
&&
JHESSThe Jacksonville radar (KJAX), 153 km away, was scanning. The volume nearest the first event began at 19:45 UTC.
1 thunderstorm wind. Local standard time, as filed.
Five trees and a privacy fence were blown down near NW 110th Avenue and NW 21st Street. The cost of damage was unknown, but it was estimated for the inclusion of the event in Storm Data.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2018Every state in 2018This day in weather historyWarnings in Florida, July 2018
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: 780347.