Numerous thunderstorms developed during the afternoon and evening ahead of a weak boundary, as deep moisture and an upper-level disturbance moved across the area. Cold temperatures aloft caused one of the storms to become severe, resulting in quarter-sized hail.
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The episode as NWS MLB wrote it up.
Numerous thunderstorms developed during the afternoon and evening ahead of a weak boundary, as deep moisture and an upper-level disturbance moved across the area. Cold temperatures aloft caused one of the storms to become severe, resulting in quarter-sized hail.
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 Melbourne, FL wrote its last area forecast discussion before the first event at Sep 10, 3:26 PM EST, 1 hour 44 minutes earlier.
Area Forecast Discussion National Weather Service Melbourne FL 426 PM EDT Fri Sep 10 2021 .DISCUSSION... Current- Tonight.... The east coast sea breeze has formed and is slowly pushing inland. Scattered showers and storms started mid afternoon, mainly across the northern coast. Storm movement was generally to the east around 10 mph. Scattered to numerous showers and storms expected later this afternoon and early evening, with PoPs around 60-70 percent. Cell movement will continue to generally be towards the east around 5-10 mph, but some storms will have erratic motion due to outflow boundaries. Strong to marginally severe storms will be possible with wind gusts in excess of 50 knots and hail up to 1 inch possible. Other storm threats for this afternoon and evening will be frequent lightning, and torrential downpours. Forecast soundings continue to show cold air aloft (500 mb temperatures of -7 to -9 C), with PW values ranging from 1.89-2.03". Overnight lows will be in the low to mid 70s under partly to mostly cloudy skies. Saturday... The mid level trough will slowly move ENE across the Atlantic as the weak frontal boundary continues to be stalled across central Florida. An area of high moisture will remain over the local area, with PW values at around 2". Increased coverage (PoPs 40-50 percent) will continue, with highest coverage starting across the interior in the early afternoon and shifting towards the north and along the coast in the late afternoon and early evening. Winds will be light and variable early in the morning, before becoming easterly around 5-10 mph in the afternoon. Afternoon highs will be in the upper 80 and low 90s under partly cloudy skies. Sun-Mon...High pressure will develop across the Atlantic with the axis reaching into the southeast, north of Florida, bringing easterly/onshore winds through the mid- and long-term periods. Drier air in addition to the easterly wind will bring down rain chances across the area Sunday, only 40%, but moisture begins to return to the Treasure Coast Monday bringing precip chances back up to 60-70%. Storms will be moving westward with activity bouncing back into the area unlikely. Still expecting warm afternoons, with highs in the upper 80s and lower 90s, and lows in the upper-70s along the coast and mid-70s inland. Tues-Fri...(Modified from previous discussion) High pressure axis will remain well north of the local area, maintaining onshore flow through the period, though veering a little more SE Thursday into Friday. Higher moisture will keep PoPs generally 40-60% each day, but easterly steering flow will help keep activity from drifting back towards the east coast later in the afternoon and evening. Towards the end of the period (Thursday timeframe), models suggest a surface wave pushing northward from the tropics well offshore of the local area. Confidence is low on this feature or any increased convective activity being generated by it, but will continue to monitor for future updates. Highs each day in the upper 80s to low 90s, with morning lows in the mid-70s, though upper 70s will be possible along the immediate coast. && .AVIATION... VFR conditions outside of convection. Scattered to numerous showers and lightnings storms this afternoon and early evening. With the front sagging steadily south today, convection will spreading southward to the central and southern aerodromes during the mid to late afternoon (18-23Z). IFR VSBYs with G35KT+ expected beneath precip cores. Overnight, winds will become light and variable with any lingering showers or storms ending around midnight. Winds will then become more northeast around 5-10 KT by mid morning. && .MARINE... Current-Tonight... Ongoing showers and storms across the Atlantic, mainly nearshore Brevard county. Cell movement is generally towards the east coast around 10 KT. Current buoy 41009 observation show seas are 4 ft with east winds around 2 kt. Seas will continue to decrease overnight with seas 3-5 ft in the nearshore waters and seas 4-6 ft in the offshore waters. Saturday... The stalled boundary front will continue to become increasingly diffuse through the time frame. Increased shower and lighting storms chances once again in the afternoon and early evening. Winds becoming onshore at 10-15kts each afternoon. Easterly winds should keep late afternoon and evening convection from drifting back towards the east coast. Seas will be 3-4 ft in the nearshore and 4-5 ft in the offshore waters. Early next week...(Modified from previous version) The ridge axis is expected to remain north of the local area, continuing onshore flow through the period. Shower and storm chances returning to near seasonal norms, with the highest chances across the interior, as winds continue to keep activity from drifting back towards the coast. Winds persisting at around 10-12kts each afternoon, with seas generally 3-4ft on Monday, diminishing to 2-3ft through mid- week. && .PRELIMINARY POINT TEMPS/POPS... DAB 73 87 75 88 / 40 60 20 40 MCO 75 91 76 92 / 40 50 20 40 MLB 75 88 77 88 / 40 50 20 40 VRB 74 89 77 90 / 40 40 20 40 LEE 75 91 76 92 / 30 40 10 40 SFB 73 89 75 90 / 30 50 20 40 ORL 74 89 76 90 / 40 50 20 40 FPR 73 89 75 88 / 40 40 20 40 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && Watson/Rodriguez/Haley
Hazardous Weather Outlook National Weather Service Melbourne FL 1119 AM EDT Fri Sep 10 2021 AMZ550-552-555-570-572-575-FLZ041-044>047-053-054-058-059-064-141- 144-147-110300- Flagler Beach to Volusia-Brevard County Line 0-20 nm-Volusia- Brevard County Line to Sebastian Inlet 0-20 nm- Sebastian Inlet to Jupiter Inlet 0-20 nm-Flagler Beach to Volusia- Brevard County Line 20-60 nm-Volusia- Brevard County Line to Sebastian Inlet 20-60 nm- Sebastian Inlet to Jupiter Inlet 20-60 nm-Inland Volusia- Northern Lake-Orange-Seminole-Southern Brevard-Osceola- Indian River-Okeechobee-St. Lucie-Martin-Coastal Volusia- Southern Lake-Northern Brevard- 1119 AM EDT Fri Sep 10 2021 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA. .DAY ONE...THIS AFTERNOON AND TONIGHT. .THUNDERSTORM IMPACT... Numerous showers and lightning storms are expected across east central Florida today. Showers and storms should develop farther south from the I-4 corridor to Lake Okeechobee and the Treasure Coast this afternoon. Storm motion will be eastward at 5 to 10 mph, becoming slower and erratic late in the day. A few strong to severe storms will be possible today, with wind gusts in excess of 50 mph, hail to 1 inch in diameter, frequent lightning strikes, and torrential downpours. Move indoors at the first sign of threatening skies, or if you hear thunder. .FLOOD IMPACT... Storms will have the potential to produce rainfall totals between 1 and 3 inches of rain in some areas, possibly higher in a couple spots. this would cause temporary flooding of roads and other urban and poorly drained, low lying areas. Never drive through water covered roadways. Turn around, don't drown. .RIP CURRENT IMPACT... Building long period swells from distant Hurricane Larry produce breaking waves up to 5 feet and maintain the High Risk for life- threatening rip currents at area beaches today. Always heed the advice of your local beach patrol. Entering the surf is strongly discouraged again today. .MARINE THUNDERSTORM GUST IMPACT... Stronger storms could produce wind gusts above 35 knots on inland lakes, the Intracoastal and near shore Atlantic waters today. .WIND AND SEA IMPACT... Swells from distant Hurricane Larry will produce seas of 6 feet well offshore the coasts of Volusia and Brevard Counties this morning, before gradually decreasing this afternoon and tonight. Small craft should exercise caution for seas up to 6 feet and hazardous conditions near inlets. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY. Scattered showers and thunderstorms are expected through the middle of next week, with increasing storm coverage possible Wednesday and Thursday. Strong gusty winds, frequent lightning and torrential downpours will accompany any stronger storms. While seas and surf will slowly subside, a High Risk of dangerous rip currents will continue Saturday, and will be at least Moderate from Sunday onward. .SPOTTER INFORMATION STATEMENT... Spotters should monitor the weather and self activate if needed. Watson
Special Weather Statement
National Weather Service Melbourne FL
536 PM EDT Fri Sep 10 2021
FLZ054-059-102230-
St. Lucie FL-Indian River FL-
536 PM EDT Fri Sep 10 2021
...A strong thunderstorm will impact portions of north central St.
Lucie and southeastern Indian River Counties through 630 PM EDT...
At 535 PM EDT, Doppler radar was tracking a strong thunderstorm near
Wabasso, moving east at 15 mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Fort Pierce, Sebastian, Vero Beach, Indian River Shores and Vero
Beach South.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 2747 8032 2765 8053 2775 8051 2778 8036
2758 8029
TIME...MOT...LOC 2135Z 288DEG 12KT 2771 8048
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
FehlingThe Melbourne radar (KMLB), 59 km away, was scanning. The volume nearest the first event began at 22:11 UTC.
1 hail. Local standard time, as filed.
A strengthening thunderstorm within Indian River County briefly became severe by producing hail up to quarter size in Vero Beach near the intersection of U.S. 1 and 17th Street. The report was relayed via social media, with a photo.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2021Every state in 2021This day in weather historyWarnings in Florida, September 2021
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: 973095.