Atlantic surface high pressure and elongated high pressure aloft at the mid-levels allowed for light southerly to southwesterly flow to prevail which allowed outflow boundaries to play a large part in convective focus. This allowed for training of heavy showers and storms which led to flooding across portions of Miami-Dade County.
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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 MFL wrote it up.
Atlantic surface high pressure and elongated high pressure aloft at the mid-levels allowed for light southerly to southwesterly flow to prevail which allowed outflow boundaries to play a large part in convective focus. This allowed for training of heavy showers and storms which led to flooding across portions of Miami-Dade 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 Miami, FL wrote its last area forecast discussion before the first event at Sep 26, 12:35 PM EST, 55 minutes earlier.
Area Forecast Discussion National Weather Service Miami FL 135 PM EDT Sat Sep 26 2020 .Aviation... Convection will focus along the sea breezes and other boundaries this afternoon and evening. Some showers and storms could move near the terminals, particularly the east coast ones, which could bring bouts of sub-VFR. Short-fused amendments will likely be necessary today. Convection should diminish after 02z. Some low cigs/mist may once again affect some of the inland east coast terminals which could cause brief bouts of sub-VFR overnight into early Sunday morning. Sea breeze pattern expected on Sunday, though convection may be focused further inland than today. && .Prev Discussion... /issued 1054 AM EDT Sat Sep 26 2020/ Update... Relatively quiet start to this Saturday morning across South Florida as some earlier showers over the local waters have diminished. Much of the area is already in the mid 80s with heating expected to continue into the afternoon. Sea breeze development is still forecast with the westerly component to the flow pinning the Atlantic sea breeze closer to the coast. The 12z MFL sounding has a precipitable water value of 2.22 inches which is still indicative of a moist atmosphere capable of efficient rainfall processes. Instability should not be an issue today unless an area has been worked over by convection and some localized stabilization has occurred. High resolution guidance is beginning to capture the potential for boundary collisions this afternoon to permit some vigorous convection which could develop around or just west of the western suburbs of South Florida and potentially push back to the coast during the late afternoon and evening hours. Have raised PoPs from slight chance to chance over portions of Dade and Broward for the evening hours to show this slight change to the forecast as the previous shift hinted might be possible with a weaker sea breeze or boundaries pushing back towards the coast. Updated zones were previously transmitted with this change included. Have a wonderful Saturday! Prev Discussion... /issued 255 AM EDT Sat Sep 26 2020/ Short Term... Today through Sunday... The pattern for the weekend is really fairly neutral. There is a weak 500mb ridge aloft, and a weak thermal low develops today over the area. But, all in all, the weather will be driven by more mesoscale features than synoptically. The GFS is showing 500mb temperatures around -5C, to maybe as low as -6C. Nothing too exciting to enhance convection. Early in the day today, the GFS does not really show any decent low level convergence. However, by this afternoon, there is multiple areas of strong convergence in the lake region and the southeast metro areas. This coincides with some areas of convergence in the sfc wind forecast as well. With high PWATs (over 2 inches) to the south, this could spell some heavy rain and some urban flooding of roadways this afternoon and evening. Looking at sea breeze development possibilities, the temperature gradient only looks marginal, with a temperature differential of only 6F between the forecast high over the coastal waters and the temperatures inland. So, would not expect a strong sea breeze today, but more some weak sea breezes that dont progress too far inland. They will probably be strong enough to initiate convection, but then it is highly likely the convection will then be dominated by boundary interactions. So there will be a lot of uncertainty as to location and timing through the day. The reasonable worst case at this time is that the Atlantic sea breeze pushes inland, allowing for convective initiation, which then, with the light steering flow, sends an outflow boundary back to towards the coast, which that interacts with the sea breeze boundary, causing some sustained heavy rain over various locations over the east coast metro area, especially over Miami-Dade, where current model runs indicate some of the best low level convergence will be. Overnight, most of the activity should diminish, with mostly quiet weather conditions overnight. Tomorrow looks to be once again sea breeze dominated, however, the convergence shifts toward the western interior, with storm motion to the west. Currently, the best convergence looks to be in the western lake region, which, while some flooding could still occur, would have much less of an impact than over the metro areas, like today. Long Term... Sunday night through Friday night... High pressure will remain over Western Atlantic waters on Monday, as a trough of low pressure develops over the Central United States. This will keep an east to southeast wind flow over South Florida allowing for the east coast sea breeze to push inland focusing the best coverage of showers and thunderstorms over the interior and west coast metro areas. The east coast metro areas could still see some showers and even a few thunderstorms on Monday. The trough of low pressure to depend Tuesday into Wednesday, as the trough moves eastward into the Eastern United States. This will allow for low pressure to develop over the Southeastern United states and move northeast up the eastern coast of the United States. This in turn will allow for a cold front to move southward down the Florida Peninsula and into South Florida. Therefore, the showers and thunderstorms will be on an increase across the region with the best coverage over the interior and east coast metro areas for middle of next week. The long range models then stalled the front over South Florida late next week keeping the deep tropical moisture in place. This will allow for scattered to numerous showers and thunderstorms late next week over the the region along with possible heavy rainfall, as the PWAT values are forecast to be between 2 to 2.3 inches which is near the maximum value for this time of year. Marine... Weak flow aloft for the next several days should keep marine conditions fairly benign. The exception will be any convective activity that develops, which could bring localized hazardous marine conditions, including gusty wind and waterspouts for the weekend. By the middle of the week, a cold front pushes into the area. This will help to enhance showers and thunderstorms over the area. However, the front is forecast to stall somewhere over the region. This stalled boundary will help to keep showers and thunderstorms in the forecast through the end of next week. There is a slight risk of rip currents, mainly around jetties and inlets. With a light wind and swell of less than 2 feet, there is no significant rip current risk for South Florida through the beginning of the week at least. && .Preliminary Point Temps/PoPs... West Palm Beach 76 89 76 89 / 20 20 20 50 Fort Lauderdale 78 89 78 88 / 30 20 20 40 Miami 77 89 78 88 / 40 30 20 50 Naples 76 90 76 88 / 20 40 30 60 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && Aviation...02/RAG
Hazardous Weather Outlook for South Florida...UPDATED National Weather Service Miami FL 1033 AM EDT Sat Sep 26 2020 AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676- 270400- Lake Okeechobee-Biscayne Bay- Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM- Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM- Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM- Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM excluding the territorial waters of Bahamas-Glades-Hendry- Inland Palm Beach-Metro Palm Beach-Coastal Collier-Inland Collier- Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade- Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami- Dade-Far South Miami-Dade- Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM- Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM- Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM- 1033 AM EDT Sat Sep 26 2020 ...Thunderstorms Possible Across South Florida... This hazardous weather outlook is for South Florida. .DAY ONE...TODAY AND TONIGHT Thunderstorms: Thunderstorms are possible across South Florida today. The main hazards will be lightning and urban street flooding in low lying and poor drainage areas, mainly for the east coast metro areas of Broward and Miami-Dade. A strong storm or two could also produce 45 to 55 mph wind gusts and funnel clouds, mainly over Southeast Florida this afternoon and evening. Waterspouts: There is a slight risk of waterspouts for all South Florida waters today. Flooding: There is a slight chance of urban flooding of the roadways for the east coast metro areas of Broward and Miami-Dade counties today, especially in typical flood prone areas, low lying areas, as well as areas with poor drainage. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Increasing rain and thunderstorm chances into the weekend, when locally heavy rainfall and flooding could become a concern. .SPOTTER INFORMATION STATEMENT... Widespread spotter activation is not anticipated, however individual spotters are encouraged to report high wind, funnel clouds, and flooding to the National Weather Service forecast office in Miami. Please relay any information about observed severe weather to the NWS while following all local, state, and CDC guidelines. For more information...visit the National Weather Service in Miami website at www.weather.gov/miami.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Law enforcement reported flooding along NE 15th Street between Bayshore Drive and Biscayne Boulevard just north of downtown Miami. The flooding was caused by a cluster of heavy showers and storms with nearby rainfall measurements around 2 inches an hour.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2020Every state in 2020This day in weather historyWarnings in Florida, September 2020
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: 920512.