High pressure in place with abundant moisture led to high temperatures and dewpoints. This led to the heat index reaching 108-110 degrees.
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The episode as NWS MFL wrote it up.
High pressure in place with abundant moisture led to high temperatures and dewpoints. This led to the heat index reaching 108-110 degrees. With these high heat indices many people were treated for heat related illness at Miami Beach.
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 Jul 25, 10:21 AM EST, 39 minutes earlier.
Area Forecast Discussion National Weather Service Miami FL 1121 AM EDT Tue Jul 25 2017 UPDATE... A strong upper level high pressure dome continues stagnant over the Florida peninsula. Subsidence from this feature is responsible for the very warm temperatures across the region. Heat index values will max out from 105 to 109 over much of the CWA. Maintained the heat advisory for interior Collier County, with many other counties approaching advisory criteria. Maximum temperatures in the lower 90s, combined with dew points near 80 degrees, will make for very oppressive and humid conditions this afternoon. The 12Z MFL sounding indicates light flow from the surface up to 500 mb. This will allow for both the Atlantic and Gulf sea breezes to develop, initiating shower a thunderstorm activity. Latest runs of HRRR and WRF show the storms moving towards the interior as the afternoon progresses. Modified DCAPE values will approach 1400 J/KG, indicating the potential for gusty downdraft winds associated with the storms. Activity should slowly diminish as the evening approaches. PREV DISCUSSION... /issued 815 AM EDT Tue Jul 25 2017/ AVIATION... Sea breeze is expected to develop along both Atlantic and Gulf coasts aft 25/1600Z. As this occurs, VCTS will form inland from the coast...mostly likely further inland than the terminals themselves. Outflow boundaries could produce brief variable gusty winds. Otherwise, expecting sct low clouds around 3000 ft msl. Winds and precipitation chances dwindle this evening. PREV DISCUSSION... /issued 348 AM EDT Tue Jul 25 2017/ DISCUSSION... Today: High pressure with deep subtropical ridge will remain in place with east to southeast flow today. Currently very high moisture content is present over the western Carribean waters with blended total pwats of 1.9 to 2 inches over South Florida and the Bahamas. Latest 00Z MFL sounding observed 1.79 as well tonight. The level of moisture will continue to increase through the mid work week with guidance sounding showing precipitable water values increasing to above 2 inches into Wednesday. There is some lingering remnant of SAL layer in the mid levels but this will not limit the chance of convection this afternoon. Best chance of showers will be over the waters early in the morning and transition to interior with sea breeze collision around or after noon. The storms that do develop will then propagate and build southwest. Temperatures will range between the mid to upper 90s across the forecast area with heat index reaching 108 degrees during peak heating for more than 2 hours over Collier County. Therefore, a heat advisory has been issued for the afternoon hours. Stay hydrated as much as possible! Overnight lows will be in the mid to upper 70s with some locations along the east coast in the lower 80s. Wednesday: With the increase in moisture, the chances of showers and thunderstorms will increase with coverage mainly over the interior and Gulf coast during the afternoon and evening hours Wednesday. Wednesday will be another hot day with temperatures ranging between the mid to upper 90s across the forecast area with heat index reaching 108 degrees once again during peak heating. During the overnight hours shower activity will shift over the Atlantic and Gulf waters. Isolated showers and storms may drift over east coast metro regions from the Atlantic. Thursday and this weekend: Subtropical ridge will weaken slightly towards the end of the week allowing a more southerly wind flow to return to South Florida. This southerly flow will bring more tropical moisture into the region allowing for more coverage to increase this weekend. East coast metro regions will see higher chances of rain towards the end of the week into the weekend. Muggy conditions will continue through the end of the week and into the weekend with high temps in the low to mid 90s. Next week: A weak mid level low pressure over the northeast plains moves a front southward into the panhandle into next week. Models show this feature making into the panhandle of FL by next week with deep moisture right ahead of it. The interaction of this trough and subtropical ridge towards the east will increase south to sw flow across the region with plenty of moisture concentrated over the area. This will allow for the continuation of this wet pattern to start the month of August. MARINE... The winds will be 10 knots or less from the east over South Florida waters through middle of this week, before swinging more to a southerly direction late this week into this weekend. This will keep the seas at 2 feet or less over both the Atlantic and Gulf waters of South Florida. Therefore, boating conditions will be good outside of any showers or thunderstorms this week. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 91 80 91 80 / 20 20 20 30 Fort Lauderdale 92 80 92 82 / 30 20 20 20 Miami 92 81 92 81 / 30 20 30 30 Naples 93 78 93 77 / 30 20 40 40 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory until 6 PM EDT this evening for FLZ070. AM...None. GM...None. && UPDATE...27/JT DISCUSSION...67/MT MARINE...67/MT AVIATION...27/JT
Hazardous Weather Outlook for South Florida National Weather Service Miami FL 1052 AM EDT Tue Jul 25 2017 AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676- 260300- 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- 1052 AM EDT Tue Jul 25 2017 ...Heat Advisory for Collier County Today... ...Thunderstorms Possible Across South Florida Today... This hazardous weather outlook is for South Florida. .DAY ONE...TODAY AND TONIGHT Thunderstorms: Thunderstorms are possible across South Florida today, with the best chances in the interior areas. The primary threats will be lightning and gusty winds. Wind: Some thunderstorms could produce isolated wind gusts 45 to 55 mph. Waterspouts: Waterspouts are possible over all the local waters today, primarily through the early afternoon hours. Temperatures: The heat index is forecast to be near 105 degrees across much of South Florida, with some areas across Collier County reaching to nearly 110 degrees. A Heat Advisory is in effect for Collier County today. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY The threat for thunderstorms will increase during the first half of the work week. Greatest coverage will be across the interior and Gulf Coast in the afternoons and evenings. Lightning, gusty wind, and torrential rainfall will be the primary hazards. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed tonight. 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 heat. Local standard time, as filed.
Miami Beach Ocean Rescue reported up to 15 heat related illnesses occurred throughout the day due to high heat and heat indices. No one was transported to a local hospital just treated locally at the beach.
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: 716468.