Massive Tornadic Storm Just Misses Dallas; Extreme Heat in South Florida, Cuba

Near-record atmospheric moisture for late April teamed up with an extremely strong jet stream to produce a fearsome night of severe weather over north Texas, mainly south of the Dallas-Fort Worth area. The most intense storms of the day developed by early afternoon southeast of Abilene, with one large supercell emerging at the south end of the complex. After producing several brief tornadoes and hail as large as softballs from a giant stacked-plate circulation, the storm grew even larger and more threatening after dark as it moved just south of the DFW area. Slowing and reoganizing, it dumped more than 5” of rain on some areas, according to Doppler radar estimates. At one point, there were three potentially tornadic circulations evident on Doppler radar along the storm’s south edge, a pattern eerily reminiscent of the deadly storm on May 30, 2013, that killed several storm chasers near El Reno, Oklahoma. Soon after midnight, the circulations congealed into a powerful comma-shaped bow echo that swept across the prairie with high winds (see Figure 1). Nineteen preliminary tornado reports were logged by NOAA's Storm Prediction Center in Texas on Sunday.


Figure 1. National Weather Service radar imagery from 11:55 pm CDT Sunday, April 26 (left) and 12:55 am CDT Monday, April 27 (right) shows the dramatic evolution of the storm complex south of Fort Worth into a bow echo (right), with a “bookend” circulation evident on its north end. Here's an animation from NCAR showing the storm's evolution on radar. Image credit: Weather Underground Storm.

Sunday night’s storm would have been far more destructive had its track been just one county north, across Fort Worth and Dallas. Just two nights earlier, parts of the Fort Worth area were racked by a powerful downburst that brought winds estimated at 80 – 85 mph. That storm went on to produce high winds all the way to Mississippi, with three brief EF1 tornadoes reported there. Another storm complex produced an even more extensive swath of high wind on Saturday, stretching nearly 500 miles from southeast Louisiana to the Georgia coast. Also on Saturday, hail up to baseball size pounded central Kentucky, with a short-lived EF2 tornado reported northwest of the town of Brownsville.


Figure 2. A hazy sunset on Saturday night, April 26, served as a prelude to Miami’s record heat on Sunday. Upper-air analyses carried out by the National Weather Service traced a smoke layer that lay a few thousand feet above the city on Saturday back to its origin several days earlier above fires on Mexico’s Yucatan Peninsula. Image credit: NWS/Miami.

Heat wave blasts April records in South Florida and Cuba
The spring of 2015, already one of the warmest on record across southeast Florida, turned it up a notch on Sunday, as residents baked in heat that would be unusual even in midsummer. Fort Lauderdale International Airport broke its all-time April heat record with 96°F, while Miami tied its April record with the same reading. Fort Lauderdale Executive Airport sizzled at 99°F; this was just 1° short of the city’s all-time any month record of 100° achieved on Aug. 4, 1944 (records date back to 1912 in the city.) In addition, one preliminary report of 100°F came in from the Boca Raton area. The day’s heat was not only intense but persistent: Miami hit 96°F at 1:27 pm and stayed above 90°F for eight torrid hours. Strong westerly winds kept the typical afternoon cooling from the sea breeze at bay.


Figure 3. The weekly U.S. Drought Monitor issued on April 23 showed an area of severe drought (orange) across far south Florida that had grown fivefold in size from the previous week. Image credit: National Drought Mitigation Center.

The heat may have also gotten a boost from parched ground across far southern Florida, where drought conditions have intensified rapidly in the last several weeks (see Figure 3). Dry ground heats up more readily than moist ground in full-sun conditions, and Sunday’s westerly winds swept across the drought area en route to the big east-coast cities. Miami is coming off its second-warmest March on record, and April is currently running at the warmest pace on record (80.4°F). Even with slightly less brutal temperatures on tap this week, April should end up toppling the monthly record of 80.1°F set in 2011.

The heat has been even more impressive in nearby Cuba, where Havana set its all-time temperature record on Sunday with a sizzling 37.0°C (98.6°F). The day also brought the second-highest temperature ever recorded anywhere in Cuba: 38.7°C (101.6°F), at Holguin. These data were provided courtesy of Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. He notes that these records are all the more impressive since July and August are usually the hottest months in Cuba.

Bob Henson