Danielle the Atlantic's Earliest 4th Storm on Record; 115°-120° Heat in SW U.S.

Tropical Storm Danielle formed on Monday morning in the Gulf of Mexico's Bay of Campeche, but won't be around long. The storm's west to west-northwest motion will carry the storm inland over Mexico between Veracruz and Tampico by Monday evening. With top winds of just 45 mph as estimated by the National Hurricane Center in their 11 am EDT Monday advisory, heavy rain is expected to be the primary threat from the storm. Satellite loops show a large area of intense thunderstorms with heavy rain are moving inland along the Mexican coast south of Texas, and total rainfall amounts of 6 - 10" are likely to cause dangerous flash flooding and mudslides in the mountainous terrain along the coast. Heavy rains from Danielle will remain just south of Texas, with Brownsville expected to pick up an inch of rain or less in scattered thunderstorms through Monday night. Danielle will dissipate by Tuesday over the rugged terrain east of Mexico City.


Figure 1. Latest satellite image of Danielle.

Danielle the Atlantic's earliest fourth named storm on record
Danielle's formation marks the earliest appearance on record for the Atlantic's fourth named storm of the season; the previous record was June 23, 2012, when Tropical Storm Debby formed. However, as wunderground member Neapolitan pointed out in the comments of our previous blog post, a lot of early storm activity is not a sure sign that there'll be a lot of late storm activity. For instance, 2011 saw fifteen named storms before the traditional September 10 - 11 halfway point of the hurricane season: one in June, three in July, eight in August, and three in early September. Some people thought the year might end with up to 30 storms--but just two more storms formed in late September, one in October, and one in November, giving a season total of nineteen. Rather than a 50/50 split between the front and back halves of the season, the ratio was 78/22. Generally, high early season activity is only a harbinger of an active Atlantic hurricane season when the early season activity occurs in the Caribbean or tropical Atlantic. This has not been the case in 2016.


Figure 2. Helicopter-related firefighting efforts were limited on Sunday at the uncontained Brown Fire in far south Arizona, which has affected more than 8000 rugged acres in the Baboquivari Mountains southwest of Tucson. Believed to be caused by humans, the fire is now under investigation. Image credit: AZ State Forestry.

Blazing Arizona: Sunday’s heat was the real deal
A well-predicted heat wave crescendoed on Sunday with some of the highest temperatures ever recorded in the larger towns and cities of southern California, Arizona, and northern Mexico. The heat was produced by an extremely strong upper-level high building over the Southwest just one day before the summer solstice, when the amount of incoming solar energy peaks. Sunday was the hottest day observed in any year prior to the summer solstice, and the hottest day on record for so early in the season, in Yuma (120°F, ahead of June 24, 1957), Phoenix (118°F, ahead of June 24, 1929), and Tucson (115°F, ahead of June 25, 1994). Sunday also tied as Phoenix’s 5th hottest day on record, and Yuma’s 5th hottest. In Tucson, only two other days have been officially hotter than Sunday: June 26, 1990 (117°F) and June 29, 1994 (116°F). However, as we reported last week, the instrumentation that was used to measure official temperatures at Tucson International Airport during the early 1990s was later found to be problematic. As a result, weather record researcher Maximiliano Herrera believes that 115°F—measured at the Tuscon NWS office on June 19, 1960; June 26, 1990; and July 28, 1995, as well as on Sunday at the airport—is a more reliable all-time high for Tucson. Herrera also reported that Altar, Mexico had its hottest temperature in recorded history on Sunday--48.5°C (119.3°F), beating the previous record of 48.3°C set in 1985. The award for the hottest place on Earth on Sunday may go to Piedra, Arizona, southwest of Phoenix, where the high temperature hit a remarkable 127°F (52.8°C). Thanks go to weather records researcher Jérôme Reynaud for this info (he maintains a database of all locations on Earth that have exceeded 50°C so far in 2016.) If confirmed, this would rank as the second hottest temperature ever measured in Arizona, and the hottest temperature measured anywhere on Earth so far in 2016. Stanwix, Arizona, about 8 miles to the west of Piedra, hit 125°F on Sunday.

Excessive heat warnings continued to plaster the far Southwest on Monday, as some areas were expected to inch even hotter while others could wind up just a shade less scorching. The warnings included Los Angeles, San Diego, Las Vegas, Phoenix, and Tucson. Later this week, a modest amount of moisture will began filtering into the region, bringing down temperatures somewhat but keeping conditions very uncomfortable. The heat will also persist across large swaths of the Plains and Southeast, though it should fall short of record-setting intensity in most areas.

Jeff Masters and Bob Henson