By John McPhaul
jpmcphaul@gmail.com
Isolated to scattered thundershowers, mainly in the interior areas southwest of San Juan during the afternoon, raised the prospect of flooding on Sunday.
In the northeastern part of the island, and as far west as the capital city, flooding was anticipated earlier in the day in urban areas, roads and small streams. Flash floods and isolated landslides were also possible, with precipitation providing little in the way of relief from extreme high temperatures.
Heat indices of 108-111 degrees were expected in most low-lying elevations and urban areas of all coastal municipalities and metropolitan regions of Puerto Rico, as well as in Vieques and Culebra.
Waves equal to or greater than seven feet were expected in Atlantic waters far from shore, creating dangerous conditions for small vessels. Deadly rip currents were also likely, particularly on the beaches of north-central Puerto Rico and the San Juan metropolitan area.
For the rest of the week, moisture from Tropical Storm Philippe’s outer bands will induce a risk of excessive rain and lightning on most islands over the next few days, forecasters said. The risks of excessive heat will remain at least until Tuesday.
The storm surges generated by Philippe, for which the National Hurricane Center (NHC) issued a tropical storm advisory Sunday, will maintain dangerous sea conditions for small boats until the next working week. A moderate to high risk of deadly rip currents is expected over the next two days.
Philippe was crawling westward Sunday, while conditions could help it strengthen and reach hurricane status in the coming days, forecasters said.
The NHC estimated that Philippe had maximum sustained winds of 50 mph, with higher gusts.
Philippe was centered near 16.4N 58.2W, or 180 miles east of Guadeloupe, moving west at 6 knots early Sunday. Maximum sustained wind speed was 45 knots with gusts to 55 knots. Peak seas were 21 feet. A turn toward the northwest with an increase in forward speed was expected later Sunday and today, followed by a northward motion on Tuesday. On the forecast track, the center of Philippe was expected to pass near or just northeast of the northern Leeward Islands today and tonight.
As Phillipe moved across the central Atlantic and higher sea surface temperatures over the weekend, it was expected to strengthen and become a hurricane, forecasters said late Saturday afternoon.
There were no coastal warnings or watches in effect, but “the northern Leeward Islands, the U.S. British and Virgin Islands and Puerto Rico should monitor the progress” of the system, forecasters said.
The Atlantic hurricane season started June 1 and runs through Nov. 30.
In late May, the National Oceanic and Atmospheric Administration (NOAA) predicted that there would be 12 to 17 named storms this year, a “near-normal” amount. On Aug. 10, NOAA officials revised their estimate upward, to 14 to 21 named storms.
There were 14 named storms last year, after two extremely busy Atlantic hurricane seasons in which forecasters ran out of names and had to resort to backup lists. (A record 30 named storms took place in 2020.)
This year features an El Nino pattern, which started in June. The intermittent climate phenomenon can have wide-ranging effects on weather around the world, and it typically impedes the number of Atlantic hurricanes.
In the Atlantic, El Nino increases the amount of wind shear, or the change in wind speed and direction from the ocean or land surface into the atmosphere. Hurricanes need a calm environment to form, and the instability caused by increased wind shear makes those conditions less likely.
At the same time, this year’s higher sea surface temperatures pose a number of threats, including the ability to supercharge storms. That unusual confluence of factors has made it more difficult to predict storms.