Special tropical forecast issued, potential system no threat to Florida
Windy conditions with gusts up to 30 mph could take a swipe at South Florida later this week with some offshore tropical activity also possible.
A tropical storm itching to form northeast of the Bahamas inspired the National Hurricane Center to issue its first outlook for the 2020 hurricane season on Tuesday, putting the chances of something developing at 50 percent over five days.
For South Florida, the churn of air and moisture, is expected to increase chances for rain and gusting 30-mph winds beginning Thursday, but it may be the beaches that feel the brunt of whatever ultimately grows as seas build through the week.
While hurricane season doesn’t officially begin until June 1, it’s not unusual to see an early-season storm gurgle up given the current conditions of the atmosphere and ocean.
A lazy frontal boundary left over from last weekend’s rains is drifting north from the Florida Straits and is expected to get a punch of energy from rushing upper-level winds. That duo combined with sea surface temperatures near 82 degrees is part of what piqued NHC’s interest.
If a tropical or subtropical storm forms, it would be named Arthur.
“This is kind of what we see early in the season and they don’t tend to get overly strong,” said AccuWeather senior meteorologist Rob Miller. “But the potential is there for 50 to 60-mph wind gusts mostly in the Bahamas with some downpours and gusty winds over Florida.”
Rain totals of between 0.75 and 2.5 inches are possible through Sunday, with the southeast coast getting the heaviest showers. Coastal Palm Beach County is down 5.5 inches of rain this year, according to the South Florida Water Management District. May’s deficit was 1.5 inches through Tuesday.
Since the late 1960s when satellites began identifying tropical cyclones in the Atlantic, 15 named storms have formed prior to June 1, according to Colorado State University researcher Phil Klotzbach.
Those early-stirring storms have included ones that formed each of the past five years, including 2019′s Subtropical Storm Andrea, 2018′s Tropical Storm Alberto, 2017′s Tropical Storm Arlene, 2016′s Hurricane Alex and Tropical Storm Bonnie and 2015′s Tropical Storm Ana.
The National Hurricane Center began naming subtropical storms in 2002.
“Part of the reason for the recent increase in early-season storm formations is likely due to microwave sensors that allow us to observe more of these marginal systems,” Klotzbach said.
Weather models had been hinting that something tropical may try to form for the past several days and the National Weather Service put out a special notice Tuesday morning for South Florida residents to be watchful for storms late in the week. The NWS forecast includes the possibility for “fresh to strong” easterly winds and the potential for gale-force gusts over near shore waters.
Gale force includes winds of 39 to 54 mph. The terms “fresh” and “strong” are based on the Beaufort Wind Scale. They equal 24 mph to 31 mph winds with wave heights up to 8 feet for fresh breezes and up to 13 feet for strong breezes.
“Whether that low has any tropical characteristics, it won’t make much difference for us,” said Molly Merrifield, an NWS meteorologist in the Miami office. “We’re going to see an increase in rain chances Thursday, Friday and possibly Saturday as the front that stalls over the Keys and Florida Straits drifts north.”
Thursday’s forecast for West Palm Beach is for an up to 50 percent chance of rain, surging to 70 percent Friday with the possibility of thunderstorms Friday night.
Saturday has a 50 percent chance of showers, but with clearing skies.
Rainfall totals for South Florida into Sunday range from 0.75 to 2.5 inches with the heaviest showers focusing along the southeast coast from Palm Beach County to the Keys.
Temperatures all week are expected to top out in the low 80s and dip to the low 70s overnight.
If something tropical or subtropical develops ahead of June 1, it has no bearing on how many storms will form this hurricane season.
Klotzbach said there is very little correlation between early season activity and overall activity because early storms form at higher latitudes “and are less representative of what the overall tropical circulation is like.”
“Note that even 2005, the most active season on record, had 0 named storm formations prior to June 1,” Klotzbach said.
Still, several key hurricane forecasts are calling for an above normal season with AccuWeather increasing its storm numbers last week to between 14 and 20 named storms, including seven to 11 hurricanes. AccuWeather is forecasting four to six major hurricanes of Category 3 or higher. An average storm season has 12 named storms, including six hurricanes and three major hurricanes.
The hike in forecast storm numbers followed information from the Climate Prediction Center that there are increased chances of a La Niña forming later this year. La Niña climate patterns – characterized by a cooling of Pacific waters - relax wind shear in the Atlantic basin, giving hurricanes a more encouraging atmosphere to grow.
“The signal is there that the waters have turned colder and that leads to an uptick in activity in the Atlantic,” Miller said.
The National Oceanic and Atmospheric Administration is scheduled to release its 2020 hurricane forecast May 21.
This story originally published to palmbeachpost.com and was shared to other Florida newspapers in the new Gannett Media network.
2020 tropical cyclone names for the Atlantic basin