There was no tropical storm activity in the north Atlantic as of Sunday night, but that could change fairly quickly, as meteorologists have their eyes on two systems that threaten to kick off the hurricane season after two fairly quiet months.
According to the National Hurricane Center, an area of low pressure, currently about midway between the Cabo Verde Islands and the Lesser Antilles, had about a 50 percent chance of formation in the next five days. The system remains elongated, the NHC said in its 2 p.m. Sunday forecast, and the associated showers and thunderstorms are not yet well organized.
“Some slow development of this system is possible during the next several days while it moves generally west-northwestward across the tropical Atlantic at about 15 mph,” the NHC reported.
Forecast models vary on where this system will go, with several showing a path through the central Lesser Antilles while others to the northern Lesser Antilles.
A second system has formed over the western Caribbean Sea, about 150 miles east of the eastern coast of Honduras. Winds just below tropical-storm-force are occurring to the northeast of the center. The NHC reported Sunday that the associated showers and thunderstorms are gradually becoming better organized, and a tropical depression or tropical storm will
likely form before the low reaches the Yucatan Peninsula of Mexico late Monday or early Tuesday.
After the system crosses the Yucatan Peninsula, it is expected to move across the Bay of Campeche by midweek where additional development is expected.
An Air Force Reserve reconnaissance aircraft is scheduled to investigate this low on Monday, if necessary.
The forecasters cautioned interests along the coasts of Honduras, Belize, and the Yucatan Peninsula to monitor the progress of
this system as heavy rains and strong winds are possible at those locations.
The NHC gave the system a high chance of formation, 80 percent during the next two days and 90 percent within five days.
The attention focused on the Atlantic came at the same time Colorado State University hurricane researchers issued an update to their forecast, saying they continue to predict an above-average Atlantic hurricane season.
In a Friday news release, the team from the Rocky Mountains cited both neutral El Niño-Southern Oscillation (ENSO) conditions and a warmer than normal tropical Atlantic as the primary reasons for this above-average prediction for the Atlantic and Caribbean.
The odds of an El Niño event have diminished considerably from what was anticipated in earlier outlooks, the CSU team said in its news release. The tropical Atlantic has been much warmer than normal for the past several months, and is likely to remain so, therefore providing more fuel for developing tropical cyclones.
However, the far North Atlantic remains quite cold, they continued, and this tends to create atmospheric conditions associated with increased sinking and drying motion.
“In general though, overall conditions appear to indicate that an above-average Atlantic hurricane season is the most likely scenario,” the team said in its forecast update.
The CSU Tropical Meteorology Project team is predicting a total of 11 additional named storms to form after Aug. 1. Of those, researchers expect eight to become hurricanes and three to reach major hurricane strength (3, 4, or 5 on the Saffir/Simpson scale) with sustained winds of 111 miles per hour or greater. These forecast numbers do not include Tropical Cyclones Arlene, Bret, Cindy, Don and Emily which formed prior to Aug. 1.
The team bases its forecasts on more than 60 years of historical data that include Atlantic sea surface temperatures, sea level pressures, vertical wind shear levels (the change in wind direction and speed with height in the atmosphere), El Niño (warming of waters in the central and eastern tropical Pacific), and other factors.
So far, the 2017 hurricane season is exhibiting characteristics similar to 1953, 1969, 1979, 2001 and 2004, they said.
“In general, most of these seasons experienced somewhat above-average activity, with 2004 being an extraordinarily active season,” said Phil Klotzbach, research scientist in the department of atmospheric science and lead author of the report.
The team predicts that 2017 hurricane activity will be about 145 percent of the average season. By comparison, 2016’s hurricane activity was about 150 percent of the average season.
This is the 34th year that the CSU hurricane research team has issued the Atlantic basin seasonal hurricane forecast. The late William Gray, professor in the department of atmospheric science for more than 40 years, launched the report in 1984.
The CSU forecast is intended to provide a best estimate of activity to be experienced during the upcoming season – not an exact measure.
Michael Bell, associate professor in the department of atmospheric science at CSU and co-author of the report, cautioned coastal residents to take proper precautions.
“It takes only one landfall event near you to make this an active season,” Bell said.
The report also includes the post- July 31 probability of major hurricanes making landfall on U.S. soil:
– 51 percent for the Caribbean (full-season average for the last century is 42 percent)
– 62 percent for the entire U.S. coastline (full-season average for the last century is 52 percent)
– 38 percent for the U.S. East Coast including the Florida peninsula (full-season average for the last century is 31 percent)
– 38 percent for the Gulf Coast from the Florida panhandle westward to Brownsville (full-season average for the last century is 30 percent)