Jeff Masters Weather Blog

Category 4 Beryl on collision course with Windward Islands » Yale Climate Connections

The southeastern islands of the Caribbean – no strangers to hurricanes, but not often struck by major ones – are confronting an unusually serious threat from Hurricane Beryl, which has rocketed from tropical storm to Category 4 strength in less than 24 hours. Beryl is on track to sweep across the Windward Islands early Monday, bringing the potential for highly destructive winds, storm surge, and torrential rains. A Hurricane Warning was in effect for Barbados, St. Lucia, St. Vincent and the Grenadine Islands, Grenada, and Tobago.

At 11:35 a.m. EDT Sunday, Beryl was upgraded to Cat 4, with top sustained winds of 130 mph and a central pressure of 962 mb, based on data from one of several hurricane-hunter flights probing the storm. Beryl was located about 350 miles east-southeast of Grenada, moving just north of due west at 21 mph.

Forecast for Beryl

The large-scale forecast through Monday for Beryl is straightforward. The hurricane will continue tracking west to west-northwest through, barreling through the Windwards between midnight and early afternoon Monday. The biggest uncertainty is how much the track might angle slightly northward, as Beryl’s track has remained slightly south of most forecasts thus far. The usual tendency of stronger storms to track more poleward, due to the influence of midlatitude steering currents as well as the influence of Earth’s rotation (the “beta effect”), is less of a factor when hurricanes are as close to the equator as Beryl is. This uncertainty means that all residents of the Windward Islands, especially from St. Vincent and the Grenadines to Grenada, need to take Beryl extremely seriously.

Winds and storm surge are normally stronger on the north side of a west-moving hurricane, and this is especially true with Beryl given its relatively fast speed. Winds will also be up to 30% stronger atop the higher elevations of the islands. Beryl’s rapid forward motion, together with its moderate size, will limit the risk of widespread catastrophic flooding, but torrential rains of 3 to 6 inches (locally 10+ inches) can still be expected to produce dangerous flash floods. Storm surge could reach 3 to 6 feet in some areas near and north of the path.

Conditions remain near-ideal for further strengthening into Monday, with record sea surface temperatures close to 29 degrees Celsius (84 degrees Fahrenheit), substantial deep oceanic heat content, light to moderate wind shear of 5-15 knots, and a moist surrounding atmosphere (mid-level relative humidity of 65-70 percent). The 12Z Sunday run of the SHIPS statistical model gave a 36 percent chance of Beryl attaining top winds of 160 mph by Monday morning, which would be Category 5 strength. NOAA’s high-resolution intensity models from Sunday morning are of limited short-term value in this case, because they had not incorporated the latest hurricane-hunter data that revealed Beryl’s vaulting to Category 4.

Some fluctuations in strength can be expected once Beryl completes its Sunday round of rapid intensification, but Beryl is predicted to remain a dangerous Category 4 storm through Tuesday morning, and it will need to be monitored closely for days beyond that. Long-range ensemble forecasts from the GFS and European models as of early Sunday agreed on Beryl tracking into the northwest Caribbean by late week, potentially moving close enough to Jamaica for hurricane-strength impacts on Wednesday. Ensembles suggest that by late Thursday or Friday, Beryl will be moving west-northwest or northwest somewhere between Belize and the western tip of Cuba, perhaps still as a hurricane, as depicted in the “cone of uncertainty” issued by NHC on Sunday morning. (Note that the width of the “cone of uncertainty” in NHC forecasts is set by the history of the past five years, not by the particulars of a current storm.)

The upper-level ridge over the United States steering Beryl this week may weaken slightly by next weekend, so there is a possibility Beryl might angle northwestward and move into the Gulf of Mexico, as suggested by several members of the Euro ensemble. However, it is too soon to assess this possibility and how it might evolve with any confidence.

Off the climatological chain

It was abundantly clear weeks ago that the deep tropical Atlantic – including the Main Development Region (MDR) between the Caribbean and Africa – was starting the hurricane season with unprecedentedly high ocean temperatures. The only question was whether atmospheric conditions would support an intense hurricane right off the bat, and whether the right “seed” would come along in the form of an easterly wave moving from Africa toward the Caribbean. We now have the answer: a resounding yes.

Here’s a running list of records already set by Hurricane Beryl as of Sunday afternoon, June 30, based on Atlantic hurricane annals going back to 1851.

  • Earliest hurricane so far east in the Atlantic (June 29, longitude 49.3°W; old record 1933 Trinidad Hurricane, June 27, longitude 58.9°W)
  • Earliest Category 3 hurricane so far east in the Atlantic (June 30, longitude 53.9°W; old record Bertha, July 7, 54.1°W)
  • Earliest Category 4 hurricane in the Atlantic (old record Dennis, July 8, 2005; next earliest was the Great Bahamas Hurricane, July 26, 1926)
  • First storm on record to undergo rapid intensification (strengthen by at least 35 mph in 24 hours) in the tropical Atlantic east of the Lesser Antilles during the month of June

Likely to be broken soon:

In 2005, Hurricane Dennis passed through the Windward Islands as a mere tropical depression on July 4, but intensified rapidly as it headed northwest, striking Cuba twice at Category 4 strength and reaching the Florida Panhandle as a Category 3 storm. Dennis caused about $4 billion in damage (USD 2005) and took 88 lives.

It’s especially unsettling to see Beryl having now overtaken the record for earliest Category 4 storm set by Dennis. Dennis was the opening salvo in the barrage of destructive storms that made 2005 the costliest and most prolific hurricane season in U.S. history up to that point (those records have since been toppled by 2017 for cost and 2020 for named storms). The 2005 season was boosted by long periods of record and near-record ocean temperatures – and this year has produced even hotter water in some areas, including the MDR, where easterly waves from Africa often serve as hurricane seeds during the heart of the season.

The 2005 analogy might get another twist in the coming days. A new system in the eastern Atlantic, Invest 96L, is predicted to become another Cabo Verdes-type tropical cyclone, and follow a track similar to Beryl into the Caribbean. The system is likely to become at least a tropical storm, and could achieve hurricane strength (see details below). Likewise, in 2005, Dennis was followed closely by Hurricane Emily, another unusually early Cabo Verdes-type storm that struck Grenada at Category 2 strength on July 14 and intensified rapidly while crossing the Caribbean. Emily became the earliest Category 5 storm on record on July 16 and struck Cozumel, Mexico, as a Category 4 storm on July 18, with a second Mexican landfall at Category 3 strength near San Fernando on July 20. Emily took 22 lives and caused close to $1 billion in damage (USD 2005).

A new threat to the Lesser Antilles for Wednesday: 96L

Another tropical wave, designated Invest 96L, has been speeding westward at 15-20 mph across the tropical Atlantic, and was located midway between the coast of Africa and the Lesser Antilles Islands on Sunday afternoonSatellite images showed 96L had a modest area of heavy thunderstorms that were steadily growing more organized, with some low-level spin apparent.

As with Beryl before it, conditions were favorable for development. Sea surface temperatures were near record warm, about 28-29 degrees Celsius (82-84°F), wind shear was a moderate 10-20 knots, and the atmosphere was moist, with a midlevel relative humidity of 70%. The system was embedded in the Intertropical Convergence Zone (ITCZ) and was relatively close to the equator (8°N), and these factors will slow development. A large area of dry air associated with the Saharan Air Layer (SAL) lies to the north of 96L, and with wind shear predicted to be higher than was the case for Beryl, this dry air may be a more significant hindrance to development than was the case for Beryl. At some point, 96L is likely to cross over the cold water wake left behind by Beryl, and this may also slow development.

96L has strong model support for development, though the models are not as aggressive in intensifying the system as they were (correctly so) for Beryl. The general model consensus is for 96L to pass through the Windward Islands a few hundred miles north of Beryl’s track on Wednesday, then continue into the central Caribbean.

In their 2 p.m. EDT Sunday Tropical Weather Outlook, the National Hurricane Center gave 96L 2-day and 7-day odds of development of 40% and 70%, respectively.

A short-lived tropical storm likely in the Gulf of Mexico

Another tropical disturbance, designated Invest 94L, has been quickly organizing in the southern Gulf of Mexico’s Bay of Campeche. Satellite images showed 94L had a large area of heavy thunderstorms that were steadily growing more organized, with plenty of spin. This disturbance was headed west-northwest at 10-15 mph, and will move ashore over northeastern Mexico on Monday morning, bringing very heavy rains and the threat of flash flooding and mudslides.

In their 2 p.m. EDT Sunday Tropical Weather Outlook, the National Hurricane Center gave 94L 2-day and 7-day odds of development of 80%. The next two names on the Atlantic list of storms are Chris and Debby.

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