Hurricane Fiona deluges Puerto Rico; Typhoon Nandamol hits Japan » Yale Climate Connections



Hurricane Fiona overcame dry air and wind shear that had stifled it to become the third hurricane of this year’s Atlantic season Sunday in waters just south of Puerto Rico. As of 11 a.m. EDT Sunday, September 18, Fiona was carrying sustained winds of 80 mph and moving west-northwest at 8 mph, about 50 miles south of Ponce, Puerto Rico.

Fiona is a relatively large hurricane, so near-hurricane force winds were already affecting Puerto Rico by noon Sunday. Sustained winds of 62 mph, gusting to 75 mph, were reported at Las Mareas on the southeast coast.

As Fiona cuts the western end of Puerto Rico on Sunday afternoon and evening, that will put the island squarely on its strongest right side, increasing the chance of wind and water. Much of the island can expect at least sustained tropical storm-force winds of 40 to 60 mph, enough to bring down trees and power lines. Puerto Rico is in a heavy multi-year process modernize its power grid, which remains compromised after the devastating effects of Hurricane Maria in 2017 and a string of earthquakes in western Puerto Rico in late 2019 and early 2020. Lights is out Saturday during a Fiona briefing from the governor, a troubling harbinger of power issues that many locals may face after Fiona. From 1 p.m. EDT on Sunday, reported that around 40% of customers on the island were without power. UPDATE: Shortly after 1 p.m., an island-wide power outage hit Puerto Rico.

Flash floods and landslides are Fiona’s biggest immediate threat. Due to Fiona’s relatively slow forward speed of 8 mph, rainfall totals of 10 to 20 inches will be widespread in Puerto Rico, and localized totals could exceed 25 inches where Fiona’s strong southerly winds hit the terrain. mountainous. The threat of wind is less in the eastern Dominican Republic, but bands of rain on the west side of Fiona could bring pockets of 4 to 12 inches there.

Fiona’s rains have already taken their toll on the Leeward Islands; St. Claude Matouba Irfa, in the mountains of southwestern Guadeloupe, on Saturday measured a 24-hour rainfall total of 19.85 inches (504.2 mm). One death in Guadeloupe is attributed to Fiona floods.

Forecast for Fiona

Track predictions for Fiona are much simpler now that the hurricane has consolidated. Fiona will experience a classic bend over the next few days, first going through the Mona Pass between Hispaniola and Puerto Rico on a northwest track, then heading north and northeast over time. Members of the forecast ensemble overwhelmingly agree on the curvature, allowing residents of the US East Coast to breathe easier.

The people of Bermuda should take Fiona very seriously. From Monday to Tuesday, Fiona’s arcing path will take her above a zone of very warm sea surface temperatures (SST) of 29 to 30 degrees Celsius (84 to 86°F), or about 1.5 degrees Celsius (2.7 °F), warmer than average. These warm waters extend to an unusual depth with a high heat content, as shown in Figure 1, preventing the cold water from rising to Fiona’s strength. Despite moderate wind shear of around 15 knots and a moderately humid atmosphere (average relative humidity around 60%), Fiona could intensify dramatically as the environment will gradually become humid and the wind shear will be largely aligned with Fiona’s. movement. The 12Z Sunday SHIPS Model DTOPS Intensification Index predicted a 51% chance of Fiona gaining 30mph of sustained wind by Monday morning.

Figure 1. Ocean heat content (OHC) levels on September 18, 2022, with the 5 a.m. EDT advisory positions for Hurricane Fiona overlaid (labeled with the time in hours of the forecast). Fiona will cross a region with high OHC values ​​of 75 to 100 kilojoules per square centimeter (orange colors) for the next three days. OHC values ​​above 75 are very favorable for rapid intensification of hurricanes. (Image credit: RAMMB/CIRA/CSU)

The National Hurricane Center brings Fiona to Category 3 strength (115 mph winds) by Wednesday, which would make it the first major hurricane of the season in the Atlantic. In a typical year (1991-2020), the third hurricane arrives on September 7, the first major hurricane is observed on September 1, and the seventh named storm (not yet observed this year) arrives on September 3, so the 2022 season continues in lag behind climatology.

Despite great confidence in Fiona’s overall curvature, it’s too early to tell if the track will pass east, west or over Bermuda on Thursday night or Friday morning. That said, a direct hit is certainly possible. Fiona has the potential to produce the largest impacts in Bermuda since Hurricane Nicole’s western eyewall passed directly over the island in 2016 when Nicole was a Category 3 storm.

Figure 2. Radar image of Typhoon Nanmadol as it made landfall on the Japanese island of Kyushu, at the head of Kagoshima Bay. (Image credit: Japan Meteorological Agency)

Powerful Typhoon Nanmadol hits Japan

Typhoon Nanmadol made landfall on the Japanese island of Kyushu around 7 p.m. local time (8 a.m. EDT) on Sunday, September 18, near the head of Kagoshima Bay. On landfall, the Joint Typhoon Warning Center (JTWC) classified Nanmadol as a high-end Category 2 storm with winds of 110 mph (1-minute average); the Japan Meteorological Agency (JMA) put Nanmadol winds at 105 mph (10-minute average), with a central pressure of 935 mb. This pressure is tied for fourth among all typhoons to make landfall on mainland Japan in the JMA database, which dates back to 1951.

About an hour later, the eye of the mighty typhoon passed over the city of Kagoshima (population 600,000), but the storm failed to follow the worst-case scenario for a devastating storm surge that pushed into the narrow bay on which the city sits, with the strongest winds in the right front quadrant of the typhoon affecting the coast just east of the bay. The stretch of coast is relatively sparsely populated and it is likely that storm surge damage from the typhoon will end up being less destructive than rain and wind damage.

Extreme rainfall and damaging winds affecting Japan

Typhoon Nanmadol tapped into a tap of intense tropical humidity, and the storm dumped truly prodigious amounts of rain on Japan’s mountainous terrain. At least five stations on the island of Kyushu recorded more than half a meter (19.69 inches) of rain in just 24 hours on Sunday. The highest amount was 694.5 mm (27.34″) at Mikado; the 48-hour rainfall at this station was 830 mm (32.68″). Rains of this magnitude are capable of causing devastating flash floods and mudslides, and Nanmadol will likely cause billions in damage from flooding alone.

Figure 3. Rainfall from Typhoon Nanmadol for the 24 hours ending at midnight Sunday (local time). The highest amount was 694.5 mm (27.34 in) at Mikado. The 48-hour rainfall at this station was 830 mm (32.68″). (Image credit: JMA)

Wind damage will also be significant. When the typhoon passed Yakushima Island, located about 30 miles south of the Nanmadol landing spot on Kyushu, the 10-minute peak hourly average sustained winds were 36.4 m/s (82 mph), with a wind gust of 50.9 m/s (114mph). However, there were few reports of high end sustained wind from some of the airports on the way to the Nanmadol eyewall on Kyushu. For example, the highest sustained winds at Kagoshima city were 18.7 m/s (42 mph), with a wind gust of 43.5 m/s (97 mph). Nevertheless, Nanmadol will subject a huge region of Japan to destructive winds. Sunday’s 11 a.m. EDT advisory from JTWC classified Nanmadol as a high-end Category 1 typhoon with winds of 90 mph, with typhoon-force winds extending up to 85 miles from the center. JTWC predicted that Nanmadol would sustain the typhoon’s strength for another 12 hours, when it was more than 150 miles from its original location in Kyushu. Nanmadol is expected to turn northeast and head straight up Japan’s main island of Honshu, bringing high winds and torrential rains to a remarkably large area of ​​Japan.

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