Fiona spreads heavy rain in the Leeward Islands; Super Typhoon Nanmadol targets Japan » Yale Climate Connection

Tropical storm warnings were in effect for the Leeward Islands, the Virgin Islands and Puerto Rico on Friday afternoon as Tropical Storm Fiona began spreading heavy rain to the islands. As of 11 a.m. Friday, Fiona was packing 50-mph winds and was moving to the west at 14 mph, about 135 miles east of Leeward. The first heavy rain from the storm had already arrived in the islands, as seen Guadeloupe Radar,

Fiona is surrounded by a large area of ​​dry air, and satellite images Friday afternoon showed little change in Fiona over the past 24 hours: the center of circulation was exposed for viewing, with heavy thunderstorms confined to the east side of the center. This condition occurred because a moderate 10-20 knots wind shear was bringing dry air to its core on the west side of Fiona. However, there was more intense thunderstorm activity near Fiona’s core than on Thursday, an indication that the shear had reduced somewhat. Sea surface temperature (SST), warmer than Thursday, was about 29.5 °C (85 °F) – about 0.5 °C (0.9 °F) higher than the average for this time of year.

Figure 1. Track 10 day forecast for Fiona from 6Z Friday, September 16 of the GFS ensemble model. The 31 ensemble members’ individual forecasts are the lines they color-coded with the wind speed in knots predicted for Fiona; The red colors correspond to Category 1 hurricanes. The heavy black line is the mean prediction of the ensemble. The time in hours is in gray text from the model initialization time. The fate of Fiona’s long-distance was unclear, with most of the ensemble predicting a recurrence to the northeast, but several members showing a potential threat to the US East Coast. (image credits:,

Fiona. forecast for

The primary threat from Fiona over the next three days will be heavy rain causing flash floods. Eastern Puerto Rico (4-8 inches of rain predicted) and the eastern Dominican Republic (6-10 inches) are particularly at risk. Even moderate-strength tropical storms can cause devastating flooding when they pour torrential downpours over already saturated soil. Tropical Storm Erica in 2015, with extreme winds that never exceeded 50 mph, up to a foot of rain lashed Dominica, causing devastating flooding that killed 35 people and caused more than $500 million in damage. Erica was one of only two tropical storms whose name was retired.

Moderate to moderate conditions are forecast for Fiona to strengthen early next week, as sustained moderate wind shear of 10-20 knots is expected to drive dry air across the core of the system. Over the weekend, however, Fiona will be moving into a humid environment with more favorable upper-level winds, which could allow the storm to become a Category 1 hurricane before its expected landfall in the Dominican Republic on Sunday night or Monday morning. Is.

This landfall is expected to result from a change in steering currents, which will result in the passage of a trough of low pressure as it moves further along the US East Coast. If Fiona remains weaker than expected, this northwest turn will be delayed and less sharp than the National Hurricane Center predicted.

Fiona’s encounter with the rugged terrain of Hispaniola will disrupt the storm, but models insist that the disruption will be temporary, and the official NHC forecast brings Fiona to hurricane strength on Tuesday, when it nears the Turks and Caicos Islands. is expected to be. and southeastern Bahamas. However, Fiona could be very vulnerable if her encounter with Hispaniola proves to be more disruptive than predicted.

Later in the week, Fiona became a threat to Bermuda or the US East Coast. It remains to be seen whether the low pressure trough that turns Fiona to the northwest will be strong enough to turn the storm northeast and out to sea, as the GFS model is predicting. The 0Z Friday run of European models predicted that Fiona would not return next week, but would instead be trapped south of a ridge of high pressure that would form to the north, forcing Fiona toward the US East Coast. stay tuned.

Figure 2. Super Typhoon Nanmadol forecast from the Joint Typhoon Warning Center on Friday, September 16, 2022 at 11 a.m. EDT.

A serious threat to Japan: Super Typhoon Nanmadol

In the Pacific Northwest, Super Typhoon Nanmadol exploded into a powerful Category 4 hurricane with gusts of 150 mph on Friday, and is set to deliver a devastating blow to Japan over the weekend.

Nanmadol intensified to 70 mph in the 24 hours ending at 8 a.m. Friday, and was moving to the northwest at 9 mph, according to the Joint Typhoon Warning Center (JTWC). 12pm EDT update Japan Meteorological Agency Keep the intensity at Nanmadol at 110 mph (10-minute average sustained winds), with a very low central pressure of 925 mb.

satellite images Friday afternoon (US EDT) showed a very large and impressive storm, with a prominent 13-mile-diameter eye surrounded by very cold clouds. According to JTWC, Nanmadol’s large size was allowing it to generate huge waves up to 52 feet high. rainwater imagery showed that Nanmadol was pulling in moisture from a vast area of ​​the northwestern Pacific, including a plume of water vapor more than 2,000 miles long, coming in thunderstorms from Southeast Asia and across the Philippines. This tremendous spigot of water vapor will enable Nanmadol to release massive amounts of rain over Japan this weekend, and the rainfall forecast there is worrisome.

Figure 3. 0Z Friday, September 16, European model running forecast for Japan, 0Z for the five-day period ending Wednesday, September 21. The model predicted extensive areas of 12+ inches (300 mm) of rain (purple) over Japan from Typhoon Nanmadol. (Image credit:
Figure 4. Total precipitated water on Friday, September 16 at 10 a.m. EDT, a plume of moisture originating from 2,000 miles away being drawn into Super Typhoon Nanmadol. (image credits: University of Wisconsin SSEC,

With sea surface temperatures of 29–30 °C (84–86 °F), mild wind shear of 5–10 knots, and a humid atmosphere, Nanmadol had favorable conditions for intensification. The Joint Typhoon Warning Center in an 11 a.m. EDT advisory called for Nanmadol to peak just below Category 5 strength on Friday night with gusts of 155 mph. Weakening is expected thereafter due to high wind shear, cooling sea surface temperatures and contact with the landmass of southern Japan. Nanmadol is predicted to be a borderline Category 2 or 3 hurricane by possible landfall on Sunday on Kyushu, southwest of Japan’s four main islands. Large-scale storms are forecast (Figure 2) to bring at least tropical-storm force winds to all of Kyushu and more than 95% of Japan’s main island of Honshu, as the storm is worst along the length of both islands. Tracks the status. Torrential rains and devastating floods will affect a large part of southern Japan later this week. The potential for storm surge and wind damage near the landfall location of Nanmadol in Kyushu will be severe, and the storm has the potential to be a multi-billion dollar disaster for Japan.

X-Meerbok brings high surf, high wind to Alaska

The Post-Tropical Cyclone that was Typhoon Merbok two days ago crossed Alaska’s Aleutian Islands and entered the Bering Sea early Thursday morning, bringing winds of 81 mph over Adak Island. On Friday, winds of up to 100 mph are possible in open areas of the Bering Sea and waves up to 54 feet are likely. The west coast of mainland Alaska is plastered Coastal Flood Alert And strong wind warnings.

As of Friday morning, Maribok’s central pressure had dropped to 937 millibars, a rate achieved only at sea level by intense tropical or extra-tropical cyclones. National Weather Service (NWS) meteorologist Jonathan Christ, no other Bering ocean storm in September is known to have a central pressure below 960 MB. told CNN, The year-long record for the Bering Sea in November 2014 is 924 MB, as noted by Christopher Burt. review One of the most intense storms in the Bering Sea.

Ex-Meerbok’s powerful winds and rapid northward motion have pulled a ribbon of tropical moisture into subpolar latitudes (see tweet below). Precipitated water within this narrow ribbon, or the amount of water vapor above a given point, was above 1.5 inches in the southern Bering Sea, which is close to the mid-September mean value in Charleston, South Carolina.

In Nome, Alaska, a southerly flow from east-Meerbok will push a major storm surge into the coast Friday night. It is estimated to be between 11 and 12 feet, depending on time, which would combine with the celestial tide to produce the storm tide. Predicted by NOAA on Friday Getting as high as 12.24 feet overnight. Many roads and structures will be flooded, NWS warning, The 8.6-foot rise from the devastating storm in the U.S. will well exceed November 2011, perhaps just short of the 13-foot surge seen in November 1974, the city’s strongest storm on modern record. Some level of buoyancy can raise the Cuscokwim River to Bethel, which is 50 miles inland from Cuscokwim Bay.

With post-tropical Merbok arriving so early in the fall season, there will be no sea ice to help protect the Bering Sea coast from buoyancy and erosion.

Figure 5. INVESTMENT 94E (left) and Tropical Storm Lester (right) at 1330Z (9:30 a.m. EDT) on Friday, Sept. 16, 2022. (image credits: RAMMB / CIRA / CSU,

Tropical Storm Lester is headed for the Pacific Coast of Mexico

A new tropical depression that formed off the Pacific coast of Mexico Thursday afternoon became Tropical Storm Lester on Friday morning. Leicester’s top sustained winds were only around 40 mph. 11 a.m. EDT Friday, A direct steering flow will push Lester to the northwest toward an expected landfall off the coast of Guerrero state late Saturday, perhaps near or west of Acapulco. This track and time will give Lester only 36 hours to strengthen, and an easterly wind shear of 15-20 knots will keep any intensification slow. At least some strengthening is expected, however, given a warm SST of about 29 °C (84 °F) and an extremely humid environment (mid-level relative humidity of 85 percent). The most likely outcome, predicted by HWRF and HMON intensity models and reflected in NHC forecasts, is for Lester to make landfall as a strong tropical storm. Rainfall of 3 to 6 inches, perhaps up to 10 inches, can cause localized flash floods and mudslides.

Another East Pacific tropical disturbance – Investment 94E located west of Leicester – will draw on similarly rich moisture and warm waters, but will suffer from strong wind shear of 25-30 knots until at least Sunday. As the shear ends, 94E could reach tropical storm strength; However, it is expected to remain well offshore.

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