Typhoon Hinnamnor powered ashore on South Korea’s southeastern coast, near Busan (population 3.4 million), around 5 p.m. EDT September 5 (6 a.m. local time). Just before landfall, the Joint Typhoon Warning Center (JTWC) rated Hinnamnor as a category 3 storm with 105 mph winds (1-minute average, as is typically used in the Atlantic); the Japan Meteorological Agency put Hinnamnor’s winds at 80 mph (10-minute average).

In JTWC records going back to 1945, Hinnamnor is the fourth-strongest typhoon to hit South Korea. JTWC does not assign landfall intensities to typhoons, instead using the last intensity before landfall.

Busan’s airport reported peak sustained winds of 43 mph, gusting to 74 mph in the weaker left eyewall of Hinnamnor near the time of landfall. As reported in koreaherald.com, Hinnamnor brought torrential rains to South Korea’s Jeju Island, which received 1,058 mm (41.69 inches) from September 4-6. On mainland South Korea, Gyeongju recorded 447.5 mm (17.62 inches); Pohang, 418.2 mm (16.46 inches); and Ulsan City, 385.5 mm (15.18 inches). Flooding and landslides from the typhoon’s torrential rains are the most serious impacts so far reported from the storm, with two people killed and 10 missing as of noon EDT Tuesday, according to the New York Times.

After battering South Korea, Hinnamnor cruised into the Sea of Japan, moving close to and roughly parallel with the coast of Russia, as a strong extratropical storm with winds near 75 mph. Tropical cyclones are rare visitors to Russia; the nation’s Sea of Japan coast has been hit by just 10 tropical storms and one typhoon since 1945, according to JTWC data.

Earl could become year’s first major Atlantic hurricane

The main story in the Atlantic on Tuesday was Tropical Storm Earl, which likely will be a potent hurricane by late this week. As of 11 a.m. EDT Tuesday, Earl’s top sustained winds were holding at 65 mph, as the storm continued drifting northward at 5 mph between the Virgin Islands and Bermuda.

Strong upper-level winds out of the west-southwest were creating about 30 knots of wind shear over Earl, pushing convection mainly to the east of its center and throwing the vertical structure of the storm out of alignment. Despite this, Earl has managed to maintain its overall integrity, with the help of a moderately moist environment (mid-level relative humidity of 55-60%) and warm sea surface temperatures (SSTs), around 29 degrees Celsius (84°F). There’s also a modest amount of oceanic heat content helping to reduce cool upwelling from Earl’s slow-moving circulation.

Wind shear should abate along Earl’s track later this week as the storm accelerates northeastward with the steering flow. That should give it a window for intensification from around Wednesday night to Saturday, before shear intensifies dramatically and Earl begins tracking over much cooler water. The HWRF and HMON intensity models have consistently projected Earl at category 3 strength by Friday or Saturday as it moves into the unusually warm area between 30-40°N. The National Hurricane Center’s forecast brings Earl to a category 3 peak on Friday.

Forecast models have been nudging Earl’s track leftward in recent runs, suggesting the weaker left-hand side of Earl’s circulation will come closer than earlier thought to Bermuda on Thursday night and Friday. It appears increasingly likely that Earl’s outer rainbands could affect the island with heavy rains and squally conditions. As of 11 a.m. EDT Tuesday, NHC gave Bermuda a 60% chance of sustained winds approaching or reaching tropical storm strength (39 mph) late this week. Only a few GFS and European model ensemble members bring Earl close enough for more significant impacts. For the time being, with Earl more than two days away from its nearest approach to Bermuda, there are no watches or warnings in effect.

Danielle continues at hurricane strength in central North Atlantic

The year’s first Atlantic hurricane remained robust on Tuesday at an unusually high latitude. At 11 a.m. EDT, Hurricane Danielle was about 805 miles west-northwest of the Azores at latitude 42.2 north, packing top sustained winds of 75 mph. Danielle will cross into waters colder than 25 degrees Celsius (77°F) on Wednesday as it accelerates east-northeast across the open Atlantic. Danielle is predicted to become post-tropical on Thursday without affecting any land areas, though its post-tropical incarnation could angle leftward and sweep toward Europe next week.

Two more tropical waves to watch

A tropical wave just west of the Cabo Verde Islands on Tuesday morning was headed westward to west-northwestward at 15-20 mph. This wave, which had not yet received an “Invest” designation by NHC, has generally favorable conditions for development, and is likely to become a tropical depression by late this week. Fortunately, the wave is predicted to move into a region of the central Atlantic where few tropical cyclones ever end up making it to North America, and long-range predictions from the GFS and European model ensembles unanimously show that this wave will recurve to the north by early next week. In its 8 a.m. EDT Tuesday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 40% and 60%, respectively. The next name on the Atlantic list of storms is Fiona.

A new tropical wave is predicted to emerge from the coast of Africa by Thursday, but no indications from the models suggest this wave will end up a concern for any land areas. In its 8 a.m. EDT Tuesday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 0% and 20%, respectively.

Hurricane Kay threatens Baja

Tropical Storm watches and warnings are up for much of Mexico’s Baja Peninsula as Hurricane Kay steams northwestward over the warm waters of the eastern Pacific. At 11 a.m. EDT Tuesday, category 1 Hurricane Kay was 340 miles south of the southern tip of Mexico’s Baja Peninsula, headed northwest at 14 mph, with top winds of 85 mph. Satellite images showed Kay as a large storm, with tropical storm-force winds that extended out 175 miles from the center.

Kay has favorable conditions for intensification, with moderate wind shear of 10-20 knots, warm SSTs near 29 degrees Celsius (84°F), and a moist atmosphere with a mid-level relative humidity near 80%. Kay is predicted to reach category 3 status by Wednesday night, as it passes about 200 miles west of the southern tip of the Baja Peninsula.

On Thursday, the storm will encounter sharply lower sea surface temperatures associated with the cold, southward-flowing California Current. These cooler waters should substantially weaken the system, and Kay is expected to be a borderline tropical storm/category 1 hurricane when it makes its closest approach to the central Baja Peninsula on Thursday night and Friday morning. The main threat from Kay is likely to be flooding from heavy rains: 4-8 inches of rain are predicted over western Mexico along Kay’s path.

Kay’s impact on Southern California

As Kay heads north this weekend, the clockwise flow of air around a high-pressure system bringing a record heat wave to California will force Kay to turn to the west before it can reach California. On Sunday, Kay will likely die over the chilly 21-degree Celsius (70°F) waters to the southwest of the California/Mexico border.

Moisture from Kay could push into extreme Southern California beginning on Friday afternoon, potentially bringing an inch or so of rain to the drought-baked region (though the latest 12Z run of the GFS model predicted the potential for damaging flooding rains of 4-5 inches inland near the California/Mexico border, see Tweet below by Kieran Bhatia). Although rain would be welcome, any strong offshore winds or dry lightning from this system could enhance the wildfire threat across parts of the region, where a record heat wave has made vegetation dangerously combustible. In its 11 a.m. EDT Tuesday wind probability forecast, NHC gave San Diego a 5% chance of experiencing tropical storm-force winds from Kay.

Tropical cyclones are rare visitors to California. Since 1850, Southern California has experienced gale-force winds from seven tropical cyclones or their remnants. Most notable were a September 1939 tropical storm that hit near Long Beach and an 1858 hurricane that passed very near San Diego.

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