An unusual Atlantic hurricane season fittingly has an oddball first hurricane: Hurricane Danielle, which became a category 1 hurricane with 75 mph winds at 11 a.m. EDT Friday, about 885 miles west of the Azores Islands. Danielle intensified by 35 mph in the 24 hours ending at 11 a.m. EDT Friday, meeting the National Hurricane Center’s minimum definition of rapid intensification.
Update: As of 11 a.m. EDT Saturday, Danielle’s top winds were down to 70 mph, making it a tropical storm. Danielle was moving at just 2 mph and churning up cooler waters. Danielle is predicted to regain hurricane strength on Sunday as it begins a gradual acceleration toward the north and northeast.
Danielle became a hurricane unusually far to the north – near 38°N, at one of the most northeasterly locations on record for the season’s first hurricane to form (see Tweet below by Tomer Burg).
Danielle took advantage of sea surface temperatures (SSTs) that were record warm for so far north: about 27 degrees Celsius (81°F), 1-2 degrees Celsius (1.8-3.6°F) above average for this time of year (see Tweet below by Michael Lowry).
Danielle’s intensification into a hurricane on September 2 comes about three weeks later than the usual appearance of the season’s first hurricane, according to the 1991-2020 climatology, and is the latest date for the appearance of a season’s first hurricane since 2013 (Humberto, on September 11). Typically, by September 3, the Atlantic has spawned 7 named storms, 2 hurricanes, and 1 intense hurricane. This year (on September 2), we are at 4 named storms and 1 hurricane, with an accumulated cyclone energy (ACE) index just 9% of average.
Danielle became a hurricane 332 days later than the Atlantic’s previous hurricane (Sam, on October 5, 2021). According to Aon’s Steve Bowen, this period is the third-longest without an Atlantic hurricane since the satellite era began in 1965.
To help understand the reasons for this year’s quiet Atlantic hurricane season, check out the excellent Tweet below by Jeff Berardelli.
Satellite images on Friday afternoon showed Danielle had formed an eye surrounded by intense thunderstorms steadily growing in intensity and areal coverage.
Forecast for Danielle
Danielle is predicted to have favorable conditions for strengthening through Sunday – especially startling given its high latitude – with light-to-moderate wind shear of 5-15 knots and SSTs holding steady near 27 degrees Celsius. The main impediment to intensification may be some dry air at mid-levels of the atmosphere. NHC predicts Danielle will peak as a category 2 hurricane with 100 mph winds on Sunday and Monday, as it meanders generally northeastward at less than 5 mph, far from any land areas. By Tuesday, Danielle is predicted to cross into cooler waters and begin experiencing moderate-to-high wind shear, causing a weakening trend. The hurricane’s final fate is unclear, with an eventual track towards Greenland or Europe both possible. Update: As of the 11 a.m. EDT Saturday forecast, Danielle is now predicted to peak as a category 1 hurricane on Monday.
91L in the central Atlantic struggling with dry air
A tropical wave a few hundred miles east of the Leeward Islands in the Lesser Antilles continues to struggle with dry air. At 12 p.m. EDT Friday, the disturbance, which NHC designated as 91L, was headed west-northwest at roughly 10 mph. 91L had warm sea surface temperatures of 29 degrees Celsius (84°F), with light wind shear of 5-10 knots favorable for development. Satellite images showed the system had a broad surface circulation and only a moderate amount of heavy thunderstorms. 91L was surrounded on three sides by a large area of dry air.
Forecast for 91L
The clockwise flow of air around the Bermuda-Azores High to the north of 91L will impart a west-northwesterly track to the system for at least the next three days, and the latest forecasts from the GFS and European models show 91L passing a few hundred miles north of the Leeward Islands on Saturday and Sunday. If 91L continues on this west-northwesterly track, it will encounter the shearing winds of a tropical upper-tropospheric trough (TUTT) by Tuesday, with high wind shear continuing during the week. This high wind shear will likely limit development of 91L, though some members of the latest GFS and European model ensemble forecasts show 91L eventually becoming a hurricane.
If 91L remains weak, a continued west-northwesterly track into the Turks and Caicos Islands and the southeastern Bahamas is a good possibility; if 91L develops into a tropical storm, the steering currents will favor a sharp recurvature of the storm to the north and northeast, before it can reach the islands. In an 8 a.m. EDT Friday Tropical Weather Outlook, NHC gave 91L two-day and five-day odds of formation of 50% and 70%, respectively. Update: 91L went directly from “invest” status to become Tropical Storm Earl at 11 p.m. Friday, with top sustained winds of 40 mph. As of 11 a.m. EDT Saturday, NHC was predicting that Earl would recurve well east of the Bahamas and well south of Bermuda as a weak to moderate tropical storm.
Tropical wave 94L in the far eastern Atlantic disorganized
A tropical wave designated Invest 94L, a few hundred miles northwest of the Cabo Verde Islands, has become disorganized, with very little heavy thunderstorm activity. The wave is moving into a region with drier air and higher wind shear, likely ending its prospects for development. In an 8 a.m. EDT Friday Tropical Weather Outlook, NHC gave the wave two-day and five-day odds of formation of 10%. Update: NHC has discontinued mention of 94L in its Tropical Weather Outlook as of Friday evening.
Hinnamnor regrouping in Northwest Pacific before potential landfall in South Korea
Former Category 5 Super Typhoon Hinnamnor weakened dramatically on Friday local time, but it was beginning to reorganize by Friday night and remained a significant threat to parts of eastern Asia, particularly South Korea. According to the Joint Typhoon Warning Center (JTWC), as of 12Z (8 a.m. EDT) Friday, September 2, 2022, Hinnamnor was about 300 miles southeast of Taipei, Taiwan, far enough away to keep its destructive winds well east of the island but close enough to deliver heavy rain.
Hinnamnor had begun heading north at 4 mph on Friday night local time after being virtually stuck in place for 24 hours, marooned between competing steering forces.
As it upwelled cooler waters during its stall and experienced strong northerly wind shear, Hinnamnor’s structure deteriorated markedly, with its eye filling in and its shield of convection becoming disorganized. As of 12Z Friday, Hinnamnor had weakened to the equivalent of Category 1, with top winds of 90 mph.
Forecast for Hinnamnor: Restrengthening and acceleration
Hinnamnor will accelerate north through the weekend as an approaching mid-latitude upper trough becomes the main steering feature. The upper flow will provide improved ventilation for the typhoon as it travels at an increasingly brisk pace over very warm SSTs of around 30 degrees Celsius (86°F) throughout the weekend. Wind shear is predicted to drop to around 10-15 knots, and Hinnamnor will be moving through a very moist environment, with mid-level relative humidity of around 80%.
All these factors should enable Hinnamnor to regain at least category 2 strength. Even category 3 strength, as predicted by JTWC and by some runs of the HWRF model, is a distinct possibility by late Sunday local time.
A strengthening Hinnamnor will pass near Ishigaki and the sparsely populated Miyako Islands, both part of Japan’s Ryukyu Islands, late Saturday. Toward Monday, the eastern parts of Hinnamnor’s circulation may affect Japan’s large western island of Kyusho.
Update: As of 8 a.m. EDT Saturday, Hinnamnor had restrengthened to peak sustained winds of 100 mph, making it a category 2 equivalent. Hinnamnor was about to pass over tiny Tarama Island, in between Ishigaki and Miyako islands. The typhoon is still predicted to reach category 3 strength, peaking around 120 mph late Sunday and Monday local time before nearing South Korea as discussed below.
Models tracking Hinnamnor are in close agreement that it will angle north-northeast just before approaching South Korea late Monday or early Tuesday local time, perhaps weakening in its last few hours of approach. Such a track would bring Hinnamnor over or near the city of Busan in southeasternmost South Korea, most likely as a sprawling Category 2 storm with torrential rains, widespread damaging winds, and a substantial storm surge. Only five typhoons of major-hurricane strength (Category 3 or stronger) are on record as passing within 100 nautical miles (115 miles) of Busan. Typhoon Maemi (2003) – which made landfall with top sustained winds of 105 mph, according to JTWC, and 120 mph – was the strongest cyclone to strike South Korea since Typhoon Sarah of 1959 (top sustained winds at landfall 115 mph) in records dating back to 1904.
A potentially dangerous storm for the eastern Pacific brewing
In the eastern Pacific a few hundred miles south of the southern coast of Mexico lies a broad region of low pressure, which NHC has designated as Invest 93E. This system has the potential to develop into a dangerous tropical storm or hurricane that could bring heavy rains to the Pacific coast of Mexico as early as Monday. The disturbance has favorable conditions for development, with moderate wind shear near 10 knots, warm SSTs near 29 degrees Celsius, and a moist atmosphere with a mid-level relative humidity near 75%.
The top models for hurricane genesis have been very bullish on development of this disturbance for an unusually long time, and it’s easy to see why, looking at the latest output from the 12Z Friday run of the SHIPS model: Nearly ideal conditions are predicted on Monday, with SSTs a very warm 30 degrees Celsius (86°F), light wind shear less than 5 knots, and a ridiculously high mid-level relative humidity, near 90%. The 6Z and 12Z Friday runs of the GFS model show 93L becoming a hurricane, as do many of its ensemble members.
In an 8 a.m. EDT Friday Tropical Weather Outlook, the National Hurricane Center gave 93L 2-day and 5-day odds of development of 50% and 80%, respectively. The next name on the eastern Pacific list of storms is Kay. Update: As of 8 a.m. EDT Saturday, the 2- and 5-day odds of development for 93L had risen to 90% and 90%.
A new post on the tropics is not planned for Saturday, September 3; any significant developments will be addressed in the current post using the tag, “UPDATE”.
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