WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.East and West Pacific Tropical Cyclone Seasons Begin With a Bang
The longest tropical cyclone-free period in Northwest Pacific history--200 days--ended on Saturday July 3, with the formation of Tropical Storm Nepartak in the waters just south of Guam. The previous tropical cyclone in the basin was Typhoon Melor , which fell below tropical storm strength on December 16, 2015. According to Colorado State University hurricane expert Dr. Phil Klotzbach, the previous longest tropical cyclone drought in the Northwest Pacific was two days shorter--198 days--during December 1972 - June 1973. The July 3 start date for the 2016 season's first named storm is the second latest start date in the 66-year period of record. Only 1998, with a July 8 start date, had a later start. All three of these late-starting years--2016, 1998, and 1973--featured strong El Niño conditions transitioning to neutral or La Niña conditions later in the year. The upper-level atmospheric circulation associated with such a transition brings an unfavorable environment for tropical cyclones--sinking air, surface high pressure, and dry conditions. Surface pressures over the past month in the waters east of the Philippines extending to the date line have been 0.5 - 1.5 mb above average.
Figure 1. Tropical Storm Nepartak (70 mph winds) at 23 UTC July 4, 2016. Image credit: NOAA.
Nepartak a potential threat to Taiwan, China, South Korea, and Japan
Nepartak was headed northwest at 22 mph on Monday evening on a track that will take it very close to the northern portion of Taiwan by Thursday afternoon (U.S. EDT.) At that time, a trough of low pressure passing to the north of the storm may pull the storm to the north and then northeast, potentially allowing Nepartak to affect the Chinese coast just south of Shanghai, South Korea, and/or Southwest Japan late this week. Nepartak is over very warm ocean waters of 31°C (88°F) with moderate wind shear of 10 - 15 knots. On Tuesday, Nepartak will cross over a region of ocean with very high heat content, and wind shear is expected to drop to the low range, 5 - 10 knots. These nearly ideal conditions for intensification will likely allow the storm to strengthen into a major Category 3 typhoon by Wednesday.
The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.
Figure 2. MODIS visible satellite image of Hurricane Blas taken on the afternoon of July 3, 2016. At the time, Blas was a Category 1 storm with 75 mph winds. Image credit: NASA.
Second latest start to the Eastern Pacific hurricane season on record
It's also been a near-record late start to the Eastern Pacific hurricane season, which finally got its first named storm on July 2 when Tropical Storm Agatha formed in the waters over 1000 miles south of the tip of Mexico's Baja Peninsula. Agatha's formation made 2016 the second latest-starting Eastern Pacific hurricane season (east of 140°W) since accurate satellite records began in 1971. The latest first tropical storm on record was Tropical Storm Ava of 1969, which strengthened to a tropical storm at 00 UTC on July 3. Agatha has now been joined by Hurricane Blas, which spun into life on July 3 about 700 miles south of the southern tip of the Baja Peninsula. Agatha and Blas are likely to be joined by Tropical Storm Celia late this week, since both the European and GFS models predict that an area of disturbed weather located several hundred miles south of Acapulco, Mexico will develop. In their 8 pm EDT Monday Tropical Weather Outlook, NHC gave this new disturbance 2-day and 5-day odds of development of 0% and 70%, respectively. Agatha and Blas are not a threat to any land areas, but Hawaii should keep an eye on the disturbance expected to become Celia. Steering currents next week may favor a more westerly track than Agatha and Blas are taking.
Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss, and none of the reliable models for tropical cyclone formation is predicting development during the remainder of the week. Much of the tropical North Atlantic is dominated by a large area of dry air and dust from the Sahara Desert, which is common in early July.
I'll have a new post on Wednesday.
Jeff Masters
Figure 1. Tropical Storm Nepartak (70 mph winds) at 23 UTC July 4, 2016. Image credit: NOAA.
Nepartak a potential threat to Taiwan, China, South Korea, and Japan
Nepartak was headed northwest at 22 mph on Monday evening on a track that will take it very close to the northern portion of Taiwan by Thursday afternoon (U.S. EDT.) At that time, a trough of low pressure passing to the north of the storm may pull the storm to the north and then northeast, potentially allowing Nepartak to affect the Chinese coast just south of Shanghai, South Korea, and/or Southwest Japan late this week. Nepartak is over very warm ocean waters of 31°C (88°F) with moderate wind shear of 10 - 15 knots. On Tuesday, Nepartak will cross over a region of ocean with very high heat content, and wind shear is expected to drop to the low range, 5 - 10 knots. These nearly ideal conditions for intensification will likely allow the storm to strengthen into a major Category 3 typhoon by Wednesday.
The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.
Figure 2. MODIS visible satellite image of Hurricane Blas taken on the afternoon of July 3, 2016. At the time, Blas was a Category 1 storm with 75 mph winds. Image credit: NASA.
Second latest start to the Eastern Pacific hurricane season on record
It's also been a near-record late start to the Eastern Pacific hurricane season, which finally got its first named storm on July 2 when Tropical Storm Agatha formed in the waters over 1000 miles south of the tip of Mexico's Baja Peninsula. Agatha's formation made 2016 the second latest-starting Eastern Pacific hurricane season (east of 140°W) since accurate satellite records began in 1971. The latest first tropical storm on record was Tropical Storm Ava of 1969, which strengthened to a tropical storm at 00 UTC on July 3. Agatha has now been joined by Hurricane Blas, which spun into life on July 3 about 700 miles south of the southern tip of the Baja Peninsula. Agatha and Blas are likely to be joined by Tropical Storm Celia late this week, since both the European and GFS models predict that an area of disturbed weather located several hundred miles south of Acapulco, Mexico will develop. In their 8 pm EDT Monday Tropical Weather Outlook, NHC gave this new disturbance 2-day and 5-day odds of development of 0% and 70%, respectively. Agatha and Blas are not a threat to any land areas, but Hawaii should keep an eye on the disturbance expected to become Celia. Steering currents next week may favor a more westerly track than Agatha and Blas are taking.
Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss, and none of the reliable models for tropical cyclone formation is predicting development during the remainder of the week. Much of the tropical North Atlantic is dominated by a large area of dry air and dust from the Sahara Desert, which is common in early July.
I'll have a new post on Wednesday.
Jeff Masters
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