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Super Typhoon Vongfong Headed Towards Okinawa; 99L May Affect Bermuda

By: Dr. Jeff Masters, 3:53 PM GMT on October 09, 2014

The winds are rising on Japan's Okinawa Island as Earth's most powerful tropical cyclone of 2014, Super Typhoon Vongfong, steams north-northwest at 8 mph. Vongfong peaked in intensity Tuesday with top sustained winds of 180 mph, and had weakened below Category 5 strength with 150 mph winds as of 11 am EDT Thursday, according to the Joint Typhoon Warning Center (JTWC.) The Japan Meteorological Agency showed Vonfong's central pressure rising to 915 mb at 9 am EDT Thursday, from a low of 900 mb on Wednesday. Satellite loops show that Vongfong is still an impressive storm with a large area of heavy thunderstorms and a prominent 30-mile diameter eye, but the cloud tops have warmed since Wednesday, and the area covered by the typhoon's heaviest thunderstorms has shrunk. Vongfong has two concentric eyewalls, and it is likely that the typhoon is undergoing an eyewall replacement cycle, where the inner eyewall will collapse and be replaced by the outer eyewall. This process should cause further weakening today.

Figure 1. Visible VIIRS image of Super Typhoon Vongfong in moonlight as seen at 2:44 pm EDT on October 8, 2014. At the time, Vongfong was a Category 5 storm with 165 mph winds. Image credit: Dan Lindsey, NOAA/NASA and RAMMB/CIRA.

Figure 2. Super Typhoon Vongfong as seen by Astonaut Reid Wiseman from the International Space Station at 7 am EDT October 9, 2014. Image credit: Reid Wiseman.

Okinawa at risk of a direct hit from Vongfong
Vongfong began a turn to the north on Wednesday morning, and is likely to pass over or just to the north of Japan's Okinawa Island near 18 UTC (2 pm EDT) Saturday. With the typhoon moving over waters that will gradually cool, and with wind shear expected to rise to the moderate range, weakening to Category 3 status is likely before Vongfong makes its closest pass by Okinawa. Rapid weakening should ensue as Vongfong approaches the main Japanese island of Kyushu this weekend, with Category 1 strength likely at landfall. In their 00Z Thursday runs, the European and GFS models predicted landfall would occur on Kyushu between 5 pm - 11 pm U.S. EDT time Sunday evening (21 UTC Sunday - 03 UTC Monday.) Heavy rains from Typhoon Vongfong are expected to fall on soils already saturated by Typhoon Phanfone's rains last week, which could lead to much more severe flooding than was observed for Phanfone. Vongfong will also be moving slower than Phanfone was, potentially leading to higher rainfall amounts.

Figure 3. MODIS satellite image of Tropical Storm Hudhud taken at approximately 2 am EDT October 9, 2014. At the time, Vongfong was intensifying and had 70 mph winds. Image credit: NASA.

Dangerous Tropical Cyclone Hudhud a threat to India
It's October, the usual time of year when the Southwest Monsoon over India begins to wane. As the monsoon retreats southwards away from India, its dominance over the atmosphere in the North Indian Ocean's Bay of Bengal weakens, allowing tropical cyclones to form after a four-month period of conditions hostile for tropical cyclone formation. The North Indian Ocean typically has two tropical cyclone seasons: one in May and early June before the arrival of the monsoon, and one in October - November as the monsoon retreats. There was one named storm this year during the first portion of the season: Tropical Storm Nanauk, which formed over the waters of the Arabian Sea on the west side of India on June 10, and dissipated on June 14 without hitting land. The second season is now at hand, as we have Tropical Cyclone Hudhud in the Bay of Bengal. Tropical Cyclone Hudhud was a strengthening tropical storm with 70 mph winds at 11 am EDT Thursday. The storm is under moderately high wind shear of 20 knots, and is over warm waters of 30°C (86°F)--conditions which favor some modest intensification. Satellite loops show a well-organized system with plenty of low-level spiral bands and an increasing amount of heavy thunderstorm activity. With warmer sea surface temperatures ahead of the storm and wind shear expected to be in the 15 - 20 knot range, intensification into at least a Category 2 cyclone appears likely before Hudhud hits the coast of northern Andhra Pradesh and southern Odisha between Visakhapatnam and Gopalpur on Sunday, October 12, between 00 - 06 UTC. Odisha was struck in 2013 by Category 4 Tropical Cyclone Phailin, which killed 45 people and did $700 million in damage. This death toll was extremely low, considering this is a region where 10,000 people died in a similar-strength cyclone in 1999. The India Meteorological Department (IMD) provided excellent early warning information for Phailin. On Thursday morning (U.S. EDT time), IMD was forecasting that Hudhud would have sustained winds of 130 - 140 kph (81 - 87 mph) at landfall, making it a strong Category 1 storm. JTWC was forecasting a stronger storm--Category 3 with 120 mph winds. IMD predicted a storm surge of 1 - 2 meters (3.3 - 6.6 feet) would occur near and to the right of where the center makes landfall.

Latest Hudhud warnings for India from the India Meteorological Department (IMD)
Latest Hudhud advisory from the India Meteorological Department (IMD).
India radar from Machilipatnam.

Figure 4. Latest satellite image of Invest 99L in the Western Caribbean.

Invest 99L in the Atlantic a possible threat to Bermuda
An area of disturbed weather associated with an upper-level cold-cored low pressure system, located a few hundred miles northeast of Puerto Rico on Thursday morning, was designated Invest 99L by the National Hurricane Center on Thursday morning. Invest 99L was headed northwest to north-northwest at about 10 mph. Satellite loops showed plenty of spin, since 99L was associated with a non-tropical low pressure system that had already established a vigorous circulation. 99L's heavy thunderstorms were poorly organized and limited to the east side of the center, due to strong upper-level winds from the west pushing dry air into the system. Sea Surface Temperatures (SSTs) were warm, near 29°C (84°F), and wind shear was moderate, 5 - 15 knots. Tthese conditions are favorable for development, but disturbances getting their start from a cold-cored upper level low like 99L have plenty of cold, dry air aloft, which retards development into a tropical system. The 8 am Thursday run of the SHIPS model predicted that conditions would remain favorable for slow development through Saturday, with moderate wind shear, a moist atmosphere, and SSTs near 29°C (84°F.) On Sunday, wind shear will rise above 25 knots and the atmosphere will dry, limiting the chances for development. One of our three reliable computer models for predicting tropical storm formation, the European, showed 99L developing in its 00Z Thursday run, and passing very close to Bermuda by Sunday evening. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 99L 2-day and 5-day development odds of 30% and 40%, respectively. An Air Force hurricane hunter aircraft has been tasked to investigate 99L on Friday afternoon, if necessary.

At longer ranges, both the GFS and European models show development of Atlantic tropical depressions in 6 - 10 days, though they don't agree on where these storms might occur (the GFS develops something over the Bahamas, while the European model develops a tropical wave between the Lesser Antilles Islands and Africa.) While 6 - 10 day genesis forecasts are not to be trusted, the fact that both of these models are showing developing systems is an indication that the large-scale atmospheric conditions that have suppressed tropical storm formation during the 2014 Atlantic hurricane season may ease some next week, possibly due to the influence of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days.

Wunderblogging hurricane expert Steve Gregory has more on the tropics in his Thursday afternoon post.

Jeff Masters


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