US JTWC: 'Rolly' to become super typhoon before Luzon landfall


Posted at Oct 29 2020 10:03 PM | Updated as of Oct 30 2020 12:06 AM

US JTWC forecast track of Tropical Cyclone Rolly (international name Goni).

'Rolly' passage may trigger Tropical Cyclone Wind Signal No. 4, PAGASA says

MANILA (UPDATED) - Tropical cyclone Rolly (international name Goni) will intensify into a super typhoon before its landfall over Luzon, the US military weather agency said Thursday.

The tropical cyclone, which is currently brewing east of the Philippines, will reach peak strength at 130 knots (240.76 kilometers per hour) maximum sustained winds and gusts reaching 160 knots (more than 296 kilometers per hour) on October 31, the United States Navy – United States Air Force Joint Typhoon Warning Center (JTWC) said.

The US JTWC classifies typhoons with wind speeds of at least 130 knots, which are equivalent to a Category 4 storm in the Saffir-Simpson scale—as super typhoons. Its readings are based on one-minute average measurements of sustained winds.

This is different from the tropical cyclone intensity scale used by the Philippine state weather bureau PAGASA, which makes readings based on 10-minute average measurements of sustained winds.

As a result, the US JTWC's wind readings are higher than PAGASA's measurements.

Himawari-8/US NOAA image

The US JTWC said Rolly, which is currently packing maximum sustained winds of nearly 130 kph based on 1-minute average readings, is still rapidly intensifying but is expected to slightly weaken before it makes landfall over eastern Luzon.

Central Luzon-Quezon area landfall likely

PAGASA's latest advisory Thursday night said Rolly rapidly strengthened into a typhoon as it entered the Philippine area of responsibility (PAR).

It added that the typhoon is forecast to move west-southwestward or southwestward Friday until Saturday evening. The typhoon will then turn more west-northwestward as it moves over the sea off the coast of Bicol Region towards the eastern coast of Central Luzon-Quezon area. 

On the forecast track, the center of the eye of “ROLLY” is likely to make landfall over the Central Luzon-Quezon area on Sunday evening or Monday morning, PAGASA said.

The state weather bureau said Rolly is forecast to continuously intensify over the Philippine Sea and is likely to make landfall at peak intensity of 165-185 kph, based on 10-minute average measurements of sustained winds.

From Thursday night until Friday morning, the trough of the typhoon will bring light to moderate with at times heavy rains over Bicol Region, Eastern Visayas, Central Visayas, and Caraga, PAGASA said. The rainbands of the typhoon will likely bring rains over Bicol Region and the eastern section of Northern and Central Luzon beginning on Saturday or Sunday.

In anticipation of the arrival of strong to near-gale conditions due to the typhoon, tropical cyclone wind signal no. 1 may be raised over several provinces in the Bicol Region by Friday morning. 

Signal No. 4 possible

"Given that it is likely for this typhoon to continue intensifying prior to landfall, the highest possible TCWS that will be raised throughout the passage of this typhoon will be TCWS #3 or #4 (associated with destructive to very destructive typhoon-force winds)," PAGASA said.

As of 10 p.m. Thursday, the eye of Typhoon Rolly was spotted 1,280 km east of Central Luzon, with the tropical cyclone packing maximum sustained winds of 120 kph near the center and gusts of up to 150 kph. 

It is moving westward at 20 kph and is expected to be 970 km east of Casiguran, Aurora by Friday night.

PAGASA forecast track of Tropical Cyclone Rolly (international name Goni).
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