By PDC’s Senior Weather
Specialist Glenn James
The Pacific Disaster Center’s (PDC Global) Sunday, December 31, 2023, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas
Current Tropical Cyclones:
Tropical Cyclone 04S (Alvaro)…is located approximately 96 NM north-northeast of Europa Island
Northeast Pacific Ocean:
The North Pacific hurricane season officially ended on November 30, 2023. Routine issuance of the Tropical Weather Outlook will resume on May 15, 2024. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant.
The eastern Pacific basin hurricane season was above normal, with 17 named storms, of which 10 were hurricanes and eight of those major hurricanes.
From August 16 to 21, Tropical Storm Hilary brought widespread heavy rainfall and flooding to Southern California, with some areas receiving up to 600% of their normal August rainfall. Hilary resulted in the first ever issuance of Tropical Storm Watches and Warnings for the Southern California coastline by NOAA’s National Hurricane Center. In addition, the Center distributed key hazard focused messages for Hilary in Spanish through the agency’s new language translation project.
Hurricane Otis made landfall near Acapulco, Mexico, on October 25 as a category-5 hurricane, with sustained winds of 165 mph. Otis holds the record as the strongest land falling hurricane in the eastern Pacific, after undergoing rapid intensification in which wind speeds increased by 115 mph in 24 hours.
Central North Pacific:
The central North Pacific hurricane season officially ended on November 30, 2023. Routine issuance of the Tropical Weather Outlook will resume on June 1, 2024. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant.
The central Pacific basin had a near-normal season with four tropical systems traversing the basin.
Hurricane Dora, a category-4 storm, passed south of Hawaii in early August, marking the first major hurricane in the central Pacific basin since 2020. The strong gradient between a high pressure system to the north and Dora to the south was a contributing factor to the wind-driven, fast-moving wildfires in Hawaii.
Western Pacific, Indian Ocean and adjacent Seas:
South Indian Ocean…
Tropical Cyclone 04S (Alvaro)
According to the JTWC warning number 2, sustained winds were 35 knots with gusts to 45 knots
Tropical cyclone 04S has consolidated quickly as depicted in recent animated enhanced infrared satellite imagery. Imagery reveals a compact, well-organized convective core with the bulk of the deep convection and deep convective banding over the eastern semicircle. A microwave image shows deep convective banding over the eastern semicircle wrapping tightly into the western quadrant with a weak microwave eye feature.
TC 04S is forecast to track east-southeastward to eastward over the next 36 hours along the southern periphery of the ridge positioned to the north. Environmental conditions should remain generally favorable with enhanced poleward outflow into the subtropical jet stream to the south and warm sea surface temperatures.
However, dry air entrainment is currently hindering development over the western semicircle and is forecast to envelop the system after 24 hours. Therefore, the intensity is expected to peak near 45 knots within the next day, then decrease as the system approaches the coast of Madagascar, with landfall near 36 hours. Further weakening will occur as the system tracks over the mountainous
terrain of Madagascar.
After 72 hours, the remnants will re-emerge over the Indian Ocean with gradual re-intensification to about 35 knots as the system interacts with strengthening subtropical westerlies.
Increasing vertical wind shear (30-40 knots) should limit this re-intensification phase. Track motion should generally be east-southeastward as the steering influence transitions to a subtropical ridge positioned to the northeast.