Current Snapshot

The Pacific Disaster Center’s (PDC Global) Monday, December 9, 2024, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas

Current Tropical Cyclones:

Tropical Cyclone 04S is located approximately 620 NM north-northeast of Port Louis, Mauritius

Northeast Pacific Ocean: There are no Tropical Cyclones

The last regularly scheduled Tropical Cyclone Activity Report of the 2024 eastern North Pacific Hurricane Season has been issued. Routine issuance of this section of the PDC product will resume on May 15, 2025. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant by the NHC.

2024 Hurricane Season Summary for the Northeast Pacific Basin

The 2024 Pacific hurricane season was a below-average Pacific hurricane season. There were 15 tropical cyclones overall, of which all but 2 became named storms. Of the 13 named storms, 5 developed into hurricanes, of which 3 intensified into major hurricanes. The season officially began on May 15 in the eastern Pacific basin (east of 140°W) and ended on November 30. These dates, adopted by convention, historically describe the period in each year when most subtropical or tropical cyclogenesis occurs in this region of the Pacific Ocean. For the third consecutive year, there were no pre-season tropical cyclones and the season got off to the slowest start of any Pacific hurricane season on record in the satellite era, with the first eastern Pacific tropical storm, Aletta, not forming until July 4. The final system of the season, Tropical Depression Fourteen‑E, dissipated on November 7.

Several storms impacted land this year. Hurricane Hone dropped very heavy rainfall over the Big Island of Hawaii after passing just offshore at Category 1 strength. The remnants of Hurricane Gilma impacted the islands several days later, though neither cyclone caused significant damage. Tropical Storm Ileana grazed the coast of northwestern Mexico, resulting in flooding and one fatality. Hurricane John made landfall on southern Mexico twice after rapidly intensifying to a Category 3 hurricane, causing 29 deaths and an estimated $1 billion in damage. The strongest storm of the season was Hurricane Kristy, which became the first Category 5 Pacific hurricane in a non-El Niño year since Celia in 2010.

Central Pacific Ocean: There are no Tropical Cyclones

The 2024 central North Pacific hurricane season has ended. As such, the final routine Tropical Cyclone Activity Report for the 2024 season has been issued. Routine issuance of this section of the PDC product will resume on June 1, 2025. During the off-season, Special Tropical Weather Outlooks will be issued as conditions warrant by the CPHC.

2024 Hurricane Season Summary for the Central Pacific Basin

The 2024 hurricane season featured two tropical cyclones in the Central Pacific Hurricane Center (CPHC) area of responsibility. Four to five tropical cyclones occur during an average year. Hurricane season runs from June 1 to November 30. The central Pacific basin extends from 140°W to the International Date Line.

Hurricane Hone was the first tropical cyclone of the season in the central Pacific, developing about 1,000 miles east-southeast of the Big Island on August 22. This was the first tropical cyclone to form in the central Pacific since Tropical Storm Ema in October 2019. Hone continued to strengthen as it approached the state, eventually becoming a hurricane late on August 24 just over 50 miles south-southeast of Ka Lae, the southern tip of the Big Island. Hone weakened to a Tropical Depression on August 29, then strengthened to a Tropical Storm again from August 30-September 1. During this time a Tropical Storm Watch was issued for Kure and Midway Atolls and portions of the Papahānaumokuākea Marine National Monument from Lisianski Island to Pearl and Hermes Atoll. Hone became extratropical just after crossing the International Date Line on September 1.

Hurricane Gilma moved into the basin from the east on August 27 and rapidly weakened before dissipating east of Hawaii.

Impacts to the State of Hawaii: Heavy rain from Hurricane Hone caused flash flooding that damaged homes and closed several roads across Hawaii County on August 25, leading to several million dollars in damage. Tropical storm force winds brought down trees and utility poles on the Big Island, with reports of damage on Maui and Oahu as well.

Western Pacific, Indian Ocean, and adjacent Seas:

Tropical Cyclone 04S

According to the JTWC Warning number 1, TC 04S had sustained winds of 40 knots with gusts to near 50 knots.

Animated enhanced infrared (eir) satellite imagery depicts a partially exposed llcc on the eastern side of a young burst of deep convection, nearly circular in shape with cloud tops cooler than -80 degrees celsius. Outer banding is evident throughout the western semicircle, but none to the east due to ongoing easterly mid-level shear of about 20 knot, denoted by cirrus streaming beneath the upper-level outflow into the llcc area from the east in eir and water vapor imagery. Another pass showed 35-40 knot winds wrapping throughout the western semicircle, with weaker winds to
the east.

Tropical cyclone 04S is currently a vertically tilted vortex, leaning westward with height with a partially exposed  llcc. Recent satellite trends suggest an improvement in deep convective coverage, partially overspreading the llcc, and vertical shear is expected to decrease from around 20 knots to around 10 knots during the next 24-36 hours. with sea surface temperatures expected to remain warm, this should result in more favorable conditions that facilitate axi-symmetrization and intensification of the cyclone during this period.

The JTWC intensity forecast shows intensification to 60 knots by 36 hours. During this time, 04S will be steered generally westward by a building subtropical ridge to its south. After 36 hours, the stronger ridge is expected to intensify mid-level easterlies pressing on the vortex, resulting in increasing vertical shear once again during the 36-72 hour period.

Numerical models are split on how well the vortex will remain aligned during this renewed period of shear, with some models like hafs-a and coamps-tc keeping the cyclone at 65+ knot intensity during this time, while other models such as ecmwf and gfs show decay as vortex tilt reappears and dry air gets pushed in from the east. The JTWC forecast hedges between these solutions, showing a peak intensity of 60 knots and then leveling off as shear restrengthens during the 48-72 hour period.

The dynamical model track guidance shows 04S approaching northern Madagascar in around 96 hours, but it is unclear whether landfall will occur. regardless, a track close to or over the steep topography of this region should significantly disrupt the inner core of the cyclone, resulting in weakening during this time. The JTWC track forecast is close to the northern tip of the island, and shows weakening during the 72-120 hour period.

The cyclone will likely track into the Mozambique channel thereafter, where models currently expect some vertical shear to persist. Any re-intensification in the channel would likely depend significantly on how much the vortex is disrupted by land interaction and how much dry air entrains into the ambient environment due to the persistent shear. There is thus low confidence in the intensity forecast during this period, with the JTWC forecast showing weakening to 35 knots by 120 hours.

>>> There’s an area of disturbed weather being referred to as Invest 91S, which is located approximately 155 NM northeast of Cocos Island.

Animated enhanced infrared (eir) satellite imagery continues to depict Invest 91S with a fully exposed llcc with persistent convection sheared to the west of the llcc. Another partial pass reveals 15-20 knots to the north and south of the llcc.

As for the environmental analysis, 91S is in a marginal environment for further development with warm sea surface temperatures offset by weak poleward upper-level outflow and high vertical wind shear of 25-30 knots. Lastly, global deterministic models continue to show the system remaining nearly quasi-stationary, while backing off on the development odds for 91S.

Global deterministic guidance now suggests the circulation isunlikely to develop into a tropical cyclone within the next 24 to 48 hours, and ensemble guidance continues to show a downward trend in the probabilities for development.

Maximum sustained surface winds are estimated at 23 to 28 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours remains low.

>>> There’s a second area of disturbed weather being referred to as Invest 93S, which is located approximately 426 NM north-northeast of Learmonth, Australia.

Enhanced infrared satellite imagery depicts a broad area of flaring convection, with a consolidating low level circulation center (llcc). Additionally, another satellite image reveals a partially exposed circulation, with fragmented formative banding slowly consolidating around the llcc.

Environmental analysis reveals that Invest 93S is in a favorable
environment for further development with, warm sea surface temperatures, good equatorward outflow aloft, and low (10-15 knot)
vertical wind shear.

Global models are in good agreement that Invest 93S will generally track southwest ward over the next 48 hours.

Maximum sustained surface winds are estimated at 23 to 28 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours is upgraded to medium.

>>> There’s a third area of disturbed weather being referred to as Invest 94S, which is located approximately 159 NM north-northwest of Darwin, Australia.

Enhanced infrared satellite imagery depicts a broad and weakly defined
asymmetric circulation, with flaring convection beginning to organize
around low level circulation center (llcc).

Environmental analysis reveals that Invest 94S is in a favorable environment for further development with warm sea surface temperatures, good equatorward outflow aloft, and low vertical wind shear (10-15 knots).

Global models are expecting the system to generally track southwestward over the next 48 hours as the system continues to intensify.

Maximum sustained surface winds are estimated at 13 to 18 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours is low.