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Global Tropical Outlook & Discussion: 29 December 2025 - 4 January 2026

PinnedAreas to watch: Grant (09S), Hayley (10S), 98P, 99P

Active cyclones

Last updated: Monday, 29 December — 03:00 UTC

Southwestern Indian

  • 09S: Grant — Satellite imagery analysis reveals that Grant has quickly strengthened to the equivalent strength of a Category 3 major hurricane. Environmental conditions are likely to remain supportive of further intensification over the next 12 to 24 hours, after which an upper-level trough will begin to restrict the storm’s outflow, causing it to weaken. Grant is expected to continue along a generally west-southwestward track over the next several days and is not likely to pose a threat to land as it remains well to the northeast of Mauritius.

Southeastern Indian

  • 10S: Hayley — Satellite imagery analysis indicates that deep convection continues to build over Hayley’s compact low-level circulation center. Environmental conditions remain generally favorable and should support further intensification over the next 24 to 36 hours. Because of the storm’s small size, this intensification could very well be unpredictably rapid. Strengthening northwesterly shear will cause Hayley to begin to weaken as it turns eastward and approaches the Kimberley coast. By the time Hayley makes landfall on Tuesday evening, its maximum sustained winds are expected to have weakened to 55 knots.

 

Active disturbances

Active disturbances are areas of showers and thunderstorms which are not organized enough to be considered full-fledged tropical cyclones. Disturbances are often designated as investigation areas (or invests, for short) by NOAA in order to allocate additional resources such as high-resolution satellite imagery or model guidance for further study of the system. Though there is no publicly disclosed set of criteria for which disturbances are designated as invests, the designation often occurs after the disturbance forms a closed area of low pressure. Invests are designated regardless of the overall potential for the disturbance to become a tropical cyclone.

Southern Pacific

  • 98P: Invest (Northern Australia) — Australia’s Bureau of Meteorology continues to issue heavy rainfall warnings for what it calls an area low pressure embedded within a broader monsoon trough. Although this system is producing tropical storm-force winds, neither BOM nor JTWC have been issuing advisories for it. The potential for this system to become a tropical cyclone is low and will remain low as it moves farther inland over the next couple of days. This system is likely to pose a widespread flash flooding risk for large portions of western Queensland.

  • 99P: Invest (Near Samoa and American Samoa) — Satellite imagery analysis indicates that a compact area of low pressure situated northeast of American Samoa is producing more organized deep convection. Environmental conditions are generally supportive of further development and a tropical cyclone could form within the next 24 to 48 hours. This system is currently moving eastward and will continue to do so for the next 24 to 48 hours, but will turn sharply southward after that point. This system does not currently pose a direct threat to land.

 

Post-tropical cyclones

Post-tropical cyclones will be listed here if they are still being tracked via the Automated Tropical Cyclone Forecast (ATCF) system. Placement in this section does not imply that these systems have any potential to redevelop into tropical cyclones.

  • There are currently no active post-tropical cyclones in any basin.

 

Potential formation areas

Potential formation areas are areas that are being monitored by various agencies for potential tropical cyclone formation within the next two weeks. These systems have not yet formed and are not considered to be disturbances until such time that a tropical wave or area of low pressure does form. Discussions are created on this subreddit for areas which are monitored by the National Hurricane Center in the eastern Pacific and northern Atlantic basins. Discussions are not typically created for areas which are monitored by the Joint Typhoon Warning Center or other agencies, as this information is not always publicly available.

Southeastern Indian

  • A pair of low pressure systems could develop near the Cocos Islands and Christmas Island, respectively, later this week.

 

Satellite imagery

Model guidance

Information sources

Regional Specialized Meteorological Centers (RSMC)

Other sources

Global outlooks

Climate Prediction Center

Posted Dec 29, 2025, 3:09 AM UTC

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