NOAA forecasts a 60% chance for a new low-pressure system off southern Mexico to develop into Tropical Storm Barbara, marking the second named storm of the Eastern Pacific season.
An area of low pressure is forecast to form offshore of the coast of southern Mexico late this week as forecasters begin monitoring conditions that could give rise to the second named storm of the 2025 Eastern Pacific hurricane season. Initial satellite and model data show that sea surface temperatures in the region are hovering around 28–29 °C, while moderate wind shear persists—a combination that remains marginally conducive for gradual development of this disturbance.
Forecasters at the National Hurricane Center (NHC) note that this system is likely to move generally westward to west-northwestward at about 10 mph. Under these motion and environmental patterns, a tropical depression could form over the weekend. If further organization occurs and sustained winds reach at least 39 mph, the system would be officially designated as Tropical Storm Barbara.
As of the latest advisory, the probability of formation within the next 48 hours remains near 0 percent. However, the seven-day outlook shows a medium, 60 percent chance that a tropical depression will develop from this low-pressure area. This seven-day probability places the system among those disturbances that warrant close observation early in the 2025 season.
Background on Pacific Hurricane Season 2025
The Eastern Pacific hurricane season officially spans May 15 through November 30, with peak activity typically occurring between July and September. To date, the basin has already produced its first named storm, Tropical Storm Alvin, which formed on May 29, 2025, roughly two weeks earlier than the seasonal average for first storm formation . Alvin’s development was aided by unusually warm waters and favorable wind patterns. Although Alvin intensified to a moderate tropical storm, its circulation remained well offshore, and it posed no direct threat to land.
Climatologically, the second named storm of the Eastern Pacific season often appears in early to mid-June. NOAA’s seasonal outlooks for 2025 predict near-average activity, forecasting between 12 and 18 named storms, of which 5 to 10 may become hurricanes (with 2 to 5 reaching major hurricane status). The season’s activity typically hinges on factors such as El Niño–Southern Oscillation (ENSO) conditions, vertical wind shear, and sea surface temperatures. As of early June, weak La Niña conditions are present, which tend to suppress wind shear and allow storms to organize more readily in the Eastern Pacific basin.
Potential Impacts and Next Steps
Should the disturbance north of the coasts of Chiapas and Oaxaca organize into Tropical Storm Barbara, the immediate impacts are most likely to include an increase in showers and thunderstorms across sections of coastal Guerrero and Michoacán by this weekend. Even if the system does not strengthen beyond tropical depression status, coastal areas could still see heavy rainfall, localized flooding, and elevated surf along beaches. Residents and mariners in the region are advised to monitor local forecasts and heed any advisories issued by regional weather services.
Further westward motion means that any developmental stages are likely to occur over open water. Still, as a developing system moves away from the coast, its broader moisture field could interact with the coastal mountains of southern Mexico, enhancing orographic rainfall. That interaction can bring even wetter conditions to inland areas, raising concerns for flash flooding and mudslides, especially in regions with steep terrain and known vulnerability.
At present, no tropical storm watches or warnings have been issued for coastal areas, but the situation remains fluid. Interests along the Mexican Pacific coast should monitor updates from the NHC twice daily as the system evolves. Should sustained winds reach 39 mph, the NHC will upgrade the disturbance to Tropical Storm Barbara, the second named storm on the 2025 list (the first being Alvin). All historical data indicate that early-season storms in this region tend to remain offshore but can still produce dangerous coastal hazards.
Climatology and Historical Context
Early-season Eastern Pacific storms occasionally serve as harbingers of the broader pattern to follow. For example, Tropical Storm Alvin’s rapid formation in late May foreshadowed the basin’s readiness to support cyclonic activity. Past seasons have shown variability: in 2022 and 2024, the first named storms formed later than average, whereas in 2021, Tropical Storm Andres formed as early as May 9. The timing often correlates with ENSO-driven changes in wind shear and mid-level humidity.
If Barbara develops and follows a typical west-northwest track, it could remain at sea for much of its lifespan. However, climatology shows that remnant moisture from similar early storms has occasionally been pulled northeastward into Mexico’s interior, leading to heavy rains far from the open Pacific. In 2018, for instance, remnants of Tropical Storm Aletta enhanced rainfall over western Mexico despite the storm’s center remaining offshore. Thus, even a relatively weak system like Barbara could indirectly affect weather patterns over southern Mexico.
Looking Ahead
As of this writing, satellite imagery shows increasing convective clusters south of the Mexican mainland, but a well-defined center of circulation has yet to emerge. Over the next 48 hours, environmental factors such as sea surface temperatures (around 28–29 °C), upper-level wind shear (moderate, but trending downward), and mid-level moisture will be critical in determining whether this disturbance can organize into a tropical depression.
Forecasters emphasize that the 0 percent chance of development within two days reflects the current lack of organization. However, rapid changes in atmospheric patterns can occur, especially when a disturbance sits over warm water. The 60 percent seven-day formation probability reflects confidence that—given favorable winds aloft and sustained thunderstorm activity—a closed circulation could form by this weekend. At that point, if sustained winds exceed 39 mph, the disturbance will be classified as Tropical Storm Barbara, joining Tropical Storm Alvin as active systems in the Eastern Pacific basin.
Communities along the coast are encouraged to stay informed through official channels. The NHC will continue to update its Tropical Weather Outlook twice each day (at 5 a.m. EDT and 11 a.m. EDT), with additional Intermediate Advisories issued if and when the system reaches tropical depression strength. Mexico’s Servicio Meteorológico Nacional (SMN) will also issue localized forecasts, watches, and warnings as needed.
References
- National Hurricane Center. “Eastern North Pacific 7-Day Graphical Tropical Weather Outlook.” June 2, 2025. nhc.noaa.gov
- Yale Climate Connections. “Tropical Storm Alvin forms off the Pacific coast of Mexico.” May 29, 2025.
- Wikipedia. “2025 Pacific hurricane season.” Accessed June 3, 2025. en.wikipedia.org
NOAA forecasts a 60% chance for a new low-pressure system off southern Mexico to develop into Tropical Storm Barbara, marking the second . . .
