Alvin to Form Off Mexico’s Coast; Brief Hurricane Possible
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| Warm seas fuel Alvin’s swirling clouds south of Acapulco as it tracks west-northwest. |
Disturbance south of Acapulco under close watch as Eastern Pacific hurricane season begins
Invest 90-E Shows Early Signs of Tropical Development Off Mexico’s Coast
MIAMI, May 28, 2025 – A large area of disturbed weather, designated as Invest 90-E by the National Hurricane Center (NHC), has formed several hundred miles south of Acapulco, Mexico. Satellite imagery late on May 27 revealed increasing organization within this broad, elongated low-pressure area, as clusters of deep convection steadily wrap around a developing center. Although scatterometer data have yet to confirm a closed surface circulation, forecasters note that sustained thunderstorm bursts suggest a well-defined low-level center could establish within 12–24 hours.
Favorable
Oceanic and Atmospheric Conditions
Current observations indicate sea-surface temperatures (SSTs) in the region are
between 29 °C and 30 °C—about 1–2 °C above the late May average—providing ample
thermal energy to fuel continued convective growth. Vertical wind shear remains
modest at approximately 5–10 knots, limiting disruptive tilting of mid-level
thunderstorms. In addition, mid-level relative humidity values are measured
around 65–70 percent, minimizing the influence of dry air entrainment and
fostering further convective consolidation.
Inner-Core
Consolidation Hints at Impending Classification
Early-morning microwave satellite passes detected preliminary signs of a
nascent inner-core structure, with convective banding tightening around a
potential low-level center situated near 16° N latitude and 100° W longitude.
According to NHC outlooks, if these trends continue, Invest 90-E could be
upgraded to Tropical Depression One-E as soon as May 28. Sustained winds of 35
knots (approximately 40 mph) would then elevate the system to Tropical Storm
Alvin, which currently holds a 95–100 percent probability of formation within
48 hours.
Projected
Track and Intensification Outlook
Forecast models—including the GFS, ECMWF, and UKMET ensembles—indicate a
west-northwestward trajectory for the next 36 hours, steering the system toward
waters between 15°–18° N and 102°–106° W. Under these conditions of sustained
low shear and high SSTs, gradual strengthening is likely, with some model runs
briefly predicting Category 1 hurricane strength by May 30 (peak winds of 65–70
knots and central pressures near 990 mb). However, beyond 48 hours, Alvin is
expected to encounter cooler waters (below 26 °C) and increasing southwesterly
shear from an upper-level trough approaching Baja California—factors that are
expected to weaken the system back to tropical storm status by May 31 and
potentially degrade it into a remnant low by June 1.
Coastal
Impacts and Precautionary Measures
As Alvin remains well offshore for the time being, immediate landfall threats
are minimal. Still, its outer rainbands are forecast to generate increased surf
and hazardous rip currents along Mexico’s Pacific shoreline—particularly west
of Guerrero state—beginning around May 29. Moisture plumes associated with the
system could also produce localized heavy rainfall and flash flooding from
Guerrero into Oaxaca and Michoacán between May 29 and May 31, especially where
coastal mountains enhance orographic lift. Coastal residents and mariners
should monitor updated NHC advisories and heed any local warnings regarding
marine conditions and flood risks.
NHC
Outlook
In its Tropical Weather Discussion issued at 11:00 PM PDT on May 27, the NHC
noted that the disturbance “continues to show signs of organization near a
broad area of low pressure,” with environmental conditions “favorable for
further development.” Forecasters caution that any sudden influx of dry air or
an unexpected uptick in shear could delay or halt intensification. Nonetheless,
the convergence of warm ocean temperatures, low shear, and sufficient
atmospheric moisture suggests Invest 90-E is poised to become Tropical Storm
Alvin—the first named system of the 2025 Eastern Pacific hurricane season.
Alvin’s Roll Call: Potential Hurricane Brewing Off Mexico
MIAMI, May 28, 2025 – Forecasters are closely monitoring a strengthening tropical system—soon to be named Alvin—that is forecast to track along the warm waters of the Eastern Pacific. While models generally agree on its initial path and possible intensification, key environmental factors may cap its strength and even determine whether it brushes Mexico’s coastline or dissipates harmlessly at sea.
Consensus Forecast Track
Numerical weather prediction ensembles (including GFS, ECMWF, and UKMET)
consistently show Alvin moving west-northwestward over the next 24 to 48 hours.
During this period, the storm should remain several hundred miles offshore,
roughly following the 16°–18° N latitude band and trending toward the longitude
range of 104°–108° W. This trajectory keeps Alvin over sea surface temperatures
(SSTs) near 29 °C–30 °C, an ideal thermal environment for ongoing convective
development.
Potential Intensification Window
Between May 29 and May 30, Alvin is expected to remain under low vertical wind
shear (approximately 5–10 kt) and within a moist mid-troposphere (65–70 percent
relative humidity). Under these favorable conditions, forecasters estimate a
high probability of gradual strengthening. Some ensemble members even suggest a
brief peak at Category 1 hurricane intensity—sustained winds of 65–75 kt with
central pressure dipping into the upper-980 mb range—sometime late May 30 or
during the early hours of May 31.
Environmental Challenges Loom
Beyond 48 hours, the outlook shifts. As Alvin crosses north of 18° N on May 31,
it will encounter cooler waters dropping beneath 26 °C and an approaching
upper-level trough over Baja California. This trough is forecast to enhance
southwesterly shear (potentially 15–20 kt), disrupting the storm’s core
convection. Simultaneously, mid-level dry air from the northeast may infiltrate
Alvin’s circulation, promoting rapid weakening. If these factors align as
expected, the system should downgrade to a tropical storm by late May 31 and
likely degenerate into a remnant low by June 1.
Uncertainty and Alternate Paths
Despite broad consensus, forecasters acknowledge two viable “what-if”
scenarios:
- Offshore Fade-Away: If the trough over Baja California digs southward more swiftly, elevated shear could undercut Alvin’s convective structure earlier, preventing any hurricane-strength phase. Under this scenario, Alvin would weaken to a long-lived remnant low drifting west-northwest into cooler, open waters—its primary impact being elevated swells and rip currents along Mexico’s Pacific coast.
- Coastal Graze: Conversely, if the trough stalls further west than anticipated, Alvin could enjoy another 12–24 hours of low shear. In that case, a potent circulation might maintain tropical storm force (35–45 kt) as it veers more north-northeast near 19° N, potentially skirting the coastline between Puerto Vallarta and Mazatlán around May 31–June 1. Even a weakened tropical storm could then trigger heavy rain, flash flooding in mountainous terrain, elevated surf, and gusty shoreline winds.
Because the National Hurricane Center’s 72-hour “cone of uncertainty” still spans roughly 150 nautical miles, small alterations in steering patterns could determine whether Alvin stays offshore or brushes land.
Impacts to Coastal Areas
- Surf and Rip Currents: Even without a landfall, Alvin’s outer rainbands and persistent onshore flow are likely to elevate wave heights to 8–10 ft along the Guerrero coastline (Acapulco to Puerto Escondido) from May 30 into May 31, creating life-threatening rip currents.
- Localized Heavy Rainfall: Should Alvin approach near the shoreline, moisture-laden squall lines could dump several inches of rain over orographically favored zones in Guerrero, Oaxaca, and Michoacán between late May 30 and May 31, increasing flash flooding and mudslide risks.
- Gusty Winds: Isolated wind gusts exceeding 40 kt may accompany embedded squall bands—especially if Alvin’s core remains intact longer than currently projected.
Recommendations for Mariners and Residents
- Marine Precautions: Mariners operating across the Gulf of Tehuantepec and along Guerrero’s coast should maintain a sharp lookout through June 1. Even a weakened system can generate hazardous swells and sudden squally conditions.
- Coastal Awareness: Beachgoers and fishing communities from Acapulco uptoward Puerto Escondido should heed rip-current advisories starting May 29. Strong onshore winds and elevated surf may persist through May 31.
- Stay Informed: Residents in low-lying and mountainous areas of Guerrero, Oaxaca, and Michoacán are urged to monitor updated forecasts for flash-flood alerts, particularly if Alvin’s path shifts closer to shore between May 31 and June 1.
forecast
guidance points
While most forecast guidance points toward a peak near
Category 1 intensity late May 30, the evolving interplay of cooling ocean
temperatures and increasing wind shear suggests Alvin will struggle to maintain
hurricane strength beyond 24–36 hours. By June 1, the most probable outcome is
a rapid weakening into a non-convective remnant low drifting westward. However,
slight shifts in the upper-level trough could extend Alvin’s window of
organization, heightening the likelihood of coastal impacts. Therefore, continued
vigilance and regular monitoring of official NHC advisories are essential over
the next 72 hours.
Potential Impacts Along Mexico’s Pacific Coast
Regardless of its final intensity, Alvin is poised to generate elevated surf and dangerous rip currents along stretches of Mexico’s Pacific shoreline west of Acapulco later this week. Coastal communities should prepare for life-threatening surf conditions. Additionally, heavy rain bands associated with the system are expected to develop near and to the north and east of Alvin’s center, raising the risk of flash flooding and mudslides in vulnerable areas.
Seasonal Context: Eastern Pacific Season Underway
The Eastern Pacific hurricane season officially commenced on May 15, two weeks ahead of the Atlantic’s start date. Traditionally, this basin produces an average of 15 named storms and eight hurricanes each year, with about four reaching major hurricane intensity. Strong oceanic heat content—particularly near the western coast of Mexico—has created a favorable environment for storm development early in the season. Conversely, waters farther north and west, including those approaching Baja California and Hawaii, remain cooler than average and may weaken any storms that venture into those regions.
Historical Comparisons: Lessons from Past Eastern Pacific Storms
In recent seasons, Eastern Pacific storms have demonstrated varying impacts on land. In 2023, the remnants of Hurricane Hilary brought significant rainfall to the Desert Southwest in the United States, while Category 5 Hurricane Otis struck Acapulco directly, resulting in extensive damage. These events underscore that although many Eastern Pacific systems curve harmlessly westward into open water, others can veer toward populated areas with little warning.
Meteorologist Insight and Next Steps
Senior meteorologists, including Chris Dolce, emphasize the importance of continuous monitoring given the rapid changes that can occur in storm structure and intensity. The NHC will issue updated advisories as Alvin evolves, with detailed track forecasts and cone projections to guide preparedness measures. Mariners and coastal residents should maintain awareness of official forecasts and heed any local advisories or evacuation orders.
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