PTC One-C heads toward Hawaii; life-threatening floods possible
PTC One-C is on a collision course with Hawaii, and the islands should prepare for heavy rainfall that could become life threatening in some areas over the next two days. The system is not yet a named storm but it carries enough moisture to produce widespread flooding as it passes through the central Pacific. Meanwhile the Atlantic basin shows signs of an early awakening with Tropical Storm Cristobal already formed and two more tropical waves heading toward the Caribbean, suggesting that this hurricane season could be active across multiple basins.
two-days-out is a critical window for island communities because flash floods can develop in minutes on steep terrain. One-C has been tracked as it moves through the central Pacific carrying a deep plume of moisture and its proximity to Hawaii means several islands will experience significant rainfall within 48 hours. The threat level varies by island depending on topography wind direction and how much rain each area has already received
What PTC One-C is and why it matters
PTC stands for potential tropical cyclone, a designation used by the Central Pacific Hurricane Center (CPHC) when an atmospheric disturbance shows enough organization to warrant monitoring. These systems begin as tropical waves - low pressure areas that move across the ocean carrying warm moist air in their eastern quadrants. As the wave moves into favorable conditions including warm sea surface temperatures above 80 degrees Fahrenheit light winds and sufficient Coriolis force it can develop a closed circulation and become a tropical depression then a tropical storm and eventually a hurricane
One-C is currently at that stage where it has enough structure to produce measurable impacts but not yet the organized wind field of a named storm. The reason this matters for Hawaii is that even an undeveloped system can dump significant rainfall if it passes close enough and carries sufficient moisture. In many cases tropical waves strengthen as they move westward across the Pacific feeding off warm ocean waters which means One-C could intensify before reaching the islands. Even if it stays weak its sheer size and moisture content are enough to produce dangerous conditions on Hawaii's varied terrain
The life cycle of these systems is a constant process in the tropical Pacific where waves emerge from the East African coast travel across the Indian Ocean into the western Pacific and then move eastward toward North America. One-C is one such wave that has traversed much of this path before arriving near Hawaii. The timing is also important because late summer months tend to see higher sea surface temperatures which can lead to more rapid intensification than in early season systems
Orographic rain and the threat to Hawaii's islands
The most dangerous rainfall hazard for Hawaii from a passing tropical system comes not just from the storm itself but from orographic lift. This is a meteorological process where moist air is forced upward by rising terrain - in this case the volcanic mountains of Maui Oahu Kauai and the Big Island. As the air rises it cools and condenses into cloud droplets releasing latent heat which further fuels convection and creates intense rainfall on the windward slopes facing the prevailing winds
On Maui the northeast side receives the brunt because the trade winds push moisture against the Koʻolāiʻalua Range. On Oahu rain falls heavily on the north shore as air rises over the Koolau Mountains while the leeward west side remains relatively dry. Kauai's Na Pali Coast is one of the wettest places in the world due to this same mechanism with steep cliffs catching moisture from every passing system. The Big Island experiences orographic rainfall across its varied terrain including Mauna Kea and Mauna Loa which can create localized flooding even when the rest of the island stays dry
Orographic rain is why Hawaii gets so much more rainfall than other Pacific islands at similar latitudes. A passing tropical system that might produce only a few inches of rain over flat land can deliver several feet on windward slopes in just hours. This concentration of water on steep terrain leads to flash floods landslides and debris flows which are the primary hazards for island residents during heavy rainfall events The runoff from these mountains also feeds Hawaii's reservoirs and streams so even beneficial rain can be dangerous when it falls too quickly
Cristobal forms as the Atlantic awakens
While One-C approaches Hawaii the Atlantic basin is showing signs of early activity with Tropical Storm Cristobal already formed. This is significant because an active start to the season often predicts a busy year ahead for the entire tropical Atlantic. The Caribbean Sea has been warming steadily and its low shear environment makes it fertile ground for storm formation in late summer as the ITCZ moves northward
Cristobal's development signals that the main hurricane season - which runs from June 1 through November 30 - is getting underway with strength. Early storms can set a precedent by establishing favorable conditions such as warm sea surface temperatures and low vertical wind shear across the basin for later systems. The Caribbean especially has been active in recent years with several major hurricanes forming there each summer
The Atlantic season is influenced by larger climate patterns including ENSO (El Niño Southern Oscillation) which affects whether storms form more in the eastern or western tropics and the AMO (Atlantic Multidecadal Oscillation). A warm North Atlantic Oscillation combined with a neutral or La Niña state can produce one of the most active hurricane seasons on record as seen in 2005 and 2017. Cristobal's early formation suggests that these conditions may be favorable for this year
Two tropical waves heading toward the Caribbean
In addition to Cristobal two more tropical waves are moving through the eastern Atlantic toward the Caribbean basin. These waves carry their own potential and could develop into additional storms as they move westward over warm waters. The combination of an existing storm plus multiple incoming waves means that the Caribbean region may experience a busy late summer with several systems forming in quick succession
The two waves are currently scattered across the eastern Atlantic with one moving toward the Lesser Antilles and the other heading for the central Caribbean Sea. Both have enough organization to warrant monitoring as they move into more favorable conditions later this month The timing of these storms is also important because multiple systems can interact or compete for moisture which can affect their intensity and track
The Caribbean basin has its own distinct hurricane season from June 1 through November 30 with peak activity typically occurring in August and September. Recent seasons have seen several major hurricanes form there each year making it one of the most active tropical basins in the world The two incoming waves could contribute to a busy late summer for the region
What this means for hurricane season outlook
The simultaneous activity in both the central Pacific and the Atlantic suggests that 2026 may be an active year across multiple tropical basins. One-C's approach toward Hawaii highlights the immediate threat posed by even undeveloped systems while Cristobal and the two incoming waves point to a busy summer ahead for the Caribbean The combination of warm ocean temperatures low wind shear and favorable atmospheric conditions creates a recipe for many storms this season