Recent research from Pao-Shin Chu, an atmospheric sciences professor at the University of Hawai’i at Mānoa, documents alarming shifts in rainfall patterns statewide. These changes are the direct product of different climate events converging in the area. The El Niño-Southern Oscillation (ENSO), for example, has for a long time been recognized for its influences on Pacific weather. New research shows that the Pacific Meridional Mode (PMM) has a significant influence, and in particular, a more important one during spring.
We’re thrilled that the study uncovered such a promising link! A positive PMM state results in significantly enhanced rainfall on the leeward sides of the Hawaiian Islands. Disrupting normal weather patterns This monumental change would likely usher in serious changes to annual weather patterns, as well. It further increases the risk and intensity of rainfall events and flooding. The research team performed detailed analyses based on actual weather and sea surface temperature observations. It included data from NOAA’s National Weather Service operational weather models to accurately model impacts and effects.
The Role of El Niño-Southern Oscillation
Climate change impacts on agriculture have traditionally been studied through the lens of the El Niño-Southern Oscillation. This natural phenomenon has a profound effect on global weather patterns. For the Hawaiian Islands, ENSO fluctuations play an essential role in exacerbating or alleviating the amount of precipitation received. For example, during an El Niño phase, the islands are generally drier.
Yet Chu’s research sheds light on one of the biggest players in the game—ENSO. Yet breakthroughs like the PMM’s creation are fundamental to giving us a fuller picture of our changing climate. The combined effect of these patterns makes it difficult to predict what the next weather event will be. So a more sophisticated understanding of both ENSO and PMM is essential for making good forecasts in Hawai’i.
Impact of Pacific Meridional Mode
The Pacific Meridional Mode, particularly when in its positive phase, has a direct effect on rainfall. This extreme weather pattern causes heightened precipitation levels in the spring months. This non-linear phenomenon is critical for understanding the amount and heaviness of rainfall. It especially affects the leeward slopes of the Hawaiian Islands. When the PMM is in a positive phase, meteorological data shows that these areas can expect significant increases in extreme rainfall events.
Chu’s diagnostic analyses have revealed that this rise in extreme weather directly relates to the PMM’s state during winter and spring months. These results indicate that homeowners and policy makers alike need to be ready for increasingly severe storms as climate patterns shift.
Increased Flood Risks for Leeward Areas
With the increase in extreme rainfall events on Hawai’i’s leeward sides comes a higher risk of flooding. The research highlights the need to identify and understand these risks as conditions change with climate change. Flooding has severe impacts—not just economic losses, but threats to human lives and ecosystem wellbeing.
Chu emphasizes that it is critical for local governments and communities to incorporate these findings into their disaster preparedness plans. By understanding how shifts in climate patterns can affect rainfall and subsequently flood risks, they can better mitigate potential impacts.
