DISCUSSION: Climatologically there are seemingly only two seasons in Hawaii, these being summer and winter. While there are over 10 climate zones experienced in Hawaii, it can be apparent that summer is often May through October with Winter from November to April. Much like the Eastern Pacific portion of the United States the winter is often the wet season for Hawaii, diminishing the coveted trade wind weather and bringing a slew of cold fronts and/or troughs of poor weather with increased precipitation, often posing major hazards to the area.
President’s Day and its week are expected to see some of this wet and typical weather for mid- winter season. The island chain is under a rather slow trough located at the surface with an upper-level disturbance bringing in round after round of thunderstorms to the islands. These unstable conditions are bringing widespread lightning, thunderstorms, and flash flooding to the island especially in windward location of the islands. With some winds out of the south, the chain has been experiencing unsettled weather associated with this moisture plume bringing increased possibilities for water spouts, thunderstorms, and lightning.
The National Weather Service Honolulu (NWS) has issued a flash flood watch for the entire state, as moderate to heavy rain falls. In addition, the NWS has issued a winter weather advisory for the Big Island summits (Mauna Loa and Mauna Kea) as snow is expected to fall with this system. Due to the precarious nature of this forecast, moisture will remain in the area as this unstable weather will be supported by a trough, and a developing upper level low. As the trough evolves into a closed low over the next day or so, heavy precipitation will persist, the atmosphere will become increasingly unstable and the NWS has indicated, “updraft strength becomes sufficiently strong to support the development of small hail and funnel clouds.”
Diagram 2, current analysis for the Skew-T diagram has indicated K-index of 33 a moderate potential for convection, total totals at 53 indicating widely scattered severe storms, as verified by radar, however Lifted index only -4 indicating marginal instability. Overall there’s increased potential for convective action and flash flooding but no determination for extreme instability regarding the slow-moving trough. This wet pattern is expected to stick throughout the week, with at least some marginal chance for precipitation each day.
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© 2018 Meteorologist Jessica Olsen