Assessing the Impacts of Kona Lows on Rainfall: Variability and Spatial Patterns in the Hawaiian Islands

Date
2014-12
Authors
Kaiser, Lauren R.
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Giambelluca, Thomas
Department
Geography and Environment
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[Honolulu] : [University of Hawaii at Manoa], [December 2014]
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Abstract
In Hawaiʻi, climate is significantly impacted by the occurrence of upper level lows in the central North Pacific region. Some of these systems become cut off from their extratropical storm track source, break away from the upper level westerlies, passing south of 30°N latitude, and form a subtropical cyclone. A total of 114 upper level lows occurred during the Hawaiian cool season (October-April) over a 34 year period from 1981 to 2014. Given the proper meteorological conditions, some upper level lows will lead to surface cyclogenesis, creating a stationary 'Kona low'. Of the 114 upper level lows that occurred, 70 had surface development and formed a Kona low. Although the frequency of these storm events has strong interannual variability, an average ~3 upper level lows form per year with ~2 developing into Kona lows. The occurrence (frequency) of both upper level low and Kona low events has increased over the past 34 years while the number of days (duration) has decreased, although none of these trends are significant. These winter storms are an important source of precipitation for the Hawaiian Islands. This analysis investigates the effect of synoptic Kona low circulation on seasonal and geographic rainfall patterns across the Islands. During Kona low events, rainfall amounts are higher statewide. Although these events generally produce relatively uniform high rainfall rates, Kona lows contribute more to the total annual precipitation on the drier, leeward sides of all islands. Averaged across all 74 stations used in this analysis, upper level lows (including Kona lows) contributed over 50% and Kona lows over 35% of the total rainfall during the cool season. At a single leeward station, Kona lows have contributed as much as 87% of the total annual rainfall in a single year.
Description
MA University of Hawaii at Manoa 2014
Includes bibliographical references (leaves 46–48).
Keywords
Kona low, rainfall, storms, Hawaii, climate change
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vi, 48 leaves
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Theses for the degree of Master of Arts (University of Hawaii at Manoa). Geography.
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