Multi-Hazard Mitigation Plan: 04. High Wind Storms

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Chapter 4:Hazard Analysis—High Wind Storms Declaration DR-613-HI) The loss on Hawaii Island was $11.7 million. Agriculture — macadamia, coffee, foliage and flower farms — had major losses. Maui was also declared a disaster area (Haraguchi, 1980).14 Other winter storms have caused much less, but more localized effects, with flooding the main problem. The flood insurance maps are intended to reflect the stream flooding from these events as well as coastal effects. 4.3 Probability of Occurrence According to the National Weather Service (NWS) (Heffner, 2002), the monthly counts of high wind events impacting the populated lower slopes and elevations of Hawaii County over a ten year period indicate the months of"winter" storms to be the most active. A high wind event by NWS definition includes sustained winds or frequent gusts of 40 mph or greater. For Hawaii County, 28 events were identified during the period January 1992 through Octo- ber 2002. The typical breakdown of events by month is: High Wind Events in Hawaii County:Jan. 1992-Oct. 2002 s �+ 6 LU W IOU 5 L m 4 0 0 3 L QJ C0 2 E L Z 1 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Figure 4-3. High Wind Events for Hawaii County by Month,January 1992 to October 2002 Thus, the average is a little over 0.2 such events per month, but for the "season" of occurrences (December through April), it averages 0.4 per month, island-wide. 4.4 Risk Assessment The distinction between the tropical cyclone hazard and high wind hazard is illustrated by the hazard curves for the Hawaiian Islands shown in Figure 4-4. The figure shows that the relatively low wind speeds that occur more frequently are more likely to be from non-tropical cyclonic winds while the relatively high but less frequent wind speeds are more likely to be 14 Haraguchi,Paul, 1980,`Storm of January 8- 10, 1980,State of Hawai'i,"DLNR,December 1980. 4-5 Hawaii County Multi-Hazard Mitigation Plan