Hawaii Was Threatened by Two Hurricanes, ISELLE and JULIO, Within a Few Days in August 2014 Dr

Hawaii was threatened by two hurricanes, ISELLE and JULIO, within a few days in August 2014 Dr. Susanne Haeseler; updated: 13 August 2014

Introduction

On 8 August, hurricane ISELLE crossed the islands of Hawaii in the Pacific Ocean from east to west. It caused local precipitation amounts of more than 300 mm and storm with gusts of more than 100 km/h. At the same time, hurricane JULIO approached from the east, but it passed to the northeast of the island (Fig. 1 and 2).

Fig. 1: Satellite image of the two hurricanes ISELLE and JULIO over the Pacific southeast of Hawaii on 5 August 2014. [Source: NASA, Earth Observatory]

Fig. 2: Tracks of ISELLE and JULIO in August 2014. Storm of hurricane force marked in red. [Data source: Unisys; Graphic: DWD]

This was a very unusual situation, because the Hawaiian islands are rarely hit by a tropical storm or a hurricane, and now they were endangered by two hurricanes.

Tropical storms and hurricanes in the area of Hawaii

The Hawaiian islands are located in the North Pacific in the area between 140° W and the Date Line. This area, the Central Pacific, is served by the Central Pacific Hurricane Center (CPHC) that provides watches and forecasts/warnings for tropical cyclones (depressions, storms, hurricanes), and also publishes results of climatological analyses. In the following, some of these results are summarized.

In the Central Pacific, the hurricane season officially runs from June to November. On average, between 4 and 5 tropical cyclones are observed there every year. They can develop at any time of the year, not only during the hurricane season.

The Hawaiian islands are rarely hit by a tropical storm or a hurricane (Fig. 3). The last time a hurricane crossed the islands was in September 1992, when hurricane INIKI made landfall on the northwestern island of Kauai. INIKI was a category 4 hurricane on the Saffir-Simpson Wind Scale at landfall. Reports about INIKI and other notable hurricanes are published on http://www.prh.noaa.gov/cphc/summaries/.

Fig. 3: Tropical storms and hurricanes passing within 200 miles (322 km; top) and 75 miles (121 km; bottom) of Hawaii from 1950 to 2012 [Source: NOAA, CPHC]

Hurricanes and El Niño

El Niño is one of the factors that may affect the number of tropical cyclones in the Central Pacific. During an El Niño, the sea surface temperatures in the central and eastern equatorial Pacific are above average, enhancing the formation and development of tropical storms. A moderate to strong El Niño is likely to result in an enhanced number of tropical storms and hurricanes.

At the time of writing, the sea surface temperatures in the central and eastern equatorial Pa- cific have increased slightly after a decrease in July (BOM). According to the most recent

3 analyses, an El Niño may develop during the next months (BOM, CPC). It remains to be seen, whether and how this will affect the activity of hurricanes in the Central Pacific.

Sources and further information

. Bureau of Meteorology (BOM), Australia: ENSO Wrap-Up. http://www.bom.gov.au/climate/enso/ . NASA, Earth Observatory: Hurricanes Iselle and Julio. http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=84145 . NOAA, Coastal Services Center (CSC): Historical Hurricane Tracks. http://csc.noaa.gov/hurricanes/index.html# . NOAA, Central Pacific Hurricane Center (CPHC) http://www.prh.noaa.gov/hnl/cphc/ . NOAA, Central Pacific Hurricane Center (CPHC): Analyses/Forecasts. http://www.prh.noaa.gov/cphc/pages/analyses.php . NOAA, Central Pacific Hurricane Center (CPHC): Climatology of Tropical Cyclones in the Central Pacific Basin. http://www.prh.noaa.gov/cphc/pages/climatology.php . NOAA, Central Pacific Hurricane Center (CPHC): Frequently Asked Questions. http://www.prh.noaa.gov/cphc/pages/FAQ/ . NOAA, Central Pacific Hurricane Center (CPHC): Previous Tropical Systems in the Central Pacific. http://www.prh.noaa.gov/cphc/summaries/ . NOAA, Central Pacific Hurricane Center (CPHC): Saffir-Simpson Hurricane Wind Scale. http://www.prh.noaa.gov/cphc/pages/aboutsshs.php . NOAA, Climate Prediction Center (CPC): El Niño – Southern Oscillation. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml . NOAA, National Hurricane Center: Saffir-Simpson Hurricane Wind Scale. http://www.nhc.noaa.gov/aboutsshws.php . NOAA, National Weather Service Forecast Office, Honolulu, HI: Climate, Local. http://www.nws.noaa.gov/climate/index.php?wfo=hnl . NOAA, National Weather Service Forecast Office, Honolulu, HI: Hawaii Public Information Statements. http://www.prh.noaa.gov/hnl/pages/pns.php . NOAA, National Weather Service Forecast Office, Honolulu, HI: Hawaii Public Information Statements. Iselle brings gusty winds across the state of Hawaii. (Aug 08 2014) http://www.prh.noaa.gov/data/HFO/PNSHFO.1408090716 . NOAA, National Weather Service Forecast Office, Honolulu, HI: Hawaii Public Information Statements. Iselle brought heavy rainfall and flooding to Hawaii. (Aug 09 2014) http://www.prh.noaa.gov/data/HFO/PNSHFO.1408092020 . NOAA, Pacific ENSO Applications Climate Center: Tropical Cyclone Climatology in the Pacific. http://www.prh.noaa.gov/peac/tropical.php . Unisys: 2014 Hurricane / Tropical Data for Eastern Pacific. http://weather.unisys.com/hurricane/e_pacific/2014/index.php