Double tap on Hawai’i?

The decaying Hurricane Iselle should be making landfall on the big island of Hawai’i in just under two days.  By then it should be a tropical storm, and impacts are forecast to be in the $10 to $20 Million range.  Here’s the forecast wind swath, using my Taru model and the Central Pacific Hurricane Center forecast track and intensity:

Next up is Hurricane Julio, which is about five days out.  It is forecast to pass north of the islands, and impacts should be light if that track holds up:

Having two or more hits in the same general area is not at all unusual.  Statistically, if you are hit by a hurricane or tropical storm, there is a one in four chance you will be hit by another tropical system that same year.  Why is that?  Hurricanes are “steered” by middle and upper level winds.  While these winds vary from day to day, they tend to follow a pattern in a given year due to the interactions of various climate cycles like the El Nino/Southern Oscillation, the Quasi-Biennial Oscillation, and others.  So the pattern that steered one storm over you tends to push any others storms that form in that same are later in the year over similar tracks.  On the plus side, when a storm passes over the ocean it cools the water, both by rain and by churning up deeper, cooler water.  So if the second storm passes too close behind the first, before the ocean has a chance to reset, the second storm will tend to be weaker because the ocean will not have as much energy to feed it.

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