Hawaii Gets Hit By A Tropical Storm and a Stronger Hurricane is Next: Why?

If you were planning a tropical vacation this week, be ready for some exciting weather.  If you want to surf big waves--bring your board as well.   Hawaii, which normally escapes the ravages of tropical storms, will be hit not one, but twice this week.

The latest infrared satellite picture (below) tells the story.  A relatively weak tropical storm (Madeline) is now affecting the big island, mainly with heavy rain.  But a much larger and more potent storm, Hurricane Lester, is right behind.  If you look closely you can even see a well-defined eye in Lester.

The maximum winds so far (see below) have gusted to 45-55 mph on the windward (eastern) side and crest of the Big Island.  Wind are weak on the sheltered Kona coast.

24-h precipitation totals have been respectable, reaching 5-6 inches on the upper windward slopes.  But the worst will soon be over there as the storm passes to the south and west overnight.

A far bigger threat is Hurricane Lester.  The National Weather Service Central Pacific Hurricane Center official track forecast has the storm going just north of the Hawaiian Island.

The latest NWS GFS model is consistent with this track (see sea level pressure and precipitation forecast for 5 PM PDT on Saturday)

Since the strongest winds are in the right front quadrant of a storm (front faces the direction of motion), the strongest winds will generally be north of the islands (see NWS wind speed probabilities below, which also include Madeline since it is for the next five days).

The big excitement will be waves, something that I would expect might attract the crazy big surf crowd.  The strong winds from Lester will result in some decent size waves to form.  To illustrate, her is the prediction of the NOAA WaveWatch III model for 11 PM on September 3rd.  Some waves getting to 8-9 meters (30 ft), with 5 meter waves over the north shores of all the northern islands.    The surf crowd will surely be out in force.

So why is Hawaii getting hit by multiple stormz right now, when they normally avoid them?  Because the water temperatures to its south and east are warmer than normal!   To show this, here are the sea surface temperature anomalies (difference from normal) right now.  Around 2C warmer than normal,

 Tropical storms depend on warm water and generally require the sea surface temperature to be at least 26.5C.  Take a look at the current sea surface temperature (SST) chart below.   26C just barely pushes north of Hawaii.  Normal temperatures are simply too cool for business, but this year the criterion is barely met for Hawaii.   Poor West Coast...sea surface temperatures are way too cool!

Announcement: My Climate Surprise Talk on September 28.

During the evening of September 28, I will be giving a talk in Seattle at UW's Kane Hall on Climate Surprise: Unexpected Impacts of Global Warming on the Pacific Northwest.   You think global warming will simply bring warmer temperatures, drought,  less snow, and more storms?  Think again. The latest climate model simulations provide a far more nuanced prediction of what will happen here, with some of the results quite surprising.   This talk is sponsored by CarbonWa and the Audubon Society To find out more or to secure tickets, please go here.