A Tropical Storm Will Hit Hawaii

A weakening tropical storm is approaching Hawaii, where heavy rainfall and strong winds are expected. Tropical Storm Calvin currently has maximum sustained winds of 45 mph.

This morning’s infrared satellite image clearly shows the center of the storm to the east of the large island. You’ll notice the absence of a distinct eye and rather amorphous rain bands.

The satellite images that can be seen at the same time are also not very impressive.

According to the latest forecast from the National Hurricane Center, Calvin will pass south of Hawaii as it weakens (see below)

The Calvin wind will interact with Hawaii’s solid terrain to produce heavy rain.

Here are the winds for Wednesday evening, with yellow indicating strongest winds (followed by greens and blues). You’ll also notice wind “dead zones” towards the lee (southwest) of the Big Island.

The total precipitation for the entire event is shown below. 4-7 inches on the windward (east) side of the Big Island. Wet on the east side of Maui as well.

Calvin has weakened rapidly over the past few days. Why?

The answer is cool water. Hurricanes/tropical storms need warm water to strengthen, usually greater than 28C (82F).

Here are the latest sea surface temperatures around Hawaii. Temperatures east of Hawaii are currently below 26 degrees Celsius. Not a healthy place for a tropical storm! No wonder Calvin is in denial.

In the end, the Calvin wind was still strong enough to produce some dramatic waves on the southwest side of the Big Island, with some reaching as high as 12-18 ft. Some good surfing opportunities!