Alaska and British Columbia are on alert to receive a very unusual dose of tropical weather: the remains of Hurricane Oho, which are on track to hurtle into the Alaska Panhandle on Friday evening. Oho completed the transition from a hurricane to an extratropical storm with 70 mph winds on Thursday morning, and after short period of weakening, is expected to interact with a powerful jet stream over the Gulf of Alaska and intensify on Friday afternoon off the coast of Alaska into a powerful 960 mb low pressure system with near-hurricane-force winds and heavy rain. A High Wind Warning is up for Sitka, Alaska for sustained winds of 40 to 55 mph with gusts of 65 to 75 mph on Friday. Sustained winds of 70 mph--just below hurricane-force--accompanied by 26-foot seas are expected over the offshore waters of the Alaska Panhandle from Cape Decision to Clarence Strait.
What's going on? Well, record-warm sea surface temperatures near the Hawaiian Islands the past two years have helped fuel highly unusual tropical cyclone activity in the waters surrounding the islands. The warmest water temperatures surrounding Hawaii are usually just below the threshold where a tropical cyclone can form and maintain itself, 26°C (79°F.) Water temperatures in these waters have been 27 - 28°C in much of the summer of 2014 and 2015, and that extra bump in temperature has pushed the Central Pacific past a threshold which allows more tropical storms and hurricane to form.