Raising Islands--Hawai'i science and environment: Wet La Nina winter shifting, to a stormy summer?

Thursday, January 11, 2018

Wet La Nina winter shifting, to a stormy summer?

Hawai`i’s wettish winter could continue, as the current La Nina climate cycle is expected to last through the winter.

That’s the latest assessment (January 11, 2018) from NOAA’s Climate Prediction Center and the International Research Institute for Climate and Society.

Long-term prediction of climate cycles is problematic, but most climate models seem to suggest that we could shift into El Nino by mid-summer. If that holds true, it could result an more tropical storms and hurricanes later this year than normal.

La Nina and El Nino are two major climate cycles affecting weather conditions in the Pacific. La Nina has cooler water in the equatorial central Pacific and El Nino has warmer waters.

Generally, for Hawaiian islands, El Nino conditions are associated with dry winters and stronger and more frequent hurricanes June to November. La Nina—which we’re now in—tend to have fewer storms from June to November and wetter winters.

Have you noticed a lot of strong tradewinds recently? La Nina conditions are also associated with stronger low-level tradewinds.

The new report suggests that La Nina conditions continued through the end of 2017 and are expected to persist through the rest of the winter, while weakening. After that, conditions should drift toward a neutral condition for the spring. And the models seem to indicate a continued shift toward El Nino as the summer progresses.

El Nino/La Nina conditions don’t only impact the climate of the Pacific, but are also associated with rainfall and temperature patterns on the Mainland.

Based on the latest climate models, “The outlooks generally favor above-average temperatures and below-median precipitation across the southern tier of the United States, and below-average temperatures and above-median precipitation across the northern tier of the United States.”

Since central Pacific ocean water temperatures are a key indicator of El Nino and La Nina cycles, the climate agencies have computerized models that track where they think water temperature is going. There are many such models, but as shown below, most of them are showing water warming into the summer months.

The bottom line shows months in three-month periods. The dynamic average shifts from negative to positive temperatures in May-June-July (MJJ)