Thursday, February 8, 2018

Return to El Nino expected by summer: NOAA. Expect more hurricanes.

The central Pacific was still cooler than normal in January, but it’s warming, and national climate experts say they are seeing clear signs of a returning El Nino by mid-year.

For Hawai`i, that potentially means drier conditions during the wet season, and more and stronger hurricanes during the hurricane season.

(Image: This chart shows how water temperature at the Pacific equator differed from normal over the past year. The big blue area at right represents the cooler water associated with the La Nina that seems to be ending. Credit: NOAA.)

The warming trend was documented in the latest report today (Feb. 8, 2018) from the Climate Prediction Center, National Centers for Environmental Prediction, National Weather Service and the International Research Center for Climate and Society.

The report confirmed that, for now, La Nina conditions are still in place, which forecasts in Hawai`i wetter weather and fewer named storms. For the Mainland, it suggests warmer weather and less rain across the southern states and cooler temperatures and more precipitation across the north.

“The atmospheric conditions over the tropical Pacific Ocean… reflected La Niña, with suppressed convection near and east of the International Date Line and enhanced convection around Indonesia.  Also, the low-level trade winds remained stronger than average over the western and central Pacific, while upper-level winds were anomalously westerly. 

“Overall, the ocean and atmosphere system remained consistent with La Niña,” the report said.

But most of the climate models used in the tracking of El Nino-La Nina cycles predict the mild warming seen in January will strengthen through the next few months, leading to neutral conditions by the period from March to May, and to full El Nino conditions by fall.

The report says that the various computerized models that predict climate trends don’t all agree with the forecast, but that on average, they clearly suggest the warming trend.

The way in which La Nina and El Nino impact storm formation in the Pacific is complex. In terms of La Nina, here’s what NOAA said in a 2016 statement.

 “La Niña typically suppresses central Pacific hurricane activity by increasing the wind shear and causing an irregular sinking motion in the atmosphere, both of which suppress storms from forming and intensifying.”

That was in place during the 2017 hurricane season. There were actually more storms than normal last year—18 named storms, 9 of which were hurricanes—but most were weak and did not last long.

But during the last active El Nino, the Pacific was a hotbed for tropical cyclones big enough to get names. In the El Nino year of 2015, there were 26 named storms, of which 16 were hurricanes. Hawai`i was spared a direct hit that year.

It was the second most active hurricane season on record. The last time there was more hurricane activity in the Pacific was in 1992, the year Hurricane Iniki hit Kauai head-on.
This latest El Nino-La Nina climate report updates the one we published last month

© 2018 Jan TenBruggencate