After months of prediction and anticipation, there is finally an official weak El Nino phase in the Equatorial Pacific Ocean.
Sea-surface temperatures remain at least slightly warmer than average across much of the Equatorial Pacific and have showed some signs of warming in parts of the eastern Pacific during the past few weeks.
The latest long-range climate models indicate this El Nino phase likely will remain weak. There is a 50 to 60 percent chance that it will persist through at least the upcoming summer months. If this holds true, parts of the Midwest, Northeast and Mid-Atlantic could see more seasonable or maybe slightly below average summer temperatures.
Meanwhile, parts of the Pacific Northwest and Rockies can see warmer than average summer temperatures during an ongoing El Nino. These trends will have to be monitored. As for May, slightly warmer than normal temperatures are forecast across the Pacific Northwest, northern Rockies and northern Plains. These regions could see a small surplus in early season cooling degree-days by between 20 and 40.
Portions of the southern Plains and Rockies are expected to see slightly below normal temperatures. Monthly cooling degree-days likely will be lower than average by between 30 and 60 in these regions. Much of the eastern third of the U.S. likely will see temperatures that average closer to normal in May.