El Niño has shown signs of further development since forecasters issued a watch for the global climate pattern a month ago.
Observations of Pacific Ocean surface temperatures along the equator show warm water being pushed deeper, according to the Weather Underground's Jeff Masters. Forecasts for surface temperature anomalies have grown by half a degree over the past month when looking ahead to the summer and fall months.
According to the National Centers for Environmental Prediction, ensemble models of Pacific Ocean temperatures show El Niño starting some time by June.
The probability of an El Niño is expected to be about 50 percent by July, compared with about a 45 percent chance of continuing "neutral" conditions and less than 10 percent chances of a La Niña.
El Niño and La Niña are defined by surface temperature anomalies in the Pacific, either warmer or colder than normal, respectively.
In Baltimore, El Niño is best known for its winter weather impacts, though the climate phenomenon can lead to different weather extremes in different parts of the world. El Niño winters are usually snowier than normal here -- the record-breaking snows of winter 2009-2010 came during an El Niño, for example.