The world is on an El Nino watch, the National Weather Service's Climate Prediction Center said Thursday.

The global climate pattern is well-known for an inundation of snow it can bring the Baltimore area, though its impacts can be varied. There is a 50 percent chance it could arrive for the first time since 2009 by next winter, according to the climate center.

Whether an El Nino is declared depends on surface water temperatures in the Pacific Ocean near the equator. Warmer-than-normal temperatures bring on El Nino, while cooler-than-normal temperatures lead to La Nina.

El Nino last began three years ago, in June 2009, and it lasted until May 2010. Cooling water temperatures then led to a La Nina, which ended in April. Since then, conditions have been considered "neutral."

The climate center's 50 percent probability of an El Nino applies to the second half of this year, which could mean one will arrive by winter.

El Nino's impacts aren't as certain in Maryland as they are in other parts of the world, but many associate the phenomenon with some of Baltimore's snowiest winters. The Feb. 11, 1983 storm that dropped 22.8 inches on Baltimore is considered one of the most notable snowstorms occurring in an El Nino.

The statistics show varying impacts based on the weakness or strength of an El Nino, but in general, Marylanders can expect a cold winter with more snow than normal. The National Weather Service office in Sterling, Va., lays out the possibilities in charts looking back at past El Nino years.

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