Odds Of Historic El Niño Soar: What It Means For VA This Winter

VIRGINIA — The probabilities have reached near certainty that strong El Niño conditions will persist through at least February, which could spur a snowier winter than D.C. and Northern Virginia saw last year, the Climate Prediction Center said this month.

Newly updated forecasts from the Climate Prediction Center upgraded the odds to 95 percent in favor of El Niño hanging on through at least February. The pattern typically reaches peak strength between November and January.

During past El Niño years, temperatures and precipitation from December through February averaged near normal in the DC-Baltimore region, while seasonal snowfall averaged above normal, the National Weather Service said.

Seasonal temperatures, precipitation, and snowfall locally at Washington, D.C. and Baltimore have been affected by the weather pattern in past years. The NWS said weak El Niño winters averaged below normal temperatures and precipitation, while strong El Niño episodes averaged above normal temperatures and precipitation.

"On average, the stronger the El Niño episode, the warmer and wetter the winters have been," the weather service said.

These findings can partly be linked to a stronger than normal sub-tropical jet that typically occurs during moderate to strong El Niño winters, which would favor more active storm systems from the south that draw warm, moist air northward as opposed to the drier Alberta clippers from the northwest. Seasonal snowfall averaged above normal, especially for moderate El Niño episodes.

Signs of El Niño are all around, especially in the very warm surface temperatures in the Pacific.

Forecasters say their increasing confidence is due to a few consistent factors, including surface temperatures in the tropical Pacific, weaker pressure in the eastern Pacific, and higher pressure in the western Pacific.

"Taken together, these are all signs of the atmospheric component of El Niño, providing more confidence that the system, is engaged and that these conditions will last through the winter," NOAA explained on its ENSO blog Thursday.

After three consecutive La Niña winters, El Niño — the warmer phase of the El Niño Southern Oscillation (ENSO) — arrived early in June. The opposing climate patterns are a departure from normal conditions in the Pacific and can have global impacts on the jet stream and weather, particularly during the winter months in the United States.

According to National Oceanic and Atmospheric Administration, El Niño causes the Pacific jet stream to shift south and spread east, which is usually associated with warmer and drier winter conditions in northern states and wetter conditions in the South and Southwest, including much of California.

Usually, the weather phenomenon's impacts are less pronounced in the summer and stronger in the winter. Since it formed a month or two ahead of schedule, its impacts this year could become apparent early. In the United States, El Niño is most associated with warmer, drier conditions in northern states as cool and wet patterns develop further south, including in D.C. and Northern Virginia.

As NOAA explains:

"El Niño can affect our weather significantly. The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern U.S. and Canada are dryer and warmer than usual. But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding."

Should El Niño continue to gain strength, scientists caution it could fan more extreme weather events in areas already hit hard by the effects of a changing climate.

"Depending on its strength, El Niño can cause a range of impacts, such as increasing the risk of heavy rainfall and droughts in certain locations around the world," Michelle L'Heureux, a NOAA climate scientist, told the AFP. "Climate change can exacerbate or mitigate certain impacts related to El Niño. For example, El Niño could lead to new records for temperatures, particularly in areas that already experience above-average temperatures during El Niño."

No two El Niños are the same and several variables can play into their overall influence, including how much strength it develops. With the table comfortably set for El Niño this winter, climatologists are also growing bullish that it might pack some punch, too.

"Given recent developments, forecasters are more confident in a 'strong' El Niño event, with roughly 2 in 3 odds of an event reaching or exceeding 1.5 C° for the November-January seasonal average in Niño-3.4," the updated advisory reads.

While it's too early to know for sure how this El Niño will play out, forecasters see trends moving in the direction of something potentially historic.

Atmospheric scientist Emily Becker writes on the ENSO blog:

"The three-month-average Niño-3.4 Index, the Oceanic Niño Index, was 0.8 °C above the long-term mean for the May­–July average, the second three-month-period in a row above the El Niño threshold of 0.5 °C. We need to see five consecutive three-month averages above this threshold before these periods will be considered a historical 'El Niño episode' and colored red in our ENSO record). Two is a good start, especially with the 0.8 °C recording from May­–July. If this El Niño were to collapse after hitting this high, dropping back below the threshold of this magnitude before next winter, it would be the first time in our historical record, dating back to 1950."

With a few more months to go until the peak El Niño influence, there are still plenty of factors to monitor in the coming weeks. ENSO forecasters update their El Niño outlooks every month, and NOAA typically releases its official U.S. Winter Outlook in October.