Friday, June 26, 2009
Weather columnist Kevin Myatt: El Nino could mean more soggy months ahead
Kevin Myatt is The Roanoke Times' weather columnist.
kevin.myatt
@roanoke.com
981-3341
Weather with Kevin Myatt
Recent columns
- We got graupel, but not on official record
- Moisture could get caught up in cold blast
- Forecast for Weather Journal: Partly print, with frequent Internet
- Column archive
Read the Weather Journal blog
- Sprinkles or flurries possible Tuesday, but maybe something bigger for the weekend?
- For now, it looks like a quiet, mostly mild week ahead for SW Virginia
- Coldest morning of winter so far likely across much of Southwest Virginia; Tuesday precipitation looking doubtful
- Weather Journal blog
#swvawx on Twitter
@KevinMyattWx
El Nino is raring to go.
In the past few weeks, the prospect of an El Nino has gone from a somewhat vague forecast to a high likelihood that it is already developing. The arrival of a new El Nino could have big implications on the Atlantic hurricane season, how wet the rest of this year is locally, and how winter plays out.
El Nino -- the "little boy," named after the Christ child because it often peaks near Christmas -- is a recurring phenomenon of warmer-than-normal sea surface temperatures in the Pacific Ocean along a streak paralleling the equator to the north, stretching west from the coast of Peru in northwestern South America deep into the open waters of the Pacific.
Predicting El Nino and its cold-water twin sister, La Nina, has been a difficult task for climatologists and oceanographers.
El Nino and La Nina don't recur in any readily discernible pattern. They do not always alternate, as multiple La Nina episodes can occur between El Ninos, and vice versa. Also, sea surface temperatures can sometimes rest in the middle between the two extremes for many years.
But as with many areas of weather and climate, forecasts are getting better.
Many computer models and experts have for months been forecasting the rise of El Nino in the Pacific. And in recent weeks, sea surface temperatures have warmed a little above normal in all sectors of the equatorial Pacific, indicating that an El Nino may be well into its development stage.
This would end more than two years when La Nina, or conditions approaching La Nina, dominated the central Pacific.
El Nino's effect on the Atlantic tropical season is usually to reduce the number of tropical storms and hurricanes that develop.
This is because the warmer waters of El Nino trigger more storminess over the central Pacific, which leads to increased high level wind flow from the west over Central America and across the Atlantic. Such strong winds shear the tops off many developing tropical systems, retarding their development into tropical storms and hurricanes.
El Nino's effect on the North American winter is less precise, but the general idea is that there are usually more wet storms across the southern half of the nation.
Temperatures can vary from warm to cold depending on the strength of the El Nino and the interplay of numerous other factors.
El Nino years in Virginia have included a warm, rainy winter in 1998; a cold winter with plenty of snow and ice in 2003; and even a mild, dry winter in 2007, when much of the wet storminess was shifted into the central U.S.
Generally, though, over the years, wetter than normal conditions are common in the cooler months during an El Nino. So, if El Nino continues to build, the odds lean on the side of a soggy spring being followed by a soggy fall and winter.
Weather Journal appears on Monday, Wednesday and Friday.
