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Washington Voices

Expect more tropical storms to form with La Niña

Thu., Sept. 2, 2010

The 2010 tropical storm and hurricane season is picking up speed.

Since the season began on June 1, there have been six named storms in the Atlantic and Caribbean waters. The latest one is Fiona, which is forming in the Atlantic Ocean.

As of early Tuesday, Hurricane Earl was a strong Category 4 storm that was bringing heavy rains and strong winds to the Caribbean. Flash flooding and mudslides were reported in Puerto Rico and the Virgin Islands. Evacuations may be in store for U.S. residents who live near the coast of the Carolinas, Mid-Atlantic states and the Northeast through the end of the week as Hurricane Earl moves close to the U.S. eastern coastline.

The peak of the tropical storm and hurricane season is usually around Sept. 10. At this time, ocean water temperatures are usually at their highest. Based on the fact that we now have the cooler-than-normal sea-surface temperature event, La Niña, expanding along the equatorial regions and warmer-than-normal ocean waters in the Carribean, we should continue to see more tropical storm and hurricane development over the next three to four weeks. During El Niño events, the warmer waters along the equator change the upper-level wind patterns to help inhibit tropical storm and hurricane development.

The overall average is 10 named storms with six becoming hurricanes during a season, which will end Nov.30.

Only three Category 5 storms, the strongest, have ever hit the U.S. mainland over the last 100 years. These were Camille in 1969, Andrew in 1992 and the Labor Day storm (no name) of 1935. In 2005, Katrina, Rita and Wilma did reach Category 5 status, but weakened before making landfall.

Within the last week, it has started to feel more like fall across the Inland Northwest. Since Aug. 27, temperatures have averaged about 5 to 10 degrees below normal. Despite the recent cooler weather, I still expect to see some days with warmer-than-normal temperatures before summer officially ends Sept. 22.

Although I’m still forecasting some occasional showers over the next three to four weeks, the annual fall rains should become more widespread in late September and early October, especially if La Niña continues to strengthen as predicted. Frosts and freezes will also be possible, even at the lower elevations, by early October. At elevations above 3,500 feet, we’ve already seen some frosty temperatures.

Weather patterns are pointing to increased snowfall around mid-to-late November. If all goes according to plan, many of area ski resorts may be open in time for Thanksgiving. It also appears that December will be colder and snowier than normal, which should also provide some great skiing conditions.

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