August 7, 2014
NOAA increases the odds that we'll have
a below-normal hurricane season
Forecasters with NOAA’s Climate Prediction Center raised the likelihood for a below-normal season in today’s update to the Atlantic Hurricane Season Outlook.
update predicts a 70 percent chance of a below-normal season, a 25
percent chance of a near-normal season and only a five percent chance
of an above-normal season. The probabilities in the initial outlook
issued on May 22 were 50 percent, 40 percent and 10 percent,
“We are more confident that a below-normal
season will occur because atmospheric and oceanic conditions that
suppress cyclone formation have developed and will persist through the
season,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at
NOAA’s Climate Prediction Center, a division of the National Weather Service.
he said, "tropical storms and hurricanes can strike the U.S. during
below-normal seasons, as we have already seen this year when Arthur
made landfall in North Carolina as a category-2 hurricane. We urge
everyone to remain prepared and be on alert throughout the season.”
The primary factors influencing the increased chance of a below-normal season are:
atmospheric conditions are not favorable for storm development. This
includes strong vertical wind shear, a weaker West African monsoon, and
the combination of increased atmospheric stability and sinking motion.
These conditions mean fewer tropical systems are spawned off the
African coast, and those that do form are less likely to become
hurricanes. These conditions are stronger than
originally predicted in May and are expected to last mid-August
through October, the peak months of the hurricane season.
oceanic conditions are not favorable for storm development. This
includes below-average temperatures across the tropical Atlantic, which
are exceptionally cool relative to the remainder of the global tropics.
This cooling is even stronger than models predicted in May and is
expected to persist through the hurricane season.
Niņo is still likely to develop and to suppress storm development by
increasing vertical wind shear, stability and sinking motion in the
updated hurricane season outlook, which includes the activity to-date
of hurricanes Arthur and Bertha, predicts a 70 percent chance of the
following ranges: seven to 12 named storms (top winds of 39 mph or
higher), including three to six hurricanes (top winds of 74 mph or
higher), of which zero to two could become major hurricanes (Category
3, 4, 5 with winds of at least 111 mph).
These ranges are
centered below the 30-year seasonal averages of 12 named storms, six
hurricanes and three major hurricanes. The initial outlook in May
predicted eight to 13 named storms, three to six hurricanes and one to
two major hurricanes.
The Atlantic hurricane region comprises
the North Atlantic Ocean, the Gulf of Mexico and the Caribbean Sea.
NOAA’s seasonal hurricane outlook is not a hurricane landfall forecast.
It does not predict how many storms will hit land or where a storm will
strike. Forecasts for individual storms and their impacts will be
provided throughout the season by NOAA’s National Hurricane Center.
Climate Prediction Center also continued the El Niņo watch today in its
scheduled monthly El Niņo/Southern Oscillation Diagnostic Discussion.
Forecasters note that although sea surface temperatures across the
central equatorial Pacific have recently returned to near average, this
cooling is expected to be temporary.
El Niņo is now favored to
emerge during August-October, and to peak at weak strength during the
late fall and early winter. The likelihood of El Niņo during
August-October has decreased to 55 percent (from 75 percent in May),
and its likelihood during the fall and winter has decreased to about 65
percent (from near 80 percent).
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