With the year's fifth named tropical storm already come and gone and more than three months remaining in the 2008 hurricane season, forecasters at the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center and Colorado State University (CSU) increased the number of named storms and hurricanes in their tropical storm forecasts.
In a report issued Thursday NOAA forecasters said atmospheric and oceanic conditions across the Atlantic Basin that favor storm development, combined with the strong activity seen in the early weeks of the season, have increased the likelihood of an above-normal hurricane season this year. NOAA, which said in May there was a 60-70% chance of 12 to 16 named storms, including six to nine hurricanes, two to five of them major (Category 3 or greater) hurricanes (see NGI, May 26), now sees a 67% change of 14 to 18 named storms, including seven to 10 hurricanes, three to six of them major hurricanes. The Atlantic hurricane season ends Nov. 30.
"Leading indicators for an above-normal season during 2008 include the continuing multi-decadal signal -- atmospheric and oceanic conditions that have spawned increased hurricane activity since 1995 -- and the lingering effects of La Nina," said NOAA hurricane forecaster Gerry Bell. "Some of these conditions include reduced wind shear, weaker trade winds, an active West African monsoon system, the winds coming off of Africa and warmer-than-average water in the Atlantic Ocean."
The CSU hurricane team last week increased the number of storms it said will form in the Atlantic Basin this year, forecasting a total of 17 named storms, including nine hurricanes, five of them intense. CSU forecasters had previously called for a well above-average hurricane season this year with 15 named storms forming in the Atlantic Basin (see NGI, June 9a). The updated forecast increased the number of forecast storms based on warm sea surface temperatures and low sea level pressures observed over the tropical Atlantic in June and July, combined with an active early season in the deep tropics.
"The primary concern with our current very active seasonal forecast numbers is the continued ocean surface warming in the eastern and central tropical Pacific," said CSU forecaster Phil Klotzbach. "Although it seems unlikely at this point, there is a possibility that a weak El Nino could develop by the latter part of the hurricane season. If this happened, it would likely reduce the number of late-season tropical cyclones."
The CSU team also issued a monthly tropical cyclone activity forecast, which forecast four named storms, three hurricanes and one intense hurricane forming in the Atlantic basin in August, approximately 180% more activity than is seen in the average August. There is a considerably higher-than-average probability of at least one intense hurricane making landfall in the United States during this year's hurricane season, the team said.
Tropical Storm Edouard, the fifth named storm of the year, came ashore Tuesday in the Sabine Pass area of southeast Texas. It never developed enough to attain hurricane status, but it remained a strong tropical storm while coming ashore with maximum sustained winds of 65 mph. By Wednesday Edouard had weakened into a tropical depression and was entering its dissipation stage in north-central Texas, according to the final Edouard advisory issued by the National Hurricane Center.
Tropical Storm Arthur, the first tropical storm of the 2008 Atlantic hurricane season, developed May 31 in the western Caribbean Sea and wasted little time in moving ashore over Mexico's Yucatan Peninsula, where it was downgraded to a tropical depression on June 1. Bertha meandered through much of the Atlantic between July 3 and July 20, threatening Bermuda and twice becoming a hurricane, but never threatened gas or oil interests.
Last month Hurricane Dolly brought heavy rain and wind speeds of more than 100 mph when it made landfall at South Padre Island near Brownsville, TX. Minerals Management Service reported more than 600 MMcf/d shut-ins of gas, 58,000 b/d of oil and 62 evacuated platforms and mobile drilling rigs associated with Dolly, which weakened to a tropical storm and then to a tropical depression as it passed into Mexican territory near Laredo, TX.
Also last month, Tropical Storm Cristobal stayed in the Atlantic as it traveled northeast, eventually being downgraded to an extratropical depression as it moved into cooler North Atlantic waters.
Most forecasters this year have called for an active or above-average Atlantic hurricane season. Last month WSI Corp. increased by one the number of named storms and hurricanes that it predicts will form in the Atlantic Basin this year, calling for 15 named storms and nine hurricanes, including four intense hurricanes to form (see NGI, July 28). Previously WSI forecasters had said they expected 14 named storms, eight hurricanes with four of them intense hurricanes (see NGI, July 7).
MDA EarthSat forecasters also said the 2008 Atlantic hurricane season will likely be busier than average but quieter than last year (see NGI, April 21). MDA EarthSat forecasters said 13 named storms, six hurricanes and three intense or major hurricanes are likely to form during the Atlantic hurricane season.
AccuWeather.com meteorologist Joe Bastardi said the East Coast will be at greater risk this coming hurricane season even though the number of named storms is expected to be about average, and Gulf of Mexico interests can expect seven to 10 days with at least the threat of weather disruptions (see NGI, May 19).
Using NOAA data and its own storm tracking tool, forecasting network WeatherBug said it expects 10-12 named storms and an above-average Atlantic hurricane season (see NGI, June 2).
In June the Energy Department's Energy Information Administration (EIA) said it expects a total of 11.3 million bbl of crude oil and 78 Bcf of natural gas to be shut in in the Gulf of Mexico during the 2008 hurricane season (see NGI, June 16). The prediction is based on the results of a Monte Carlo hurricane outage simulation, which is conditioned on how NOAA's most recent predictions for the level of Atlantic Basin hurricane activity compare to historical activity, the EIA said. A report issued this summer by energy consultant IHS Inc. said average impact on U.S. oil and natural gas production from Gulf of Mexico hurricanes over a 45-year period was "relatively modest" and the impact on energy supplies "typically short-lived" (see NGI, June 9b).
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