95% of above normal seasons have 2 Gulf hurricanes, 50% have at least one in June-July
Across the entire Atlantic Basin for the six-month season, which begins June 1, NOAA is projecting a 70 percent probability of the following ranges:
* 14 to 23 Named Storms (top winds of 39 mph or higher), including:
* 8 to 14 Hurricanes (top winds of 74 mph or higher), of which:
* 3 to 7 could be Major Hurricanes (Category 3, 4 or 5; winds of at least 111 mph)
NOAA’s Climate Prediction Center issued its seasonal outlook today.
It is a worrisome. Administrator Lubchenco, says, “If this outlook holds true, this season could be one of the more active on record.”
What is the biggest uncertainty in the forecast?
“The main uncertainty in this outlook is how much above normal the season will be. Whether or not we approach the high end of the predicted ranges depends partly on whether or not La Ni±a develops this summer,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center. “At present we are in a neutral state, but conditions are becoming increasingly favorable for La Ni±a to develop.”
The CPC report explains:
La Ni±a contributes to reduced vertical wind shear over the western tropical Atlantic which, when combined with conditions associated with the ongoing high activity era and warm Atlantic SSTs, increases the probability of an exceptionally active Atlantic hurricane season (Bell and Chelliah 2006). NOAA’s high-resolution CFS model indicates the development of La Ni±a-like circulation and precipitation anomalies during July.
One of the three key factors leading NOAA to this forecast is the high sea surface temperatures:
Warm Atlantic Ocean water. Sea surface temperatures are expected to remain above average where storms often develop and move across the Atlantic. Record warm temperatures – up to four degrees Fahrenheit above average – are now present in this region.
Here is more of the forecast:
An important measure of the total overall seasonal activity is the NOAA Accumulated Cyclone Energy (ACE) index, which accounts for the intensity and duration of named storms and hurricanes during the season. We estimate a 70% chance that the 2010 seasonal ACE range will be 155%-270% of the median. According to NOAA’s hurricane season classifications, an ACE value above 117% of the 1950-2000 median reflects an above-normal season. An ACE value above 175% of the median reflects an exceptionally active (or hyperactive) season.
And what about the Gulf where a massive oil spill resides:
Because of the ongoing oil crisis in the Gulf of Mexico, we are including some historical statistics of tropical cyclone activity for this region (excluding the Bay of Campeche) based on past above normal seasons. These statistics do not represent an explicit forecast for tropical cyclones in the Gulf of Mexico during 2010, as it is impossible to reliably predict such activity so far in advance. Historically, all above normal seasons have produced at least one named storm in the Gulf of Mexico, and 95% of those seasons have at least two named storms in the Gulf. Most of this activity (80%) occurs during August-October. However, 50% of above normal seasons have had at least one named storm in the region during June-July.
If you want a comprehensive discussion of what a Gulf hurricane might mean for the oil disaster, Dr. Jeff Masters has a good post, “What a hurricane would do the Deepwater Horizon oil spill.”
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