NOAA scientists are forecasting a 70% probability of a below-normal eastern Pacific hurricane season during 2007, a 25% chance of a near-normal season, and only a 5% chance of an above-normal season. This hurricane outlook is made jointly by the scientists at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC), National Hurricane Center (NHC), and the Hydrometeorological Prediction Center (HPC). See Background Information for NOAA’s definitions of above-, near-, and below-normal seasons.

NOAA’s 2007 outlook for the eastern Pacific hurricane season calls for 12-16 tropical storms (average is 15-16), with 6-9 becoming hurricanes (average is 9), and 2-4 becoming major hurricanes (average is 4-5). This outlook reflects the ongoing multi-decadal climate signal that has been acting to suppress eastern Pacific hurricane activity since 1995, combined with the strong likelihood of either ENSO neutral or La Niña conditions during much of the season. The ongoing reduction in eastern Pacific hurricane activity since 1995 is coincident with generally above-normal Atlantic hurricane activity.

The eastern Pacific hurricane region covers the eastern Pacific Ocean east of 140^oW north of the equator. There will be no further updates to this 2007 outlook.

DISCUSSION

1. Expected Activity - 70% Chance Below Normal, 25% Chance Near Normal, 5% Chance Above Normal

An important measure of total seasonal activity is NOAA’s Accumulated Cyclone Energy (ACE) index, which accounts for the collective strength and duration of tropical storms and hurricanes during a given hurricane season (see Background Information). The ACE index is also used to define the above-, near-, and below-normal seasons. A value of 92% of the median (Median value is 109) corresponds to the upper boundary for a below-normal season.

For the 2007 eastern Pacific hurricane season, the ACE index is expected to be 50%-100% of the median. The main climate signals for this prediction are a) the ongoing multi-decadal climate signal that has favored generally below-normal activity since 1995, and b) the strong likelihood of either ENSO-neutral or weak La Niña conditions throughout the season. The Climate Prediction Center is currently indicating that La Niña conditions could develop within the next 1-3 months.

The 2007 eastern Pacific hurricane season is expected to bring 12-16 tropical storms, with 6-9 becoming hurricanes, and 2-4 becoming major hurricanes. There is the expectation that many of the named storms will remain relatively weak, and that some hurricanes and major hurricanes are likely to be short-lived compared to normal. While it is reasonable to expect this range of tropical storms, hurricanes, and major hurricanes, the total seasonal activity as measured by the ACE index can certainly be in the expected range without all three of these criteria being met.

Most tropical storms that form in the eastern North Pacific track westward into open waters, sometimes reaching Hawaii and beyond. On average, one to two tropical storms per season either head northward or recurve toward western Mexico. These storms often bring rainfall to western Mexico, and sometimes also supply moisture to the arid southwestern United States.

CAUTIONARY NOTES

1) It is important to recognize that it is currently not possible to confidently predict at these extended ranges the number or intensity of land falling hurricanes, or whether a particular locality will be impacted by a hurricane this season. Therefore, residents and government agencies coastal and near-coastal regions should always maintain hurricane preparedness efforts regardless of the overall seasonal outlook.

2) Far more damage can be done by one major hurricane hitting a heavily populated area than by several hurricanes hitting sparsely populated areas or, of course, not making landfall at all. Therefore, hurricane-spawned disasters can occur even in years with near-normal or below-normal levels of activity.

NOAA FORECASTERS

Climate Prediction Center
Dr. Gerald Bell, Meteorologist, Gerry.Bell@noaa.gov
Dr. Kingtse Mo, Physical Scientist, Kingtse.Mo@noaa.gov

National Hurricane Center
Eric Blake, Hurricane Specialist, Eric.S.Blake@noaa.gov
Dr. Christopher Landsea, Meteorologist, Chris.Landsea@noaa.gov

Hydrometeorological Prediction Center
Todd Kimberlain, Meteorologist, Todd.Kimberlain@noaa.gov