1. Expected 2008 Activity

This Outlook is a general guide to the expected overall activity for the 2008 Atlantic hurricane season. It is not a seasonal hurricane landfall forecast, and it does not imply levels of activity for any particular area

The expected conditions during the 2008 Atlantic hurricane season are related to two main climate signals: 1) the continuation of conditions (called the multi-decadal signal) that have been conducive to above-normal Atlantic hurricane activity since 1995 , including above-normal sea-surface temperatures in the eastern tropical Atlantic Ocean, and 2) a possible La Niña influence or ENSO-neutral conditions during the peak months (August-October) of the season.

Historically, seasons with climate patterns similar to those expected this year have produced a wide range of activity, and have been associated with both near-normal and above-normal seasons. This outlook considers the historical distribution of activity for these climate factors, uncertainties in the La Niña impacts, and the possibility of other unpredictable factors also influencing the season. Based on these factors, we estimate a 90% chance of a near-normal to above-normal 2008 Atlantic hurricane season. While an above-normal season is most likely (65% chance), there is a significant 25% chance of a near-normal season and a 10% chance of a below-normal season. See NOAA definitions of above-, near-, and below-normal seasons.

An important measure of the total seasonal activity is NOAA’s Accumulated Cyclone Energy (ACE) index, which accounts for the collective intensity and duration of named storms and hurricanes during the season. Based on the above factors, we estimate a 60%-70% chance the 2008 seasonal ACE range will be 100%-210% of the median. This range can be satisfied even if the numbers of named storms, hurricanes, or major hurricanes fall outside their likely ranges. If La Niña persists, the probability increases that the activity could be at or above the high end of the indicated ACE range.

The likely (60%-70% chance) ranges of activity for 2008 (each of which is seen in about two-thirds of similar seasons in the historical record): are 12-16 Named Storms, 6-9 Hurricanes, and 2-5 Major Hurricanes. Most of this activity is expected during August through October, the peak months of the Atlantic hurricane season.

“In contrast to NOAA’s prediction, Colorado State’s Klotzbach and Gray forecast an above average hurricane season for the East Coast.”

NOAA’s prediction, at least in the context of this post was for the Pacific East Coast, not the Atlantic.

I don’t know beans about the Pacific, but I’d assume that a negative PDO with its cold current along the coast would make life challenging for eastern Pacific storms. The main connecton between the Pacific Ocean and the Atlantic Hurricanes is that La Nina is associated with less vertical shear, and TCs can’t handle shear. El Ninos bring shear, and a developing El Nino can clobber a hurricane season.

The Klotzbach/Gray forecast in April used a new forecasting scheme they say worked much better in hindcasting. Their next update will be on June 3rd. It will be interesting to see if the negative PDO has impacts beyond the prevalence of fewer El Ninos and more La Ninas.

One thing I like about their forecasts and season review is their openness when things go wrong.

http://typhoon.atmos.colostate.edu/forecasts/2008/april2008/apr2008.pdf

The models were completely wrong, and we may well be seeing a cyclical decline in hurricane/cyclone frequency due to PDO, AMO, etc.

Note, hurricanes are called cyclones or tropical cyclones in the SH and tropics.

Based on the recent success rate of these predictions I think people should evacuate coastal areas at once.

http://www.intellicast.com/Community/Content.aspx?a=129