Tropical Forecast Parameters
Determining if a season is going to be as active as 1995, 1996 or 1998 naturally requires analyses of various atmospheric variables.
For example, Dr. William Gray of Colorado State University, in his updated tropical forecast issued in early August 1995, forecasted a hurricane season far above normal.
Despite predicting an above average season, the forecasted 16 named storms, 9 hurricanes and 3 major hurricanes actually fell short of the observed numbers, which were 19 named storms, of which 11 became hurricanes, 5 of them major!
Check out this year's forecasts by Dr. Gray and his associates.
A number of parameters are now known to be associated with Atlantic seasonal hurricane variability, including El Niņo. However, remember the total number of named tropical cyclones and hurricane is not well related to the number that make landfall in the U.S. Always be prepared.
The Stratospheric Quasi-Biennial Oscillation (QBO)The QBO refers to east-west (or west-east) winds circling the earth near the equator 60,000 to 70,000 feet above the surface. It takes about two years for these winds to complete a cycle from east-west through west-east back to east-west.
The El Niņo-Southern Oscillation (ENSO)El Niņo years are characterized by warm sea-surface temperatures over the equatorial eastern Pacific. This anomaly is related to 200 millibar westerly winds and surface pressure over the Caribbean and the western Atlantic.
During El Niņo years, stronger 200 millibar westerlies produce shearing over the hurricane generating areas of the Caribbean and the western Atlantic, as well as higher surface pressure ? of which suppress hurricane development. In the record-making year 1995, there was no El Niņo.
African Rainfall (AR)The incidence of Atlantic hurricane activity is related to current year June-July Western Sahel rainfall and previous year August-November Gulf of Guinea rainfall.
Influence Of West Africa West-To-East Surface Pressure And Temperature GradientsAtlantic hurricane activity is enhanced when the February-May east-west pressure gradient is higher than normal or when the west-east temperature gradient is lower than normal.
Tropical Prediction CenterThe Tropical Prediction Center (TPC) is dedicated to saving lives and protecting property by issuing tropical cyclone watches, warnings, forecasts, and analyses of hazardous weather conditions in the tropics. Their tropical products are generated for use by both domestic and international communities. There are three branches of this Center's activities.
Perhaps the most well known branch of the TPC, the National Hurricane Center (NHC) maintains a continuous watch on tropical cyclones over the Atlantic, Caribbean, and the Gulf of Mexico from June 1st through November 30th. They are also responsible for tracking tropical activity in the Eastern North Pacific from May 15th through November 30th.
A second branch of TPC, the Tropical Analysis and Forecast Branch (TAFB), provides year-round products involving marine forecasting, aviation forecasts and warnings (SIGMETs), and surface analyses.
The third branch of TPC is the Technical Support Branch (TSB), which provides support for TPC computer and communications systems, including satellite data processing systems, work stations, and the Doppler radar.