Roatan Forecast - Roatan Weather Report - Review

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There is a common misconception that since the global temperature has increased, hurricanes also must increase in number and intensity. The primary factor in the ability of a hurricane to strengthen or weaken is the wind shear profile of the atmosphere - not water temperature. It has always been warm enough in the tropics to produce hurricanes. This temperature equates to a sea surface temperature of about 80°F. If you study the behavior of hurricanes you can find cases where hurricanes have strengthened over cooler water and have weakened over warmer water. There may be a small "boost" to a hurricane's strength as it moves over the Gulf Stream, if upper air wind profiles do not change much. Some of the computer generated hurricane models have this bias built in and will rapidly strengthen a tropical cyclone if predicted to go over a warm pool of water.

The recent upturn in tropical cyclone activity was predicted long before Global Warming became a household name. The tropical Atlantic has been known to vary in cycles, and this recent upturn was expected. If you were to compare the period from 1900 to about 1950 with the 1950's until now, you would find an actual decrease in the average number of hurricanes and their intensity. It also is noted that the upswing in hurricane numbers over the past ten years or more has been in the Atlantic basin. Other hurricane formation regions have not shown this same trend.

There has been a noted increase in the numbers of hurricanes in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico since the mid-1990's. The long term average is 10 tropical storms that will form per year, of which about 6 will become hurricanes. Since the mid-1990's the average has been 15 tropical storms, of which 8 will become hurricanes. There has also been an upward trend in the greenhouse gas carbon dioxide over the past 100 years. During this time, hurricanes have gone through cycles where they have been more numerous. Some scientists have drawn a one to one correlation that since temperatures have increased, then the number of hurricanes and their intensity must increase too. As we have noted, the number one factor in tropical cyclone intensity is related to the wind profile. The upward cycle in hurricane numbers is expected to stay above average for several more years. If this trend were to continue for a considerably longer period, only then could you draw a conclusion that increased temperatures have led to increased tropical cyclone formation. It is still prudent that nations make environmentally sound decisions to use the Earth's resources wisely.

Article Submitted by: Rich Johnson TropicalWeather.net

The art of hurricane forecasting
How are hurricane forecasts made? Why are some hurricanes easier to forecast than others? Are long range hurricane forecasts reliable? Here are the answers to some common questions about hurricane forecasting.

Hurricane forecasting is heavily reliant on computer models. There are many different forecasts available which are built on different mathematical equations. Because of this, hurricane track and intensity forecasts will differ. One must know which of the hurricane forecast models is performing the best.

Hurricane forecasts are dependent on available observational data. Unfortunately, over the tropics, data is sparse. Sometimes a hurricane will seem to weaken when this was not the forecast. This can be attributed to "unseen" wind shear. The forecasts can be only as accurate as the data will allow.

Good hurricane forecasters know how to interpret all of the tools at their disposal. This includes visible, IR, and water vapor satellite imagery. It is essential to be able to correctly analyze wind flow patterns at low, middle, and high levels. Satellite derived winds are also very useful. Buoy data, ship reports, radar imagery and Hurricane Hunter information are also extremely important to interpret correctly.

It is also not wise to jump on a forecast model that deviates significantly from previous forecasts. Watch for trends in the forecast track. Also, do not focus on the forecast track many days in the future. The farther out in time, the greater the average forecast error. Any correct forecast based on a track a week or more in the future would require a great deal of luck.

Hurricane intensity forecasts are less understood than hurricane track forecasts. Sometimes hurricanes deepen or strengthen very rapidly. This process is not well understood yet, but likely occurs when a combination of synoptic and mesoscale features both favor an increase in strength.

In recent years the media has obtained hurricane forecast information without forecasters trained in proper interpretation. This has led to the improper dissemination of information to the public. The most important aspect in hurricane forecasting is experience. Nothing can replace lessons learned after many years studying the eccentricities of hurricanes.

In summary, hurricane forecasters should be experienced and know how to correctly use the tools available to them. Forecasting is also an art. A good hurricane forecaster must know how to assimilate the intangibles.

Article Submitted by: Rich Johnson TropicalWeather.net