3 September 2008 MAR 110 HW9 Hurricane Forecasts 1Homework 9: Hurricane Forecasts (adapted from Pipkin et al.) Movement of Hurricanes The advance of a tropical storm or hurricane is controlled by the prevailing surface currents of the equatorial Atlantic Ocean. Tropical storms are moved westward by the North Equatorial Current, but there is extreme variability in the latitudinal (north-south) location of the storm track. Tropical cyclones may move through the Caribbean Sea between South America and the east-west chain of islands east of Cuba and Hispaniola, or they may be deflected north of Cuba into the Bahamas. Storms approaching the Atlantic coast of North America may be deflected northward by the Gulf Stream, or their advance may be sufficiently rapid to move them onshore into Florida or Georgia. Tropical cyclones developing in the Caribbean may move westward to Central America, or as did Hurricane Mitch in 1998, they may be forced northward across the Gulf of Mexico by the Loop Current. Since 1949, seven Atlantic hurricanes have crossed into the eastern Pacific Ocean, becoming Northeast Pacific hurricanes or tropical storms. Another factor that may influence the advance of tropical storms in the Atlantic Ocean is the presence of warm or cold weather fronts or cells on the North American continent during the approach of the storm. Strong clockwise (anti-cyclonic) winds of high-pressure weather cells may slow the approach of tropical storms, or even stop their approach entirely. Hurricanes "stalled" in the Gulf of Mexico or the Atlantic Ocean may intensify, degenerate, or be deflected to the northeast without making any landfall on the North American continent. The unpredictable nature of hurricane movement is perhaps best shown by the "zig-zag" approach of Hurricane Elena in September 1985 (Figure 9-7). Figure 9-7 Hurricane Elena Trajectory The track of Hurricane Elena in the Gulf of Mexico during September, 1995. Elena strengthened to hurricane status in the northern Caribbean Sea between Cuba and Hispaniola, then moved westward until it encountered the Loop Current in the Gulf of Mexico. The Loop Current deflected the storm to the northeast, where it "stalled" off Florida, then made a "retrograde" motion nearly due westward across the coastal areas of the Florida Panhandle and3 September 2008 MAR 110 HW9 Hurricane Forecasts 2Alabama-before making landfall on the Mississippi coast. Forecasting of Hurricanes Because it is so critical to assess the strength of tropical cyclonic storms, the National Oceanic and Atmospheric Administration (NOAA) operates the National Hurricane Center in Miami, Florida. The National Hurricane Center distributes tropical weather, hurricane, and severe storm information to the public by television, radio, and the Internet. Its web site, at <http://www.nhc.noaa.gov>, contains the latest forecasts for tropical storm activity, reconnaissance data, and historical storm data for the North Atlantic, Eastern Pacific, Central Pacific, Western Pacific, and other regions. Another «official" source of information is the NOAA National Climatic Data Center, which contains information on hurricanes, El Nino, global climate, and other weather data. The NCDC has images and movies of hurricanes, tropical storms, typhoons, and other severe storms at <http://www.nodc.noaa.gov/ol/ satellite/oIimages.html>. Other web sites providing hurricane information and graphics are listed in the Bibliography. REFERENCES Pipkin, B.W., D.S. Gorsline, R.E. Casey, D.A. Dunn & S.A. Schellenberg, “Laboratory Exercises in Oceanography”, 3rd Edition, W.H. Freeman & Co., 2001. (LEiO)3 September 2008 MAR 110 HW9 Hurricane Forecasts 3 EXERCIZE 9-1 HURRICANE FORECASTING 1. The hurricane tracking chart in Figure 9-8 is a modified version of one available from the National Oceanic and Atmospheric Administration (NOAA). Plot the location of the eye of hurricane Zeke from July 12 to 14 1998 using the information in Table 9-4. TABLE 9-4 (a) If the radius of maximum wind from the eye of the hurricane is 150 nautical miles, and the radius of all storm winds is 300 nautical miles, predict the location and estimated time of landfall for Hurricane Zeke. Recall that one degree of latitude equals 60 nautical miles. (b) At what date and time would you issue a hurricane watch for the Miami region? (a) When would you issue a hurricane warning for the Miami region?3 September 2008 MAR 110 HW9 Hurricane Forecasts 4 Figure 9-8 Hurricane Tracking Chart TABLE 9-5 2. Plot the location of the eye of Hurricane Zeke during July 15 and 16 1998 on Figure 9-8 using the data in Table 9-5 (a) Compare your estimated landfall from Question 2 to the true landfall. How accurate (day and time) was your estimate? _ (b) Compare your hurricane watch and warning predictions to the ultimate landfall. Did3 September 2008 MAR 110 HW9 Hurricane Forecasts 5Hurricane Zeke make landfall at your predicted geographic location? _ (c) If Hurricane Zeke did not make landfall at your predicted location, why not? (What atmospheric or oceanographic factors might have affected the storm's path?)