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| Cliff Harris |
Everything about hurricanesEditor's note: Cliff Harris is on vacation, Meteorologist Randy Mann fills in for him.
PART I ...
Hurricanes are very intense storms that form over warm waters in tropical origins that include the Atlantic Ocean, the Caribbean Sea and the eastern Pacific Ocean west of Mexico and Central America. Hurricanes are called cyclones or typhoons in the Indian Ocean and the far western Pacific regions. Here in the Inland Northwest, we are too far to the north and west to be affected by any hurricane or tropical storm from the Pacific or Atlantic regions.
The Atlantic hurricane season normally runs from June 1 to November 30, peaking around mid-September. During this time of year, intensifying thunderstorms off the northwest coast of Africa are watched carefully, as they may soon organize and become a tropical storm or a hurricane. A tropical storm becomes a hurricane when its winds increase to above 74 miles per hour and we often see the formation of the eye. Believe it or not, inside the eye of a hurricane, the weather is usually clear or partly cloudy and the winds are generally calm. However, the wall that surrounds the eye is the most deadly and intense part of the storm.
Nearly twice as many hurricanes form in the Eastern Pacific west of Mexico and Central America than in either the Atlantic or Caribbean regions. Because of the dense populations near the Gulf of Mexico and Florida, hurricanes in the Caribbean normally receive more media attention. Since two or more hurricanes may be present at any one time, they were given alternate female and male names to avoid potential confusion.
The 2004 hurricane season has become one of the most active in recorded history. After getting off to a rather slow start, the Atlantic and Caribbean hurricane season is making up for lost time. We have now seen FOUR strong storms hit the U.S. Mainland, Hurricane Alex, Tropical Storm Bonnie, Hurricane Charley, a devastating Category 4 storm, and Hurricane Frances. It's likely that a FIFTH hurricane, Ivan, will hit the U.S. mainland soon.
The effect of warmer sea-surface temperatures definitely plays a role on hurricane development. For example, between the 1920s and 1970, ocean waters were warmer and hurricane activity was high. However, as sea-surface temperatures cooled in the 1970s, 1980s and early 1990s, we saw a decrease in tropical storms and hurricanes. This year, however, ocean temperatures have warmed up in the Caribbean and Atlantic Ocean that may be helping to fuel the development of these major storms of 2004.
Earlier this year, Cliff and I predicted that we would see about 12-15 named storms this season, with up to 8-10 of these becoming hurricane status. With the PEAK of the hurricane season arriving this week, it's very possible we may have to raise our earlier predictions, since we do expect to see more of these intense storms well into October and perhaps into November.
Whether a hurricane strengthens or falls apart depends on "wind sheer," or the difference between wind direction and speed at various levels in our atmosphere. During El Nino years, we see much warmer sea-surface temperatures along the Equatorial regions that ultimately produces strong westerly winds that often "sheer off" the tops of hurricanes. However, during La Nina (the abnormal cooling of ocean waters) and years of normal ocean water temperatures near the Equator, we see the "opposite" effect that will promote stronger and higher numbers of tropical storms and hurricanes, as is the case this season.
Much of the damage from hurricanes is caused by flooding rains, strong winds in excess of 74 miles per hour or more and even tornadoes. Perhaps the biggest threat to coastal areas from these massive storms is the "storm surge." As the hurricane approaches land, water begins to "pile up" against the shores as sea levels rise. Storm surges are essentially huge walls of water, sometimes as high as 20 feet or more and exceeding 30 to 50 miles wide that sweep onshore and often destroy everything in their paths. This phenomenon can be worsened during periods of high tides, especially during a "full moon" or "new moon" lunar phase.
Next week, I'll discuss some of the major hurricanes in U.S. history, plus the Saffir-Simpson scale, a classification on how hurricanes are measured in terms of damage and strength.
LONG-RANGE WEATHER OUTLOOK
After a period of partly cloudy skies and pleasant temperatures, it does look a bit cooler and wetter across the Inland Northwest as we approach the "new moon" cycle of Sept. 14-21. The wet weather should continue at least on-and-off into mid-October.
It's possible that we'll see one more warm period, or "Indian Summer"-type conditions toward late September and early October. Hard freezes will be likely in the region, even at the lower elevations, by no later than Oct. 13-20, probably earlier than that in some areas away from the warming waters of the lakes.
Once again, much like last year, we may see some measurable snowfalls in the Spokane/Coeur d'Alene areas by no later than Veterans Day, November 11, probably earlier than that at some elevations above 2,200 to 2,500 feet. Again, stay tuned ...
