More than four out of every five forest fires are started by people. Negligent human behavior such as smoking in forested areas or improperly extinguishing campfires are the cause of about 90% of fires. The other 10 % of forest fires are due to lightning. The 1991 wildland fires in Oakland, California, caused 25 deaths and 148 injuries. The fires destroyed over 3,000 structures, left over 5,000 people homeless and resulted in $2.5 billion in damages.
The greater Yellowstone National Park fire of 1988 destroyed or damaged private structures, including 17 mobile homes, 4 dwellings, a general store, 12 garages and outbuildings, 19 cabins, and several storage structures, and burned 1,210,730 acres of wildland. Approximately 10,000 forest fires are started each year by lightning. Approximately $100 million in annual losses result from forest and building fires caused by lightning.
Turning to the tropics, the hurricance season usually peaks in September and early October. The primary time of year for tropical cyclone formation is during the summer and autumn: July-October for the Northern Hemisphere and December-March for the Southern Hemisphere (though there are differences from basin to basin). The peak in the summer/autumn is due to having all of the necessary ingredients most favorable during this time of year: warm ocean waters (at least 26 degrees C or 80 degrees F), a tropical atmosphere that can quite easily kick off convection (i.e. thunderstorms), low vertical shear in the troposphere, and a substantial amount of large-scale spin available (either through the monsoon trough or easterly waves).
While one would intuitively expect tropical cyclones to peak right at the time of maximum solar radiation (late June for the tropical Northern Hemisphere and late December for the tropical Southern Hemisphere), it takes several more weeks for the oceans to reach their warmest temperatures The atmospheric circulation in the tropics also reaches its most pronounced (and favorable for tropical cyclones) at the same time. This time lag of the tropical ocean and atmospheric circulation is analogous to the daily cycle of surface air temperatures - they are warmest in mid-afternoon, yet the sun's incident radiation peaks at noon. See the National Hurricane Center's Frequently Asked Questions page for additional information.
Weather Log - September 1 - 10, 2001
The featured image in this months report are the Flathead fires in western Montana near Glacier National Park. The satellite image was taken on the 4th of September 2001 and shows hot spots (red) areas and smoke plumes from these fires. For updates on the 2001 fire season and activity elsewhere see the National Interagency Fire Center .
Winds and heavy rains continue to affect South Africa. Weather forecaster Rian Smit said the wind that battered Cape Town was the worst of the year and the worst he could recall for several years. "As far as the wind is concerned, this is the worst storm we have had in a very long time," he said, adding that the wind would blow through the night (5th) but probably would calm on the (6th) Thursday. Smit said the storm had brought brief but intense rains to areas already flooded by the heaviest rains in 44 years. City officials reported roofs blown off, trees toppled and roads flooded throughout the city.
Early season snow fell in the Rocky mountains in Colorado above 7,000 feet on the 7th and 8th. Weather spotters around Estes Park, Colorado reported the following snowfall amounts: 3 NE Allenspark, CO, 7.0 in; 3NE Nederland, CO, 7.0in; and 4 SW Estes Park, CO, 7.0 in.
Typhoon Danas delivered torrential rains to parts of Japan causing flooding and landslides and several deaths. The storm is the second such storm in less than a month. The storm dumped torrential rain and five people were killed. The heavy rains caused serious flooding. Rainfall could reach as high as 200 -400 millimeters (~ 8.0 inches - 16 inches) in some areas of the storm's path by Tuesday morning, the Meteorological Agency said, the storm is expected to head into northern Japan after making landfall. Typhoon Nari, meanwhile was near the islands of the Okinawan chain of Japan's southernmost prefecture (state) as of the morning of the 10th.
Meanwhile, Hurricane Erin has weakened on the 12th, and is expected to dissipate in the cool waters of the north Atlantic.
Weather Log - September 11 - 20, 2001
Tropical storm Nari has killed at least 36 people in northern Taiwan, as the capital was submerged under a torrent of floodwater. The victims were drowned, buried in landslides or electrocuted by broken power lines in the north of the island. Emergency officials stated the storm left 32 inches of rainfall in its wake since Sunday (16th). Taipei Mayor Ma Ying-jeou said the amount of rain was "unprecedented."
** Update ** - According to media reports, the death toll from Typhoon Nari climbed to 80 on Thursday (23rd) after the storm dumped record amounts of rain and triggered the worst-ever flooding in the island's capital. At least 19 people were missing and 208 injured. Nari has caused an estimated $20 million in agricultural losses, inundating nearly 10,000 hectares of farmland island-wide, the cabinet's Council of Agriculture told Reuters news agency. Nari hit the island two months after Typhoon Toraji caused flash flooding and landslides that killed more than 100 people in eastern and central Taiwan. Taiwan, a mountainous island of 23 million people, is one of the most densely populated places in the world. Many Taiwanese live or farm on mountain slopes that are prone to mudslides when soaked.
Note: Hazard event satellite images available courtesy of NOAA OSEI Satellite Images WWW site.
The Selected U.S. City and State Extremes provides a list of new monthly or unusual records that were set across the U.S. during September 2001.
For further information, contact:
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