DataStreme WES Week Four: 27 September-1 October 2004

• The travels of Hurricane Jeanne -
• Jeanne traveled across Florida on Sunday after making landfall along Florida's Atlantic coast near Vero Beach late Saturday night as a Category 3 on the Saffir-Simpson Hurricane Intensity Scale. As it moved across the Florida Peninsula on Sunday, Jeanne weakened to a marginal hurricane, but still was accompanied by strong winds and locally heavy rain. More than one million customers were without electric power. [CNN]
• Jeanne swept across the Bahamas on Friday and early Saturday with winds of up to 100 mph and torrential rains. [CNN]
• While moving along the northern coast of Hispaniola as a tropical storm, Jeanne left a trail of destruction due to the heavy rains and resulting mudslides. As many as 1500 people died in Haiti, where civil unrest has arisen during this past week despite humanitarian relief efforts. [CNN] The Haitian flooding has been caused in part by the widespread and unregulated deforestation that has removed much of the ground cover. [CNN]
• Inspecting the eyewall of Hurricane Jeanne-- A portfolio of pictures taken of the clouds that formed the eyewall of Jeanne was posted by NOAA scientists. These photos were taken by from NOAA hurricane hunter aircraft that penetrated the eye of Hurricane Jeanne last week when the hurricane was over the western Atlantic. [NOAA News]
• An aerial view of Ivan's destruction --Last week NOAA posted more than 1300 aerial images of the destruction caused by Hurricane Ivan over the previous weekend when the hurricane made its first landfall along the Gulf Coast near Mobile Bay. [NOAA News]
• Summer flooding in China is deadly -- Chinese government officials reported last week that the torrential rains during this past summer's rainy season had been responsible for the deaths of 1029 people by mudslides and swollen mountain streams. Nearly $8 billion in damage was also caused by the rain. [USA Today]
• Coral reefs in the Caribbean threatened -- The World Resources Institute recently reported that a study indicates that approximately two-thirds of the coral reefs in the Caribbean are now threatened by a variety of pressures associated with human activity, to include overfishing and pollution. This environmental research group recommends better protection efforts be instituted. [ENN]
• Water in the skies may not be safe -- The US Environmental Protection Agency (EPA) has reported that tests run on the water carried on one of eight passenger liners flying over the US fails EPA standards because it contains unsafe levels of coliform bacteria. [ENN]
• Agreement reached for international water sharing talks in South Asia -- Officials from India and Bangladesh have agreed to jointly study the availability of water from the Teesta River that runs through the two countries in an effort to arrive at water-sharing negotiations. [ENN]
• Canadian coastal cities cited as major sewage polluters -- The Sierra Legal Defense Fund recently reported that at least one-half dozen coastal cities in Canada continue to dispense millions of gallons of nearly untreated sewage into surrounding waters. [US Water News Online]
• International help requested in water dispute -- State and provincial officials from Missouri, Minnesota and Manitoba are petitioning the International Joint Commission to review and reconcile the dispute over two North Dakota water projects that could carry invasive species and diseases between the watersheds of the Missouri River and Red River of the North. [US Water News Online]
• New structure within the West Antarctic ice sheet found -- A group of British and US scientists recently reported finding a huge fold in the ice of the West Antarctic ice sheet using radar, suggesting a relatively rapid flow of the ice sheet. They believe that their discovery means that the ice sheet is more susceptible to change than previously thought and could potentially cause a rise in sea level over the next several centuries. [EurekAlert!]
• Global and US Hazards/Climate Extremes -- A review and analysis of the global impacts of various weather-related events, including drought, floods, and storms during the current month. [NCDC]
• Global Water News Watch -- Other water news sources can be obtained through the SAHRA Project at the University of Arizona [SAHRA Project]
• Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Controlling Indoor Humidity

In public buildings as well as individual homes, it is sometimes desirable to alter extremes of relative humidity so that living spaces are more comfortable. For human comfort, optimum relative humidity is between about 30% and 50%. When indoor air is exceptionally dry, a humidifier may be used to add water vapor to the air, but when indoor air is excessively muggy, a dehumidifier may be used to remove water vapor from the air.

As cold, dry winter air is drawn indoors and heated by a furnace, its relative humidity declines--sometimes to uncomfortably low levels. Suppose, for example, that outdoor air has a temperature of -20 ºC (-5 ºF) and relative humidity of 50%. If that air were brought indoors and heated to 21 ºC (70 ºF), its relative humidity drops to about 2% -- well below the optimal winter indoor relative humidity of 30% to 50%. At such very low relative humidity values, people often feel discomfort caused by dry skin and irritation of the mucus membranes in their nose and throat. Also, wood furniture dries out and may crack and become unjointed. Discharge of static electricity (e.g., after walking across a carpet and touching a metal doorknob) can be a nuisance in dry rooms.

One remedy for excessively low indoor relative humidity is a device known as a humidifier. A humidifier elevates the relative humidity of indoor air to more comfortable levels by evaporating water into the air (increasing the vapor pressure). A common humidifier design consists of a wheel that continually rotates a porous belt (or pads) into and out of a reservoir of water. A fan blows air through the wetted belt, water evaporates into the air stream, and the more humid air circulates through the dwelling.

On the other hand, a dehumidifier may be desirable during warm muggy summer days. In addition to discomfort caused by reduced evaporative cooling, high values of indoor humidity can increase the incidence of mold and mites. A dehumidifier lowers the relative humidity of indoor air to more comfortable levels by inducing condensation of water vapor (decreasing the vapor pressure). In a standard dehumidifier, a fan draws humid air past a cold refrigerated coil. Air in contact with the coil is chilled to saturation, water vapor condenses on the coils and liquid water drips from the coils into a collection reservoir or through a hose into a drain. Most dehumidifiers function best when the air temperature is at or above 18 ºC (65 ºF).

Click on forecast map for locations across the country where today's indoor relative humidity is expected to be too high or too low in the absence of any controls on indoor humidity. For an interactive applet (from the University of Wisconsin-Madison) that explores the relationships between temperature, dewpoint, and relative humidity, go to http://profhorn.meteor.wisc.edu/wxwise/museum/a7/a7exercise1.html. Follow instructions and note how the indoor relative humidity changes with changes in outdoor conditions.

Concept of the Week: Questions

1. A humidifier elevates the relative humidity by causing [(evaporation)(condensation)].
2. A dehumidifier reduces the relative humidity by causing [(evaporation)(condensation)].

• 28 September 1986...Flash flooding swept a car into a swollen creek from off the Kamehameha Highway on the Hawaiian island of Oahu. The driver held onto some branches until help arrived, but the strong current stripped him of his clothes and watch. (Accord Weather Calendar)
• 28 September 1986...Torrential rains and floods were responsible for South Africa's worst natural disaster in Natal. As much as 35 in. of rain fell between the 25^th and 29^th to the northeast of Empangen, resulting in 317 deaths and 163 people missing. Topsoil from some farms was completely washed away leaving only bedrock. (Accord Weather Calendar)
• 29 September 1959...Hurricane Gracie made landfall near Beaufort, SC with sustained winds of 97 mph and a peak gust of 138 mph. Ten people were killed in South Carolina and Georgia. As the weakening storm moved through Virginia on the 30th, she spawned an F3 tornado at Ivy, VA, which killed 11 people. On the same day, a storm produced 28 inches of snow at Colorado Springs, CO. (David Ludlum)
• 29 September 1983...Heavy rains began in central and eastern Arizona that culminated in the worst flooding in that state's history. Eight to ten inch rains across the area caused severe flooding in southeastern Arizona that resulted in thirteen deaths and 178 million dollars damage. President Reagan declared eight counties of Arizona to be disaster areas. (The Weather Channel)
• 30 September 1882...The world's first hydroelectric power plant (later known as Appleton Edison Light Company) began operation on the Fox River in Appleton, WI using a 42-inch waterwheel that powered two direct current generators to provide a total of 25 kilowatts of power. (Wikipedia, Energy Quest)
• 30 September 1932...Tropical cyclone rainfall of 4.38 inches at Tehachapi in southern California over 7 hours caused flash floods on Auga Caliente and Tehachapi Creeks resulting in 15 deaths. (The Weather Doctor)
• 30 September1935...The Boulder Dam, renamed the Hoover Dam in 1947 was dedicated at Boulder City, NV. This concrete-arch dam supplied the first U.S. hydroelectric plant to produce a million kilowatts, with much of the power serving the Los Angeles area. (Today in Science)
• 1 October 1976...Hurricane Liza brought heavy rains and winds to Brazos Santiago, Mexico, causing a dam to break on the Cajoncito River, which killed 630 people as a wall of water crashed into the town of La Paz. (The Weather Doctor)
• 1 October 1893...The second great hurricane of the 1893 season hit the Mississippi Delta Region drowning more than 1000 persons. (David Ludlum)
• 1 October 1997... Flash flooding in Nogales, AZ resulted from 2 to 3 inches of rain. One hundred homes and 30 businesses were flooded and five vehicles floated down Western Avenue. (Accord Weather Calendar)
• 2 October 1867...A hurricane struck Galveston, TX with a storm tide that produced $1 million damage. (Intellicast)
• 2 October 1882...A major hurricane struck the Louisiana Delta with 100-mph winds and 12-foot storm tide which inundated the bayous resulting in 1500 deaths. (Intellicast)
• 2 October 1898...A hurricane struck the Weather Bureau (now National Weather Service) hurricane observation post at Carolina Beach, North Carolina and swept away the office's outhouse. The storm became known as the "Privy Hurricane". (Northern Indiana NWSFO)
• 3 October 1841...The "October Gale," the worst of record for Nantucket, MA, caught the Cape Cod fishing fleet at sea. Forty ships were driven ashore on Cape Cod, and 57 men perished from the town of Truro alone. Heavy snow fell inland, with 18 inches near Middletown, CT and 3 inches at Concord, MA. (David Ludlum)
• 3 October 1912...The longest dry spell of record in the U.S. commenced as Bagdad, CA went 767 days without rain, ending on 9 November 1914. (David Ludlum)

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Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2004, The American Meteorological Society.