Irene could have many siblings
Weekly Weather Almanac
• Week's warmest temperature: 97 degrees on Aug. 28
• Week's coldest temperature: 52 degrees on Aug. 22
• Weekly precipitation: 0.00 inches
• Precipitation month to date: trace
• Normal precipitation month to date: 1.14 inches
• Precipitation month to date last year: 0.47 inches
• Precipitation year to date: 22.62 inches
• Normal precipitation year to date: 15.58 inches
• Precipitation last year to date: 19.26 inches
• Normal annual precipitation: 26.77 inches
• Total precipitation last year: 33.15 inches
• Precipitation predicted this year: 35.19 inches
• Record annual precipitation: 38.77 inches in 1996
• All-time least annual precipitation: 15.18 inches in 1929
Readings taken week ending Sunday, 3 p.m., Aug. 28
With powerful Category 3 Hurricane 'Irene' (as of this Thursday, Aug. 25 writing) threatening much of the East Coast later this last weekend of August, I've received numerous questions concerning hurricanes and tropical storms.
Many subscribers have asked me to explain how hurricanes are 'born' and where their 'birthplaces' are found, including Irene.
Like most Atlantic hurricanes, Irene was born just off the coast of West Africa about 10 days ago as a 'tropical wave.' Within 72 hours, it became a tropical storm, the ninth thus far of this very active 2011 season with at least another dozen named storms still likely between now and the end of the hurricane season on Nov. 30.
On Monday, Irene became a Category 1 hurricane, raking Puerto Rico with 80 mph sustained winds that damaged many roofs, uprooted trees and caused widespread lowland flooding on the island. By Wednesday, Irene was a very dangerous Category 3 hurricane nearing Florida and the Bahamas.
Irene was expected to travel up the East Coast over the weekend. By the time one reads this column, we'll know if this massive storm hit places like Boston and New York City over the weekend. We're hoping Irene is not like the disastrous September 1938 hurricane that moved through the Northeast and caused billions of dollars in damage and killed hundreds of people.
Irene was earlier formed as hot, dry air flowed westward from North Africa's Sahara Desert toward the Atlantic Ocean. An atmospheric 'imbalance' was created that developed a 'kink' in the wind patterns near the Canary Islands. Sparked by the increased friction of these widely-opposing air masses, strong thunderstorms are ignited, eventually developing into a series of tropical waves, that become tropical storms and later sometimes deadly hurricanes that rip through the Caribbean Islands and occasionally, like Irene, into the U.S. Mainland.
It takes a complex series of chain reactions and self-feeding processes to create a monster hurricane like Irene. As the tropical storm intensifies, the pressure in its central core or 'column' is further lowered, creating a partial vacuum, a dangerous situation.
The lower the barometric pressure, the more warm and moist ocean air is sucked into the storm. The faster this whirlpool-like vortex spins, the higher the walls of the hurricane extend into the atmosphere.
I should likewise mention that an important feature of a hurricane is the 'inward spiraling motion' that is initiated by the earth's rotation - a 'counterclockwise' motion in the Northern Hemisphere and a 'clockwise' motion in the Southern Hemisphere.
As seen from above, a hurricane appears to be a huge spiraling mass of clouds converging around a small area called an 'eye' that is usually entirely free of clouds. Many people have been lured from protective shelters when the eye passed overhead thinking that the worst was over, only to be caught by violent winds often exceeding 120 miles per hour on the back side of the hurricane.
The main areas of high winds and torrential rains usually extend some 35 to 50 miles out from the center of the hurricane's eye. Farther out, stretching over thousands of square miles in spiral bands, conditions are less extreme, but winds can still be violent and rains quite heavy at times.
Hurricanes usually move at speeds ranging from 10 to 20 miles per hour. However, as a hurricane pushes from the Caribbean towards the U.S. Mainland, it often accelerates over the warm, open waters, gaining strength, again like Irene, before reaching Florida and points north into New England.
Once a hurricane hits land or encounters cooler waters in the northern latitudes, it usually loses much of its intensity, being starved of both its heat-energy resources and vital supplies of moisture. But, not always.
Hurricane Irene actually strengthened on Wednesday to a dangerous Category 3 storm as it headed towards the Bahamas with the entire East Coast in its sights. Irene could later reach a Category 4, the second highest level on the Saffir-Simpson Scale.
This is the first hurricane in several years to threaten the Mid-Atlantic States and New England. Already, as of this writing, Ocracoke Island, located on a tiny barrier reef off North Carolina, has been evacuated. Navy ships on Thursday were moved far out to sea away from the potential wrath of Irene.
By the time one reads this column on Monday, Irene should have brought its high winds and heavy rains to much of New England before heading into extreme southeastern Canada. Stay tuned.
North Idaho weather review
It's been more than six weeks since we've had a significant storm in our part of the country. No measurable precipitation has been gauged in town in more than a full month. It was 92 degrees on Wednesday for the opening of the fair, August's hottest day yet.
The good weather has been great for outdoor activities, especially near the lakes, and most recently during this week's 2011 edition of the North Idaho Fair and Rodeo. As always, I thoroughly enjoyed talking with my fans in the Coeur d'Alene Press booth on Thursday. Sharon and I spent hours Thursday evening visiting this year's interesting exhibits and attractions.
Longer-term weatherwise, the current prolonged dry spell may not end until late September, early October or even farther down the meteorological roadway, if the strong stationary high pressure ridge centered over the Inland Empire doesn't break apart anytime soon. There are no significant storms in sight for at least another week, just isolated sprinkles.
This means that we'll continue to see high fire danger levels locally well into the fall season. We've already seen several forest and brush fires in the past few weeks including the one started by kids playing with matches in mid August near Kellogg.
Our next chance for a bit cooler temperatures and a few scattered light showers should be in early September, but don't hold your breath.