The Atlantic came alive with tropical cyclones this week, and the eastern Pacific continues to send storms towards Hawaii, one of which has crossed the International Date Line and become a typhoon.
The Southern California heat wave has ended, but fire danger remains high.
Let’s go Around The World.
Storms In The Tropical Atlantic
The peak of the Atlantic hurricane season is statistically September 10.
The Cape Verde season, during which waves come off Africa and develop near the Cape Verde Islands, is in full swing. Three consecutive waves have developed into named storms now that the water near Africa has warmed to 80 degrees, considered the minimum to support tropical development.
A wave came off the African coast on August 16, and despite hostile conditions (dry Saharan air in the vicinity), survived into the central Atlantic where conditions were more favorable for development. The system was named Tropical Storm Danny on August 18 and became a hurricane on August 20. The next day, winds reached the category three minimum of 115 miles per hour and Danny became the first major hurricane (category three or greater) of the 2015 season.
Danny was not so lucky after that. Strong vertical wind shear (change of wind speed or direction with height) rapidly weakened the storm east of the Caribbean islands, and once it moved into the Western Caribbean, where conditions are normally not favorable for tropical cyclones, Danny dissipated on August 24.
The same day Danny disappeared, the next wave attained tropical storm strength and was named Erika. Erika battled difficult conditions to reach the Leeward Islands where its torrential rains killed 20 people on the island of Dominica. Despite never reaching hurricane force, Erika caused widespread flooding from the Leeward Islands to Haiti. Eventually, interaction with the mountains of Hispaniola did Erika in, and the remnants drifted into the Gulf of Mexico.
Yesterday, what was left of Erika, just an area of deep moisture moving on southwest winds, caused flooding in South Carolina. At the National Weather Service’s official station at Charleston airport, more than six inches of rain was recorded.
The moral of Erika is that a tropical system doesn’t have to include powerful wind speeds to be dangerous. Rain causing mudslides and flash floods can be a killer with even a minimal tropical storm or its remnants.
Next in the series of developing African waves is now Hurricane Fred, unusual in that it developed into a hurricane so close to the African coast. Fred crossed the Cape Verde Islands yesterday, the first hurricane to do so since 1892.
Fred has now been downgraded to a tropical storm and is on a course that will take it into the central Atlantic, where it will dissipate, never threatening any large land masses.
The next named storm of the Atlantic season — and there will be one — will be called Grace.
Hurricane Kilo: A Trans-Pacific Storm
Tropical systems in the eastern Pacific typically move northwestward, where cold water is to a hurricane as a beam of sunlight is to a vampire — deadly.
Occasionally a hurricane stays far enough south to travel across the International Date Line (IDL). At this point the storm becomes a typhoon.
Hurricane Kilo is such a storm. The system formed well southwest of Mexico, dumped heavy rain on Hawaii, then turned west and crossed the 180 degree longitude line (IDL) Monday night. It is now Typhoon Kilo. Whether Kilo, whatever its designation (yes storms have crossed from west to east over the IDL) will threaten any land is uncertain, but the Pacific is a big ocean with a lot of warm water, and there is always the possibility that a hurricane/typhoon will be long-lived. Current forecasts call for Kilo to strengthen into a Super-Typhoon and continue heading west towards Asia.
In 1994, a wave south of Acapulco, Mexico became a tropical storm named John. It would last for 31 days and travel 7165 miles — both current records — before ending its journey in the North Pacific Ocean. Despite reaching category five strength and crossing the IDL not once but twice, John never threatened any land except a few small islands as either a hurricane or a typhoon.
Hurricane/Typhoon Kilo is now 12 days old. Will it approach John’s records for longevity or distance traveled? Probably not, but you never know.
Eastern Pacific Tropical Cyclones
The eastern Pacific is typically active in an El Niño year and this year is no exception. Currently Hurricane Jimena is spinning northwestward and will meet its demise in the cold north Pacific.
Of more interest is tropical depression Fourteen-E, southwest of Acapulco. This system could develop into a tropical storm and threaten Baja California by the weekend.
Finally, Hurricane Ignacio is now passing to the northeast of Hawaii and is no longer a threat to the island chain.
West Coast Fire Danger Normally Increases In The Fall
Fall and fire threat are generally correlated in southern California, as high pressure typically settles to the north and brings hot chinook (downslope) winds to the western slopes of the Coastal Range and the Sierras.
This summer, the high pressure regime over the western states has been challenged a couple of times by a more southwesterly flow associated with El Niño. The recent spate of fires in southern California has been brought under control thanks to an influx of cooler, moister air.
High temperatures in the nineties in Los Angeles the last five days have now cooled to the low 80s with the change of weather pattern.
If this new pattern continues, as it is forecast to do for the next week, the normally fiery fall might be more noted for precipitation than wildfires.
Changing Seasons; Changing Weather
In New York today, September First, the sun will be aloft for 13 hours and six minutes; on the last day of the month, there will be 11 hours and 49 minutes of daylight. This differential in the amount of sunlight is bound to affect the temperature of the earth, atmosphere, and ocean.
How do you see the seasons changing where you are?
Decoding Science. One article at a time.