“Rapid intensification is an increase in a tropical cyclone’s maximum sustained wind speed of at least 35 miles per hour in a 24-hour period,” explains NCEI researcher Jim Kossin. It’s one that has been growing in recent years and one that’s on our minds this week as multiple systems are brewing in the Atlantic and Pacific.
The National Hurricane Center is monitoring a tropical wave off Guinea-Bissau in Africa. Although there is low chance of development in the next 48 hours, there is a 60% likelihood of becoming a tropical depression within seven days, which forecasters have given. If it does get its act together, it will be the next one on the Atlantic list: Gabrielle. Continuing its west to west-northwest direction at around 15 mph, the wave should remain out over open ocean at least for now. Climatologically, the sixth named Atlantic season storm historically forms on August 29, so this would-be system is showing up just in time.
In the eastern Pacific, Tropical Storm Kiko is already showing its strength. Up to September 1, winds had been at a sustained 65 mph, and the NHC projection shows hurricane force with 85 mph winds on September 2. By September 4, Kiko will likely have winds up to 110 mph as it slowly moves westward between Hawaii and Central America. AccuWeather Lead Hurricane Expert Alex DaSilva says, Hurricane Kiko will be entering an area where atmospheric conditions are conducive to strengthening. It is not out of the question that Kiko can reach major hurricane status over the coming days. There are no near-term impacts to land expected, but Hawaii should be prepared for changes, as next week’s midweek could bring tropical rain, windy breezes, and higher surf if the track drifts in closer.
Off Mexico’s south-central coast, another tropical wave is quickly organizing. It is around 100 miles from the coast, and this system has been assigned a 90% chance of becoming a tropical cyclone within 48 hours. It will be named Lorena when it is named. Forecast models indicate Lorena might take a path towards Baja California Sur later in the week, and tropical storm watches might be posted as soon as September 2. Heavy rain along southwestern and west-central coastal Mexico will be widespread even if full cyclone development does not occur, with flash flooding a true threat in mountainous areas. The NHC alerts, Heavy rainfall associated with Tropical Storm Lorena will begin to affect Baja California Sur on Wednesday, and southwestern Sonora by Thursday. This will increase the risk of life-threatening flash flooding and mudslides, especially in those areas of higher terrain.
The effects do not have to be contained at the borders of Mexico. As Lorena wanders north, copious tropical moisture can swamp the U.S. Southwest. Predictions are that areas of Arizona and New Mexico stand a chance at 1–2 inches of rain, with locally heavier totals Thursday through the weekend. For arid regions of the Desert Southwest, the rain is a blessing and a curse refreshing dry soils but also causing flash flooding in sensitive areas.
Meteorologists say that the beginning of September is ideal for tropical cyclone formation in the Atlantic and Pacific. During the historic 2020 season, ten storms developed in September alone, the majority of them rapidly intensifying sustained by record-warm ocean waters. Although this Atlantic hurricane season has to date been comparitively subdued to date with such conditions as the high wind shear and stable upper-atmospheric conditions, it by no means is yet at its peak. With the African monsoon continuing south and wind shear dropping, there could become more conducive conditions for growth such storms as the present Atlantic wave being well worth watching very closely.
For coastal dwellers and those in areas of possible impact, the message is this: listen up, prepare ahead, and be prepared to move quickly if watches or warnings are issued. The tropics are warming up, and with multiple systems moving across the face of the earth, preparation is the best defense.
