A tropical wave located a few hundred miles southwest of the Cabo Verde Islands on Tuesday morning was headed west at about 15 mph. Satellite imagery showed that the wave had a modest-sized area of heavy thunderstorms that were poorly organized. The system was located far enough south of the dry air of the Saharan Air Layer to favor development, and sea surface temperatures near 27-28 degrees Celsius (81-82°F) were also favorable for development. However, moderate to high wind shear of 15-25 knots was interfering with development.
The wave has considerable support for development from the major models, with most of them showing a tropical depression or tropical storm forming by the end of the week. The system is expected to follow a west to west-northwest track through next week, with most of the models showing it tracking a few hundred miles northeast of the Leeward Islands by the middle of next week. However, some of the model ensemble forecasts do show a potential threat to the islands, and residents there should monitor future forecasts.
In their 8 a.m. EDT Tuesday Tropical Weather Outlook, the National Hurricane Center gave the wave 2-day and 7-day odds of development of 20% and 60%, respectively. The next name on the Atlantic list of storms is Gabrielle.
Tropical Storm Lorena aiming to make landfall in Mexico and bring moisture to U.S. Southwest
A tropical depression that formed off the west coast of Mexico on Sunday night was upgraded to Tropical Storm Lorena at 11 a.m. EDT Tuesday. Lorena developed about three weeks ahead of the typical formation date of September 21 for the twelfth named storm of the year in the Eastern Pacific. Lorena was centered around 240 miles (385 km) west of Manzanillo, heading northwest (parallel to the coast) at 14 mph (75 km/h). Top sustained winds were 45 mph (75 km/h).
Sea surface temperatures ahead of Lorena through Wednesday will be 29-30 degrees Celsius (84-86 degrees Fahrenheit), about 0.5-1.0°C (1-2°F) above average for early September. Moreover, Lorena is embedded in a moist atmosphere (mid-level relative humidity 75-80%), and wind shear will remain light (5-10 knots) through at least Thursday. With these favorable factors in play, Lorena will likely become a strong tropical storm, as predicted by the HMON, HWRF, HAFS-A, and HAFS-B intensity models and reflected in the National Hurricane Center forecast, and it could hit Category 1 hurricane strength as soon as late Wednesday, as predicted by NHC.
Increasing wind shear and sharply chillier waters will likely weaken Lorena – perhaps back to tropical storm strength – before a recurving path brings it onto the sparsely populated west coast of Mexico’s middle Baja Peninsula on Friday or Saturday, bringing rains of as much as 8-12 inches near its path across the peninsula and the Gulf of California. By late weekend, Lorena’s weakening remnants will sweep into the U.S. Southwest, perhaps bringing heavy showers and thunderstorms to parts of drought-stricken Arizona and New Mexico and into northwest Texas.
Intensifying Kiko could become a major hurricane between Mexico and Hawaii
Well west of Lorena over the remote northeast Pacific, Hurricane Kiko will be flexing its muscles this weekend. Despite conditions that aren’t stunningly favorable – a mid-level atmospheric humidity of only around 55-60 percent, moderate wind shear of 10-15 knots, and sea surface temperatures around 28 degrees Celsius (82°F) that are near-average for early September – Kiko was a well-organized hurricane on Tuesday morning, already wrapping intense showers and thunderstorms (convection) and trying to carve out an eye. As of 11 a.m. EDT Tuesday, Kiko was centered about 1,800 miles (2,900 km) east of Hilo, Hawaii, heading west at 6 mph (9 km/h) with top sustained winds of 85 mph (140 km/h).
The HWRF, HAFS-A, and HAFS-B intensify models all bring Kiko to Category 3 major-hurricane strength by Wednesday or Thursday as the hurricane plows just north of due west across open water far from land. Kiko’s strengthening is expected to level off toward the weekend as the storm traverses slightly cooler water and hits drier upper-level air.
There’s high uncertainty on the long-term track of Kiko among the GFS, European, and experimental Google ensemble models. Some of the ensemble members bring Kiko over or near Hawaii about a week from now, while others take it north or south of the islands. Most hurricanes in the Central Pacific that carve out such a track weaken to tropical-storm or tropical-depression strength before they reach Hawaii, if they make it there at all, and there’s plenty of time to keep an eye on how Kiko fares.
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