Super-Typhoon Jelawat (Lawin) weakened slightly to 145mph last night in response to an eyewall replacement cycle, however, it was one of the most flawless such cycles I’ve seen in a while. No dry air was entrained into the core during the cycle and it occurred quickly. Jelawat now has a larger eye and has restrengthened back to 150mph. The larger eye means that typhoon force winds extend farther from the center, making Jelawat more dangerous than before.
Some strengthening is possible before Jelawat moves over the slightly cooler waters left in the wake of Super-Typhoon Sanba. After three days of a slow northwards motion, the forecast is very uncertain; the storm could turn towards Taiwan and China, or towards the Korean peninsula, Japan and the Pacific depending on the timing and strength of a frontal system over western China and how Jelawat interacts with the newly formed Tropical Storm Ewiniar to its East. This uncertainty is shown in the spread of the JTWC forecast cone. Meanwhile, the outer bands of the super-typhoon will continue to bring squally weather to the Philippines that could result in some flooding.
Tropical Storm Ewiniar could threaten the Japanese Ogasawara Islands in two to three days. But Ewiniar is expected to stay relatively weak compared to Jelawat.
Less of a threat to land are Major Hurricane Miriam in the East Pacific and Tropical Storm Nadine in the Northeast Atlantic. Hurricane Miriam rapidly strengthened from a tropical storm last night to a Category 3 hurricane this morning with 120mph winds and 958mb. It developed a pin-hole eye similar to Jelawat on the other side of the basin. There is room for further strengthening, but an eyewall replacement cycle is likely to cause weakening in the next 24-48hours.
The National Hurricane Center forecast has the hurricane moving over cooler waters and weakening into a tropical storm before being drawn Northeastwards towards Mexico’s Baja California Peninsula. Moisture from this storm could make it into the United States as it gets absorbed into a trough over the southern Inter-Mountain West states.
Tropical Storm Nadine is feeling the effects of cooler waters and has weakened to 50mph and it has a ragged convective pattern to show for it. The storm is no longer expected to regain hurricane strength. Nadine is still expected to head Westwards before being absorbed into a deep extra-tropical low that could move over the British isles. Nadine is churning up a lot of cooler waters in the northeastern Atlantic. This could have interesting implications for tropical activity in the Caribbean later this month and into October should the upward/rising phase of the Madden-Julian Oscillation return to the basin.
Bermuda – Scattered showers and thunderstorms are moving in from the West, courtesy of a slow moving trough and stationary front. They are providing a chance for rain for most of the working week. Temperatures should stay fairly warm, in the low 80s for the first full week of Fall.