Invest 97L Spinning Near Bermuda; Phanfone a Potential Threat to Japan

By: Dr. Jeff Masters , 2:27PM,GMT on September 29,2014

An area of low pressure (Invest 97L) has formed just west of Bermuda, and is bringing heavy rain showers and gusty winds to the island. At 9:45 am AST Monday, the Bermuda Airport reported a waterspout. Winds have gusted as high as 39 mph on the island this morning, and 0.47" of rain had fallen between midnight at 11 am local time on Monday. Satellite loops and Bermuda radar show that 97L has a pronounced low-level spin, but very little in the way of heavy thunderstorms near the center of circulation. The heaviest thunderstorms were in a band 100 - 150 miles to the northeast of the center, and this structure is characteristic of a subtropical storm, not a tropical storm. With wind shear expected to stay a moderate 15 - 20 knots through Monday night, there is a small window of opportunity for 97L to develop into a subtropical cyclone before wind shear rises to a prohibitive 30 - 45 knots on Tuesday. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 97L 2-day and 5-day odds of development of 30%.


Figure 1. MODIS satellite image of 97L, taken at approximately 1 pm EDT Monday September 29, 2014. Image credit: NASA.

Eastern Pacific's Rachel no threat
In the Eastern Pacific, Hurricane Rachel peaked as a Category 1 storm with 85 mph winds on Sunday morning off the Pacific coast of Baja Mexico, and is now on a weakening trend due to steadily increasing wind shear. Rachel will move little this week and dissipate without affecting any land areas. Rachel's formation gives the Eastern Pacific east of 140°W 17 named storms, 12 hurricanes, and 7 intense hurricanes so far this year. An average Eastern Pacific hurricane season sees 15 named storms, 8 hurricanes, and 3 intense hurricanes during the entire year, with three of those named storms and one hurricane occurring after September 25.

Another area of disturbed weather (Invest 90E) was located near the coast of southern Mexico on Monday morning, and was headed slowly west-northwest to northwest. This disturbance has good support from all three of our top tropical cyclone genesis models to develop late this week. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 90E 2-day and 5-day odds of development of 20% and 70%, respectively. 90E is a threat to bring heavy rains to the Pacific coast of Mexico throughout the week.


Figure 2. MODIS satellite image of Hurricane Rachel, taken at approximately 6 pm EDT Sunday September 28, 2014. At the time, Rachel was a Category 1 storm with top sustained winds of 75 mph. Image credit: NASA.

Tropical Storm Phanfone a potential threat to Japan
In the Western Pacific, Tropical Storm Phanfone is steadily intensifying as it heads west-northwest at 13 mph towards the Northern Mariana Islands. Phanfone is expected to be near Category 1 typhoon strength when is passes about 250 miles north of Guam near 18 UTC on Tuesday. The storm is expected to intensify into a major typhoon, possibly a super typhoon, late in the week, and the 00Z Monday run of the GFS model shows the storm coming very close to the coast of Japan this weekend.

Hurricane expert Steve Gregory has a more detailed look at 97L in his Monday afternoon post.

Jeff Masters