Nadine is back; Jelawat explodes into a Category 4 typhoon

Tropical Storm Nadine is back, like a nasty cold you just can't get rid of. Nadine had moved southeastwards over cool waters on Friday and Saturday, which robbed the storm of its heavy thunderstorms and tropical characteristics. But Nadine wandered back to the west this Sunday morning over slightly warmer waters, allowing the storm to regain its heavy thunderstorms and its name. Steering currents favor a continued westwards motion for Nadine, keeping the storm far enough south of the Azores Islands that they will see only very sporadic rain showers over the next few days. Nadine will likely turn to the north over the middle Atlantic late this week, but will still probably be around a week from now. The storm is not likely to threaten any land areas for at least the next seven days.


Figure 1. True-color MODIS satellite image of Tropical Storm Nadine, taken at 9:50 am EDT Sunday, September 23, 2012. At the time, Nadine had top winds of 60 mph. Image credit: NASA.

Typhoon Jelawat explodes into a Category 4 storm
In the Western Pacific, Typhoon Jelawat put on a remarkable burst of rapid intensification, strengthening from a tropical storm with 65 mph winds to a Category 4 typhoon with 140 mph winds in just 24 hours. Jelawat is located about 200 miles to the east of the Philippine Islands, and the storm's outer spiral bands are bringing moderate rains to the eastern Philippines. Jelawat is expected to move slowly to the north-northwest to northwest, roughly parallel to the Philippines, through Tuesday. The predicted path is far enough from the Philippines to spare the islands the kind of torrential rains capable of causing major flooding. Wind shear is a light 5 - 10 knots, and Jelawat is over very warm ocean waters of 29°C. These warm waters extend to great depth, resulting in a total ocean heat content of over 100 KJ/cm^2, which is exceptionally high. These favorable conditions for intensification have prompted the Joint Typhoon Warning Center to predict that Jelawat will become a Category 5 typhoon by Monday. Satellite loops show an impressive, well-organzied typhoon with a large symmetric area of heavy thunderstorms with cold cloud tops. There remains a huge uncertainty on where Jelawat might go. The computer models fall into two distinct camps, 350 miles apart, for Jelawat's 3-day position. The models are even more divergent--700 miles apart--for the storm's 5-day position. The more westward solution provided by our two top models, the ECMWF and GFS, is the one currently depicted in the official Joint Typhoon Warning Center forecast. Given the large spread in models, the 3 - 5 day forecast for Jelawat is low-confidence.


Figure 2. Visible satellite image of Jelawat taken at 4:32 am EDT Sunday, September 23, 2012. Image credit: NOAA.

Tropical Storm Miriam in the Eastern Pacific growing more organized
In the Eastern Pacific, Tropical Storm Miriam appears poised to put on a burst of rapid intensification that would make it a hurricane on Monday. Our two top models, the GFS and ECMWF, are divergent in their long-range predictions for Miriam. The GFS shows Miriam hitting central Baja on Friday, while the ECMWF keeps the storm offshore, dissipating it a few hundred miles off the Baja coast.

Jeff Masters