Typhoon Choi-Wan passed the island of Iwo To stirring up heavy surf, hurricane-force winds and torrential, flooding rains. This weekend, it will continue on its northeasterly track paralleling Japan, while its center remains in the open Western Pacific Ocean.

Microwave and infrared imagery from NASA’s Aqua satellite during the early morning hours of September 18 revealed extremely high thunderstorms in Typhoon Choi-Wan as it passed the island of Iwo To and was approaching Chichi Jima.

NASA satellite imagery showed that the tops of the thunderstorms are so high they reached the tropopause, the level of atmosphere between the troposphere and stratosphere. Those high thunderstorms mean very heavy rainfall for the area underneath. The cloud tops extended to the 200 millibar level in the atmosphere where temperatures are as cold or colder than -63 Fahrenheit.

Microwave images are created when data from NASA’s Aqua satellite Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) instruments are combined. These microwave images indicate where there is precipitation or ice in the cloud tops and the latest microwave image revealed Choi-Wan had cold, high thunderstorms.

On September 18 at 11 a.m. EDT, Choi-Wan was located 120 miles west-northwest of Iwo To, near 25.8 north and 139.4 east. It was moving north-northeast near 13 mph. Choi-Wan’s maximum sustained winds were near 126 mph and those winds were still generating huge waves, as high as 41 feet.

AIRS Infrared satellite imagery showed that Choi-Wan has maintained a very well-defined eye with a secondary outer eyewall. The infrared imagery also showed the stark temperature contrast between the icy cloud tops in the storm against the warm waters in the Western Pacific Ocean that continue to power the storm.

The Joint Typhoon Warning Center (JWTC) noted their “environmental analysis indicates Choi-Wan has crested the western edge of the mid-level steering subtropical ridge axis in a corridor of low vertical wind shear and warm sea surface temperatures (well in excess of 28 Celsius or 82 Fahrenheit).”

The JWTC said that Choi-Wan may intensify a little over the next day because it’s in a favorable environment. After that, the storm will begin weakening and transitioning into an extra-tropical storm.

Marty was still holding onto tropical storm status on September 18, with maximum sustained winds near 40 mph and taking a slow march through the Eastern Pacific Ocean. At 11 a.m. EDT he was located about 360 miles west-southwest of the southern tip of Baja California, near 18.9 north and 112.4 west. Marty is moving near 7 mph and has a minimum central pressure near 1004 millibars. Over the past two days, he only moved 40 miles!

The GOES-11 satellite captured an image of Tropical Storm Marty off the western Mexican coast on September 18 at 12:45 p.m. EDT. GOES is operated by the National Oceanic and Atmospheric Administration. NASA’s GOES Project, located at NASA’s Goddard Space Flight Center, Greenbelt, Md. creates some of the satellite images from the GOES satellites.

The National Hurricane Center reported that there was a “burst of deep convection (rising air and thunderstorm development)” near Marty’s center this morning, however, cloud top temperatures (as measured by NASA’s Atmospheric Infrared Sounder (AIRS) instrument on the Aqua satellite) have begun to warm. Warming cloud top temperatures are indicative of thunderstorms that have less strength than those in stronger tropical cyclones.

Marty’s fate over the weekend lies in cooler waters and drier air. Those are the two factors he’s going to face as he continues moving, and they’ll weaken him over the weekend. Marty will likely be a remnant low pressure area by the beginning of next week.