https://phys.org/news/2018-07-aqua-satellite-large-tropical-storm.html

MODIS imagery revealed powerful thunderstorms surrounded the center of circulation and a large feeder band of thunderstorms extended from the eastern quadrant to the south. Satellite imagery shows that Ampil is about 500 miles in diameter.

The Joint Typhoon Warning Center or JTWC noted at 5 a.m. EDT (0900 UTC) on July 18 that Ampil's maximum sustained winds were near 40 knots (46 mph/74 kph). Ampil was centered near 20.9 degrees north latitude and 131.1 degrees east longitude, approximately 398 nautical miles south-southeast of Kadena Air Base.