 The Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert on the system on August 4 and it was designated a tropical depression by both the JTWC and the Japan Meteorological Agency (JMA) later that day.The depression strengthened into a tropical storm on August 5, and the JMA designated it Tropical Storm Saomai.Saomai continued moving toward the northwest and passed over the Mariana Islands on August 6 while continuing to strengthen, and was upgraded to a severe tropical storm by the JMA later that day.