A reconnaissance aircraft confirmed a weakening trend in Hurricane Guillermo that had been suggested by satellite imagery.  At 11:00 p.m. EDT on Sunday the center of Hurricane Guillermo was located at latitude 15.5°N and longitude 145.0°W which put it about 725 miles (1165 km) east-southeast of Hilo, Hawaii.  Guillermo was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 85 m.p.h. (145 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 981 mb.

An upper level trough north of Guillermo is producing southwesterly winds over the top of the circulation.  Those winds are causing vertical wind shear and are inhibiting the upper level divergence on the western side of the circulation.  In addition Guillermo is gradually moving over cooler Sea Surface Temperatures (SSTs).  A combination of wind shear and cooler SSTs will continue to weaken the hurricane.

A subtropical ridge is steering Guillermo toward the west-northwest and that general motion is expected to continue.  On its anticipated track Guillermo would approach the Big Island of Hawaii in about 72 hours.  It will likely be a tropical storm at that time.