Carlos weakened to a tropical storm as it moved west of Acapulco, Mexico on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Carlos was located at latitude 16.7°N and longitude 101.3°W which put it about 95 miles (150 km) west of Acapulco and about 110 miles (175 km) southeast of Lazaro Cardenas.  Carlos was moving toward the northwest at 6 m.p.h. (9 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 998 mb.  Carlos is a small tropical cyclone.  The tropical storm force winds only extend out about 50 miles (80 km) from the center and it has a Hurricane Size Index (HSI) of 1.7.  The government of Mexico has issued a Hurricane Warning for the portion of the coast that extends from Punta San Telmo to Tecpan de Galeana.  A Hurricane Watch has been issued for the portion of the coast from Playa Perula to Punta San Telmo.

Carlos was nearly stationary for several days and its winds mixed cooler water to the surface.  In addition the circulation pulled in drier air from Mexico as it got closer to the coast.  The combined effects of cooler water and drier resulted in less energy to drive the circulation and Carlos weakened to a tropical storm on Sunday.  Late in the day it started to move toward the northwest and get away from the cooler water.  Carlos is moving over an area where the Sea Surface Temperature (SST) is near 30°C.  Recent satellite images indicate that stronger thunderstorms are forming near the center of circulation.  The flow around Carlos is still pulling in drier air from Mexico and there are fewer thunderstorms in the northern half of the tropical storm.  The small size of Carlos means that it can strengthen or weaken more quickly than a larger storm because there is less mass to accelerate.  The upper level winds over Carlos have lessened and there is not as much vertical wind shear.  If Carlos remains over water, it is likely to intensify back to a hurricane on Monday.

An upper level ridge over Mexico is moving slowly toward the east and it is starting to steer Carlos toward the northwest.  The ridge is expected to continue to steer the tropical storm toward the northwest or west-northwest on Monday.  As Carlos approaches the western end of the ridge is expected to turn more toward the west-northwest.  There is some uncertainty about where the turn will occur.  Guidance from some models have Carlos turning farther east and making a landfall between Manzanillo and Cabo Corientes, while some other models have the tropical storm moving farther west before turning.  Either scenario is plausible and hence, the high degree of uncertainty about the future track of Carlos.