Tropical Storm Marty intensified on Sunday and the government of Mexico issued a Tropical Storm Watch for a portion of the west coast.  At 2:00 p.m. EDT on Sunday the center of Tropical Storm Marty was located at latitude 15.0°N and longitude 102.8°W which put it about 235 miles (380 km) southwest of Acapulco, Mexico.  Marty was moving toward the north-northeast at 6 m.p.h.  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 997 mb.  A Tropical Storm Watch has been issued for the portion of the coast from Acapulco to Lazaro Cardenas, Mexico.

The structure of Tropical Storm Marty improved on Sunday morning.  A long rainband stretched around the southern and eastern sides of the circulation and more thunderstorms developed near the center or circulation.  Marty is over water where the Sea Surface Temperature (SST) is near 30°C, which means there is a lot of energy in the upper ocean.  However, an upper level trough extends from the western Gulf of Mexico across northern Mexico.  The upper level trough is causing westerly winds, which could already be producing vertical wind shear over the northern half of the circulation of Tropical Storm Marty.  Very warm SSTs mean that the potential for intensification exists, but the vertical wind shear will limit how much intensification actually occurs.  If the upper level winds get stronger, they could shear the top half of the circulation away from the bottom half and cause Marty to dissipate.

The upper level trough is beginning to steer Marty toward the north-northeast and the tropical storm is likely to move in that direction over the short term.  The ultimate track of Marty will be determined by the vertical integrity of the circulation and the strength of the vertical wind shear.  If the wind shear is not too strong and the upper and lower portions of the circulation remain together, then the trough will steer all of Marty toward the northeast.  In that case it could make landfall on the Mexican coast in several days.  However, if the vertical wind shear blows then top off of the circulation, then the upper level portion will move northeast toward Mexico, while the lower part of the tropical storm is left behind.  The upper half of the circulation could still bring heavy rain and the potential for floods to parts of Mexico, even if the surface circulation does not make landfall.