Tropical Depression 03E strengthened into Tropical Storm Calvin on Monday as it lingered south of Mexico.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Calvin was located at latitude 15.5°N and longitude 95.5°W which put it about 70 miles (110 km) east-southeast of Puerto Angel, Mexico.  Calvin was moving toward the west-northwest at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.  A Tropical Storm Warning remains in effect for the portion of the coast from Boca De Pijijiapan to Punta Maldonado.

A band of thunderstorms wrapped tightly around the southern side of the center of circulation of former Tropical Depression 03E and the National Hurricane Center upgraded the system to Tropical Storm Calvin in its 5:00 p.m. EDT advisory on Monday.  Calvin is a small tropical storm and winds to tropical storm force only extend out about 60 miles (95 km) from the center of circulation.  Additional bands of showers and thunderstorms are occurring in the outer portions of the circulation which are over the Pacific Ocean.

Tropical Storm Calvin is in an environment that is marginally favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.  However, Calvin is also very near the coast of Mexico and it could start to pull drier air into the western part of the circulation at any time.  Calvin is under the eastern end of an upper level ridge which is producing northerly winds which are blowing toward the top of the tropical storm.  The northerly winds are producing moderate vertical wind shear and the shear may be contributing to the location of the main band thunderstorms south of the center of circulation.

The future intensity of Tropical Storm Calvin will depend on whether or not it remains over the Pacific Ocean.  If Calvin stays over the open water, then further intensification is possible.  If Calvin moves closer to the coast, then further intensification is much less likely.  If Calvin moves inland, it will dissipate quickly.

Tropical Storm Calvin is in an area where the steering currents are weak and it moved very slowly toward the west-northwest during the past 18 hours.  A subtropical ridge north of Calvin is forecast to begin to steer the tropical storm more quickly toward the west-northwest.  If that happens, Calvin could make landfall on the coast of Mexico near Puerto Angel in 12 to 24 hours.  Locally heavy rainfall remain the biggest risks with Tropical Storm Calvin.