Unusual development of a tropical or subtropical cyclone is possible southwest of Baja California during the next few days.  The National Hurricane Center (NHC) issued a special Tropical Weather Outlook on Thursday afternoon for a weather system southwest of Baja California.  NHC indicated that there is a 50% probability of development of a tropical or subtropical cyclone during the next five days.  No tropical cyclone or subtropical cyclone is known to have developed over the Eastern North Pacific Ocean in January.  The record extends back to 1949, but it is most complete for the era of Geostationary Operational Environmental Satellites (GOES) which extends from 1970 to the present.

A broad area of low pressure was located about 1300 miles (2100 km) southwest of the southern tip of Baja California.  Clusters of showers and thunderstorms were occurring in parts of the low pressure system.  Visible satellite images were not showing evidence that the showers and thunderstorms were forming into rainbands.  There was a broad area of low pressure, but there was no evidence of a distinct low level center of circulation.

The broad area of low pressure will move through an environment somewhat favorable for the formation of a tropical or subtropical cyclone during the next few days.  It will move over water where the Sea Surface Temperature is near 27°C, which means that there will be enough energy in the ocean to support a tropical cyclone.  An upper level low is northwest of the broad surface low pressure system.  The upper level low is producing strong southwesterly winds which are blowing across the top of the broad low pressure system.  Those winds will cause moderate vertical wind shear, which will inhibit the formation of a tropical cyclone.  If the winds weaken, a tropical cyclone could form, but if the wind shear remains stronger, a subtropical cyclone could develop.  As mentioned above, the National Hurricane Center indicates that there is a 50% probability of development of a tropical or subtropical cyclone.

The broad area of low pressure is forecast to move slowly toward the north during the next several days.  If a tropical or subtropical cyclone develops with taller thunderstorms, then the southwesterly winds blowing around the upper low will steer the cyclone toward Baja California.  The system could bring gusty winds and heavy rain to Baja California and northern Mexico in a few days.