The structure of Tropical Storm Blanca continued to improve on Tuesday and it intensified into a hurricane.  At 5:00 p.m. EDT on Tuesday the center of Hurricane Blanca was located at latitude 13.1°N and longitude 104.6°W which put it about 375 miles (605 km) south-southwest of Zihuatanejo, Mexico and about 410 miles (655 km) south of Manzanillo, Mexico.  Blanca was stationary.  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 960 mb.  The Hurricane Intensity Index (HII) was 10.4, the Hurricane Size Index (HSI) was 5.8 and the Hurricane Wind Intensity Size Index (HWISI) was 16.2.  Since Blanca and Andres both became hurricanes this year, June 2 becomes the earliest date on record by which time two hurricanes formed over the Eastern North Pacific Ocean.  However, it should be noted that the most reliable records only go back to 1971.

Hurricane Blanca is sitting over water where the Sea Surface Temperature (SST) is near 30°C.  It is efficiently extracting energy from the upper ocean and that energy is fueling its intensification.  Spiral bands of thunderstorms are well organized and the strongest storms are near the center of circulation.  The thermodynamic environment is very favorable for further intensification and rapid intensification is possible.  There are a several of factors that could slow the rate of intensification at times.  Upper level outflow from Hurricane Andres, which is about a thousand miles west of Blanca, appears to be generating some vertical wind shear on the northern and western sides of Blanca.  Thunderstorms in Blanca are producing upper level divergence, but some of the divergence may be reduced in the northwestern quadrant of the hurricane.  Andres is slowly spinning down and the wind shear is likely to lessen during the next several days.  A second potential inhibiting factor is the fact that Blanca is not moving much.  The warm water underneath Blanca is relatively deep, but if it sits in one location long enough, its winds will eventually begin  to mix some cooler water to the surface.  For the time being Blanca has sufficient energy in the upper ocean to support further intensification.  Once Blanca starts moving, then it will be over warm SSTs until it approaches latitude 20°N.  Finally, if Blanca gets as strong as some guidance suggest it could, then eyewall replacement cycles also could produce fluctuations in intensity.  As I mentioned above, Blanca is likely to intensify further and it could intensify rapidly at times.

A ridge in the middle levels centered near Baja California is blocking the northward progress of Blanca and the hurricane is in an area where the steering currents are weak.  The ridge is forecast to move slowly eastward toward a position over northern Mexico and Texas.  As the ridge moves eastward it will initially steer Blanca toward the northwest.  In several days the ridge will cause Blanca to turn more toward the north.  On its anticipated track, Blanca could approach the southern tip of Baja California in a few days.  It is too early to know how strong Blanca might be at that time or how much of a risk it might pose to that area.