Hurricanes Madeline and Lester intensified quickly on Monday into Major Hurricanes as they moved toward Hawaii.  The approach of Hurricane Madeline prompted the Central Pacific Hurricane Center to issue a Hurricane Watch for Hawaii County.  Both hurricanes have the potential to affect the weather around Hawaii during the next few days.

At 5:00 p.m. EDT on Monday the center of Hurricane Madeline was located at latitude 18.6°N and longitude 145.5°W which put it about 630 miles (1015 km) east of Hilo, Hawaii.  Madeline was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 135 m.p.h. (220 km/h).  That made Hurricane Madeline the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale.  The minimum surface pressure was 966 mb.

At 5:00 p.m. EDT on Monday the center of Hurricane Lester was located at latitude 18.0°N and longitude 130.5°W which put it about 1375 miles (2210 km) west of the southern tip of Baja California.  Lester was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  That made Hurricane Lester a Category 4 hurricane on the Saffir-Simpson Scale.  The minimum surface pressure was 951 mb.

Both Hurricanes Madeline and Lester are relatively compact hurricanes and the winds to hurricane force only extend out about 30 miles (50 km) from the center of circulation.  In Hurricane Madeline the Hurricane Intensity Index (HII) is 20.6.  The Hurricane Size Index (HSI) is 11.4 and the Hurricane Wind Intensity Size Index (HWISI) is 32.0.  Hurricane Lester is stronger, but slightly smaller.  The HII for Hurricane Lester is 25.1, while HSI is 10.3 and HWISI is 35.4.

Both hurricanes have well formed symmetrical eyes surrounded by rings of tall thunderstorms.  Each is producing well developed upper level divergence which is pumping out mass in all directions.  Hurricane Madeline has more spiral rainbands, and Hurricane Lester shows some indications that the structure might be assuming more of the shape of an annular hurricane.

Hurricanes Madeline and Lester responded to a favorable environment by intensifying rapidly on Monday.  The maximum sustained wind speed in Hurricane Madeline increased from 65 m.p.h. (105 km/h) to 115 m.p.h. (185 km/h) during the past 24 hours.  The maximum sustained wind speed in Hurricane Lester increased from 85 m.p.h. (140 km/h) to 130 m.p.h. (215 km/h) during the past 24 hours.

Hurricanes Madeline and Lester will remain in a favorable environment during the short term.  They are moving over water where the Sea Surface Temperatures (SSTs) are near 27.5°C.  The upper level winds are light and there is little vertical wind shear.  Thus, both hurricanes could maintain their intensity for another 12 to 24 hours.  When the hurricanes move closer to Hawaii, they will move over slightly cooler SSTs.  In addition, an upper level trough approaching from the northwest could increase the vertical wind shear later this week.  Hurricane Lester may also move over some cooler water mixed to the surface by Hurricane Madeline.

A subtropical ridge is steering Hurricanes Madeline and Lester toward the west and that general motion is expected to continue for the next several days.  On its anticipated track Hurricane Madeline could approach Hawaii in a couple of days.  Hurricane Lester could approach Hawaii in about five days.