After not changing much during the overnight hours, Hilda intensified rapidly into a hurricane on Friday afternoon.  At 5:00 p.m. EDT on Friday the center of Hurricane Hilda was located at latitude 12.8°N and longitude 138.3°W which put it about 1215 miles (1950 km) east-southeast of Hilo, Hawaii.  Hilda was moving toward the wet at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 984 mb.

Hurricane has a very small circulation.  Hurricane force winds extend out less than 15 miles (25 km) from the center of circulation and tropical storm force winds extend out about 70 miles (110 km) from the center.  In spite of its small size, the circulation is well organized.  A clear eye is visible on satellite images and there is a well formed eyewall around the eye.  There are not  many spiral bands because of the small size of the circulation.

Hilda is moving over water where the Sea Surface Temperature (SST) is near 29°C.  It is in an area where the upper level winds are light and there is not much vertical wind shear.  Further intensification is likely and rapid intensification is possible during the next 24 hours.  Eventually, when Hilda moves farther west it will move over cooler SSTs and encounter more vertical wind shear.  Given the small size of Hilda, it could also weaken very quickly when it moves into a more hostile environment.

A subtropical ridge is steering Hilda toward the west and that general motion is expected to continue for several more days.  When Hilda gets closer to Hawaii, southwesterly winds in the upper levels are expected to turn it more toward the northwest.

Small Tropical Storm Hilda intensified rapidly on Thursday.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Hilda was located at latitude 12.7°N and longitude 133.4°W which put it about 1590 miles (2550 km) east-southeast of Hilo, Hawaii.  Hilda was moving toward the west at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 70 m.p.h. (115 km).  The minimum surface pressure was 1001 mb.

Hilda is a very small tropical storm.  The area of tropical storm force winds only extends outward about 40 miles (65 km) from the center.  Even though the circulation is small, it is well organized and there are hints of a tiny eye trying to form in the center of Hilda.  Hilda is moving over water where the Sea Surface Temperature is near 28.5°C.  The upper level winds are very light and there is little vertical wind shear.  The thunderstorms in the core of Hilda are generating upper level divergence which is pumping out mass.  Hilda is likely to strengthen more during the next day or two because of the favorable environment.  However, small tropical cyclones can weaken just as fast as they intensify.  When Hilda moves farther west it will encounter some of the same wind shear that is affecting Tropical Storm Guillermo.  As a result, Hilda is likely to weaken when it gets closer to Hawaii.

A subtropical ridge is steering HIlda toward the west and a generally west-northwestward track is expected during the next several days.  As Hilda moves farther west it could turn more toward the northwest, much like Guillermo did when it neared Hawaii.

Tropical Storm Guillermo weakened further and the Tropical Storm Watch for portions of Hawaii was discontinued.  At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Guillermo was located at latitude 21.4°N and longitude 151.7°W which put it about 250 miles (400 km) east-northeast of Hilo, Hawaii and about 400 miles (640 km) east of Honolulu.  Guillermo was moving toward the west-northwest at 9 m.p.h. (13 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 70 m.p.h. (110 km/h).  The minimum surface pressure was 1001 mb.  The Tropical Storm Watch for Hawaii County and Maui County including the islands of Maui, Molokai, Lanai and Kahoolawe has been discontinued.

Strong southwesterly winds in the upper levels are creating significant vertical wind shear over Tropical Storm Guillermo.  The wind shear has distorted the circulation and the only thunderstorms are in outer rainbands well northeast of the center of the tropical storm.  The wind shear is expected to continue and Guillermo will continue to weaken during the next several days.

Since Guillermo is no longer producing tall thunderstorms near the center of circulation, it is being steered by winds in the lower troposphere.  Those winds are expected to carry the weakening tropical storm north of the Hawaiian Islands.  Since Guillermo or its remnants is expected to move north of Hawaii, the Tropical Storm Watch was discontinued.

Guillermo weakened below hurricane intensity on Monday and the Central Pacific Hurricane Center issued a Tropical Storm Watch for some of the Hawaiian Islands.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Guillermo was located at latitude 18.1°N and longitude 147.4°W which put it about 515 miles (830 km) east of Hilo, Hawaii.  Guillermo was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 65 m.p.h. (100 km/h) and there were gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 991 mb.  A Tropical Storm Watch has been issued for Hawaii County and Maui County including the islands of Maui, Molokai, Lanai and Kahoolawe.

An upper level trough north of Guillermo is causing strong southwesterly winds over the top of the circulation.  Significant vertical wind shear is affecting the tropical storm and is weakening it.  The southwesterly winds are also inhibiting upper level divergence on the western side of the storm.  Most of the thunderstorms are occurring in rainbands east of the center of circulation.  The vertical wind shear is expected to increase later this week and Guillermo will be moving over cooler Sea Surface Temperatures.  The weakening trend is expected to continue.

A subtropical ridge is pushing Guillermo toward the west-northwest and the southwesterly winds in the upper levels are turning it more toward the northwest.  That general motion is expected to continue for the next day or two.  On its anticipated track Guillermo is expected to pass north of Hawaii.  However, if it weakens a little faster than expected and the circulation is not as tall, then it could be steered by winds lower in the atmosphere.  Those winds could steer it more toward the west which would bring it nearer to Hawaii.  That possibility prompted the issuance of a Tropical Storm Watch for some of the Hawaiian Islands.

A reconnaissance aircraft confirmed a weakening trend in Hurricane Guillermo that had been suggested by satellite imagery.  At 11:00 p.m. EDT on Sunday the center of Hurricane Guillermo was located at latitude 15.5°N and longitude 145.0°W which put it about 725 miles (1165 km) east-southeast of Hilo, Hawaii.  Guillermo was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 85 m.p.h. (145 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 981 mb.

An upper level trough north of Guillermo is producing southwesterly winds over the top of the circulation.  Those winds are causing vertical wind shear and are inhibiting the upper level divergence on the western side of the circulation.  In addition Guillermo is gradually moving over cooler Sea Surface Temperatures (SSTs).  A combination of wind shear and cooler SSTs will continue to weaken the hurricane.

A subtropical ridge is steering Guillermo toward the west-northwest and that general motion is expected to continue.  On its anticipated track Guillermo would approach the Big Island of Hawaii in about 72 hours.  It will likely be a tropical storm at that time.

Hurricane Guillermo moved west of longitude 140°W on Saturday, which means it officially crossed into the Central Pacific Ocean.  The responsibility for issuing advisories on Guillermo shifted from the National Hurricane Center in Miami, Florida to the Central Pacific Hurricane Center in Honolulu, Hawaii when Guillermo moved west of 140°W.  At 11:00 p.m. EDT on Saturday the center of Hurricane Guillermo was located at latitude 14.0°N and longitude 141.0°W which put it about 1010 miles (1625 km) east-southeast Hilo, Hawaii.  Guillermo was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 970 mb.

The structure of Hurricane Guillermo appeared to become less organized on Saturday.  There are fewer thunderstorms and the spiral bands appear to be weaker.  Guillermo is nearing water where the Sea Surface Temperature is near 27°C, and it will gradually move over even cooler water.  Westerly winds in the upper levels appear to be generating some vertical wind shear over the northern portion of the circulation.  Guillermo is still producing upper level divergence near the center of circulation, but the divergence appears to less over the western half of the hurricane.  The circulation may be pulling some drier more stable air into the western part of the circulation.  Guillermo will be moving into a less favorable environment and weakening is likely.

A subtropical ridge is steering Guillermo toward the west-northwest and that general motion is expected to continue during the next several days.  On its anticipated track Guillermo could approach the Big Island of Hawaii in about four days.  It is likely to be a tropical storm at that time.

Guillermo intensified rapidly during the past 24 hours and it is now a hurricane.  At 5:00 p.m. EDT on Friday the center of Hurricane Guillermo was located at latitude 12.7°N and longitude 134.8°W which put it about 1430 miles (2300 km) east of Hilo, Hawaii.  Guillermo was moving toward the west-northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 970 mb.

Guillermo moved through a very favorable environment of warm Sea Surface Temperatures and little vertical wind shear which allowed it to intensify rapidly from a tropical storm into a hurricane.  An eye was visible earlier today on satellite images, but it is either obscured or has filled with clouds on the most recent images.  The hurricane is moving over water where the Sea Surface Temperature (SST) is near 29°C.  The upper level winds are light, but the rapid movement toward the west-northwest may be generating some vertical wind shear.  If Guillermo moves more slowly, it has about another 24 hours before it starts to move over cooler SSTs.  Once Guillermo gets west of longitude 140°W, it will gradually move over cooler SSTs.  As it moves farther north, it will also get closer to stronger upper level winds blowing from the west.  The combination of cooler SSTs and more vertical wind shear are likely to weaken Guillermo as it approaches Hawaii.

A subtropical ridge north of Guillermo is steering the hurricane toward the west-northwest and that steering is likely to continue for several more days,  In a few days a trough approaching from the west will turn Guillermo toward the northwest.  On its anticipated track Guillermo could approach Hawaii in about five days.  The higher probability is that a weaker Guillermo will move north of Hawaii, but the guidance from numerical models has been changing today.

An area of low pressure organized on Wednesday well east-southeast of Hawaii and it has been classified as Tropical Storm Guillermo.  At 5:00 a.m. EDT on Thursday the center of Tropical Storm Guillermo was located at latitude 8.5°N and longitude 126.3°W which put it about 2070 miles (3340 km) east-southeast of Hilo, Hawaii and about 1475 miles (2370 km) southwest of the southern tip of Baja California.  Guillermo was moving toward the northwest at 15 m.p.h. (24 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 1003 mb.

Guillermo formed at an unusually low latitude over the eastern North Pacific.  It is over an area where the Sea Surface Temperatures (SSTs) are near 29°C.  The upper level winds are light over the circulation and there is not much vertical wind shear.  Guillermo will be moving through an environment favorable for intensification during the next two or three days and a period of rapid intensification will be possible when it nears hurricane intensity.  Guillermo will move over cooler SSTs when it gets closer to Hawaii and the wind shear may also increase.

A subtropical ridge north of Guillermo is steering the tropical storm toward the northwest and the ridge is expected to continue to steer the tropical storm toward the west-northwest during the next 48 to 72 hours.  Later in the weekend an upper level trough approaching from the west could turn Guillermo more toward the northwest.