Category 1 Hurricane Hector Headed Towards Hawaii

Hurricane Hector is rapidly intensifying as it steams west at 14 mph across the Central Pacific, and could pose a long-range threat to Hawaii August 8 - 9. Hector was upgraded to an 85 mph Category 1 storm at 11 am EDT Thursday, and satellite imagery shows that Hector has developed a well-formed eye surrounded by an eyewall with very cold cloud tops.

Intensity forecast for Hector

The SHIPS model predicts that Hector will be over warm waters of 27.5 – 28°C (81 - 82°F) on Thursday, slightly cooler waters of 26.5 - 27.5°C (80 - 81°F) on Friday and Saturday, then warmer waters again early next week. With wind shear expected to be a low to moderate 5 – 15 knots during the period, intensification into a Category 3 hurricane, as predicted by NHC, seems reasonable.

Track forecast for Hector

The 0Z Thursday run of the European model showed Hector passing about 300 miles south of the Big Island on Wednesday; the 0Z Thursday run of the UKMET model had Hector passing even farther to the south. However, recent runs of the GFS model have been trending more to the north, and the 6Z Thursday run of the model had Hector passing within 50 miles of the Big Island on Thursday, August 9. The models have large errors for 7-day forecasts, so we will just have to wait and see how the situation clarifies in the coming days. Over the past 3 years, the European model has been the top hurricane track model in the Eastern Pacific, followed by the GFS, then the UKMET.

Figure 1. One of several storm parade for Hawaii during the years 2014 - 2016: VIIRS visible satellite image of ex-Hurricane Celia, Hurricane Darby, and Tropical Storm Estelle as seen on July 17, 2016. Image credit: NASA.

Recent Hawaiian hurricane history

After seeing three consecutive years of unprecedented hurricane threats in 2014, 2015 and 2016, the Hawaiian Islands got a break in 2017, when no named storms passed nearby. The most recent named storm to make landfall on a Hawaiian island was Tropical Storm Darby, which hit the Big Island of Hawaii with sustained winds of 40 mph on July 23, 2016, becoming just the fifth named storm since 1949 to make landfall on a Hawaiian Island. The next day, Darby made the closest approach on record by a tropical storm to the island of Oahu, which resulted in torrential rains in excess of 10 inches. Darby passed just 40 miles to the south and west of Honolulu with sustained winds of 40 mph. Darby’s formation was aided by ocean temperatures that were more than 1°C (1.8°F) warmer than average. Darby caused no deaths and only minimal damage.

Prior to Darby, the most recent landfall by a named storm in Hawaii was Tropical Storm Iselle, which hit the Big Island on August 8, 2014, with sustained winds of 60 mph. With estimated damages of $79 million (2014 USD), Iselle surpassed Hurricane Dot of 1959 as the third-costliest tropical cyclone to ever hit Hawaii. The only more damaging Hawaiian storms were Iniki in 1992 and Iwa in 1982.

The most recent hurricane warning in Hawaii was for the Big Island on August 31, 2016, for Hurricane Madeline, which peaked as a Category 4 storm with 130 mph winds on August 30, 2016. The Big Island was fortunate to receive only a glancing blow from a weakening Tropical Storm Madeline, with a few wind gusts in excess of 40 mph and some minor flooding from heavy rains in excess of 5”. Just three days later, on September 3, 2016, the outer rainbands from Hurricane Lester, which had also peaked as a Category 4 storm east of the Hawaiian Islands, produced heavy showers and minor flooding over the leeward slopes of the Big Island and portions of east Maui. Winds were light, however.

As I explained in my August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes, warming sea surface temperatures may help shift the tracks of Eastern Pacific hurricanes closer to Hawaii.

Figure 2.  Infrared satellite image from 12Z (8 am EDT) Thursday, August 2, 2018, showing Hurricane Hector (left) and the next two disturbances being tracked in the East Pacific. Image credit: NASA/MSFC Earth Science Branch.

More activity in the queue for the East Pacific

Two disturbances along the wave train east of Hector are being monitored by NHC. One, located a few hundred miles south of Cabo San Lucas (labeled #1 in the image above), is unlikely to develop. In its 8 am EDT tropical weather discussion, NHC gave this system only 10% odds of becoming at least a tropical depression over the next two days, and 30% odds in the next five days.

The more easterly disturbance (labeled #2 in the image above), located about 500 miles south of the Gulf of Tehuantepec, has a better chance of becoming the East Pacific’s next named storm. As it moves west-northwest, it will be tucked beneath a building upper-level ridge, helping to keep wind shear on the light side. An envelope of rich moisture will support development, as will SSTs in the range of 27-28°C (81-82°F). NHC gives the system a 10% chance of formation by Friday but an 80% chance by Monday. This system will likely remain far enough offshore to avoid affecting any land areas. The next name on the East Pacific list is Ileana.

CSU forecast update: still calling for a below-average Atlantic season

In their seasonal forecast update issued August 2, forecasters based at Colorado State University continued to predict that the Atlantic would see less hurricane activity than average in 2018. Dr. Phil Klotzbach and Dr. Michael Bell are now calling for a total of 12 named storms, 5 hurricanes, and 1 major hurricane, up just slightly from their July 2 forecast of 11 named storms, 4 hurricanes, and 1 major hurricane. The median numbers (1981-2010) are 12, 6.5, and 2. We'll have more to say about the seasonal prognosis when NOAA issues its forecast update on August 9.

Conditions are looking quiet for the Atlantic, with none of our reliable tropical cyclone genesis models showing tropical cyclone genesis for at least the next 7 days.

Bob Henson co-wrote this post.