Tropical Storm Fernanda strengthened into the third hurricane of the 2017 Pacific hurricane season Thursday afternoon, and is likely entering a period of rapid intensification in very favorable conditions. Fernanda is expected to become the second major hurricane of the 2017 Pacific hurricane season, and could pose a long-range threat to Hawaii. The Atlantic remains quiet, with no tropical cyclone development expected in the short term.

Forecast for Fernanda

As of 2:00 p.m. PDT (5:00 p.m. EDT) Thursday, Fernanda was centered near 11.2°N 116.0°W and was moving west at about 12 mph. Maximum sustained winds were 70 knots (80 mph) with an estimated minimum pressure of 990 mb, making Fernanda a Category 1 hurricane on the Saffir-Simpson scale. Fernanda is still yet to display the classic appearance of a hurricane, as an eye is not yet visible on visible satellite. The eye should clear out overnight and be visible by tomorrow. Fernanda is expected to rapidly intensify over the open Pacific waters in very favorable conditions. During the next 72 hours, Fernanda is expected to be in an environment with light wind shear of about 5 knots, sea surface temperatures a warm 28.5°C (83.3°F), and relative humidity values of about 70 percent. This should allow Fernanda to strengthen into a major hurricane by late tomorrow, and the official National Hurricane Center (NHC) forecast expects Fernanda to peak as a category 4 hurricane with maximum sustained winds of 125 knots (145 mph). NHC noted that this forecast could even be conservative, and category 5 status is not out of the question with Fernanda, although unlikely. However, the possibility of eyewall replacement cycles could complicate the medium-range intensity forecast.

By Day 4, wind shear should remain light, but sea surface temperatures will begin to decrease and relative humidity values will drop below 60 percent. This should induce a slow weakening as Fernanda emerges into the Central Pacific basin by the middle of next week. Sea surface temperatures are expected to drop below the typical threshold of tropical cyclone development – 26°C (78.8°F) – by next Tuesday, and this is good news for the Hawaiian Islands. Regardless, Fernanda is likely to be in the vicinity of the Hawaiian Islands by next week, although the cool sea surface temperatures will likely weaken it to a tropical storm or remnant low by this time. The Hawaiian Islands should continue to monitor the progress of Fernanda.

All quiet in the Atlantic, another East Pacific storm could form next week

The Atlantic basin continues to remain quiet with no new tropical cyclone activity expected during the next five days. The current lack of activity is due to Saharan Air Layer (SAL) outbreaks and the suppressed MJO state. SAL outbreaks are normal for this time of year, and typically peak in mid-July. There are some indications on global models that the Atlantic could become more favorable for tropical cyclone activity by early August.

The East Pacific will likely remain active after Fernanda. A broad area of low pressure is expected to form south of Mexico this weekend, and could develop into a tropical depression by early next week. The NHC gives this system a near zero percent chance of development within 48 hours, and a 50 percent chance within five days. This system is not expected to be a threat to land.

I will be back tomorrow with an update on Fernanda.