There are several areas to watch in the tropical Atlantic, Eastern Pacific, and Western Pacific today as the global tropics remain active. In the Eastern Pacific, Hurricane Hilary and Tropical Storm Irwin expected to begin Fujiwhara Interaction this weekend. The global models continue to indicate that the larger and stronger Hilary will be the dominant cyclone. In the Atlantic, an area of low pressure has formed from a tropical wave southwest of the Cape Verde Islands, and has a chance to slowly develop by early next week. In the Western Pacific, Tropical Storm Nesat has developed and is likely to strike Taiwan as a typhoon this weekend.

Weakening Hurricane Hilary expected to absorb Tropical Storm Irwin

The Eastern Pacific July tropical cyclone outbreak is nearly over. Hurricane Hilary has continued to weaken today, and is on the cusp of being downgraded to a tropical storm. Tropical Storm Irwin has changed little in intensity today and is likely to slowly weaken as it gets absorbed into the circulation of Hilary by Monday.

As of 2:00 p.m. PDT (5:00 p.m. EDT), Hurricane Hilary was centered near 17.9°N 116.6°W and was moving west-northwestward at about 9 mph. Maximum sustained winds were 65 knots (75 mph), with an estimated minimum pressure of 989 mb. Hilary does not have the classical appearance of a hurricane, with no eye. Instead, Hilary consists of a long band lacking very deep convection, but convection has increased near the center during the past few hours. Hilary is currently being impacted by vertical shear of about 10 knots and is located over sea surface temperatures just under 27°C (80.6°F), and is likely to cross the 26°C (78.8°F) isotherm tomorrow. Due to these somewhat unfavorable conditions, Hilary is likely to weaken to a tropical storm tonight or on Friday. The official National Hurricane Center (NHC) forecast calls for Hilary to continue on a west-northwestward path, eventually pulling Tropical Storm Irwin into its circulation by Monday and becoming post-tropical by Tuesday.

As of 2:00 p.m. PDT (5:00 p.m. EDT), Tropical Storm Irwin was centered near 14.9°N 124.3°W and was moving very slowly westward at about 2 mph. Maximum sustained winds were 50 knots (60 mph), with an estimated minimum pressure of 1000 mb. Irwin is a sheared cyclone, with the center periodically moving in and out of the convective mass. Irwin is currently experiencing over 15 knots of vertical wind shear, and it is not likely the cyclone will strengthen. Instead, the cyclone is likely to gradually weaken before being absorbed by Hilary early next week. Irwin is expected to move very little during the next two days or so before accelerating to the north as it is absorbed.

Severe Tropical Storm Nesat headed for Taiwan, likely to become a typhoon

Severe Tropical Storm Nesat has developed over the Western Pacific, and is expected to strike Taiwan as a typhoon early on Sunday local time. As of 00:00 UTC Friday, Tropical Storm Nesat was centered near 20.0°N 125.9°E and was moving north-northwestward. Maximum 1-minute and 10-minute sustained winds were 55 knots (65 mph) with an estimated minimum pressure of 988 mb. Moderate wind shear has limited significant organization today, but the cyclone has become slightly better organized this evening. The Joint Typhoon Warning Center (JTWC) expects Nesat to strengthen to a category 2-equivalent typhoon at landfall. Nesat is likely to become the first typhoon of 2017 to make landfall, and Taiwan should monitor the progress of Nesat very closely.

Area of low pressure in eastern Atlantic may develop

A broad area of low pressure, located about 800 miles west-southwest of the Cabo Verde Islands, is producing disorganized showers and thunderstorms. Some slow development of this low pressure system is possible during the next several days as it moves very slowly westward to west-northwestward at about 5 to 10 mph. The NHC gives this system a near zero percent chance of development within 48 hours, and a 30 percent chance of development within five days. The 12z Thursday GFS and ECMWF models did not predict development of this system. In contrast, the 12z CMC and UKMET models, as well as a few GEFS and EPS ensemble members, supported some slight development of this disturbance. This system is no imminent threat to land, but the Lesser Antilles should be closely monitoring this system. I give this system a 20 percent chance of development within five days and a 40 percent chance within ten days. This may end up being a long-tracked disturbance that does not develop until the western Atlantic.

I will be back tomorrow with an update on these systems. August is almost here!