Tropical Storm Dora rapidly intensified last night to become the first hurricane of the 2017 Pacific hurricane season. Dora strengthened to a high-end category 1 hurricane this afternoon, but cooling sea surface temperatures are likely to induce a weakening trend beginning tonight. Dora should weaken to a remnant low by Thursday as it continues moving northwestward in the Eastern Pacific.

Forecast for Dora

As of 3:00 p.m. MDT (5:00 p.m. EDT), Hurricane Dora was centered in the Eastern Pacific near 17.8°N 107.3°W and was moving to the west-northwest at 13 mph. Maximum sustained winds were 80 knots (90 mph) with an estimated minimum pressure of 981 mb. This intensity is based off TAFB and SAB Dvorak satellite estimates of T4.5/77 kt and automated Dvorak values of 80-82 kt. This makes Dora a strong category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale, the Northern Hemisphere’s strongest tropical cyclone in 2017 by wind speed thus far. Dora is a well-organized hurricane, with a nearly symmetric ring of deep convection surrounding a cloud-filled eye.

The intensity and track forecast for Dora remains straightforward. The hurricane is currently crossing the 26°C (78.8°F) isotherm and a slow weakening trend should commence soon, if it has not already. However, wind shear remains very light (less than 10 knots), and this could slow Dora’s rate of weakening. Dora should fall below hurricane strength tomorrow, eventually degrading to a remnant low by Thursday. Dora is expected to continue on its west-northwestward motion and is likely to pass near the sparsely populated Socorro Island tomorrow.

Another system could develop in East Pacific, African tropical wave also bears watching

There are two additional systems in the tropics that will need to be monitored over the next several days. First, the National Hurricane Center (NHC) has noted the possibility of development from a broad area of low pressure in the East Pacific south of Mexico. NHC gives this system a near zero percent chance of development within 48 hours and a 20 percent chance of development within five days. Neither the 18z GFS model run nor the 12z ECMWF model run predicts development of this system within five days. The next name on the East Pacific naming list is Eugene.

In the Atlantic, a strong tropical wave is expected to emerge off the African coast on Wednesday. The 12z ECMWF run, in addition to several GEFS and EPS ensemble members, indicated the possibility for this wave to develop into a tropical cyclone later this week. The 12z Monday ECMWF run quickly develops this wave into Tropical Storm Don by Friday. This is also supported by several EPS ensemble members. While the 18z Monday GFS operational model does not predict development of this wave, several GEFS ensemble members have hinted at the possibility of development as it approaches the Lesser Antilles by next week. Wind shear is expected to be somewhat favorable, with light trade winds. However, an unfavorable Convectively Coupled Kelvin Wave (CCKW) and Saharan Air Layer (SAL) could suppress development. The NHC has not included this tropical wave on its Tropical Weather Outlook.

Based on current trends, I give a 50 percent chance of Tropical Storm Eugene forming over the next ten days, and a 20 percent chance of Tropical Storm Don forming over the next ten days. I will be back tomorrow for another post on Dora and the two other systems.