We are watching an area of low pressure that has developed within a larger-scale trough located several hundred miles south of Manzanillo, Mexico.
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Showers and thunderstorms associated with this system have become better organized today, and further development is now expected.
A tropical depression is likely to form by early next week as it moves slowly to the west-northwest well off the coast of Mexico.
- Formation chance through 48 hours…medium…50 percent.
- Formation chance through 5 days…high…70 percent.
The Hurricane season officially began on May 15 in the Eastern Pacific Ocean, and on June 1 in the Central Pacific; both will end on November 30. These dates historically describe the period each year when most tropical cyclones form in the Pacific Ocean basin and are adopted by the convention. However, the formation of tropical cyclones is possible at any time of the year, as illustrated by the formation of Tropical Storm Andres on May 9. Andres was the earliest forming tropical storm in the northeastern Pacific, beating Tropical Storm Adrian of 2017 by just 12 hours.
Tropical Storm Andres
On May 7, a low-pressure system formed several hundred miles southwest of the southern coast of Mexico and was forecast to move into more favorable conditions by the weekend. By May 8, the disturbance’s thunderstorms started to quickly organize, and the system was designated as Tropical Depression One-E at 09:00 UTC on the next day. At the time, the system’s center became well-defined and located east of a well-organized mass of convection despite the negative impact of moderate west-southwesterly wind shear on the system. According to scatterometer data and satellite estimates, the depression strengthened into Tropical Storm Andres six hours later, becoming the earliest named storm in the Northeast Pacific (east of 140°W) on record in the satellite era, breaking the previous record of Tropical Storm Adrian in 2017 by 12 hours. However, Andres did not have any banding features, and its appearance became more ragged on satellite imagery as it moved into an area with increasingly hostile conditions. Soon afterward, wind shear caused the storm’s circulation to become elongated and its cloud tops to warm. Andres weakened to a tropical depression at 21:00 UTC on May 10 as its center became devoid of convective activity and the remaining thunderstorms were displaced well to the east of the storm’s center of circulation. Andres subsequently degenerated into a remnant low at 15:00 UTC on May 11.
The outer storms of Andres produced heavy rainfall in Southwestern Mexico. Moisture from the storm caused intense rain and even a hailstorm as far east as the State of Mexico, including in the state’s capital, Toluca. Vehicles became stranded in floods, some small trees got knocked over, and about 50 houses were damaged by a flooding river. 30 cars were also stranded in a flooded parking lot of a church in Metepec.
Tropical Storm Blanca
On May 24, the National Hurricane Center first noted the chance for an area of low pressure to develop south of the coast of Mexico. Four days later, a low-pressure area finally formed a couple of hundred kilometers south of the country. The low was initially embedded within a large monsoon trough and was interacting with another system to its east. However, as it gradually moved west-northwestwards, the system became more organized and better defined, and by 21:00 UTC on May 30, was classified as Tropical Depression Two-E. The depression continued to gradually become more symmetric, despite its displaced low- and mid-level circulations. The next day, Two-E strengthened to a tropical storm and received the name, Blanca. A relatively compact cyclone, Tropical Storm Blanca quickly gained strength throughout the day of May 31, reaching its peak intensity at 09:00 UTC on June 1 with winds of 60 mph (95 km/h) and a pressure of 998 mb (29.47 inHg). Shortly afterward, vertical wind shear weakened Blanca as its low-level circulation became partially exposed on satellite images later into the day. Blanca continued to weaken on June 2 due to wind shear and the entrainment of dry, stable air into its circulation. Blanca further weakened into a tropical depression later that day, and as thunderstorm activity dissipated completely, degenerated into a post-tropical cyclone early on June 4.