In 2021, while the busy Atlantic hurricane season caused several dangerous storms, tropical storms also formed in the eastern Pacific, including Hurricane Pamela, which made landfall in Mexico on 13 October.
10 June 2022
19 October 2021
By Jochen Kerkmann (Germany)
The Category 1 hurricane came ashore northwest of the city of Mazatlán on Mexico’s west coast, downing trees, flooding streets and causing power outages.
On 7 October, the National Hurricane Center (NHC), in Miami, began monitoring a tropical wave centered over the southwestern Caribbean Sea for potential development in the Eastern Pacific. The wave crossed Nicaragua and Costa Rica, emerging over the Pacific the following day. The system strengthened into Tropical Storm Pamela at 21:00 UTC on 10 October. On 11 October, Pamela became a Category 1 hurricane, as the hurricane developed a large area of deep convection (but no eye).
This can be seen on Figure 1, which shows Hurricane Pamela on 12 October. Note the proximity of Hurricane Pamela and the deep upper-level trough over California. Figure 2 shows the landfall of Pamela and its decay over northern Mexico. The remnants of Pamela over Mexico, and the cold front of the mid-latitude cyclone (ex-Californian Low), would eventually start to interact, bringing strong rains to Texas and Oklahoma.
To better discriminate water from ice clouds within the frontal band over Texas on 13 October, Figure 3 shows an animation of the so-called Day Snow/Cloud Layers RGB product developed by CIRA. This product combines information from six different bands on the GOES ABI, to help distinguish water clouds from snow and ice clouds. Low water clouds are depicted in yellow, high ice clouds in pink/magenta. The algorithm uses combinations of reflective and infrared bands, that includes a cirrus mask from the 1.38μm channel (band 4), and a normalized difference snow index (NDSI). See the quick guide of the RGB product.
The moisture from ex-Pamela, and the approaching cold front from the mid-latitude cyclone over the central US, likely contributed to the development of a supercell storm over southern Texas on 14 October (Figure 4).
Unfortunately, no mesoscale sector (special GOES ABI 1-min scanning mode) was placed over Texas on that day; so Figure 5 shows the standard five-minute GeoColor RGB images of that storm. Note the long shadow of the cirrus anvil on the low-level clouds.
Note: according to the New York Times, eastern Pacific hurricanes rarely hit land. Similarly to Atlantic storm, the majority of Pacific storm systems track from east to west. This means that very few make any impact on land, i.e. they don’t really pose a threat to the US West Coast. The last time a hurricane struck California, according to the National Oceanic and Atmospheric Administration, was the San Diego hurricane of 1858, which brought winds of about 75mph.
With a Month Left, the Pacific Hurricane Season Reaches 16 Storms (New York Times, registration needed)
Severe Storms Target Oklahoma Again Tonight (WeatherNation TV)
Hurricane Pamela hits with 120km/h winds in Mazatlán, Sinaloa, Mexico (chave weather - daily videos/YouTube)