Hurricane Hilary a Threat to Mexico and the United States

Hurricane Hilary formed over the eastern Pacific earlier this week and has rapidly intensified into a category 4 hurricane [1]. As of the latest advisory from the National Hurricane Center (NHC), Hilary had maximum sustained winds of 145 miles per hour [2]. Despite the storm’s rapid intensification, Hilary is expected to weaken over the next couple of days as it approaches Baja California, Mexico [1]. Currently, tropical storm watches/warnings have been issued for large parts of Baja California along with a hurricane watch for the west-central coast of the state [3].

Figure 1: Projected wind swath of Hurricane Hilary, generated by KinetiCast™ models using forecast data from the National Hurricane Center. The solid hurricane symbol denotes the storm position for this forecast. The filled circles are color-coded by intensity. The circles on the dashed line represent the forecast position of the cyclone at 12-hour intervals, and the circles on the solid line depict the past position of the storm at 6-hour intervals.

Hilary will likely make landfall in Baja California as a category 1 hurricane or strong tropical storm (see Figure 1). After this point, however, the system will go on to threaten the United States. The latest forecast calls for the center of circulation of Hilary to be located over Southern California as a moderate tropical storm with winds of approximately 58 miles per hour (see Figure 2). If this forecast verifies, it would make Hilary one of only 3 tropical storms to make landfall in the state of California in the last 100 years [4]. The other two storms were Nora in 1997 and the Long Beach Tropical Storm of 1939 [4]. As such, the current forecast for Hilary is an impressive one that is not seen very often for residents of the Golden State. The lack of significant tropical activity in California is primarily the result of a permanent Pacific Ocean current that brings cold water from higher latitudes down near the coast of California [5]. For anyone who has ever been surfing on the mighty Pacific waters off the coast of Southern California, they will tell you firsthand how chilly the water there can be. This cool ocean current is enough to keep water temperatures well below the threshold for sustaining a tropical cyclone. However, the other major reason has to do with the wind direction. Simply put, wind patterns along the eastern Pacific typically direct tropical storms out to sea rather than curving them north or northeast into places like California [5]. When you combine these two factors together, it has resulted in only 2 direct tropical storm landfalls in the state since the 1930’s.

Regardless of the rarity of an event like Hilary in California, the primary impacts will not be from the wind itself. Hilary is expected to bring several inches of rain to parts of Southern California over the next several days (Figure 3), heightening concerns around flash flooding, landslides, and mudslides [6]. In fact, if current forecasts hold steady, the storm could bring over a year’s worth of rain to parts of Palm Springs and Death Valley, CA [7]. When you add in the fact that California already experienced a record wet winter in many parts of the state [8], the several inches of rain that could fall during Hilary will only add insult to injury.

Figure 2: Zoomed-in view of the predicted wind field from Hilary while it is over Southern California.

Figure 3: Forecast rainfall from Hilary, generated by KinetiCast™ models using forecast data from the National Hurricane Center. The purple area is highlighted to show the potential for 3-6 inches of rain to fall over portions of Southern California.

The Pacific Ocean remains active this season, as we have tracked multiple tropical cyclones across the eastern, central, and western Pacific basins in recent weeks. Global weather forecast models continue to show additional tropical storms forming in different ocean basins over the next several days [9], which means we will likely have more to watch over the coming weeks. Here at Kinetic Analysis Corporation, we provide you with accurate, near real-time information about a tropical cyclone as it unfolds. We do this by synthesizing information from a variety of sources and translating the meteorological hazards into easily digestible impact information. This includes populations affected by tropical storm/hurricane force winds and storm surge, economic loss and structural damage estimates, and shutdown times for facilities such as airports and seaports. All this information is available in our state-of-the-art web app, KinetiCast™. If you would like more information, please reach out to aagastra@kinanco.com.

References

1.     https://www.nbcnews.com/news/us-news/live-blog/hurricane-hilary-live-updates-rcna100563

2.     https://www.nhc.noaa.gov/?epac

3.     https://www.nhc.noaa.gov/text/refresh/MIATCDEP4+shtml/180858.shtml?

4.     https://kesq.com/news/local-news/2023/08/17/why-tropical-weather-is-so-rare-in-southern-california/

5.     https://www.abc10.com/article/weather/ever-wondered-why-hurricanes-dont-hit-california/103-b4d7cc6f-6a33-439b-9e9c-c95e782283a0

6.     https://www.cbsnews.com/news/hurricane-hilary-path-and-timeline-heres-when-and-where-the-storm-is-projected-to-hit-california/

7.     https://www.desertsun.com/story/news/local/2023/08/17/hurricane-hilary-southern-california-could-see-over-5-inches-of-rain/70611357007/

8.     https://www.usatoday.com/story/news/nation/2023/03/29/californias-snow-rain-totals-explained/11525451002/

9.     https://www.tropicaltidbits.com/analysis/models/