Tropical Storm Agatha is expected to be a rare and dangerous early season hurricane for Mexico » Yale Climate Connections

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Hurricane watches are posted for parts of Mexico’s southern coast as the first named storm of the 2022 Eastern Pacific hurricane season, Tropical Storm Agatha, strengthens in warm waters about 200 miles offshore . Agatha formed at 5 a.m. EDT Saturday May 28 and is poised to intensify into a rare early-season Category 2 hurricane before making landfall.

As of 11 a.m. EDT Saturday, Agatha was located approximately 215 miles southwest of Puerto Angel, Mexico, moving west-northwest at 5 mph with sustained winds of 45 mph and a central pressure of 1002 mb. Agatha enjoyed very favorable conditions for intensification, with very warm waters of 30 to 31 degrees Celsius (86 to 88°F), light wind shear of 5 to 10 knots and a humid atmosphere with an average relative humidity of 75%. These favorable conditions should persist until the landing. Steering currents favor a curved northeasterly track Sunday and Monday, with a landfall in southeast Mexico Monday afternoon or evening. Damaging winds, a large storm surge and torrential rains of 10 to 16 inches will all present significant hazards to Mexico. The first hurricane-hunting mission to Agatha is scheduled for Sunday afternoon, if a plane is available.

Figure 1. Up to seven-day forecast tracking for Agatha from 6Z (2 a.m. EDT) on Saturday, May 28, running the GFS ensemble model (GEFS). The black line is the average of the 31 ensemble members; the individual ensemble member forecasts are the thin lines, color-coded by the central pressure they predict for Agatha. Several members predicted that Agatha would regenerate into a tropical storm over the Bay of Campeche in the southern Gulf of Mexico. (Image credit: Tropical bites)

Agatha’s remnants could cause the first named Atlantic storm of the year

Agatha is expected to dissipate over the upper reaches of Mexico about a day after making landfall, but the remnants of the storm will be caught in a southwesterly flow that will bring moisture from the storm and turn over the southern Gulf of Mexico and the western Caribbean on Wednesday. and Thursday. A number of members of the GFS and European model ensemble show Agatha regenerating into the first Atlantic storm named 2022 in the Atlantic by mid-week.

If Agatha was able to maintain a well-defined circulation and reformation on the Gulf of Mexico, as the 0Z race Saturday of the indicated European model is possible, she would probably retain the Agatha name. Otherwise, any storm formed from Agatha’s remnants in the Atlantic would be named Alex. Saturday’s 6Z run of the GFS model favored the latter scenario, with potential Tropical Storm Alex forming in the western Caribbean near central Cuba on Thursday. In its Tropical Weather Outlook for Saturday at 8 a.m. EDT, the National Hurricane Center gave a five-day chance of tropical cyclones forming over the southern Gulf of Mexico at Agatha (or its remnants) of 20 percent. Preliminary forecasts suggest that any storm that forms in the Gulf or the western Caribbean will experience strong wind shear that will keep it weak, making it primarily a heavy rain threat.

Figure 2. There were 14 hurricanes during the month of May in the Eastern Pacific. (Image credit: NOAA)

Hurricanes that make landfall in the eastern Pacific are rare in May

Hurricanes are rare in May in the eastern Pacific, with 14 hurricanes recorded over the 51-year period 1971-2021 (Figure 2). May hurricanes that make landfall are very rare in the Eastern Pacific. NOAA’s Hurricane History Database lists only two: a previous incarnation of Hurricane Agatha on May 24, 1971 (85 mph winds at landfall) and Hurricane Barbara on May 29 2013 (80 mph winds on landing). The latest forecast from the NHC indicates that the 2022 version of Hurricane Agatha made landfall as a Category 2 storm with winds of 100 mph, making it the strongest Pacific hurricane on record so early in the year. ‘year.

Major hurricanes are also rare in the Eastern Pacific in May, with only five recorded and none making landfall:

Andres, May 31, 2015, winds 125 mph (Cat 3);
Amanda, May 25, 2014, winds 155 mph (Cat 4);
Bud, May 25, 2012, winds 115 mph (Cat 3);
Alma, May 24, 2002, winds of 115 mph (Cat 3); and
Adolph, May 29, 2001, winds 145 mph (Cat 4)

Figure 3. Average date of first named storm in the Eastern Pacific.

No evidence the Eastern Pacific hurricane season is getting longer

Agatha’s May 28 formation date comes nearly two weeks earlier than the average June 10 formation date of the season’s first named storm in the eastern Pacific (for the period 1991-2020). And last year, the basin experienced its first-ever named storm, Tropical Storm Andres, on May 9. So, is the season getting longer?

The hurricane season might be expected to start earlier and end later in the coming decades, as warming oceans allow more storms to form when ocean temperatures are slightly warmer for hurricane formation. tropical cyclones. However, hurricane genesis also requires low wind shear, high levels of humidity at mid-levels of the atmosphere, and something to spin the low-level atmosphere. In some ocean basins, climate change may inhibit early-season genesis events by decreasing these other factors necessary for a hurricane to occur. Looking at the longer-term statistics for the Eastern Pacific, there is no evidence that the hurricane season is starting earlier (Figure 3).

No research has been published so far showing a change in the length of the Eastern Pacific hurricane season. A 2015 study on how climate change could influence season length in climate models, led by John Dwyer of MIT, gave mixed results for the eastern Pacific, depending on the model used to simulate hurricane activity. Most models, but not all, projected an increase in the length of the eastern Pacific hurricane season in a future warmer climate.

The Atlantic hurricane season appears to be lengthening in the region south of 30°N and east of 75°W, according to a paper 2008 in Geophysical Research Letters published by Dr. James Kossin of the University of Wisconsin and titled “Is the North Atlantic Hurricane Season Getting Longer?” » A 2016 analysis by Dr. Ryan Truchelut from WeatherTiger also supported this idea. However, Juliana Karloski and Clark Evans of the University of Wisconsin-Milwaukee found no trend in tropical cyclone formation dates looking at the entire Atlantic for the period 1979-2014.

NOAA predicts below-average season in the central and eastern Pacific

In its May 24 seasonal forecast, NOAA predicted a below-average 2022 hurricane season in both Eastern Pacific (for storms affecting Mexico) and Central Pacific (for storms affecting Hawaii). NOAA, in its forecast for the Eastern Pacific, predicted a 70% chance of 10 to 17 named storms, of which 4 to 8 were expected to become hurricanes, including 0 to 3 major hurricanes. A AS 45% to 100% of the median was also predicted. Using the midpoint of these ranges, NOAA predicted 13.5 named storms, 6 hurricanes, and 1.5 major hurricanes, falling below the Averages 1991-2020 of 15 named storms, eight hurricanes, four major hurricanes.

The Central Pacific outlook predicted a 70% chance of 2 to 4 tropical cyclones (which includes tropical depressions, tropical storms and hurricanes). A near-average season has 4-5 tropical cyclones. La Niña conditions generally lead to relatively calm hurricane seasons in the Eastern and Central Pacific due to colder than average ocean temperatures and higher wind shear.

Below average activity in the Eastern Pacific in 2021

As is often the case when the Atlantic experiences an active hurricane season, tropical cyclone activity in the eastern Pacific was below average in 2021, with 19 named storms, eight hurricanes, two major hurricanes and an index ACE of 94, or 71% on average.

However, five of 2021’s named Eastern Pacific storms hit Mexico, and a sixth, Enrique, did $50 million in damage. The Eastern Pacific’s five named storms are the most numerous in the country since 2018, when six named storms struck. A summary of the named Pacific storms of 2021 to wreak havoc in Mexico:

  • Hurricane Rick made landfall as a Category 2 storm with winds of 105 mph in Guerrero, Mexico on October 25; damage estimates run into the tens of millions.
  • Hurricane Pamela made landfall as a Category 1 storm with winds of 75 mph 40 miles northwest of Mazatlán, Mexico on October 13, killing two people; damage estimates run into the tens of millions. Pamela’s remains swept across Texas, causing flooding that killed two people.
  • Hurricane Olaf made landfall in Mexico’s Baja California on September 9 as a Category 2 storm, killing one and causing tens of millions of dollars in damage. Olaf’s wetness also caused flood damage in Jalisco and Colima states.
  • Tropical Storm Dolores made landfall near the border of the Mexican states of Michoacán and Colima on June 19 with winds of 70 mph, killing three people and causing $50 million in damage.
  • Category 1 Hurricane Enrique tracked parallel to the southwest coast of Mexico June 25-30, eventually dissipating into the Gulf of California without making landfall. Enrique’s floods killed two people and caused $50 million in damage.
  • Hurricane Nora made landfall Aug. 28 in the Mexican state of Jalisco near Puerto Vallarta as a Category 1 storm, killing three people and causing $125 million in damage.

Two major hurricanes have occurred in the eastern Pacific in 2021 – Hurricane Felicia, which peaked as a Category 4 storm with winds of 145 mph in July, and Hurricane Linda, which peaked as that category 4 storm with winds of 130 mph in August. Neither hurricane made landfall.

Our next article on Agatha is due Monday, May 30 at the earliest.

Bob Henson contributed to this post.

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