While no impacts from the storm are expected over land, it’s the latest example of an early-forming storm probably connected to climate change.
The latest on Andres
As daylight dawned Monday morning, it illuminated a ragged and disheveled Andres struggling to maintain any semblance of organization. On satellite images, roiling storm tops could be seen bubbling upward east of the center of circulation, where most of the thunderstorm activity was concentrated.
Infrared satellite imagery revealed virtually no thunderstorms west of the center. Instead, an orphaned low-level spin remained mostly exposed as Andres churned slowly northwest. Technically, it meets the definition of a tropical storm though, because it exhibits a clear and closed low-level circulation with several thunderstorms anchored to it, even if robust thunderstorm coverage is lacking.
Although the low-level circulation was improving, the overall storm continued to struggle thanks to shear, or a change in wind speed and/or direction with height, that was responsible for the system’s lopsided thunderstorm coverage. That was unlikely to change early Monday, because Andres was ingesting dry air on its western side.
Tropical storm-force winds of 39 mph were estimated only in the northeast quadrant of the storm beneath the more vigorous thunderstorm updrafts; those winds were predicted to extend up to 80 miles from the center. Tropical storm-force winds were not believed to exist in the northwest, southwest and southeast quadrants of the storm.
The National Hurricane Center stated that Andres is no threat to any land areas; what is known as the fish storm is expected to degenerate into a remnant tropical low pressure system on Tuesday.
A growing trend of preseason storms
The main story with Andres doesn’t pertain to its winds or the weather itself; rather, what meteorologists are more interested in is that, once again, the eastern Pacific has managed to spit out a storm before the “official” start of the season, May 15. In fact, Colorado State University hurricane expert Philip Klotzbach confirms it’s the earliest named storm on record in the east Pacific, beating out the record previously set by Adrian, which formed May 10, 2017.
While ship reports of tropical systems date back to the 1800s, reliable satellite data of storms has been collected since around 1970.
Preseason tropical systems such as Andres are becoming increasingly common as ocean temperatures warm, probably linked to human-induced climate change. In three of the last five years, a tropical depression or storm has formed in the eastern Pacific Ocean before the official start of hurricane season.
Before 2000, the eastern Pacific hurricane season started in May less than half of the time. Since 2000, it has been more than 70 percent of the time.
The formation of Andres is particularly impressive, since the ongoing weak La Niña has resulted in relatively cooler ocean waters in the east tropical Pacific, although a localized warm spot exists where Andres materialized.
The uptick in preseason storms is also reflected in the Atlantic Ocean, where meteorologists at the National Hurricane Center are considering moving the “official” start date of the season up from June 1 to May 15.
The 2020 Atlantic hurricane season, for instance, began May 16, when Tropical Storm Arthur formed east of Florida, interacting with another atmospheric wave to dump up to 10 inches of rain on Marathon, Fla., and inundating Miami and Fort Lauderdale with six to eight inches. It later produced sustained winds of 39 mph at Alligator River Bridge on the Outer Banks of North Carolina.
That proved the sixth-consecutive year with a preseason storm forming in the Atlantic; while most preseason and early-season storms before August are generally on the weaker side apropos to winds, they can still bring significant flooding. Tropical Storm Ana scraped the East Coast in mid-May of 2015, dropping 6.7 inches of rainfall in North Carolina.
Last year, James Kossin, an atmospheric scientist with the National Oceanic and Atmospheric Administration, told the Capital Weather Gang that the uptick in preseason storm activity “seems to be, certainly, very attached to sea surface temperatures.”