Noteworthy storms, tropical and otherwise, continued to pepper the Eastern and Central Pacific and North Atlantic on Sunday. The big landfall threat is Hurricane Polo (see below), but several other systems were making news this weekend – including a lumbering coastal storm in the Northeast U.S. that’s been unusually prolonged.

Former Category 5 Polo is still a powerful weathermaker

Hurricane warnings were in place on Sunday across much of the Baja California peninsula with the approach of Hurricane Polo. After several days on a contorted track off the Mexican coast, where Polo oscillated between Category 4 and 5 strength, the hurricane is now taking a classic track for Eastern Pacific hurricanes that will bring it north and eventually northeast into Baja California on Monday. As of 11 a.m. EDT Sunday, Polo’s satellite presentation had sharpened and the storm’s intensity was nudged upward to 125 mph, which kept it a Category 3 major hurricane. Landfall is predicted for Monday afternoon in the sparsely populated section of Baja California Sur (South) near or just north of Las Barrancas. Update: As of 5 p.m. EDT Sunday, hurricane warnings were added on the other side of the Gulf of California, encompassing a stretch of the mainland coast of Mexico from Guaymas to Huatabampito.

Before it makes landfall, Polo will continue traversing unusually warm waters (28-29 degrees Celsius or 82–84 degrees Fahrenheit), and wind shear is predicted to remain light to moderate (mostly below 10 knots). If Polo can keep itself walled off from somewhat drier air nearby, it could rival Norbert (2008) and Jimena (2009), which are the two strongest landfalling storms on record along the west coast of Baja California. Norbert and Jimena both came onshore just south of Puerto San Carlos at Cat 2 strength with top sustained winds of 105 mph. The official National Hurricane Center forecast on Sunday morning predicted that Polo would make landfall with 110-mph sustained winds, and NHC noted that the workhorse HAFS-B  model showed Polo arriving at Cat 3 strength.

Rains of 4-8 inches (locally 12”) over central Baja California Sur and 4-6 inches (locally 8”) in parts of southern Sonora state could lead to life-threatening floods and mudslides. Dangerous surf and rip currents will continue through Monday. And on the heels of Polo, residents of Baja California will be keeping a close eye on Tropical Depression 18E, which was predicted to become Tropical Storm Rachel by Sunday night and a hurricane by Monday. This system is predicted to stay well offshore all week, paralleling the coast but heading in the general direction of Baja California by next weekend. Cooler waters upwelled by Polo could help modulate this new storm’s strength. Update: TD 18E was upgraded to Tropical Storm Rachel at 5 p.m. EDT Sunday.

As for Polo, it will rapidly weaken as it passes across the rugged terrain of Baja California following landfall. Yet even as a tropical storm on Tuesday, and eventually a remnant low, Polo will be hauling moisture across northwest Mexico and into parts of the Southwest and Central United States. Moisture from fast-weakening Tropical Storm Odalys, which peaked as a Cat 4 northwest of Polo, will also be entrained. Together with the large upper-level low steering Polo inland, plus ample low-level moisture streaming north from the Gulf of Mexico, the stage will be set this week for widespread multi-day rainfall totals of 3 to 5 inches, including some pockets of torrential rains.

Parts of the drought-stricken Southwest and Plains will benefit immensely from the moisture, but episodes of deadly flash flooding will be a real concern. The NOAA/NWS Weather Prediction Center predicted a moderate risk (level 3 of 4) of rainfall exceeding flash-flood guidance across the Four Corners region on Monday and from southeast Arizona to the Texas Panhandle on Tuesday. Although large areas of significant rain are pretty much a certainty, there remains quite a bit of uncertainty as to where the main corridor of substantial rain will be positioned. There’s likely to be a sharp gradient from southeast to northwest, as shown in Fig. 1, that would have some drought-stricken areas missing out.

Figure 1. 5-day rainfall forecast from the NOAA/NWS Weather Prediction Center from 8 a.m. EDT Sunday through Friday, Sept. 27–Oct. 2. (Image credit: WPC)Nolo spares Hawaii from its heaviest rains

An earlier-than-expected westward turn this weekend kept Hurricane Nolo just far enough south of Hawaii’s Big Island to avoid some of the most dire rainfall potential there. As of 11 a.m. EDT Sunday, Nolo was centered about 260 miles southwest of South Point (on the Big Island’s southern end), heading west at 10 mph. Nolo’s top sustained winds were up to 105 mph, and NHC predicts the hurricane will peak as a Category 4 major hurricane on Monday as it arcs northwestward well away from the Hawaiian Islands. Update: With Nolo having suddenly embarked on a round of rapid intensification, NHC upgraded it to Cat 4 strength at 8 p.m. EDT Sunday, with top sustained winds of 130 mph.

Squalls on the outer edge of Nolo have led to periods of heavy rain and high wind in eastern Hawaii. More than 15,000 customers in Maui and Hawaii counties were without power as of Sunday morning, according to poweroutage.us.

The Atlantic simmers down

In the remote central tropical Atlantic, Tropical Depression Fay had top sustained winds of 35 mph as of 11 a.m. EDT Sunday. It could hang on for several more days as it drifts southward, posing no threat to land. Elsewhere in the Atlantic, a center of low pressure east of Bermuda could take on tropical characteristics around midweek, but it’s predicted to move generally eastward, away from any potential land threat.

In its second of two stints as a tropical storm, Fay once again fell short of hurricane strength, which leaves the Atlantic set to enter October without having recorded a single hurricane. As we discussed a few days ago, no Atlantic season in the modern era (since the advent of reconnaissance aircraft and satellites) has gone this long. And in the full Atlantic database going back to 1851, the only season that took till October for its first observed hurricane was 1905 (October 8) – keeping in mind that some hurricanes could have been missed in the pre-satellite, pre-recon era.

A weird September nor’easter rocks the coast from New Jersey to New England

Round after round of gale-force winds and squally rains hammered the coastal mid-Atlantic and Northeast over the weekend, courtesy of a slow-moving coastal storm that was one of the area’s earliest nor’easter-type storms in memory. Many weekend events were cancelled or postponed, and the prolonged wind stress on leafed-out trees helped bring down limbs and power lines. More than 100,000 customers across the region were without power as of midday Sunday, according to poweroutage.us, after the number had peaked at close to 180,000. One Brooklyn resident was killed by a falling tree on Saturday night, and New York City reported hundreds of requests for help related to falling trees and limbs.

Rains of 2 to 4 inches were widespread across the prolonged storm, with a number of 4-5” reports in southeastern Massachusetts (see Fig. 2 below). The storm also coincided with the full moon, which helped stoke multiple tidal cycles of onshore flow that led to widespread minor to moderate coastal flooding. Raritan Bay in New Jersey experienced major flooding on Sunday morning, with its highest water levels at Keansburg since 2018, as reported by Alan Gerard on Substack.

Figure 2. Rainfall totals for the 24-hour period ending Sunday morning, September 27, as reported by volunteers with the national CoCoRaHS rain gauge network. (Image credit: CoCoRaHS)

Although the storm’s appearance on satellite was dramatic – even with a briefly cleared-out “eye,” as seen in the embedded post above, moving onto the New Jersey coast – the storm’s flooding was far below levels observed during Hurricane/Superstorm Sandy. As the New York Times put it: “The nor’easter has not come close to the deadly toll brought by Hurricane Sandy in 2012, but the whistling winds and flooded roads certainly brought back memories for some residents.”

Irene Sans contributed to this post.

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