Dr. Jeff Masters ·

Above: Damage on the Lesser Antilles island of Dominica, after Hurricane Maria hit as a Category 5 storm with 160 mph winds. Maria killed at least 7 people on Dominica, and 2 on neighboring Guadeloupe. Image from a video by the Caribbean Disaster Emergency Management Agency.

After making landfall in southeast Puerto Rico near 6:15 am Wednesday as a top-end Category 4 storm with 155 mph winds, Hurricane Maria finished a devastating pummeling of the island near 1:30 pm, when its eye emerged over the ocean off the northwest coast. An Air Force hurricane hunter aircraft found that Maria’s 70-mile traverse of Puerto Rico had knocked the top winds of the storm down to 110 mph by 5 pm Wednesday, making it a high-end Category 2 hurricane. Satellite images show the hurricane is still well-organized, though, and the Hurricane Hunters found that Maria’s pressure was falling again late Wednesday afternoon: 957 mb at 5 pm, compared to a 961 mb reading at 2 pm. Maria will continue to bring dangerous torrential rains and powerful winds to Puerto Rico and the eastern Dominican Republic into Thursday.

Figure 1. Infrared GOES-16 image of Hurricane Maria at 5:15 pm EDT Wednesday, September 20, 2017. GOES-16 data are preliminary and non-operational. Image credit: RAMMB / CIRA @ CSU.

Maria brought extreme rainfall amounts to large portions of Puerto Rico that caused record or near-record flash flooding. Numerous stations in Puerto Rico recorded rainfall amounts in excess of ten inches. Rainfall amounts in excess of 47 inches in 24 hours were recorded at three stations on the southwest side of El Yunque, the high mountainous area in the northeast corner of Puerto Rico; these are so extreme as to be unbelievable, and the gauges may have been impacted by flash flooding, or by a callibration problem at extreme precipitaion rates:

96.65” at Quebrada Arenas, including 67.75” in one hour ending at 6 am.

72.07” at Barrio Montones, including 34.04” in one hour ending at 8:45 am.

47.25” at Rio Valenciano, including 19.66” in one hour ending at 7:11 am.

These rainfall amounts would break virtually every world record for precipitation, and are highly likely to be in error. Water levels at the Rio Gurabo at Gurabo, where the nearby Gurabo Abajo rain gauge recorded 23.64” of rain in less than 24 hours, jumped by 27 feet in less than 12 hours (see Figure 2), so that rainfall amount is believable.

Figure 2. Water levels at Rio Gurabo at Gurabo, on the southwest side of El Yunque, shot up 27 feet in less than 12 hours. The river crested just 0.76’ below the record set during Hurricane Donna of 1960. Image credit: NOAA.

An island-wide power outage in Puerto Rico

Not since the great Category 5 1928 San Felipe Segundo hurricane has Puerto Rico experienced a hurricane catastrophe as extreme as that wrought by Hurricane Maria. The storm’s powerful winds caused catastrophic damage to the island’s power grid, knocking out power to 100% of Puerto Rico’s 3.4 million residents. In the Virgin Islands, there was also heavy damage on St. Croix, and serious flooding has been reported on St. Thomas. Maria is almost assured to be the most expensive hurricane in Puerto Rico history, and may challenge Hurricane Hugo (1989) and Irma (2 weeks ago) as the most expensive hurricane on record for the U.S. Virgin Islands.

Moderate storm surge flooding from Maria

Storm surge flooding of 1.5 – 5.3 feet affected locations along coasts of Puerto Rico and the Virgin Islands where we have tide gauges. Storm surge damage will not be the big story from this hurricane, though--wind damage and inland flash flood damage will be. According to the Quicklook page at NOAA’s Tides and Currents, here are the peak storm surges from Maria:

5.3’, Yabucoa Harbor, PR

2.8’, Vieques Island, PR

2.5’, Mayaguez, PR

2.4’, Arecibo, PR

2.3’, San Juan, PR

2.0’, Christiansted Harbor on the north side of St. Croix, VI

1.7’, Culebra Island, PR

1.5’, St. John, VI

Forecast for Maria

Satellite imagery late Wednesday showed that Maria’s eye was already beginning to clear out after becoming cloud-filled during its path across Puerto Rico. Maria will be traversing very warm sea surface temperatures (SSTs) of around 29°C into the weekend, and there is substantial oceanic heat content along its path that will help keep Maria from churning up cooler water that might dent its strength (see Figure 3 below). Wind shear around Maria will remain less than 10 knots into Thursday, which also suggests restrengthening; also, there are no large masses of dry air that would impede growth. Starting late Friday, wind shear is predicted to increase to the 15 – 20 knot range; this would suppress further strengthening and might eventually weaken Maria. Moreover, at least part of Maria’s circulation will pass over the cold wake left by Jose (see Figure 3), which may also cut into Maria’s strength somewhat. These conditions suggest Maria will become at least a mid-strength Category 3 hurricane with 120 mph winds, and has a shot to regain Category 4 status.

Figure 3. Total Ocean Heat Content (OHC) along the track of Hurricane Maria. Maria had very high OHC values of 80 – 110 kilojoules per square centimeter during its rapid intensification phase just east of the Lesser Antilles and in the northeast Caribbean. OHC values will continue to be high until the storm reaches 27°N, when it will begin crossing the cold wake left behind by Hurricane Jose, which performed a clockwise loop in that vicinity over a 3-day period last week. Image credit: Rosenstiel School of Marine and Atmospheric Science, University of Miami.

Maria will be steered northwest and eventually north over the next five days, around the edge of an upper-level ridge situated to its east. By Monday, Maria is expected to be a strong Category 2 or 3 hurricane positioned several hundred miles southeast of the North Carolina coast, and the Outer Banks of North Carolina are close to being in NHC’s 5-day cone of uncertainty. In the subsequent 5- to 7-day forecast range, there is more uncertainty than usual on how close Maria might get to the U.S. East Coast, since the hurricane’s track will depend upon how fast Jose decays, and where Jose moves. As Tropical Storm Jose weakens (see below), it is possible that the Atlantic ridge could build west and block Maria’s progress, forcing the storm to move toward the north-northwest to a landfall between North Carolina and New Jersey. Alternatively, a trough of low pressure passing to the north of Maria next week, in combination with the remains of Jose, may pull Maria to the east northeast without the storm making landfall along the mid-Atlantic coast. In this case, though, Maria might still be a threat to New England—particularly Southeast Massachusetts—or possibly the Canadian maritime provinces. Maria would most likely be at tropical storm strength in this scenario, due to the cool waters north of North Carolina.

Figure 4. Visible GOES-16 image of Tropical Storm Jose at 2:57 pm EDT Wednesday, September 20, 2017. Image credit: RAMMB / CIRA @ CSU.

Jose spinning down south of New England

Downgraded late Tuesday after more than 12 days at hurricane strength, Tropical Storm Jose continued its ever-so-gradual weakening off the coast of New England on Wednesday. At 2 pm EDT, Jose was located about 140 miles south-southeast of Nantucket, Massachusetts. Jose’s top sustained winds were 70 mph, just below hurricane force, but a broad field of tropical-storm-force winds extended more than 200 miles south of Jose’s center. A NOAA buoy about 65 miles southeast of Nantucket notched winds of 40 mph, gusting to 52 mph. Top winds as of 2 pm at Nantucket’s airport were a mere 32 mph, gusting to 43 mph, and just 0.54” of rain had fallen since midnight.

Although Jose bears some resemblance to a nor’easter or a hybrid storm on satellite, phase-space diagrams from Florida State University show that it remains a warm-core tropical cyclone. Tropical storm warnings remained in effect Wednesday afternoon for the outermost islands of southeast New England. Most of Jose’s modest rainbands were located west of its large eye, with a few brushing southeastern Massachusetts.

Models agree that Jose will continue its slow decline over waters that are too cool to sustain a tropical cyclone. Now moving northeast at 7 mph, Jose is expected to slow down and then begin looping back westward on Thursday. The official NHC forecast holds Jose stationary near 70°W longitude as a weakening post-tropical cyclone from Saturday through Monday. The 12Z run of the European model goes with the stationary solution. However, the GFS, HWRF, and HMON models keep Jose or its remnants heading west, reaching New Jersey late Sunday or Monday with minimal impact other than some breezy showers.

Jose is much weaker than Maria, so it should have little direct effect on Maria’s track regardless of where it ends up. The importance of Jose is in its effect on upper-level ridging to its west and east. The weakness created by Jose will make it difficult for the Atlantic ridge to build west and block Maria’s northward motion. If Jose does weaken quickly enough, it is possible the ridge will strengthen enough to at least slow Maria down, as discussed above.

Figure 5. The four rapid-intensifier hurricanes of 2017, compared with Hurricane Wilma of 2005. Shown are the last periods in which the hurricanes were at various levels (tropical depression, tropical storm, or Category 1 hurricane) along with the intervals from that point to the first point at which they achieved their top rating (either Cat 4 or 5).

This year is chock-full of rapidly intensifying hurricanes

If it seems like this year’s Category 4 and 5 storms made it to that level in a big hurry, you’re not imagining things. In the Washington Post, Chris Mooney spotlights a few of the leaps in strength that this year’s four major Atlantic hurricanes have taken, including:

Harvey: Cat 1 to Cat 4 in 24 hours

Irma: Cat 3 to Cat 5 in 24 hours

Jose: Cat 1 to Cat 4 in 24 hours

Maria: Cat 1 to Cat 4 in 12 hours, and Cat 1 to Cat 5 in 15 hours

Most of the rapid intensification records for major Atlantic hurricanes were set by 2005’s phenomenal Hurricane Wilma. However, Maria has tied Wilma for the fastest vault from tropical depression to Cat 5 hurricane (54 hours), as shown in Figure 5 above.

Bob Henson co-wrote this post.