After punishing Haiti and the Dominican Republic overnight with heavy rain while still a tropical depression, Grace strengthened into a tropical storm Tuesday morning, then pounded Jamaica and eastern Cuba with heavy rain on Tuesday afternoon.

At 11 a.m. EDT Tuesday, Grace was located along the northern coast of Jamaica, about 75 miles east of Montego Bay. A personal weather station in Kingston, Jamaica picked up 3.69” of rain in the 12 hours ending at 1 p.m. EDT Tuesday from Grace.

Grace was a strengthening tropical storm, with top winds of 50 mph and a central pressure of 1005 mb, moving west at 15 mph. Grace’s tropical-storm force winds had expanded, extending out 70 miles from its center even as wind shear of 10-15 knots was pushing dry air into the core of Grace, slowing intensification. Satellite imagery showed Grace’s heavy thunderstorms much more organized than on Monday, with increased intensity and more low-level spiral bands.

Grace brought heavy rains to Haiti’s earthquake zone

Official weather observations are sparse in Haiti, but there are three personal weather stations in southwest Haiti in the Weather Underground network. The highest rainfall amount recorded at these three stations from Grace was 3.12” in the 16 hours ending at noon EDT Tuesday. It is likely that heavier rains fell over portions of this region, adding significant misery for the survivors of a devastating magnitude 7.2 earthquake on Saturday morning that killed an estimated 1,400 people, with more fatalities expected.

Figure 1. Predicted wind speed (colors) and sea level pressure (black lines) for Tropical Storm Grace at 8 a.m. EDT (12Z) Wednesday, August 18, from the 6Z Tuesday, August 17, run of the HWRF model. The model predicted Grace would be just northwest of Grand Cayman Island as a tropical storm with 65 mph winds. The island was expected to be on the weaker left side of Grace. (Image credit: Tropical Tidbits)

Forecast for Grace

A broad ridge of high pressure over the western Atlantic is steering Grace. The ridge is expected to keep the storm on a west to west-northwesterly path along the north coast of Jamaica on Tuesday, bring the storm very close to Grand Cayman Island on Wednesday morning, followed by two probable landfalls in Mexico, one on the Yucatan Peninsula and one in Veracruz state.

With a large expanse of warm waters near 30 degrees Celsius (86°F) ahead of it, an atmosphere with a mid-level relative humidity of 55-60%, and light-to-moderate wind shear of 5-15 knots, Grace could undergo significant strengthening when it is not suffering from land interaction with Jamaica or Mexico’s Yucatan Peninsula. The waters of the western Caribbean that Grace will be traversing have the highest heat content of anywhere in the Atlantic, giving Grace plenty of fuel for rapid intensification.

The 12Z Tuesday run of the SHIPS model gave a 22% chance that Grace would rapidly intensify by 35 mph into an 85-mph category 1 hurricane by 8 a.m. Wednesday, when the storm will be close to Grand Cayman Island. The National Hurricane Center was predicting that Grace would be a 75-mph hurricane at that time. More eye-opening was the model’s prediction that Grace had a 33% chance of intensifying into a 125-mph category 3 hurricane by Friday morning, as it approached its final landfall in Mexico’s Veracruz state on the western Gulf of Mexico. Citing the unknown amount of disruption Grace might encounter while crossing the Yucatan Peninsula, NHC was conservative in its intensity forecast for that time, calling for Grace to be a minimal category 1 hurricane with 75 mph winds.

Figure 2. Radar image of Tropical Storm Fred as it was making landfall 25 miles west of Apalachicola, Florida, at 3:16 p.m. EDT August 16, 2021. (Image credit: Mark Nissenbaum/ Florida State University)

Fred hits Florida, pushes inland

Tropical Storm Fred made landfall in the Florida Panhandle 25 miles west of Apalachicola at 3:15 p.m. EDT Monday, August 16, with sustained 65 mph winds and central pressure of 994 mb. The peak storm surge at a NOAA tide gauge occurred at Apalachicola, where the surge peaked at 4.67’. The peak surge occurred around time of low tide, so only minor coastal flooding was observed (see drone footage of the flooding below).

A gust to 68 mph was observed Monday afternoon at the Apalachicola Airport; four coastal locations reported wind gusts of 70-73 mph. There were numerous reports of flooded roads and downed trees; at least 36,000 customers in Florida lost power at the height of the storm, and one person was injured by a falling tree in Millville.

Fred brought a swath of 2-6” of rain from its landfall location inland into Alabama and Georgia; Panama City recorded a 24-hour rainfall amount of 6.58”. The highest rainfall amount reported was 9.02” at Southport, Florida; 8.40” was reported at Hilton Head Island, South Carolina. As of 3 p.m. EDT Tuesday, NOAA’s Storm Prediction Center had logged 13 preliminary tornado reports from Fred: seven in Georgia, four in North Carolina, and two in South Carolina. No major damage or injuries had been reported from the tornadoes.

Figure 3. Storm total rainfall from Fred estimated by the Tallahassee, Florida, radar as of 10:44 a.m. EDT August 17, 2021. (Image credit: Weather Underground, an IBM company)

Fred was downgraded to a tropical depression Tuesday morning, and at 11 a.m. EDT Tuesday was in northern Georgia, 30 miles south-southwest of Atlanta, moving north-northeast at 17 mph with top winds of 30 mph. Fred continued to dump heavy rain, and flooding rains of 4-8” and a few tornadoes are expected along its track through northern Georgia and the southern Appalachian Mountains over the next day.

Figure 4. Visible satellite image of Tropical Depression Fred over the southern Appalachians at 11:50 a.m. EDT August 17, 2021. (Image credit: NOAA/RAMMB/Colorado State University )

Fred already the fourth U.S. landfalling storm of 2021

Fred was the fourth named storm to make landfall in the U.S. this year, coming after Elsa (landfall on July 7 with 65 mph winds in Florida, killing one and causing $775 million in damage); Danny (landfall in South Carolina on June 28 with 45 mph winds, no deaths or damages reported); and Claudette (landfall on June 19 in Louisiana, killing 14 and causing $350 million in damage).

Last year had a record 11 named storms make landfall in the contiguous U.S., beating the previous record of nine set in 1916. The fourth U.S. landfall of 2020 (Hanna in Texas) occurred on July 25. Both 2020 and 2021 have had the same number of U.S. landfalls for the first eight storms: four. That’s not a ratio we want to maintain. The record-earliest fourth landfall in the U.S. is held by Hurricane Four of 1886, which hit Florida on July 19.

Over the 71-year period 1950-2020, the U.S. averaged three landfalling tropical storms (with one being a hurricane) per year, according to the website Tropical Storm Risk, so 2021 has already had more than an average season’s worth of landfalling storms. On average, more than 75% of the Atlantic’s named storms occur after August 16; the average peak date of the season (September 10).

Figure 5. GeoColor visible satellite image of Tropical Storm Henri near Bermuda (outlined in yellow) at 1520Z (11:20 a.m. EDT) Tuesday, August 17, 2021. (Image credit: RAMMB/CIRA/CSU)
 

Henri continues its lazy loop around Bermuda

Tropical Storm Henri is now heading westward as it continues a multiday circuit around the island of Bermuda, staying far enough away to avoid any major impacts there. At 11 a.m. EDT Tuesday, Henri was about 135 miles south-southeast of Bermuda, heading west-southwest at 6 mph. Top sustained winds were holding at 50 mph. Northwesterly wind shear was only about 10 knots, and upper-level outflow was gradually improving on Tuesday around a well-defined core of thunderstorms, located mainly to the east of Henri’s surface center.

Henri burst onto the scene as a tropical depression late Sunday and as a tropical storm Monday evening while many hurricane watchers were focused on Fred and Grace. The poorly forecast upper-level impulse that evolved into Henry had dipped south from the midlatitude jet stream after spawning severe weather while traversing the United States, as analyzed by Stu Ostro of The Weather Channel via satellite imagery and Philippe Papin of NHC via GFS output. Papin added that both the GFS and European model were slow on the uptake with Henri’s formation: “The fact remains, global models just do poorly w/ [tropical cyclone] genesis in the Atlantic subtropics between 20-40N.”

A tropical storm watch has been in effect for Bermuda since late Sunday night. However, with Henri’s tropical-storm-force winds extending out only some 35 miles from its center, its effects on Bermuda have been minimal, which is likely to continue to be the case. Henri’s small size will also make it easier for the storm to both intensify and to weaken. There will be a brief window for Henri to potentially strengthen to a higher-end tropical storm as it moves westward through Wednesday, while wind shear remains light to moderate and Henri traverses warm subtropical SSTs of 28-29 degrees Celsius (82-84°F). Wind shear will increase markedly on Wednesday and Thursday, to around 20-25 knots, but SSTs will remain warm, and mid-level relative humidity is predicted to increase from around 50% to around 60% by Thursday and Friday. All told, these factors give Henri a reasonable chance of maintaining its strength for several days.

By around Friday, Henri is expected to recurve sharply northeastward, staying a few hundred miles east of the U.S. East Coast. Leading track models and their ensembles are in strong consensus on this outcome. After it recurves, Henri may gradually take on more subtropical characteristics. The U.S. East Coast may see increasing swells from Henri by later this week, as the storm’s radius of tropical-storm-force winds gradually expands.

Henri the 4th-earliest 8th storm on record

Henri’s formation date of August 16 is exceptionally early for the appearance of the season’s eighth named storm. Only three seasons have had an earlier eighth storm: 2020 (July 24), 2005 (August 3), and 1936 (August 15).

As of Tuesday, only one of this year’s eight named systems – category 1 Hurricane Elsa – had managed top sustained winds above 65 mph. This reality is eerily similar to last year, in which only one of the first eight named systems – category 1 Hurricane Hanna – had top winds stronger than 65 mph.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...