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Fred Heading for Cape Verde Islands; Ignacio Skirting Hawaii

By: Bob Henson and Jeff Masters 7:00 PM GMT on August 30, 2015

Residents of the Cape Verde islands are going through a rare experience today--a hurricane warning--as Tropical Storm Fred intensifies in the far eastern North Atlantic. As of 2:00 pm EDT, Fred was located near 14.1°N, 20.7°W, or about 195 miles east of the Cape Verde capital city of Praia. Outer rainbands are already beginning to reach the islands. The National Hurricane Center upgraded the storm from Invest 99L to Tropical Storm Fred in its 5:00 am EDT advisory, when it was located at 18.9°W longitude. This made Fred one of just a handful of systems in the last 60 years of satellite monitoring to become tropical storms east of 20°W, as reflected in NOAA’s HURDAT database. Others include eastward-moving, high-latitude Vince, 2005 (subtropical storm at 20.6°W, tropical storm at 19.3°W); Jeanne, 1998 (depression at 17.4°W, tropical storm at 19.4°W); and cyclonically arcing Ginger, 1967 (depression 18.3°W, tropical storm 18.1°W). Several unnamed storms in the HURDAT database are believed to have attained tropical storm strength east of 20.0°W, including:

Storm 3, 1900: 18.5°W
Storm 2, 1927: 19.3°W
Storm 6, 1948: 19.7°W
Storm 5, 1982: 19.5°W
Storm 6, 1988: 18.5°W

Figure 1. MODIS image of Tropical Storm Fred from NASA's Aqua satellite taken at approximately 9:00 am EDT Sunday, August 30, 2015. At the time, Fred had top sustained winds of 50 mph. The Cape Verde islands are outlined in the upper left corner. Image credit: NASA.

Fred is moving into a well-defined pocket of unusually warm sea-surface temperatures (1-2°C above average, or about 27-28°C) that surrounds the Cape Verdes. Since SSTs are often just marginally warm enough to support tropical cyclones near the islands, this warm pocket is a important piece of Fred’s future. Computer models differ enormously in where Fred will be by Thursday; the 120-hour positions from the early-cycle guidance produced at 1200 GMT Sunday vary by more than 500 miles. However, the models agree much more closely on track for the upcoming 48 hours, as Fred is projected to move steadily northwest through the heart of the northern Cape Verde islands. Neither of the high-resolution HWRF nor GFDL models bring Fred to hurricane strength, but statistical models push Fred just beyond that threshold, and NHC is citing these as well as the GFS and ECMWF models in predicting Fred to become a minimal hurricane by midday Monday local time. A hurricane warning is in effect for the Republic of Cabo Verde (the official name for the nation since 2013). To our knowledge, these are the first hurricane warnings on record for the islands; tropical storm warnings were posted for Humberto in 2013 and Julia in 2010 (see below).

Figure 2. Tracks of all tropical cyclones in the vicinity of the Cape Verde islands from the NOAA historical database, which extends back to 1851 (although reports were scanty from the far eastern Atlantic until the satellite era began in the 1960s). Only a handful of tropical depressions (blue lines) and tropical storms (green lines) have affected the islands, and no direct hurricane landfalls (yellow lines) have been recorded. The two yellow tracks labeled above are an unnamed 1892 hurricane and 1998’s Hurricane Jeanne. Image credit: NOAA Historical Hurricane Tracks.

A historic hurricane for the Cape Verdes?
The Atlantic's most terrifying and destructive hurricanes typically start as tropical waves that move off the coast of Africa and pass near the Cape Verde islands. This class of storms is referred to as "Cape Verde hurricanes", in reference to their origin. Despite the fact that the Atlantic's most feared type of hurricanes are named after the Cape Verde islands, the islands themselves rarely receive significant impacts from one of their namesake storms. This is because tropical waves coming off the coast of Africa have very little time to organize into tropical storms before arriving at the Cape Verde islands, which lie just 350 miles west of the African coast. There is no reliable record of any bona fide hurricane having made landfall on the Cape Verde islands (see Figure 2). The closest analogue for Fred is an 1892 storm that bisected the islands, moving between the northern cluster (Ilhas do Barlavento, or windward islands) and the southern cluster (Ilhas do Sotavento, or leeward islands). This 1892 storm reportedly intensified to hurricane strength while passing south of the northwestern Cape Verde islands. Another close approach came from 1998’s Hurricane Jeanne, which reached hurricane strength while passing about 100 miles south of the southern islands. Decaying tropical cyclones in the open Atlantic have occasionally circled southeastward to take a swipe at the Cape Verdes as extratropical storms, but none have reached the island at hurricane strength.

According to EM-DAT, the International Disaster Database, there have been only two deadly tropical cyclones in Cape Verde history. Like Jeanne, they both passed south of the Ilhas do Sotavento. The deadliest was Tropical Storm Fran of 1984, which brushed the southermost islands on September 16 as a tropical storm with 50-mph winds. Fran brought sustained winds of 35 mph and torrential rains to the islands. The rains triggered flash flooding that killed more than two dozen people and caused damages of almost $3 million (1984 dollars.) The other deadly named storm was Tropical Storm Beryl of 1982, which passed about 30 miles south of the southwestern islands on August 29, with 45-mph winds. The storm's heavy rains killed three people on Brava Island, injured 122, and caused $3 million in damage.

Figure 3. Track of Tropical Storm Fran of 1984, which brushed the southwestern Cape Verde islands on September 16 as a tropical storm with 50 mph winds. Torrential rains from Fran killed more than two dozen people in the Cape Verde islands, making it the deadliest storm in their history.

The most recent named storm to affect the islands was Hurricane Humberto of 2013, which passed the islands to the south as a tropical storm. Humberto brought wind gusts of up to 35 mph and heavy rain squalls to the islands, triggering flooding that washed out roads and damaged homes. Hurricane Julia of 2010, the easternmost Category 4 hurricane ever recorded in the Atlantic, passed about 50 miles south of Sao Filipe, on the island of Fogo in the southern Cape Verde islands, as a tropical storm with 45 mph winds, bringing wind gusts of 30 mph and some minor flooding.

Figure 4. Map of the Cape Verde islands (officially the Republic of Cabo Verde). Image credit: Wikimedia Commons/Oona Räisänen (Mysid).

Figure 5. Projected track of Tropical Storm Fred from the 11:00 am Sunday advisory issued by the U.S. National Hurricane Center. Image created with the WU Storm app.

Although all of the Cape Verde islands should prepare for a potential hurricane, Fred’s predicted track would bring the worst impacts across the northern islands (Ilhas do Barlavento), which are even less experienced than the southern islands at dealing with the high winds and heavy rain of tropical cyclones. Fred could make a direct landfall on more than one of the northern islands, as its track will be roughly parallel to this chain. Among the islands in line to feel Fred’s impacts first are the heavily touristed islands of Boa Vista and Sal, which lie on the stronger (right-hand) side of the projected path. Despite their name (which translates to “green cape” in English), the Cape Verde islands have a semi-desert climate, with an average annual rainfall of only around 10 inches, so the torrential rains of a tropical cyclone could have a big impact. Rains of 3-5” are predicted from Fred, with isolated totals of up to 8”. A direct landfall on the northwestern islands could produce not only heavy rain but high winds that would be extremely unusual, if not unprecedented.

Erika’s remnants are pouring on Florida, Cuba
Western Cuba and South Florida are getting a welcome dousing from the remnants of Tropical Storm Erika, which remain disorganized in the far southeast Gulf of Mexico. NHC gives the remnants only a 10 percent chance of regenerating into a tropical cyclone (which would again be named Erika) over the next five days as they slide northward along the west coast of Florida. The heavy rain is not so appreciated along the western half of the peninsula, where the last month has already brought 10-20” of rain and widespread flooding. Tampa needs less than an inch of rain through midnight Monday night to score its wettest July-August since records began in 1890 (old record 28.31” in 1960; total through noon EDT Sunday, 27.48”). Flash flood watches now cover all of central and southern Florida. “Our aquifers are full. There's no more areas for the water to percolate to," Ed Caum, a spokesman for Pasco County's emergency operations center, told the Associated Press on Saturday. Even as a leftover tropical cyclone, Erika may still cause significant damage in Florida over the next day or two. WU contributor Lee Grenci has some early thoughts on why Erika may have left forecast models, and forecasters, so perplexed.

Figure 6. Predicted total rainfall from 1200 GMT (8:00 am EDT) Sunday, August 30, through Friday, September 4. Image credit: NOAA Weather Prediction Center.

Three Category 4 storms lace the Pacific
It’s not every day you see three well-formed Category 4 hurricanes in a row. That’s been the case for the last 24 hours over the North Pacific, where Hurricane Jimena, Hurricane Ignacio, and Hurricane Kilo have made a most impressive trio. All three reached Category 4 strength on Saturday and remained there on Sunday morning, a rare feat.

Figure . Infrared satellite imagery from GOES-West reveals the crisp eyes of Category 4 hurricanes Kilo, Ignacio, and Jimena (left to right) at 1000 GMT (6:00 am EDT) Sunday, August 30. Image credit: NOAA National Hurricane Center.

A Tropical Storm Watch remains in effect for the eastern Hawaiian islands of Maui, Molokai, Lanai, Kahoolawe, and Hawaii (the Big Island), with Ignacio located about 420 miles east of Hilo as of 8:00 am HST (2:00 pm EDT) Sunday. Ignacio is packing winds of 130 mph, but its steady northwest track will take it well north of the islands. Tropical storm force winds extend out to 125 miles (mainly on the north side), so gusty conditions may occur, especially at higher elevations. The Central Pacific Hurricane Center is warning that rainfall amounts of 2-4”, with isolated totals up to 6” at higher terrain, are still possible. There’s much higher confidence that huge waves will be impacting the islands: the CPHC warns of potential life-threatening surf, especially on the Big Island. There’s no record in the modern database of a hurricane this strong tracking north of the islands, so even well-experienced surfers could find themselves in unexpectedly treacherous conditions. Meanwhile, Jimena and Kilo are raging far away from any populated land areas; Jimena is expected to slowly weaken, while the Joint Typhoon Warning Center projects that long-lived Kilo will maintain at least Category 3 strength for the next five days as it undergoes a gradual westward turn through the subtropical North Pacific. Kilo may cross the International Date Line around Tuesday, at which point it would be dubbed Typhoon Kilo. This was the case for Genevieve in 2014 and Ioke in 2006.

We’ll be back with another update on Monday. Enjoy the rest of your weekend!

Bob Henson and Jeff Masters


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