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Matthew Holding Its Own; Threat Shifting to Bahamas, Southeast U.S.

By: Jeff Masters and Bob Henson 9:20 PM GMT on October 04, 2016

Mighty Hurricane Matthew has shrugged off its encounter with a landfall on the southwestern tip of Haiti between 7 - 9 am Tuesday morning, and remains an extremely dangerous Category 4 storm with 140 mph winds as it plows north at about 9 mph over the eastern tip of Cuba. Update: As of 11 PM EDT Tuesday, a Hurricane Warning is in effect for the east coast of Florida from Golden Beach northward (including all of Broward County] to Sebastian Inlet, as well as for Lake Okeechobee. A Hurricane Watch extends north from Sebastian Inlet to the Flagler/Volusia County line, and a Tropical Storm Warning extends from Chokoloskee (near Everglades City) around the south end of Florida through Miami-Dade County, as well as Florida Bay and the Florida Keys from Seven Mile Bridge northeastward. See the National Hurricane Center graphics for Matthew for other watches and warnings now in effect.

Satellite loops late Tuesday morning showed that the encounter with Haiti’s southwest peninsula weakened the storm, with the eye growing indistinct and the cloud tops of the eyewall thunderstorms warming. However, early Tuesday afternoon the eye began clearing out, and an Air Force hurricane hunter aircraft found that the central pressure had begun to drop again. At 12:38 pm Tuesday, during their final penetration of the eye, the Air Force Hurricane Hunters measured a central pressure of 949 mb, down two mb from their previous two passes through the eye. Peak surface winds measured by their SFMR instrument were 135 mph, and a dropsonde measured 141 mph winds at the surface. Matthew clearly remained a solid Category 4 storm, as reflected in the 5 pm EDT advisory from the National Hurricane Center.

Figure 1. MODIS satellite image of Matthew taken at 11 am EDT October 4, 2016, four hours after the hurricane had made landfall on the southwestern tip of Haiti as a Category 4 storm with 145 mph winds. Image credit: NASA.

Other than the land interaction going on with the eastern tip of Cuba, Matthew has favorable conditions for development. Light wind shear of 5 - 10 knots is affecting the storm, it has warm ocean waters of 29°C (84°F), and plenty of moisture--70 - 75% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model.

Figure 2. Radar image of Hurricane Matthew as it was approaching the eastern tip of Cuba at 3:35 pm EDT October 4, 2016. Image credit: NOAA.

Extreme rains over Haiti, Cuba and the Dominican Republic
Extreme rains from Matthew are a huge concern for eastern Cuba and the entire island of Hispaniola. The mountainous terrain of these islands creates tremendous uplift to the thunderstorms moving ashore, resulting in extremely intense rainfall. According to Oficina Nacional de Meteorología (ONAMET), the official weather service of the Dominican Republic, total rainfall amounts in the Dominican Republic on October 3 were as high as 233.9 mm (9.21”). The capital of Santo Domingo received 170.2 mm (6.81”). Additional heavy rains fell across southern portions of the country on Tuesday. The huge rainfall amounts we’ve been mentioning here from the personal weather station (PWS) in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti--22.89” of rain on Monday--are not mentioned on the ONAMET web site, even though they operate the station. Thus, these rainfall numbers may be unreliable.

Figure 3. Total rainfall amounts in the Dominican Republic on October 3, 2016. Rainfall amounts of up to 233.9 mm (9.21”) fell. The capital of Santo Domingo received 170.2 mm (6.81”). Image credit: Oficina Nacional de Meteorología (ONAMET), the official weather service of the Dominican Republic,

Catastrophe in Haiti?
Matthew’s extreme rains, large storm surge, and Category 4 winds were likely catastrophic for the southwestern portion of Haiti where landfall occurred. Matthew was the third strongest hurricane ever recorded in Haiti, and their strongest hurricane in 52 years. The only Haitian hurricanes stronger than Matthew were two Category 4 storms with 150 mph winds: Hurricane Cleo of 1964 and Hurricane Flora of 1963. According to a Tuesday afternoon news story from weather.com, two deaths in Haiti and four in the Dominican Republic are being blamed on Matthew so far.

We don’t have many weather stations in Haiti, so it is difficult to say what the conditions are on the ground. However, all three weather stations in southern Haiti that send us data continued transmitting through mid-afternoon Tuesday, which is a good sign. The Port-Au-Prince airport did not receive strong winds; top winds as of 2 pm EDT Tuesday were 34 mph, gusting to 52 mph. However, they did report several hours of heavy rain, which is the main danger in this heavily populated region, due to the high flash flooding risk. A personal weather station (PWS) on the south coast Haiti at Aquin, about 70 miles east of Matthew’s landfall, recorded a wind gust of 59 mph at 6:50 am EDT Tuesday. A PWS near Port-Au-Prince, Haiti recorded about 2.81” of rain for the day, ending at  3 pm EDT Tuesday.

Matthew set to carve a destructive swath across The Bahamas
Matthew’s assault on the Greater Antilles is just in the first of what could be a week-long sequence of damaging events as the massive hurricane churns toward the U.S. East Coast. The most immediate threat is to The Bahamas, where the entire nation is now under a Hurricane Warning. Matthew has a good chance of retaining its current strength, or perhaps even intensifying a bit, as it passes through The Bahamas from late Tuesday through early Thursday. Wind shear is expected to remain low to moderate (around 5 - 15 knots) through at least Thursday, with a very moist atmosphere (relative humidities at mid-levels of 70 - 80%). Moreover, the waters of The Bahamas are close to record-warm levels for early October, with sea surface temperatures around 29-30°C (84-86°F), about 1°C above average. There is also plenty of deep oceanic heat; together with the shallow undersea topography of The Bahamas, this will reduce the chance that Matthew’s fierce winds and waves will churn up enough cool water to significantly dent its strength. The fact that Matthew lost little strength during its trek across the Greater Antilles testifies to its very large and well-structured circulation. The NHC forecast issued at 11 AM EDT Tuesday keeps Matthew as a Category 4 through Thursday.

Matthew will produce very heavy rains, high winds, and huge surf across The Bahamas, but the greatest risk for the islands will be the potential for a devastating storm surge. Only a year ago, Category 4 Hurricane Joaquin looped near the easternmost islands at the start of October 2015, inflicting more than $100 million in damage and killing 33 crew members aboard the ill-fated El Faro cargo ship. There is still some uncertainty about Matthew’s path, but it is likely to slice through the heart of The Bahamas, putting many islands on its more dangerous right-hand side. Direct hits on Nassau and/or Freeport are quite possible. Since Matthew’s core of hurricane-force winds is fairly compact, it’s possible that only a few islands will experience such winds, but widespread storm surge of up to 10 - 15 feet is a major concern to the east of Matthew’s expected path. Joaquin produced a 12- to 15-foot surge on Rum Cay, Crooked Island, and Acklins Island.

Figure 4. Official NHC forecast for Matthew as of 5 PM ET Tuesday, October 4, 2016.

Southeast U.S.: Huge surf, heavy rain, high winds, and perhaps a hurricane landfall
The 12Z Tuesday morning suite of computer model guidance doesn’t exactly give us a definitive sense of whether Matthew will make landfall along the Southeast U.S. coast. Of our three top track models, the 12Z operational GFS run brings Matthew to within about 50 miles of the central Florida coast late Thursday, and even closer to the Carolinas, before taking Matthew out to sea without any landfall. The 12Z ECMWF and UKMET runs both bring Matthew ashore in central Florida. The less-reliable GFDL model produces a landfall in South Florida, followed by a track back offshore and a second landfall in North Carolina by Sunday. The HWRF run keeps Matthew more than 100 miles off the Florida coast, then brings Matthew ashore in North Carolina on Saturday. As for ensemble runs, a sizable minority of the 20 members of the GEFS (GFS ensemble) from 12Z Tuesday bring Matthew into central Florida. In the most recent ECMWF ensemble available (00Z Tuesday), all four of the high-probability ensemble members produced a central Florida landfall. Some members of the 12Z Tuesday UKMET and ECMWF ensembles, as well as the 12Z ECMWF operational run, even suggest that Matthew might actually carry out a large cyclonic (right-hand) loop, extending east and then south from the Carolinas back toward Florida--a scenario reminiscent of the huge loop carved out by Hurricane Ivan in 2004. These solutions are outliers, and we will have to wait for additional model support for this idea before considering it as a real possibility.

Forecaster Lixion Avila noted in the 5 PM Tuesday NHC discussion: “It will likely take another day or so for the potential impacts of Matthew in the United States to clarify.” If today’s model solutions haven’t yet given us clarity, they do confirm that landfall remains a very real possibility, particularly along the midsection of the Florida coast and again over eastern North Carolina.

Figure 5. In September 1999, Hurricane Floyd approached the Southeast U.S. at Category 3 strength, then carried out an arcing path that brought it ashore as a Category 2 storm at Cape Fear, North Carolina.

Because Matthew will be tracing an arcing path that echoes the coastline itself, it is impossible to tell at this point exactly where that arc will overlap the coast (as evidenced by the model disagreement above). Even in those stretches where Matthew remains just offshore, coastal locations may still experience winds of tropical-storm or even hurricane strength, as well as very heavy rain. At least some flooding can be expected along most of the Southeast coast, as Matthew’s winds drive water ashore. Any direct landfall could lead to a major storm surge. Matthew’s intensity may drop somewhat as wind shear increases after Thursday, but it will likely remain a major hurricane as it threatens the Southeast coast.

One analog for Matthew is Hurricane Floyd (September 1999--see Figure 5 above), which arrived in the Bahamas as a Category 4 storm, then carried out a path near the Southeast coast roughly similar to the one that Matthew might carve out if it were to remain offshore until North Carolina. After triggering the largest peacetime evacuation in U.S. history up to that point, Floyd inflicted close to $10 billion in damage (2016 dollars) and caused 72 U.S. deaths, making it the nation’s deadliest hurricane in more than 25 years. Floyd interacted with a frontal system over the East Coast that led to extremely heavy rains over a large area. The rains in North Carolina, which arrived after heavy rain less than three weeks earlier from Hurricane Dennis, produced all-time record flooding. The high water ruined some 24,000 homes and drowned millions of pigs and chickens. Parts of the east-central U.S. coast have experienced 10” - 15” in rain over the last two weeks (see Figure 6 below), which could exacerbate any potential flood-related impact of heavy rainfall from Matthew.

Figure 6. Observed 14-day precipitation totals (in inches) from 8:00 am EDT Tuesday, September 20, 2016, to 8 am Tuesday, October 4. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

Figure 7. Projected 7-day precipitation totals (in inches) from 8:00 am EDT Tuesday, October 4, 2016, to 8 am Tuesday, October 11. The actual amounts will hinge on the final track of Hurricane Matthew. Image credit: NOAA/NWS Weather Prediction Center.

Could Matthew hit the Northeast U.S.?
It’s quite possible that Matthew will affect the Northeast U.S. after it swings past the Carolinas this weekend, but given the continued divergence in model solutions, it’s too soon to pin down just how likely this is or what the impacts would be. The trend over the last day or two has been for Matthew to continue northeastward past the Carolinas, which reduces the odds of a left-track hook that would produce the worst direct impacts for the Northeast and/or New England. Only a couple of GFS ensemble members from 12Z Tuesday show a direct Matthew landfall north of Virginia, and the ECMWF ensemble suggests that any path over the Northeast coast for Matthew would have a good chance of occurring after a fair bit of time inland. The official NHC outlook as of 5 PM Tuesday has Matthew located about 100 miles south of the Rhode Island coast by Sunday afternoon, still as a Category 1 hurricane (see Figure 4 above).

Coastal residents north of the Carolinas and Virginias all the way to the Canadian Maritimes need to keep an eye on Matthew, as there is plenty of time for the forecast to evolve. Even if Matthew were to weaken and/or stay offshore, very heavy rains and high winds could affect a huge swath of the East Coast if the storm heads in that direction.

Figure 8. MODIS satellite image of Tropical Storm Nicole taken at 1 pm EDT October 4, 2016. At the time, Nicole had sustained winds of 50 mph, and was headed northwest at 8 mph. Upper-level outflow clouds from Hurricane Matthew can be seen at the lower left of the image. Image credit: NASA.

Tropical Storm Nicole forms from 98L
The tropical wave about 500 hundred miles northeast of Puerto Rico that we were tracking as Invest 98L developed a well-defined surface circulation and enough persistent heavy thunderstorm activity to be upgraded to Tropical Storm Nicole at 11 am EDT Tuesday. Nicole is the fourteenth named storm of this busy 2016 Atlantic hurricane season. Satellite imagery shows Nicole has the classic appearance of a tropical storm under high wind shear, with the circulation center exposed to view and all the heavy thunderstorm activity limited to the southeast side. Strong upper-level winds out of the northwest, partially due to upper-level outflow from Hurricane Matthew, are creating 30 - 35 knots of wind shear over Nicole. The latest SHIPS model forecast shows gradually increasing wind shear for Nicole over the next five days, which should weaken the storm to a tropical depression by the weekend. Nicole is not a threat to any land areas this week.

Tropical wave approaching Lesser Antilles has a low chance of development
A large tropical wave located several hundred miles east of the Lesser Antilles Islands is moving west at 10 - 15 mph, and will spread heavy rains and gusty winds into the islands on Wednesday and Thursday. The wave is unlikely to develop over the next two days, due to high wind shear from the upper-level outflow from Hurricane Matthew. Once the wave reaches the central Caribbean on Friday, wind shear should drop, and the latest GFS model ensemble forecast has about 10% of its members showing development into a tropical depression or tropical storm sometime Friday - Sunday. In their 2 pm EDT Tuesday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 10% and 20%, respectively.

We’ll be back with our next update by late morning Wednesday at the latest.

Jeff Masters and Bob Henson

Figure 9. Enhanced infrared satellite image of Hurricane Matthew (left), much smaller Tropical Storm Nicole (top center), and a tropical wave approaching the Lesser Antilles Islands (right), as of 3:45 pm EDT Tuesday, October 4, 2016. Image credit: NASA/MSFC Earth Science Office.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.