By: Bob Henson and Jeff Masters From Weather Underground

Hurricane Matthew is once again an extremely dangerous Category 4 storm. Matthew’s top sustained winds were upgraded to 140 mph in the 11 am EDT advisory from the National Hurricane Center, based on surface wind data collected by dropsondes (parachute-borne instrument packages) and the SFMR radiometer aboard Hurricane Hunter aircraft. Matthew’s central pressure dropped more than 12 millibars overnight, and a jump in surface winds typically follows such a drop after 12-24 hours. Hurricane Warnings are now in place from Broward County, Florida, to Ediston Beach, South Carolina. As of 2 pm EDT Thursday, Matthew’s sustained winds were holding at 140 mph, with the storm located about 125 miles east-southeast of West Palm Beach, Florida.

Matthew’s eye, clearly visible on satellite, was approaching the north end of Andros Island in The Bahamas around noon on Thursday. The especially dangerous right-hand side of Matthew’s eyewall passed over or very near New Providence Island, including Nassau. Since the city lies on the north side of the island, it is shielded to a large extent from storm surge with a northwestward-moving hurricane such as Matthew.
Figure 1. Satellite image of Hurricane Matthew as of 1:18 pm EDT Thursday, October 6, 2016.

The northwest Bahamas getting pounded
Over the past day, The Bahamas have taken a severe pounding from Hurricane Matthew. On Thursday evening, the hurricane passed within 50 miles of Exuma, where WU member ExumaMET had this to report: Morning all. It was an intense night here. I recorded Sustained winds over 100 and gusts way into category 4 strength with one gust hitting 153 mph before something took out my instrument. We’re still in tropical storm force and it should be interesting to see what the island looks like as the sun comes up.

At 2:19 am EDT Thursday, winds at a personal weather station (PWS) on Staniel Cay, Exumas, located in the strong right eyewall of Matthew, about 30 miles east-northeast of hurricane’s center, peaked at 92 mph, gusting to 101 mph. The pressure bottomed out at 984 mb at that time, and 14.13” of rain fell in the period midnight to 1 pm EDT.

After passing Exuma, Matthew marched northwest, passing between Andros Island to the west and New Providence Island to the east. The strongest winds of the right-front quadrant of Matthew hit New Providence between 9 – 11 am today. Winds at 9 am EDT at the Nassau airport on New Providence were 58 mph, gusting to 85 mph. The airport stopped transmitting data after that, as did the four PWS’s on the island. It is likely that the island experienced a ten-foot storm surge on the south shore.

Matthew is continuing northwest, and will pass between the Berry Islands and Grand Bahama Island this afternoon and this evening. At 2 pm EDT Thursday, an automated station in the Berry Islands, located about 50 miles to the northeast of Matthew’s center, reported a sustained wind of 59 mph, with gusts to 76 mph. A personal weather station (PWS) on the Berry Islands reported sustained winds of 85 mph—but the quality of the wind data was suspect. The pressure was 971 mb.

Settlement Point on Grand Bahama Island will be in the northeast eyewall of Matthew at approximately 8 pm tonight. As of 1 pm EDT, the winds were 43 mph, gusting to 47 mph.
Figure 2. Latest NHC forecast for Hurricane Matthew as of 11 am EDT Thursday, October 6, 2016.

The forecast for Matthew through Friday
Matthew may well strengthen further on Thursday afternoon and evening, but there is only a small chance (estimated at 23% in the 12Z Thursday SHIPS model) that it will reach Category 5 strength. More likely, Matthew will approach the Florida coast tonight as a Category 4 storm, then slide up the coast on Friday with a gradual weakening trend, as greater wind shear, drier air, and land interactions take their toll. How long Matthew retains its strength depends largely on how long the center stays entirely offshore, rolls along the coast, or nudges just inland at some point.

Confidence is now very high with Matthew’s large-scale track through Saturday, as the hurricane will be tracing a very predictable loop around the west side of high pressure over the western Atlantic. The challenge is on the smaller scale, where variations of just 20 or 30 miles relative to the shore can make a great difference in terms of impact. The uncertainty in Matthew’s east-west position near the shore means that coastal residents in central and northern Florida must prepare for the possibility of receiving winds from Matthew’s eyewall, as well as the potential for record-smashing storm surge in some parts of northern Florida and Georgia (see embedded tweet at bottom).

The small-scale uncertainty in Matthew’s track does not affect the larger-scale picture, which includes:
—Winds of tropical storm strength (40 – 75 mph) across the eastern half of the Florida peninsula from Lake Okeechobee northward, including Orlando.
—Rainfall totals of 5” to 15” within 50 miles of the coast from central Florida to southern North Carolina. Rainfall of 3” – 6” could extend further north across eastern North Carolina. Falling atop ground saturated by recent rains, this could produce widespread flooding far north of Matthew’s center and will raise the risk of power outages (see Figure 4 below), as gusty winds bring down trees in soggy soil.
Figure 3. Probability of hurricane-force winds from Matthew for the 120 hours from 8 am EDT Thursday, October 6, to Tuesday, October 11. Probabilities are highest (greater than 70%) along the immediate coast from around Port St. Lucie to Cape Canaveral. There is a greater than 90% chance of tropical-storm-force winds as far west as Lake Okeechobee and Orlando. Matthew’s peak winds were upgraded following the creation of this image, but the breadth of the expected wind swath has not changed significantly. Image credit: NOAA/NHC.

A unique storm in Florida hurricane annals
There are no ideal analogs for Matthew’s expected track and strength along the Florida coast. Only a handful of hurricanes have struck Florida with winds as strong as Matthew’s current 140 mph, and the only hurricanes known to have been “coast scrapers” along the central and northern Florida coast were considerably weaker than Matthew. For most residents along the north half of Florida’s Atlantic coast, and perhaps the Georgia coast as well, Matthew will be the strongest hurricane in living memory. (The last major hurricane to affect the Jacksonville area was in 1898.) Breaking waves as high as 15 to 25 feet on top of potential major storm surge are likely to inflict severe damage to beaches and barrier islands along the central and northern Florida coast.

Matthew is on track to become the first major hurricane to make landfall on U.S. shores since Wilma in 2005. It is virtually certain to be the most destructive since Hurricane/Superstorm Sandy in 2012, and it could easily end up among the ten most expensive landfalls in U.S. history adjusted for inflation, perhaps rivaling or topping such recent storms as Wilma, Irene (2011), Ike (2008), Ivan (2004), and Charley (2004). Latest estimates from a University of Michigan-based research group are that as many as 9.6 million people from Florida to North Carolina may lose power as a result of Matthew.
Figure 4. Estimated fraction of the population that is projected to experience power outages with the passage of Hurricane Matthew, based on data from early Thursday morning. Even though Matthew will pass well south of North Carolina, strong winds below hurricane strength combined with very heavy rains will pose the risk of tree damage and outages.

A quick guide to potential impacts
Below is a general summary of potential impacts from Matthew as of midday Thursday. For the latest local details, be sure to check the NWS local statements page, and heed any evacuation advice from local authorities.

FL Treasure Coast (including Port St. Lucie and Vero Beach)
There is still a chance Matthew will make landfall as far south as Port St. Lucie, but movement trends and computer model guidance suggest that the center is more likely to be just offshore by late Thursday night, moving along the coast and very gradually toward it. This would put some or all of the Treasure Coast in the western eyewall of Matthew, where sustained winds would probably be less than Category 4 strength but still potentially very damaging. A storm surge of up to 5 to 8 feet is expected on the barrier islands of Martin and Saint Lucie counties, with the surge risk highest if Matthew does edge inland along the Treasure Coast.

FL Space Coast (including Melbourne and the Kennedy Space Center)
This is the most likely area to experience the highest winds from Matthew (see Figure 3 above) with Daytona Beach at high risk. The wind threat is especially serious at Cape Canaveral, which juts out into the Atlantic about 10-15 miles. If Matthew does make landfall along the Florida coast, this would be the most likely spot for it. Billions of dollars of facilities and equipment are at risk at Kennedy Space Center and nearby bases, which have never before experienced a major hurricane. Some of KSC’s older facilities were designed only to withstand Category 2 or 3 winds, while facilities built after Hurricane Andrew (1992) are designed to withstand Category 4 or 5 storms. Storm surge could reach 7 to 11 feet over the barrier islands of Volusia and Brevard counties. Matthew is likely to traverse the Space Coast during the overnight hours Thursday. (Ironically, the GOES-R satellite—originally scheduled to be airborne by now, where it would be gathering data on Matthew—is instead at the space center, awaiting its rescheduled launch in November.)

FL First Coast (including St. Augustine and Jacksonville)
The wind threat here will hinge not only on Matthew’s track but also on whether some or all of the storm’s eyewall makes it inland further south and is weakened by land interaction. Even if Matthew is curving slightly offshore by this point, winds of at least Category 1 strength can be expected along the immediate coast, with somewhat lesser winds toward the west side of the Jacksonville metro area. Severe flooding is possible at the coast and along the St. Johns River east of Jacksonville. The area should experience its greatest impacts from Matthew early Friday morning, although surge could intensify a number of hours before Matthew’s arrival. Storm surge flooding could reach 6 to 9 feet at St. Augustine and Jacksonville Beach, as well as Fernandina Beach and Amelia City to the north.

Georgia and South Carolina Coast
Matthew’s track should be gradually edging away from the coast by the time it nears Georgia late Friday, but the hurricane may still be at Category 1 strength less than 100 miles from Hilton Head, South Carolina, by Saturday morning. The concave angle of the GA/SC coastline combined with Matthew’s gradual approach could lead to very dangerous high-water impacts as Matthew approaches. Storm surge flooding is expected to be 7 to 9 feet over southeast Georgia, with isolated amounts up to 11 feet, and 3 to 5 feet in southeast Georgia, with isolated amounts up to 8 feet. Heavy rains to the north of Matthew will exacerbate the risk of flooding, especially near the coast.
Figure 5. Hurricane Nicole (far right) was more than 700 miles east of Hurricane Matthew (far left) at 1:37 pm EDT Thursday, October 6, 2016. Image credit: NASA/MSFC Earth Science Office.

Nicole now a hurricane
While all eyes are on Matthew (and rightly so), the sixth hurricane of this busy Atlantic season has developed far to the east. Compact Hurricane Nicole was centered about 345 miles south of Bermuda as of 2:00 pm EDT, with top sustained winds of 80 mph. Steering currents are quite weak around Nicole, and it is likely to meander across the open Northwest Atlantic for the next several days, perhaps strengthening a bit more before it weakens early next week. Nicole and Matthew are now separated by about 1350 kilometers, which is the maximum distance where we need to take into account the Fujiwhara effect (the tendency for two tropical cyclones near each other to rotate around a common midpoint). Since Matthew is moving further away from Nicole with time, and is so much stronger than Nicole, we need not worry about the Fujiwhara effect at this point as a major steering influence on Matthew.

We’ll be back with an update on Thursday night.

Bob Henson and Jeff Masters

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