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Matthew Raking Bahamas; Could Be First Major Hurricane for Florida’s Space Coast

By: Bob Henson 10:34 PM GMT on October 05, 2016

Hurricane Warnings are in place along much of Florida’s Atlantic coastline, where Category 3 Hurricane Matthew is expected to trace a grinding path on or very close to shore on Friday. As of the 5 pm EDT advisory from the National Hurricane Center (NHC), Matthew was located about 400 miles southeast of West Palm Beach, FL, moving northwest at 12 mph. After weakening during its passage over Cuba, Matthew is gradually regaining its strength over the near-record-warm waters of The Bahamas, where sea surface temperatures of 29-30°C (84-86°F) are more than 1°C above average. A Hurricane Hunter flight observed 106-knot (122-mph) surface winds on Wednesday morning, and with little change in the storm’s overall structure since then, NHC estimated Matthew’s top sustained winds at 120 mph in the 5 pm advisory.

Matthew is already a large storm, with hurricane-force winds extending 45 miles from its center and tropical-storm-force extending out to 175 miles. Matthew’s wind field may expand further in the next several days as the hurricane matures. A Hurricane Hunter flight late Wednesday afternoon was finding Category 2 winds. Satellite imagery late Wednesday afternoon showed intense “hot towers” of thunderstorm activity beginning to develop around Matthew’s eye. Outflow channels extended southward and northward near the top of the storm, although weaker than the channels that supported Matthew’s growth to Category 5 strength in the Caribbean. Overall, Matthew could dip slightly in strength tonight before the reorganization now in process provides a chance for restrengthening on Thursday. The 18Z Wednesday SHIPS model forecast gave a 9% chance that Matthew would intensify enough to become a Category 5 storm again by Thursday afternoon.

The take-home message: it still appears likely that Matthew will approach Florida early Friday as a major hurricane. A Hurricane Warning was in effect late Wednesday from Broward County, FL, to the Flagler/Volisua county line (including the Orlando area and Lake Okeechobee), with a Hurricane Watch extending further northward to the Savannah River, including all of the Georgia coast. A Tropical Storm Warning covers much of far South Florida, including the Miami area. See the NHC update for a full rundown on warnings and watches.

Figure 1. Visible satellite image of Hurricane Matthew from 5:15 pm EDT Wednesday, October 5, 2016. Image credit: NOAA/NESDIS.

Conditions are easing in Greater Antilles, worsening in Bahamas
Matthew’s outer rainbands were still strafing Haiti, Jamaica, and much of eastern Cuba late Wednesday, but the strongest winds had moved north, out of the area. Matthew’s thread-the-needle track included only brief spells over the westernmost tip of Haiti and extreme eastern Cuba. This land-avoiding track allowed the hurricane to move into The Bahamas with its structure largely intact, but it also greatly limited the extent of strong winds over the Greater Antilles. Satellite data showed that rainfall has been intense over many areas, although surface reports are limited. Thus far, at least 25 deaths have been attributed to Matthew, according to weather.com. We can only hope these numbers stay relatively low, although they will undoubtedly rise as more damage reports come in. See the embedded video at bottom for a sense of Matthew’s rampage over eastern Cuba.

Especially if Matthew strengthens, it could bring vicious winds well above hurricane force to several Bahamian islands, depending on its exact track. Torrential rains will also plague the islands. The biggest concern for the Bahamas is storm surge, which could reach 10 to 15 feet along and east of Matthew’s track. Wunderground member ExumaMET sent this update from the southeast Bahamas early Wednesday afternoon: “Reporting in from little Exuma at the very South East of the chain. I'm able to still get cell data but we're getting frequent hurricane force gusts and the recent more NNW move I've seen on satellite is troubling and I hope not a trend. I live on high ground but I do fear for a lot of those living on the south side in particular a large settlement called Moss Town.”

Central and northern Florida bracing for a historic hurricane hit
An unusual confluence of ingredients is in place that may bring hurricane conditions to the Atlantic coast of northern Florida and Georgia, a place where major hurricane landfalls (Category 3 or stronger) are surprisingly uncommon, especially this late in the season. When Florida does get hurricanes in October, they almost always move northeast from the Gulf of Mexico and strike the Gulf Coast, rather than moving west or northwest from the Atlantic.

Thoughout the year as well, major landfalls seldom occur here, as shown in Figure 3. This may partly be a matter of dumb luck, but it’s also because the shape of the Florida coast here—angling from southeast to northwest—reduces the odds of a direct hit. The only hurricane known to have made landfall in Florida north of Port St. Lucie while maintaining Category 3 strength is Dora, which arrived with 125-mph sustained winds near St. Augustine in September 1964. It’s actually more common for hurricanes to strike the northern half of Florida’s coast after having traveled across the state—as was the case with Donna (1960) and Charley (2004), both of which entered the Atlantic just north of Palm Coast. The most recent major hurricane along the Georgia coast was in 1898.

Figure 2. Tracks of all hurricanes since 1851 that are known to have passed within 175 nautical miles miles (the shaded circle) while at Category 3 or stronger intensity. Image credit: NOAA.

FIgure 3. The official NHC forecast for Matthew as of 5 pm EDT Wednesday, October 5, 2016.

An unusual threat for the coast from central Florida to Georgia
The latest tracking map from NHC, shown above, depicts a Category Four hurricane centered just north of the Kennedy Space Center (KSC, in Titusville, FL) at 2:00 pm EDT Friday. If Matthew does move along the coast or just inland, it could bring severe hurricane conditions to a heavily populated coastal region that’s had precious little experience with such a storm. Hurricanes Jeanne and Frances (2004) caused billions in damage as they moved from the Atlantic onto the central Florida coast, and Matthew may be stronger than either of them as it nears the coast. Even though winds near KSC were only in the neighborhood of minimal hurricane strength, Frances inflicted an estimated $100 million in damage to the area’s space and military operations.

In 1979, Hurricane David (1979) ground its way up the central and northern Florida and Georgia coastlines along a track similar to that expected with Matthew. David produced hundreds of millions in damage, even though it was only at Category 1 strength during its Florida/Georgia trek. Even if Matthew reaches Florida as a major hurricane, we can expect it to weaken during the course of Friday and Friday night as it works its way northward along or near the coast.

Figure 4. Hurricane Frances brought sustained winds of 70 mph, gusting to 94 mph, to the Kennedy Space Center, and ripped 820 panels off of the gargantuan 525-foot tall Vehicle Assembly Building (shown above). The Space Center suffered millions in damage, including heavy damage to the Thermal Protection System Facility and the Processing Control Center. Two weeks later, Category 3 Hurricane Jeanne made landfall very close to where Frances did, and took 30 more panels off the Vehicle Assembly Building. According to NASA documents, the building was designed to withstand winds of 114 miles per hour—what a weak Category 3 storm would deliver. Image credit: NASA.

An excruciating track for the Southeast U.S.
Our top track models differ on the exact location of Matthew over the next several days, but they agree that Matthew will be heading on a concave track from Florida to the Carolinas that will largely duplicate the concave outline of the Southeast U.S. This makes for an extremely challenging forecast, especially from a public-safety point of view. NHC has put it very nicely in their key-message summaries for Matthew:

“When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. For example, only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida. However, a small deviation to the right could keep the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch area in northern Florida and Georgia.”

Main threat for the Carolinas: water
Regardless of whether Matthew hugs the coast or not, it will deliver a significant storm-surge threat, especially toward the Georgia coast. NHC projects that coastal inundation (water level above ground) could reach the following levels at high tide:

Sebastian Inlet to Savannah River...5 to 8 ft
Deerfield Beach to Sebastian Inlet...3 to 5 ft
Virginia Key to Deerfield Beach...1 to 2 ft

Figure 5. Areas of flooding expected to result from typical hurricanes of various strengths over Chatham County, Georgia. Even a Category 1 strike (4-11 foot inundation) is capable of producing extensive flooding across the county, including all of Tybee Island, where officials are urging that residents evacuate. Image credit: Chatham County Emergency Management

The latest model guidance (12Z Wednesday) suggests that Matthew will be arcing away from the Southeast coast as it approaches the Carolinas. This is very good news from the standpoint of high wind, but it does not eliminate the risk of very heavy rain and at least some coastal flooding for the Carolinas. The NOAA/NWS Weather Prediction Center is projecting 6” to 10” of rain along and near the coast from central Florida to extreme southern North Carolina. If Matthew’s arc away from shore holds up, the risk of major flooding over saturated ground from eastern North Carolina northward will be greatly reduced.

Will Matthew do the loop-de-loop?
The 12Z Wednesday suite of computer models points toward a result that seemed preposterous just days ago: Matthew may well carry out a clockwise (right-hand) loop off the Southeast coast and head back toward Florida early next week. If so, it would likely be in a much-weakened state, heading over waters it churned up. The European model has pulled back from its enthusiasm for this idea, while the GFS is more bullish. Only 8% of the 50 Euro ensemble members from 12Z Wednesday, but about half of the 20 GFS ensemble members from 18Z Wednesday, carry out tracks that bring Matthew across Florida or Cuba next week and into the Gulf of Mexico or Caribbean. The loop-de-loop back to Florida thus remains possible, but we’ll have to give the models several more days to work out these possibilities.

Meteorologist Steve Gregory is making regular updates on Matthew.
Rapid-scan 7-minute time resolution loop of Matthew from NASA/MSFC

Bahama/Port Nassau:: http://www.portnassauwebcam.com/
Ft. Lauderdale: http://www.ftlauderdalewebcam.com/
Port Canaveral: http://www.portcanaveralwebcam.com/

Tropical Storm Nicole no threat
Tropical Storm Nicole, the fourteenth named storm of this busy 2016 Atlantic hurricane season, is not expected to be a threat to any land areas as it meanders in a circle over the central Atlantic over the next five days. Satellite imagery shows Nicole is a small storm with a modest amount of heavy thunderstorm activity. The latest SHIPS model forecast shows increasing wind shear for Nicole over the weekend, which should weaken the storm.

I'll be back with an update on Matthew between 11 PM and midnight tonight. Jeff Masters and I will be posting 2 to 3 updates a day while Matthew remains a significant threat.

Bob Henson and Jeff Masters

Figure 6. The 50 forecasts from the 12Z Wednesday European (ECMWF) model ensemble (left) and the 20 forecasts from the 18Z Wednesday GFS model ensemble (right). Ensemble model runs are produced by running the same model for the same timeslice a number of times, with the starting-point conditions for each run varied randomly in order to mimic the uncertainty in our observations of the atmosphere. This produces a better sense of the future uncertainty in a given forecast. Image credit: Image credit: Climate Forecast Applications Network (CFAN).


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