|Above: Infrared GOES-16 image of Hurricane Maria as of 10:51 am EDT Tuesday, September 19, 2017. Image credit: RAMMB / CIRA@CSU.|
After a direct hit on the small Lesser Antilles island of Dominica on Monday night, followed by a brief weakening, Hurricane Maria reintensified to Category 5 strength with winds of 160 mph on Tuesday morning. Maria will likely be a catastrophic Category 5 or high-end Category 4 storm when it hits the U.S. Virgin Islands and Puerto Rico on Wednesday morning. Preliminary reports out of Dominica indicate that Maria likely did catastrophic damage there. The northern eyewall of Maria also grazed the southwest corner of Guadaloupe Island on Monday night, and heavy damage was reported there. The core of the hurricane missed Montserrat, Saba, and St. Kitts and Nevis, but these islands have been experiencing sustained tropical storm-force winds and heavy rain squalls.
Maria’s encounter with Dominica bruised the storm slightly, with the top winds falling to 155 mph and the central pressure rising from 924 mb to 934 mb between 11 pm Monday and 5 am Tuesday. This took the storm briefly down to a Category 4 rating. However, an Air Force hurricane hunter aircraft on Tuesday morning found a falling pressure and rising winds. Maria’s central pressure was down to 927 mb, and the winds were back up to 160 mph as of 11 am EDT Tuesday. Maria passed just east of Buoy 42060 late Tuesday morning; the buoy reported a pressure of 956 mb and sustained winds of 74 mph, gusting to 94 mph, at 11:10 am EDT Tuesday.
Unfortunately for the islands in its path, Maria’s appearance on satellite imagery is truly spectacular, and the outer spiral bands of the hurricane are already lashing the Virgin Islands and Puerto Rico, as seen on long- range radar and CatherineHope’s Webcam on St. Croix.
|Figure 1. GOES-16 visible image of Maria at 10:15 am Tuesday, September 19, 2017. At the time, Maria was a Category 5 storm with 160 mph winds, a central pressure of 927 mb, and a small "pinhole" eye with a diameter of 10 nautical miles. Image credit: NOAA/RAMMB. GOES-16 data is considered preliminary and non-operational.|
The dreaded "pinhole" eye
Maria developed a tiny “pinhole” eye during its rapid intensification burst on Monday, with a diameter of 8 nautical miles (nm). The hurricane has maintained a small eye so far on Tuesday, with the diameter fluctuating between 7 nm and 10 nm (10 nm = 11.5 miles). Hurricanes that develop pinhole eyes often intensify into some of the strongest storms we observe, since they concentrate their wind energy around a narrow ring surrounding the tiny eye. These small eyes tend to be unstable, resulting in an eyewall replacement cycle (EWRC) shortly after the pinhole eye is observed. Some other examples of tropical cyclones with pinhole eyes with a diameter less than 10 nm (thanks go to Michael Cavaliere, Howard Diamond, and Boris Konon):
Hurricane Wilma - 2005 (185 MPH / 882 MB) - Western Caribbean - 1.5 nm
Hurricane Iris – 2001 (140 MPH / 950 MB) - Western Caribbean – 3 nm
Hurricane Beta - 2005 (115 MPH / 962 MB) - Nicaragua - 5 nm
Hurricane Dennis - 2005 (120 MPH / 930 MB) - Florida - 4 nm
Hurricane Charley - 2004 (150 MPH / 941 MB) - Florida - 2.5 nm
Hurricane Opal - 1995 (150 MPH / 919 MB) - Florida - 5 nm
Hurricane Andrew - 1992 (165 MPH / 921 MB) - Florida - 6 nm
Typhoon Forrest - 1983 (165 MPH / 883 MB) - Philippines - 4 nm
Cyclone Tracy - 1974 (125 MPH / 950 MB) - Australia - 7 nm
Short-term forecast for Maria
There is increasing confidence that Maria will reach St. Croix and Puerto Rico on Wednesday with catastrophic results. Now that Maria has regained Cat 5 intensity, there is nothing between the storm and these islands that would lead to a major drop in strength. In fact, conditions are just about as favorable as they can be for sustaining a Category 5 hurricane, and it's not out of the question that Maria could become even stronger. Wind shear is predicted to stay very low (6 knots or less) for at least the next 48 hours, and Maria will be passing over very warm waters of 29-30°C (84-86°F). These warm waters are deep enough to provide substantial oceanic heat content (greater than 50 kilojoules per square centimeter), which will limit the potential of Maria’s fierce winds to churn up cooler water. If Maria embarks on an eyewall replacement cycle (EWRC) on Tuesday, the storm could drop to Category 4 strength by the time it approaches Puerto Rico. This process would spread Maria’s hurricane-force winds over a broader area, though.
Models are in very close agreement on Maria’s west-northwest path. Among our top track models, the European and UKMET model runs from 00Z Tuesday, and the GFS and HMON runs from 06Z Tuesday, all bring Maria’s center very close to St. Croix and across Puerto Rico from southeast to northwest on Wednesday. Conditions would be worst on the right-hand side of Maria’s track, but the entire island is at risk of severe hurricane conditions—likely the worst and most extensive in almost a century. The outlier among our better track models has been HWRF, which has consistently called for Maria to angle northwest toward the British Virgin Islands and just miss Puerto Rico. Several runs ago, the GFS and HMON were predicting a similar track, but they now agree with the Euro and UKMET on a direct hit to Puerto Rico, so we are best off discounting the HWRF (especially since the 12Z Tuesday run of the HWRF trended further west, in closer agreement with the other models).
A track crossing Puerto Rico from southeast to northwest will bring torrential rainfall and the risk of landslides to both northern- and southern-facing mountainsides. Localized rainfal of 25" or more is possible in Puerto Rico, with amounts of 20" possible in the U.S. and British Virgin Islands. Rainbands sweeping into Maria from the south could also dump as much as 12" of rain on southern parts of the Dominican Republic, again posing a threat of landslides.
Along with the direct impacts likely in St. Croix, one of the three U.S. Virgin Islands, Maria could move far enough north for severe hurricane conditions to affect the other two U.S. Virgin Islands—St. Thomas and St. John—and perhaps the British Virgin Islands as well. All of these except for St. Croix took a fierce hit from Hurricane Irma just weeks ago, so even a lesser blow from Maria could have outsized consequences to residents and structures left vulnerable in the wake of Irma. Storm surge could bring worst-case inundation levels of 6' - 9' over parts of Puerto Rico and the U.S. Virgin Islands.
|Figure 2. Hurricane Hugo caused severe damage to Puerto Rico’s El Yunque rain forest on September 18, 1989. Image credit: NOAA Photo Library.|
Puerto Rico hurricane history
Only one Category 5 hurricane has hit Puerto Rico in recorded history: the 1928 San Felipe Segundo hurricane, which killed 328 people on the island and caused catastrophic damage. This is one of only four Category 5 hurricanes ever to hit the U.S. (the others: Hurricane Andrew of 1992 in South Florida, Hurricane Camille of 1969 in Mississippi, and the Labor Day Hurricane of 1935 in the Florida Keys). Puerto Rico’s main island has also been hit by two Category 4 hurricanes, the 1932 San Ciprian Hurricane, and the 1899 San Ciriaco Hurricane.
Even though Hurricane Irma did not make landfall in Puerto Rico, it produced up to $1 billion in damage as it passed just northeast of Puerto Rico's main island. The last hurricane to come ashore in Puerto Rico was Category 1 Hurricane Irene of 2011, which dumped up to 22” of rain, caused power outages to over 1 million customers, and did over $500 million in damage. The most recent Category 3 hurricanes to make landfall were Hurricane Georges (1998) and Hurricane Hugo (1989). Georges brought a 10’ storm surge to Fajardo in northeast Puerto Rico, and up to 30” of rain to interior portions of the island. No deaths were blamed on the hurricane, but it did $3.6 billion in damage. Hurricane Hugo killed 12 people in Puerto Rico, and did over $1 billion in damage.
|Figure 3. Category 4 Hurricane Hugo bearing down on St. Croix on September 17, 1989. Image credit: NOAA HURSAT project.|
St. Croix hurricane history
Only one Category 4 or stronger hurricane has made a direct hit on St. Croix in the U.S. Virgin Islands in recorded history: Hurricane Hugo (140 mph winds), which killed two people on the island and injured 80. About 90% of the buildings were damaged or destroyed, and the island's entire infrastructure was nearly wiped out. Six weeks after the hurricane, only 25% of the public roads had been cleared, and only 25% of the island had power. President Bush was forced to send over 1,000 troops to the island to maintain order.
Alexander Hamilton, first Secretary of the Treasury of the United States, aide-de-camp to General George Washington during the Revolutionary War, and recipient of a fatal bullet in a duel with Aaron Burr, was fifteen years old and living in the town of Christiansted, St. Croix, when the great hurricane of August 31, 1772, struck the island of St. Croix. From Hamilton's description, the eye of this storm passed directly over Christiansted. After the hurricane, he wrote a letter to his father in St. Kitts that was so well-written and moving, that after it was published in a local newspaper, a fund was taken up to bring him to New York. This launched him on his career to become a founding father of the U.S. The storm that changed Hamilton's life is referenced in the song "Hurricane" in the smash-hit Broadway musical "Hamilton". (Thanks go to wunderground commenter RobinsonCrusoe for this information.)
Long-term outlook for Maria
Maria is expected to head into the Northwest Atlantic after passing the Greater Antilles. If Maria moves over Puerto Rico, its circulation will experience major disruption, and the hurricane could also ingest dry air flowing off Hispaniola on Thursday. Wind shear will also be increasing to the 10 – 20 knot range by Friday. Considering all these factors, it would not be surprising to see Maria weaken to Category 3 or even high-end Category 2 strength by this weekend, as predicted by NHC. It will become a larger storm, though, with its wind field spread over a broader area.
By Saturday, models agree on placing Maria just northeast of the Bahamas, heading north-northwest. If this track holds, it would most likely keep Maria just east of the Turks and Caicos Islands and the southeast Bahamas, perhaps sparing those islands from Maria’s worst. Nevertheless, Maria is too strong and the track too close for residents of those islands to relax their vigilance. Even Maria’s left-hand side could produce severe hurricane conditions.
Beyond the Bahamas, there is strong agreement among our best track models that Maria will be following in the footsteps of Hurricane Jose, moving into a weakness carved out in the upper-level steering flow by Jose’s week-long presence. The GFS, UKMET, and European model runs from 00Z Tuesday all place Maria several hundred miles east of the Carolinas early next week, moving north, with the GFS the closest to the coast and the Euro the farthest. The 12Z Tuesday run of the GFS shifted east, which lends even more confidence to the idea of an offshore track. By the time Maria gets to higher latitudes, models suggest there will be enough west-to-east flow in the jet stream to push the hurricane out to sea. Only about 10 – 20% of the 70 GFS and Euro ensemble members from 00Z Tuesday bring Maria into the U.S. East Coast. The amount of model agreement on an offshore track is encouraging, but this is a distant-enough time frame that we cannot yet be fully confident in Maria’s long-term future.
|Figure 4. The 50 track forecasts for Maria from the 0Z Tuesday, September 19, 2017 European model ensemble forecast. The operational European model is the red line, adjusted by CFAN using a proprietary technique that accounts for storm movement since 0Z Sunday. The track of the average of the 50 members of the European model ensemble is the heavy black line. Image credit: CFAN.|
|Figure 5. The 20 track forecasts for Maria from the 0Z Tuesday, September 19, 2017 GFS model ensemble forecast. Image credit: CFAN.|
|Figure 6. Infrared satellite image of Jose at noon EDT Tuesday, September 19, 2017. Image credit: RAMMB / CIRA@CSU.|
Jose to linger off northeast U.S. coast for days to come
Hurricane Jose is about to enter the next phase of its long life: a gradual, multi-day loop south of New England that may help keep Maria from moving toward the U.S. East Coast. At 11 am EDT Tuesday, Jose was located about 230 miles east-northeast of Cape Hatteras, heading north at 7 mph. Officially, Jose remains a minimal hurricane, with top sustained winds estimated by NHC at 75 mph. The SFMR radiometer aboard Hurricane Hunter flights into Jose has not found any surface winds of hurricane strength for more than a day now. However, Jose’s wind field is so large that these flights are probably undersampling the storm, according to NHC. Jose’s field of convection (showers and thunderstorms) is fairly weak and mostly focused on the storm’s western side, leaving Jose quite asymmetric.
The outlook for Jose has changed little since Monday. Jose is expected to arc north and northeast, remaining at least 150 miles southeast of the Massachusetts coast. This could be near enough for Jose’s outer bands to bring as much as 5” of rain and tropical-storm-force winds to Cape Cod and nearby islands, though models have been trending downward on New England impacts. High surf and beach erosion will continue to plague the mid-Atlantic and northeast U.S. coast for several more days. Jose will weaken to tropical-storm strength as it gradually transitions into a large mid-latitude storm, but that process may take the entire week to unfold.
It now appears that a long-awaited loop in Jose’s path will take place well offshore, and strengthening upper-level winds will haul Jose out to sea by early next week. In the meantime, Jose’s lingering presence will leave a weakness in the upper-level ridge steering Maria, and this is expected to create a path for Maria to angle northward along a track similar to Jose’s.
Dr. Jeff Masters co-wrote this post.