Above: GOES-16 view of Tropical Storm Jose at 10:15 am EDT September 15, 2017. Image credit: NOAA/RAMMB. GOES-16 data is considered preliminary and non-operational.
Tropical Storm Jose was headed northwest at 9 mph towards North Carolina on Friday morning, but is expected to turn to the north over the weekend and pass several hundred miles east of the North Carolina coast over the weekend. Jose's tropical storm-force winds cover a large area of ocean, extending out 140 miles from the center. These winds are generating large swells that are bringing rough surf and the risk of rip currents to Bermuda, The Bahamas, the northern coasts of Hispaniola and Puerto Rico, and the Southeast U.S. coast. These conditions will spread northward along the U.S. Mid-Atlantic coast over the weekend. Jose may bring 1 – 2” of rain to North Carolina’s Outer Banks on Monday, and heavier rains of 2 – 4” to Eastern Massachusetts beginning on Tuesday. The U.S. coast from Maryland to Cape Cod, Massachusetts is at the edge of Jose’s 5-day cone of uncertainty. An Air Force hurricane hunter aircraft will investigate Jose on Friday afternoon.
Track forecast for Jose
A high-pressure system building in to the northeast of Jose will steer the storm to the northwest and then north over the weekend, putting Jose a few hundred miles east of North Carolina’s Outer Banks on Monday, then close to the coast of southeast Massachusetts on Wednesday. The large waves from the storm will be capable of causing high surf and considerable beach erosion along the shores of the mid-Atlantic and New England coasts during this period. Jose’s fate beyond Wednesday is uncertain, with some models predicting a rapid motion to the east-northeast, out to sea, and other models predicting that Jose will get trapped in an area of weak steering currents, wandering in the waters between North Carolina and Massachusetts for multiple days.
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Figure 1. The 20 track forecasts for Jose from the 0Z Friday, September 15, 2017 GFS model ensemble forecast. They call these types of images “spaghetti plots” for good reason! There is a lot of disagreement on where Jose will go. Image credit: CFAN. |
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| Figure 2. The 0Z Friday September 15, 2017, track forecast by the operational European model for Jose (red line, adjusted by CFAN using a proprietary technique that accounts for storm movement since 0Z Friday), along with the track of the average of the 50 members of the European model ensemble (heavy black line), and the track forecasts from all 50 members of the ensemble. Like the GFS ensemble, there is a lot of uncertainty on the long-range fate of Jose. Image credit: CFAN. |
Intensity forecast for Jose
Jose was under moderate wind shear of 15 – 20 knots Friday morning, and with sea surface temperatures (SSTs) near 29.5°C (85°F), Jose should be able to regain hurricane status by Friday night. High wind shear is expected to affect Jose Sunday through Tuesday, keeping it from intensifying beyond Category 1 status, and Jose is likely to be a Category 1 hurricane or strong tropical storm over the next five days. Satellite images on Friday morning showed that Jose had plenty of intense heavy thunderstorm activity that was growing more organized, with more spiral banding and a ragged eye beginning to appear. The waters beneath Jose will be cooler as the storm heads north, and SSTs are about 28°C (82°F) a few hundred miles off the coast of North Carolina, where Jose will be on Monday. Once Jose moves north of about 37°N (the latitude of Washington D.C.), the storm will be north of the warm waters of the Gulf Stream, making it difficult for Jose to retain its tropical characteristics. Water temperatures within about 400 miles of the coast, from New Jersey to Maine, are generally below 26°C (79°F).
Phase space diagrams from Florida State University indicate that the transition to an extratropical storm will begin to occur once Jose moves north of the Gulf Stream. This won’t necessarily weaken Jose’s winds, since the storm can still derive energy from non-tropical (baroclinic) processes. Most of the intensity models show Jose as a strong tropical storm with 60 – 70 mph winds throughout its closest approach to the New England coast, Wednesday and beyond.
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| Figure 3. Invest 96L at 10:45 am EDT Friday, September 15, 2017. Image credit: NOAA/SSD. |
Invest 96L a concern for the Eastern Caribbean
A strong tropical wave located at 11 am EDT Friday near 10°N, 42°W, about 1150 miles east of the Lesser Antilles Islands, was headed west to west-northwest at about 15 mph. This system was designated 96L by the National Hurricane Center on Thursday, and has the potential to be a tropical storm that will affect the islands of the eastern Caribbean beginning on Monday. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 96L 2-day and 5-day odds of development of 50% and 90%, respectively.
96L had very favorable conditions for development on Friday morning. Wind shear was a light to moderate 5 – 15 knots, SSTs were a very warm 29 – 29.5°C (84 - 85°F), and relative humidity at mid-levels of the atmosphere (as analyzed by the 12Z Thursday run of the SHIPS model) was high--about 70%. Satellite loops showed that 96L had a good deal of spin, and heavy thunderstorm activity, though limited, was steadily increasing and growing more organized.
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| Figure 4. The 20 track forecasts for 96L from the 0Z Friday, September 15, 2017 GFS model ensemble forecast. Image credit: CFAN. |
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| Figure 5. The 50 track forecasts for 96L from the 0Z Friday, September 15, 2017 European model ensemble forecast. Image credit: CFAN. |
Track forecast for 96L
Our three top models for predicting tropical cyclone genesis—the European, GFS, and UKMET—have been predicting development of 96L over multiple runs, with Sunday being the preferred day of development into a tropical depression. 96L will begin affecting the Lesser Antilles Islands on Monday. After that, the course of the system is less certain, as the models have differences in their predictions for the forward speed of 96L. The European and GFS models predict a threat to Puerto Rico by Tuesday and the Dominican Republic by Wednesday, while the UKMET model predicts that 96L will move very slowly through the northern Lesser Antilles on Monday, Tuesday, and Wednesday. This model has not been performing as well as the GFS and European model with this system, and a more rapid motion of 96L to the Dominican Republic by Wednesday is a more likely solution.
Beyond Wednesday, the path of 96L will depend in part upon what Jose is up to. If Jose is still wandering off the U.S. mid-Atlantic coast, this will create a weakness in the ridge of high pressure steering 96L to the west-northwest, and 96L will turn more toward the northwest. If Jose is out of the picture, the ridge could keep 96L rolling west-northwestward. In either case, it is possible that 96L will approach the U.S. East Coast more than a week from now. A strong autumn-like upper-level trough will be moving across the western and central U.S. late next week. This will tend to pump up a ridge toward the northeast U.S. and northwest Atlantic, which could end up blocking 96L from moving out to sea (and could even affect Jose).
Intensity forecast for 96L
The 12Z Friday run of the SHIPS model predicted that 96L would have very favorable conditions for development over the next five days, with wind shear low to moderate, very warm SSTs near 29 – 29.5°C (84 - 85°F), and high relative humidity at mid-levels of the atmosphere. These conditions should allow for steady strengthening of 96L once it organizes into a tropical depression. The next two names on the list of Atlantic storms are Lee and Maria.
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| Figure 6. Infrared image of TD 14 at 7:45 am EDT Friday, September 15, 2017. Image credit: NOAA/NESDIS. |
TD 14 likely to develop into Tropical Storm Lee, but not expected to be a threat
All but two of the 13 Atlantic depressions or potential tropical cyclones in this active year have gone on to become a named storm, and TD 14 is likely to keep that streak going. As of 11 am EDT, TD 14 was located in the eastern tropical Atlantic at 11.4°N, 28.3°W, or about 400 miles southwest of the Cabo Verde Islands. TD 14 is already close to tropical storm strength, with top winds of 35 mph. The depression had a well-organized shield of showers and thunderstorms (convection) on Thursday, but it failed to take full advantage of the typical nighttime peak in convection on Thursday night and was looking a bit less organized Friday morning.
TD 14 is expected to continue rolling westward at about 10 mph, with a gradual turn toward the west-northwest early next week. Our top track models agree that an upper-level trough should pull TD 14 northwestward long before it has a chance to reach the Lesser Antilles. If TD 14 remains very weak, it could be steered by the trade winds in a more westerly direction. Either way, the potential for impacts will be minimized.
Conditions are modestly favorable for TD 14 to develop into a tropical storm, with warm SSTs of 28-29°C (82-84°F) and a fairly moist atmosphere (mid-level relative humidity of around 60%). Wind shear is the main inhibitor: it will remain in the moderate range (10 – 15 knots) through Sunday, then increase markedly to 20 – 30 knots as TD 14 encounters the upper-level trough. The most likely outcome is that TD 14 will become a tropical storm—perhaps as soon as Friday night, as predicted by NHC—but fail to intensify much further. Only about a third of the 50 European ensemble members from 0Z Friday made TD 14 a tropical storm, and none brought it to hurricane strength. The GFS ensemble is more bullish on tropical-storm strength (18 of 20 ensemble members), but as with the Euro ensemble, the GFS members are unanimous that TD 14 will not become a hurricane.
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| Figure 7. People walk under a downpour on a flooded street in Acapulco, Guerrero state, Mexico, on Thursday, Sept. 14, 2017. Hurricane Max hit Mexico's southern Pacific coast as a Category 1 storm Thursday and was expected to move inland into Guerrero state, a region that includes the resort city of Acapulco. Image credit: AP Photo/Bernandino Hernandez. |
East Pacific: Max strikes Mexico
The short but eventful life of former Hurricane Max is over. Max was reclassified as a remnant low at 6 am EDT Friday, after less than 48 hours as a tropical cyclone and less than a day as a hurricane. Max came ashore on the coast of Mexico’s Guerrero state about 55 miles east-southeast of Acapulco around 6 pm EDT Thursday as a small Category 1 storm with top winds of 80 mph. Heavy rains extended across the landfall area, with street flooding reported in Acapulco, but peak wind gusts at the international airport on Thursday were only 47 mph.
Tropical Storm Norma heading towards Baja Peninsula
Tropical Storm Norma is on its way to becoming Mexico’s next landfall threat. Located about 300 miles south of Cabo San Lucas at 11 am EDT Friday, Norma was packing top winds of 65 mph and was drifting north-northwest at 2 mph. Norma has been intensifying at a steady clip, with an expanding field of convection organizing into spiral bands. Wind shear will remain quite low (less than 10 knots) through the weekend, and Norma will be traversing SSTs of 28-29°C (82-84°F), so rapid intensification is a real possibility. The 12Z Friday run of the SHIPS model gave Norma a 40% chance of gaining at least 30 knots of intensity in 24 hours, and a 37% chance of gaining 45 knots in the next 36 hours.
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| Figure 8. Infrared GOES-16 image of Tropical Storm Norma at 11:32 am EDT Friday, September 15, 2017. Image credit: NASA/MSFC Earth Science Branch. |
Norma will remain a slow mover through Saturday, but it should begin accelerating northward toward the Baja Peninsula on Sunday. A hurricane or tropical storm watch may be required for the southern peninsula as soon as Friday night. Our top track models disagree on whether Norma will move briskly across the southern peninsula into the Gulf of California (GFS), or linger just offshore in the Pacific for a day or more (UKMET and Euro). SSTs are considerably cooler just west of the Baja Peninsula, so if Norma hangs out there for long, it will likely weaken. Moisture from Norma could make its way into Texas by late next week ahead of a strong upper-level trough.
TD 15E languishing in the Eastern Pacific
Further out in the East Pacific, TD 15E is in its fourth day as a small tropical depression, and apparently in no hurry to progress. Wind shear will drop to the 5 – 10 knot range over the next couple of days, and SSTs are adequate for development (27-28°C or 81-82°F), so it’s possible TD 15E will become a tropical storm this weekend. It will be ambling west or northwest in the remote tropical Pacific for some days to come, posing no threat to land.
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| Figure 9. Enhanced infrared image of TD 15E at 11 am EDT Friday, September 15, 2017. Image credit: NOAA/NESDIS. |
Bob Henson co-wrote this post.
