|Above: GOES-16 view of Hurricane Jose at 10:15 am EDT September 13, 2017. Image credit: NOAA/RAMMB. GOES-16 data is considered preliminary and non-operational.|
Hurricane Jose is continuing its leisurely loop over the waters a few hundred miles north of Puerto Rico, and is not expected to threaten any land areas this week. The latest computer models now say that Jose may be with us a very long time--at least another week. Jose may be a landfall threat next week for the U.S. East Coast or Canada, but that is too far in the future to make a reliable forecast. Bermuda is near the edge of Jose’s 5-day cone of uncertainty, and residents of that island should monitor the storm.
Intensity forecast for Jose
Jose is under high wind shear of 20 - 30 knots, and high shear is expected to affect Jose all week, keeping it a Category 1 hurricane or tropical storm. Satellite images on Wednesday morning showed that Jose still had plenty of intense heavy thunderstorm activity, but the storm was misshapen and asymmetrical due to the high wind shear. Passage over its own cold wake in the ocean may be able to weaken Jose to a tropical storm by Friday. After crossing its cold wake, Jose will be over very warm waters with sea surface temperatures (SSTs) near 29.5°C (85°F). These warm waters extend all the way to the coast of North Carolina.
|Figure 1. The 20 track forecasts for Jose from the 0Z Wednesday, September 13, 2017 GFS model ensemble forecast. The majority of the solutions resulted in no landfall, though 6 of 20 did predict an eventual U.S. landfall. Image credit: CFAN.|
|Figure 2. The 0Z Wednesday September 13, 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 Wednesday), 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. The majority of the forecasts keep Jose offshore, with the operational version of the model predicting that Jose will perform another loop. Image credit: CFAN.|
Track forecast for Jose
There are two big stories today in the track forecast for Jose. Number one is the shift by the UKMET model forecast towards what the rest of the models were predicting—a motion towards the north by Jose on Friday and Saturday, which would keep Jose from making landfall in the U.S. this week. The normally reliable UKMET model had been predicting a Florida landfall late this week, and it is good to see the model going away from that outcome. The other big story is the new consensus among our long-range models that Jose will potentially be around for a long time—a week or longer.
On Wednesday morning, Jose was headed southeast at 7 mph, and was in the midst of a slow clockwise loop that it will complete by Thursday evening. (Such loops are uncommon, but not unheard of--in 2004, Hurricane Ivan did a much larger clockwise loop that resulted in two U.S. landfalls.) The slow, looping path Jose is taking in an area of weak steering currents is the sort of behavior that our computer models don’t predict with a high degree of accuracy, and the 5-day error in the latest track forecast is likely to be higher than average.
A high-pressure system will build in to the northeast of Jose late this week, and will begin steering the hurricane to the northwest and then north, between North Carolina and Bermuda, over the weekend. After that, the future track of the storm gets very murky. Jose will be in an area of weak steering currents next week in the waters several hundred miles southeast of New England, and may wander erratically off the coast all week. 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. Water temperatures within about 400 miles of the coast, from New Jersey to Maine, are generally below 26°C (79°F), which will make it difficult for Jose to intensify, fortunately. Bottom line: It’s too soon to know what Jose will do, and the storm is likely to be around for a week or longer.
|Figure 3. Infrared satellite image of TD 15E and TD 16E in the eastern Pacific as of 1500Z (11 am EDT) Wednesday, September 13, 2017. Image credit: NASA/MSFC Earth Science Branch.|
The first new tropical cyclones in two weeks in Eastern Pacific
While Harvey, Irma, and Jose raged across the Atlantic over the last three weeks, it’s been relatively quiet over the Eastern Pacific. This has changed with the formation of Tropical Depression 15E on Tuesday night and Tropical Depression 16E on Wednesday morning. TD 15E is the first tropical cyclone to form in the eastern Pacific since TD 14 formed on August 30 and became Tropical Storm Lidia the next day. Our last East Pacific hurricane was Kenneth, which peaked as a Category 4 on August 21.
Of our two new depressions, the immediate concern is TD 16E, located about 130 miles west-southwest of Acapulco as of 11 am EDT Wednesday. TD 16E is already moving north-northeast at 5 mph with a rich swath of moisture and widespread but relatively weak thunderstorm activity (convection). Conditions are favorable for development, but TD 16E hasn’t much time: it will be arcing into the Mexican coastline not far from Acapulco on Thursday, most likely still at depression strength. Rainfall of 5 – 10” is expected as TD 16E pushes inland, with higher localized totals possible.
Meanwhile, TD 15E was moving west through the open tropical Pacific about 900 miles southwest of Cabo San Lucas, Mexico, as of 11 am EDT Wednesday. The depression is poorly organized, and moderate wind shear of about 15 knots is hindering its growth, but its convection increased notably on Tuesday night. The 12Z Wednesday run of the SHIPS model indicates that shear across TD 15E will drop below 10 knots on Thursday and will remain light into the weekend. Since TD 15E will be over warm enough water to support development (27-28°F or 81-82°C), it has a shot at becoming a tropical storm as it continues west. Out top models have been producing only modest development of TD 15, but the 06Z run of the HWRF model intensifies the depression into a hurricane by this weekend. If so, TD 15E will need to produce a core soon enough to fend off the effects of increasingly dry air around it. In any event, TD 15E poses no threat to land.
In between 15E and 16E, we have yet another disturbance, dubbed Invest 95E, embedded in the same swath of moist air that favors development. Wind shear should remain light to moderate (around 10 knots) over the next couple of days as 95E travels over very warm waters (SSTs of 29-30°C or 84-86°F). The wind shear will be increasing by this weekend, but it is possible 95E will become a tropical storm before that point. In its tropical weather outlook issued at 8 am EDT Wednesday, NHC gave 95E a 60% chance of developing into at least a depression by Friday, and an 80% chance by Monday.
Why does the East Pacific often go quiet while the Atlantic lights up, and vice versa?
What goes up must come down, and it’s often the case that when conditions favor rising air and hurricane formation in the Atlantic, we have sinking air and reduced hurricane activity in the East Pacific. This is especially common during La Niña events, but it can also occur when the El Niño/Southern Oscillation (ENSO) is in its neutral mode. On the other hand, during El Niño, subsidence and increased wind shear become more common across the Atlantic, typically reducing hurricane activity there. Forecasters raised their predictions of an active Atlantic hurricane season this spring and summer when it became apparent that no El Niño would develop. Dr. Phil Klotzbach explained the process in an August post for the NOAA ENSO Blog.
|Figure 4. Typical effects of El Niño abd La Niña on hurricanes across the Eastern Pacific and Atlantic. Image credit: NOAA Climate.gov, based on originals by Gerry Bell.|
While ENSO is officially in a neutral mode right now (NOAA’s Michelle L’Heureux called it “extreme neutral” in August), there has since been substantial cooling of the eastern tropical Pacific. This is in conjunction with the upwelling part of a Kelvin wave (a weak but large disturbance that moves slowly east across the uppermost waters of the tropical Pacific). The latest weekly value of the Niño3.4 index is -0.6°C, which suggests enough cooling to qualify as La Niña conditions if it were to persist for a few months. Most global models in August were predicting a neutral winter for 2017-18, but the most recent runs of NOAA’s CFSv2 model strongly suggest that we are already in the onset phase of a La Niña event. As of mid-September, climate prediction models from the Australian Bureau of Meteorology (BOM) and MeteoFrance agree with CFSv2 that La Niña conditions will expand into early 2017-18. (This is based on NOAA’s definition of La Niña, which is less stringent than BOM’s.) Four other global models were still calling for a neutral 2017-18.
|Figure 5. ENSO outlook from NOAA’s Climate Forecast System, version 2 (CFSv2) as of Sept. 10, 2017. The graph at left shows sea-surface temperatures across the Niño3.4 region of the eastern tropical Pacific, as predicted by the CFSv2 model ensemble (thin lines) and the model mean (black dashed line). Readings below -0.5°C are associated with La Niña, so the CFSv2 favors La Niña development for 2017-18, as shown in the sea-surface temperatures maps at right. Image credit: NOAA/NWS/CPC.|
Bob Henson co-wrote this post.