Tropical Storm Josephine forms in Atlantic as season sees possible uptick
Tropical Storm Josephine formed in the Atlantic on Thursday morning, becoming the earliest J-named storm on record and marking the 10th named storm in a season that’s already been brimming with activity.
The Atlantic hurricane season only looks to become more active in the coming weeks, with a possible barrage of tropical cyclones not out of the question as a highly favorable atmospheric setup for tropical cyclones looms.
Josephine earned its name two days after being dubbed a “tropical depression,” the precursor to a tropical storm. Its appearance on satellite improved on Thursday enough to give the National Hurricane Center confidence its maximum sustained winds of 45 mph exceeded the threshold needed to pick up a name.
Tropical Storm Josephine beats out Jose, which formed on Aug. 22, 2005, as the earliest-named J storm in the Atlantic basin on record. The hyperactive storm season to date also has featured record-early C, E, F, G, H and I storms — Cristobal, Edouard, Fay, Gonzalo, Hanna and Isaias, respectively.
The average date for a season’s 10th named storm is Oct. 19. The ongoing hurricane season already has been twice as active compared to average.
Tropical Storm Josephine, which was a little over 1,000 miles east of the Leeward Islands on Thursday morning, is a compact storm. Its zone of tropical storm-force winds only extends outward about 80 miles, primarily north of the storm’s center. That makes it more susceptible to sudden fluctuations in intensity as it navigates through pockets of more and less supportive conditions.
On satellite images Thursday morning, Josephine appeared less ragged after becoming more organized during the previous days. Its low-level center of circulation was no longer detached from shower and thunderstorm activity. Instead, it was nestled beneath more intense showers and thunderstorms.
Strips of high-altitude cirrus clouds indicated that Josephine had developed some healthy upper-level outflow. The more efficient air can be evacuated from the top of a storm to reduce its barometric pressure, the easier it is for a system to draw in more air near the surface, increasing its winds.
In addition, Josephine was working its way into an area of reduced wind shear, which should allow for some intensification. Wind shear is a change in wind speed and/ or direction with height. The presence of wind shear can stifle the intensification, or even wipe out, tropical storms and hurricanes by knocking their inner cores off balance and allowing dry air to penetrate their circulation.
The National Hurricane Center is forecasting some strengthening in the days ahead as the storm churns west-northwest at 15 miles per hour, and Josephine could peak as a 60 mph tropical storm late today into Saturday.
The system is expected to pass well north of the Lesser Antilles and Puerto Rico as it curves northward over the open Atlantic this weekend.
The storm could affect Puerto Rico indirectly, depending on its intensity and proximity to the island. Its tropical moisture could increase the chances of afternoon downpours this weekend, for example, but major impacts there are not expected.
Thereafter, Josephine looks to gradually weaken as conditions become less supportive for maintaining it. It could affect Bermuda’s weather into early next week.
Behind Josephine, there’s no immediate next system to watch — for now. That may change late next week as a series of weather and climate cycles conspire to bring about a dramatically increased risk of Atlantic tropical storms and hurricanes, and perhaps a slew of storms.
Among the systems is a convectively-coupled Kelvin wave. This may sound complicated, but the concept is simple — it’s a large overturning circulation, sort of like a wave, that meanders about the tropical atmosphere. On one side of this wave, air is more prone to rise, while on the other side, it sinks.
The Atlantic is beneath the sinking branch now, which squashes the prospects of tropical development. But that will reverse in about seven to 10 days’ time, when the “enhanced” branch of the Kelvin wave drifts overhead.
Around that same time, the Madden-Julian Oscillation, another large-scale cycle, will begin to bolster shower and thunderstorm activity across the Atlantic, enhancing the Kelvin wave’s effects.
The combination of the two features likely will result in more storminess. And with a Bermuda high pressure system a bit stronger and farther south and west than usual, there is an increased probability that any of the tropical storms and hurricanes that do develop could wind up tracking close to the U.S.
Storms that do form this season are likely to be made stronger and wetter thanks to anomalously warm sea surface temperatures, which are in part the result of human-induced climate change. That also boosts a storm’s propensity to rapidly intensify, which can complicate storm preparation and response decisions and present an additional challenge to forecasts.
The period of robust activity could extend from much of late August into the first half of September.
It’s the earliest J-named storm on record and marking the 10th named storm of the season. The average date for a season’s 10th named storm is Oct. 19. The ongoing hurricane season already has been twice as active compared to average.