Tropical Storm Imelda (2019)

Storm Active: September 17-19

Around September 13, an upper level low was located over the eastern Gulf of Mexico. This feature produced an area of showers and storms west of the Florida peninsula and also influenced the path of Tropical Storm Humberto to its east. Over the next few days, it moved westward, out of range of Humberto and into more favorable conditions for tropical cyclone genesis. By September 16, the disturbance was offshore from the Texas coastline, where it began to bring beneficial rainfall to southeastern Texas. Pressures began to fall in the area and a surface low formed early on September 17. Despite its proximity to land, the system was classified Tropical Depression Eleven early that afternoon. At the time of formation, its center was nearly over the coastline. Land observations indicated sustained winds near 40 mph, so the storm was named Tropical Storm Imelda at landfall around 1:00pm local time. Despite the fact that Tropical Depression Ten (which was to be named Jerry) formed slightly earlier the same day east of the Leeward Islands, Tropical Depression Eleven became a tropical storm sooner and therefore received the "I" name.

The center pushed slowly northward inland that evening and Imelda was downgraded to a tropical depression. Despite this, the circulation remained quite vigorous and it generated very heavy rain over portions of eastern Texas for the next several days. Finally, on September 19, it degenerated into an open wave, and by the 20th rains had mostly come to a close. However, this was not before Imelda dumped rain totals over 40 inches in a few locations over southeast Texas, with a large swath reporting 20 inches or more. Devastating flooding followed these rains, analogous to (though not as widespread or intense) the flooding following Hurricane Harvey in 2017.

The above image shows Tropical Storm Imelda shortly after landfall.

Imelda peaked as a minimal tropical storm, but its persistent circulation moved great swaths of Gulf moisture over southeast Texas and southwest Louisiana, inundating the region.

Hurricane Jerry (2019)

Storm Active: September 17-25

On September 13, a tropical wave located south of the Cape Verde Islands began to produce shower and thunderstorm activity. It moved generally west-northwestward over the following days and merged with another disturbance located to its west-southwest. The resulting system produced a vigorous but elongated area of convection and was slow to organize further. A small low pressure center appeared along the wave axis on September 15. Gradual improvement continued until the system was classified Tropical Depression Ten during the morning of September 17. During the evening, very cold cloud tops exploded throughout the circulation and winds increased. Tropical Depression Ten became Tropical Storm Jerry (though Tropical Depression Ten formed before Tropical Storm Imelda, the latter system strengthened to a tropical storm and stole the "I" name first).

Jerry faced little wind shear and had the advantage of warming ocean waters for strengthening. The only inhibiting factor was a fairly dry atmosphere, but in a low shear environment, cyclones are often able to "wall off" dry air from disrupting their circulations. The cyclone had impressive outflow and nascent banding features by the morning of September 18, with one notable feature arcing northeast from the circulation center. Hence, steady intensification occurred that day. A significant burst of convection occurred near the center that afternoon. This allowed a inner core to develop and winds increased some more overnight, bringing Jerry to hurricane strength on September 19 as it continued its journey west-northwestward. The cyclone peaked that evening as a category 2 hurricane with maximum sustained winds of 105 mph winds and a minimum pressure of 976 mb.

The next day, wind shear out of the northwest increased substantially and destabilized Jerry's core. Thunderstorm activity was pushed to the southeastern side of the circulation and the system quickly weakened. Nevertheless, bands of locally heavy rain swept across the Northern Leeward Islands through the afternoon and early evening as Jerry passed to the north. The cyclone remained on the smaller side so damage was minimal. The circulation fought back some against shear that evening with new deep convection blossoming about the core. However, maximum winds were still decreasing and the system weakened to a tropical storm by September 21. Following a weakness in the subtropical ridge in part created by Hurricane Humberto, Jerry turned toward the northwest that day and north-northwest on the 22nd. During that time, convection fluctuated but shear out of the west or northwest was a constant for the system. As a result, it remained a strong tropical storm.

On September 23, Jerry turned due north as its center became exposed to the west side of its thunderstorm activity. The atmosphere only became more hostile over the next day as drier air was entrained into the circulation from the southwest. Soon, the system's center was little more than a naked swirl of clouds, and weakening commenced by the 24th. The system began to move northeast and approach Bermuda. Fortunately for the island, which had just been hit by Hurricane Humberto last week, there was almost no rain associated with Jerry, and at worst some tropical storm force wind gusts. In fact, lacking convection for over 12 hours, the cyclone was classified post-tropical early on September 25. The center passed near Bermuda late that day, causing minimal impacts.

This image shows Hurricane Jerry approaching the northern Leeward Islands. Even near peak intensity, the effects of shear are evident in the relatively dry western semicircle.

Jerry brought some heavy rain to the northeasternmost Caribbean islands, but did not have major land impacts.

Hurricane Humberto (2019)

Storm Active: September 13-19

Starting the first week of September, a trough of low pressure tracked across the central Atlantic. It took a route a little north of the typical train of tropical waves and passed north of the Caribbean islands. The disturbance was moving over warm water, but wind shear was high in the area and little organization occurred. Matters improved slightly by the time the system reached the southeastern Bahamas on September 12 and it developed a circulation center. An upper-level low over the eastern Gulf of Mexico was still shearing the system, but it found a pocket of favorable conditions and was classified Tropical Depression Nine on September 13 while located over the northwestern Bahamas. Fortunately for those islands just devastated by Hurricane Dorian, most of the rainfall occurred north and east of the center.

The steering flow was rather complex and difficult to predict due to the influence and evolution of the aforementioned upper-level low. However, it soon became clear that a weakness was developing in the subtropical ridge to the north of the depression, allowing it to turn toward the north on September 14. Meanwhile, the system strengthened into Tropical Storm Humberto and became more symmetric as shear diminished. By the 15th, a central dense overcast had covered the center of circulation on satellite imagery and it gained strength more quickly. That evening, the storm was upgraded to a category 1 hurricane. A strong autumn-like trough over the U.S. east coast turned Humberto sharply to the northeast out to sea that night. A developing eye had difficulty closing off on satellite imagery the next day due to apparent dry air intrusions as Humberto consolidated its inner core. Its central pressure dropped steadily, but aircraft reconnaissance measurements indicated that winds lagged behind somewhat. This was in part due to the significant expansion of the cyclone's windfield on the 16th. Nevertheless, anomalously warm subtropical Atlantic waters supported Humberto's ascent to category 2 status by the morning of September 17.

That day, a large eye finally broke through and hurricane hunters found that the system had become a major hurricane. It accelerated some to the east-northeast overnight and Bermuda began to experience wind and rain from the system's outer edge early on September 18. Conditions worsened quickly on the island and it was experiencing hurricane force winds by late that afternoon. Humberto was already taking on a more extratropical appearance, losing its eye and becoming asymmetric. Nevertheless, it maintained its strength as it made its closest approach to Bermuda late on the 18th. Sustained winds of 100 mph and higher gusts were measured on the island despite the center of Humberto passing a few dozen miles to the north. Just after moving away from the island, the storm reached peak intensity of 125 mph winds, measured with a pressure of 952 mb (up from a previous minimum of 951 mb). It turned northeast, accelerated further, and lost most of its central convection to strong wind shear on the 19th. This also resulted in gradual weakening and Humberto was extratropical by the afternoon of September 19. The remnant low sped northeastward toward the frigid north Atlantic before merging with another system.

The above image shows Hurricane Humberto as a large and dangerous major hurricane in the western Atlantic.

Humberto's large wind radii resulted in extensive impacts in Bermuda even as the center of circulation passed to the north.

Tropical Storm Gabrielle (2019)

Storm Active: September 3-10

As August came to an end, another tropical wave moved over the Atlantic waters from its origin in west Africa. A circulation quickly developed over the next few days, but thunderstorm activity remained rather scattered. The system tracked west-northwest and more intense convection appeared on September 3. It was therefore designated Tropical Depression Eight. Due to a weakness in the Bermuda high about halfway Bermuda and the Azores, the cyclone was able to steadily gain latitude on a northwest heading over the next several days. The waters under the system were hovering right around the benchmark 80 ° F (26.6 ° C) typically needed for tropical development and the atmospheric conditions were only marginally favorable. Despite this, Seven strengthened steadily into Tropical Storm Gabrielle on September 4.

Southerly shear helped to give the storm a "comma" shape, with convection nearest the center on the northwest side, arcing off to the northeast. It lost some convection that day as shear increased a bit more, making conditions actually fairly hostile. Nevertheless, Gabrielle maintained its intensity into September 5. During the day though, shear eliminated any remaining cloud cover from near the system. Devoid of convection for 24 hours, the system was briefly declared extratropical during the morning of September 6. However, the storm redeveloped just 6 hours later as thunderstorm activity reappeared. Meanwhile, the storm continued northwest, but accelerated a little. Shear from the south decreased the next day, only to be replaced by strong shear out of the northeast! In fact, this drove a reformation of the center of the circulation farther west that morning.

Conditions finally improved a bit for Gabrielle later that day, and it strengthened some overnight. As it gained latitude, the system moved around the edge of the high pressure to its east and began to recurve northeastward. Meanwhile, it reached its peak intensity of 65 mph sustained winds and a pressure of 995 mb. By the morning of September 9, Gabrielle was speeding off toward the northeast. It weakened gradually in response to increasing wind shear and cooler ocean temperatures that day. Extratropical transition began that day and completed during the morning of September 10. The remnants of Gabrielle continued northeast until dissipation within a couple days.

Gabrielle was a relatively small cyclone, beset by shear most of its life.

Gabrielle did not affect any landmasses as a tropical cyclone.

Tropical Storm Fernand (2019)

Storm Active: September 3-4

During the last couple days of August, a broad low pressure system located near western Cuba produced scattered storms in the neighboring southeastern Gulf of Mexico and northwestern Caribbean. The disturbance moved generally west over the next few days, passing north of the Yucatán Peninsula. On September 2, thunderstorms increased near the low. Conditions in the western Gulf of Mexico were favorable for development and Tropical Depression Seven formed during the morning of September 3. Deep convection blowups appeared west of the circulation center that afternoon. These were measured to contain tropical storm force winds, so the system was upgraded to Tropical Storm Fernand. Even in the face of southeasterly wind shear, the system intensified a little more that evening, reaching its peak intensity of 50 mph sustained winds and a pressure of 1000 mb. Heavy rain bands in Fernand's western semicircle had already swept across northeastern Mexico by that point.

Since the heaviest thunderstorms were ahead of the center, they moved over land first, and Fernand's maximum winds began to drop ahead of its landfall along the Mexican coast during the afternoon of September 4. The center crossed the coast about 150 miles south of the Texas border. Fernand's circulation quickly lost definition after landfall and it weakened to a tropical depression. Late that evening, it dissipated. The cyclone caused some flash flooding in the mountainous terrain of northeastern Mexico, where over 10 inches of rain fell in some places.

The primary threat from Tropical Storm Fernand was heavy rainfall.

Fernand had only a day over water before its landfall in Mexico, but managed to strengthen into a moderate tropical storm.

Tropical Storm Erin (2019)

Storm Active: August 26-29

On August 21, an trough of low pressure near the eastern Bahamas began to produce a scattered area of shower and thunderstorm activity. It moved slowly west-northwestward, but developed only slowly due to wind shear. Just as the storm became more concentrated on August 23, the newly formed low pressure center moved over southern Florida. The land interaction temporarily hampered further progress toward tropical depression status and most rainfall remained offshore to the east. Within another day, the system felt the tug of an approaching cold front and turned northeast, emerging over water once again. The low pressure center remained elongated, though, and westerly shear kept the western half of the circulation dry. Nevertheless, Tropical Depression Six formed during the afternoon of August 26, well offshore of North Carolina. At that time, Six had slowed to a near standstill due to the influence of nearby mid-level high pressure systems.

For the next day, the cyclone moved little and the circulation center remained exposed to the northwest of the cloud cover. Nevertheless, it became a little more organized on August 27 and was upgraded to Tropical Storm Erin. That night, it picked up speed toward the north under the influence of an upper-level trough and passed about halfway in between Bermuda and the coast of North Carolina. Shear increased again and Erin weakened back to a tropical depression on August 28. The circulation began to lose definition too. By the morning of the 29th, Erin had started to merge with a nearby front and became post-tropical.

The above image shows Tropical Depression Six just before being upgraded to a tropical storm.

Erin did not affect any landmasses, but its remnants eventually brought heavy rainfall to Atlantic Canada.

Hurricane Dorian (2019)

Storm Active: August 24-September 7

Through mid-August, the presence of Saharan dry air in the main development region (MDR) of the Atlantic between west Africa and the Lesser Antilles stifled the tropical waves that periodically traversed the basin east to west. This finally began to change on August 23 when a low pressure system formed in association with a tropical wave a bit more than halfway to the Caribbean from Africa. Already, spin was evident on satellite imagery, but thunderstorm activity was at first quite limited. However, the low managed to battle the aforementioned dry air in its vicinity and consolidate further, becoming Tropical Depression Five late in the morning on August 24. Not long after, convection concentrated near the center of circulation and it strengthened into Tropical Storm Dorian.

At first, wind shear gave the cyclone a ragged appearance on satellite imagery and limited the upper-level outflow characteristic of a healthy tropical cyclone. This shear lessened on the 25th and Dorian took advantage, beginning to intensify slowly. Meanwhile, the system maintained its heading due west. Deep convection blossomed more consistently, keeping dry air at bay. The inner core was struggling, with multiple vortices and an ill-defined circulation center. This did not prevent it from bringing heavy rains to Barbados late on August 26, when Dorian became one of the only tropical cyclones recorded to pass directly over the island. The system also entered a weakness in the ambient subtropical ridge and turned west-northwest. Several factors favored intensification for Dorian, including low shear and warm ocean temperatures, but the circulation had dry air to contend with and could not get its center together; the mid-level and surface circulations were decoupled (displaced over 100km from one another). Further, the structure that Dorian managed to accumulate was torn apart when it passed directly over St. Lucia early on August 27 and entered the Caribbean.

The battered low-level center dissipated after contact with land and reformed farther north, resulting in a more vertically stacked circulation. This also had a significant impact on the eventual track, because it put Dorian on a northwestward heading. Late on the 27th, intensification resumed and an eyewall appeared on radar imagery. As the cyclone passed over the U.S. Virgin Islands early on August 28, a massive burst of convection appeared in the eyewall. Within hours, Dorian reached hurricane status. Some islands recorded sustained winds to near hurricane force and over 5 inches of rain. The storm's winds increased a bit further through the evening, though patches of dry air out of the south gave a few parting shots at Dorian's core as it moved northwestward into a moister atmosphere. By early on the 29th, Dorian had left the Caribbean behind.

Hints of an eye appeared on microwave satellite imagery that day, but the core only slowly improved. This was in part due to an upper-level low over the Bahamas imparting moderate shear out of the southwest. The limited shear did not prevent Dorian from reaching category 2 status that evening. For most of the day of August 30, the cyclone still had a curious “squashed” appearance, with excellent outflow channels toward the east and west, but a relatively narrow cloud shield north-to-south. The eye did begin to clear out in earnest though, and Dorian steadily intensified into the first major hurricane of the 2019 season. Simultaneously, the same upper-level low that had sheared Dorian helped it to turn back toward the west, in conjunction with a building ridge over the western subtropical Atlantic. Once the hurricane was north of the upper-level low and moving west, the flow was aligned with Dorian’s forward motion. Shear therefore diminished and left the system in near-perfect conditions for rapid intensification.

Late on August 30, it took advantage. A large, symmetric she cleared out at last on visible satellite. Dorian’s central pressure plummeted and its winds increased to match; within a few hours, it was a category 4 hurricane. The trends continued on the 31st as sustained winds reached 150 mph, high-end category 4 strength. Even colder cloud tops appeared in the now very circular storm, bringing Dorian to category 5 status early on September 1. The extraordinary bout of strengthening did not abate until that afternoon, when Dorian reached its peak intensity of 185 mph sustained winds and a central pressure of 910 mb. Only a handful of Atlantic hurricanes on record had ever achieved winds of this magnitude, and none had ever impacted the Bahamas at such an intensity. The eye of Dorian passed over Abacos Island of the northern Bahamas at peak intensity, causing catastrophic damage to the island. Even worse, steering currents collapsed that evening and the system stalled early on September 2 near the neighboring Grand Bahama. These two islands, especially the second, therefore spent many hours in the destructive eyewall of the hurricane.

Dorian’s strength finally began to ebb as the strong winds caused upwelling of cooler ocean water from beneath the surface (a common occurrence for stalled hurricanes). Late in the morning on the 2nd, it weakened to a category 4. This did little to improve the situation in Grand Bahama, however, for the eye remained stationary just north of the island that whole day. An eyewall replacement cycle occurred during the afternoon, having the net effect of enlarging wind radii but lowering the peak strength of the cyclone. Early on September 3, Dorian weakened to a category 3 and finally budged northwest as a weakness developed in the ridge. The core of the storm ingested some dry air that afternoon, though it was quickly incorporated into a ragged eye that evening. As often occurs for systems gaining latitude, Dorian continued to expand, and it passed close enough to the central Florida coastline to cause tropical storm force winds in its outer rainbands. Maximum winds dropped a little more though and the cyclone weakened to a category 2 later on the 3rd.

As Dorian moved away from its own cold wake, it produced colder cloud tops again, aided by the Gulf Stream waters. It picked up a little more speed and turned north-northwest during the morning of September 4. Fortunately for the U.S. southeast, an approaching front facilitated Dorian turning farther to the right. It traveled roughly parallel to the coastline that day, turning due north around the latitude of northern Florida and then north-northeastward as it moved toward the Carolinas. Meanwhile, its structural improvements allowed slight strengthening, and Dorian regained major hurricane strength late on the 4th, reaching 115 mph winds and a 955 mb pressure. During the morning of September 5, the western eyewall swept over coastal South Carolina and it weakened back to category 2 strength. The close brush caused significant storm surge inundation and hurricane force wind gusts. Overnight, Dorian's center made an even closer approach to North Carolina. The winds decreased to category 1 strength, but the central pressure remained steady just below 960 mb, and the inner core structure was remarkably stable. Late in the morning on September 6, the cyclone made an official landfall in Cape Hatteras, North Carolina as it accelerated northeastward. Even as it gained latitude, Dorian continued to generate new deep convection in the eyewall through that night.

Finally, early on September 7, the cyclone began to lose its warm core and extratropical transition began over the cold waters north of the Gulf Stream. Even as Dorian became asymmetric, it actually deepened and intensified. This was due to baroclinic processes by which extratropical cyclones intensify, such as large temperature gradients in the atmosphere along frontal boundaries. Dorian regained category 2 status that morning, peaking again at 100 mph winds and a pressure of 953 mb southwest of Nova Scotia. Hurricane force winds and heavy rain caused widespread damage and loss of power in Atlantic Canada. During the afternoon, Dorian at last became post-tropical just before making landfall near Halifax, Nova Scotia. Its effects continued overnight though as it moved across the Gulf of St. Lawrence toward Newfoundland. The extratropical cyclone's winds dropped below hurricane strength during the afternoon of September 8 before the center passed over northwestern Newfoundland. During the night, ex-Dorian finally moved away from land over the far northern Atlantic. It moved east-northeastward for a few days before dissipation.

The above shows Dorian at peak intensity over the Bahamas. It was the strongest Atlantic hurricane ever recorded that far north (at 26.6 °N).

The above shows the long track of Dorian. Its worst impacts were in the Bahamas, the coastal Carolinas, and Atlantic Canada (as a post-tropical storm).

Tropical Storm Chantal (2019)

Storm Active: August 20-23

In the middle of August, a frontal system moving toward the U.S. southeast coast began to stir up thunderstorm activity over the Carolinas and northeastern Florida. Near its southern end, a trough developed, and on August 17 a low pressure center. It moved steadily northeastward along the Carolina coastline and then out over the open ocean. Conditions were not very favorable but nevertheless a small area of thunderstorm activity persisted near the center. On August 19, the disturbance turned due east, traveling out to sea at a fast clip. The next day, the circulation became well-defined enough for the system to unexpectedly develop into Tropical Storm Chantal.

As the tropical storm moved slightly south of east, sea temperatures actually warmed modestly and wind shear decreased. However, these favorable factors were balanced by a major inhibitor: the atmosphere was very dry over the open northern Atlantic. As a result, Chantal struggled to maintain its convection and gradually weakened, becoming a tropical depression by August 22. The gradual spin-down continued the next day and the cyclone degenerated into a remnant low late on August 23. By this time, the low had turned southeast and slowed down. It dissipated soon after.

The above image shows Chantal moving eastward away from the North American coastline.

Chantal was a short-lived and weak tropical storm which did not affect land during its time as a tropical cyclone.

Tropical Depression Three (2019)

Storm Active: July 22-23

Around July 12, a tropical wave moved off the coast of Africa. It was among the first of the season to be seriously monitored for cyclone development, but it traversed the Atlantic basin for the following week without incident. A portion of the wave axis took a northern route, passing north of the Caribbean islands and approaching the Bahamas by July 21. Stable dry air in the region made progress difficult for the disturbance, but it managed to spin up a small area of convection driven by very warm ocean waters. This led to a tiny circulation and the system strengthened into Tropical Depression Three on July 22 over the western Bahamas.

Soon after, the depression began to feel the influence of an approaching cold front and turned northward on July 23. The center passed just offshore of east Florida, but its small size meant that only a few showers and occasional gusty winds impacted land. By the late morning, the system had already lost its identity and dissipated as it combined with the front.

Even though the tropical depression formed over very warm water, it succumbed quickly to dry mid-level air.

Tropical Depression Three was a small and short-lived system with minimal land impacts.

Hurricane Barry (2019)

Storm Active: July 11-14

During the second week of July, a trough of over the southeast United States drifted slowly south-southeastward, producing some scattered afternoon thunderstorms as it went. A few days later, on July 9, this anomalous motion brought it into the extreme northeastern Gulf of Mexico, where more consistent convection began to flare up. Weak steering currents allowed the system to meander west-southwestward and it gradually organized, developing a broad circulation. By July 10, a clear low-level center had formed, but it was displaced well to the northeast of the mid-level circulation. Moreover, the strongest thunderstorms were actually located over southeast Louisiana, where significant flooding occurred before the tropical disturbance had even been classified.

Finally, on July 11, improvements in organization prompted the naming of Tropical Storm Barry, located now nearly due south of the Mississippi delta. Even after naming, however, dry continental air pushing in from the other restricted cloud cover to the southern portion of the tropical storm, and several small low-level vortices were evident on satellite imagery. This disorganized hampered Barry's intensification. Nevertheless, the pressure fell appreciably over the next day and aircraft reconnaissance indicated that the system's maximum winds steadily increased to strong tropical storm strength by July 12.

Meanwhile, Barry took a turn north of west around the edge of the mid-level steering ridge and began to move toward Louisiana. Even by the afternoon of July 12, however, the northern semicircle remained very dry, so few effects were felt over land even with the system less than 100 miles offshore. Despite its unconventional structure, Barry steadily strengthened through landfall. It peaked as a category 1 hurricane with 75 mph winds and a pressure of 993 mb on July 13 as it crossed the central Louisiana coastline around noon local time. The slow movement of the system resulted in only a gradual weakening trend and prolonged heavy rainfall, especially just east of the landfall point. Nevertheless, Barry weakened to a tropical storm shortly after landfall and a tropical depression on July 14 as the center of circulation pushed further inland. Upper level winds out of the north kept most of the precipitation over water even as the center moved away, sparing inland areas from more severe flooding. Soon after, the storm became extratropical over the midwest.

The above image shows Hurricane Barry near landfall, with most of the northern half of the circulation exposed.

Barry originated from a non-tropical disturbance over the southeast U.S.