Sunday, September 17, 2017

Hurricane Maria (2017)

Storm Active: September 16-

Maria formed from a tropical wave that first left Africa around September 10 or 11. At first, conditions did not support development of the broad system, but they steadily improved over the next several days. On September 15, the disturbance appeared much more organized on satellite imagery, and some rotation became evident. By the morning of the 16th, only a well-defined center of circulation separated it from tropical cyclone status. It cleared this hurdle during the afternoon, becoming Tropical Depression Fifteen. From this point, its maximum winds increased almost immediately, and the depression was upgraded to Tropical Storm Maria shortly thereafter.

The tropical storm was already quite large, though gaps remained in the satellite presentation of the cyclone in between rain bands. Despite this, the inner core strengthened fairly swiftly, and Maria became a strong tropical storm by the morning of September 17. That afternoon, a large burst of convective activity ignited near the center of circulation, overcoming the dry slot that had been hampering intensification. Soon, Maria had a well-formed eyewall and was upgraded to a hurricane. The outer bands were starting to affect the Lesser Antilles and the system continued west-northwestward toward the islands. September 18 saw incredibly rapid strengthening of Maria. In the morning, it strengthened into a major hurricane, and while an eye was apparent on radar, it had not yet cleared out on satellite imagery. The clearing came that afternoon; a very small "pinhole" eye developed, indicating a small core but extremely intense winds. Its intensity shot up through category 4, and Maria achieved category 5 intensity with 160 mph winds and a pressure of 924 mb during that evening. The eye then made landfall small island of Dominica in the Lesser Antilles.

Though small, the island was mountainous, and briefly disrupted Maria's core, bringing the intensity down slightly to category 4. However, as moved west-northwest into the Caribbean, its central pressure began to drop again, and the hurricane regained category 5 status early in the morning of September 19. Remarkably, the cyclone was not done intensifying: it became more symmetric on satellite imagery that day, and thunderstorm activity around the centered grew even further. That evening, Maria reached a peak intensity of 175 mph winds and a central pressure of 909 mb, one of the top ten lowest pressures ever recorded in an Atlantic hurricane at the time, even though its maximum winds were slightly weaker than those of Hurricane Irma a few weeks earlier.

By this time, the center was approaching Puerto Rico and the U.S. Virgin Islands. As is typical with powerful hurricanes, a secondary eyewall then formed and the inner one weakened somewhat, causing a decrease in maximum winds. When Maria made landfall in Puerto Rico early on September 20, it was a high-end category 4 hurricane with maximum winds of 155 mph, but the area of maximum winds had expanded in the wake of the eyewall replacement. Regardless, it was the strongest cyclone to make landfall in Puerto Rico since 1928. The hurricane brought extremely strong winds and damaging flooding rains to the island, causing several rivers to exceed their previous record stages. Nevertheless, land interaction took a significant toll on Maria and it quickly weakened over the next several hours. After traversing much of Puerto Rico from east-southeast to west-northwest, the center emerged over water early in the afternoon. The system had dropped to high-end category 2 strength, but reorganization began as it moved further northwest. A ragged eye developed by the evening and the circulation recovered some overnight, bringing Maria back up to major hurricane strength early on September 21. The southern portion of the circulation brought widespread tropical storm conditions and occasional hurricane conditions to the Dominican Republic that day.

As of 8:00 am EDT on September 21, 2017, Tropical Storm Maria had winds of 115 mph, and central pressure of 959 mb, and was moving toward the northwest at 9 mph. Please see the National Hurricane Center for current information, watches, and warnings.

Friday, September 15, 2017

Tropical Storm Lee (2017)

Storm Active: September 14-18

As is typical during mid-September, a strong tropical wave moved off of Africa and showed signs of organization by the morning of September 14. It was a fairly low-latitude system, passing well south of the Cape Verde Islands. The disturbance developed rather quickly, becoming Tropical Depression Fourteen that same night. After this, however, the system became a bit less organized, with the center becoming exposed to the north of the cloud canopy on September 15. However, as the system moved toward the west, it stayed south of the worst shear, and was able to slowly consolidate. Much more deep convection appeared during the morning of September 16, and the depression was upgraded to Tropical Storm Lee.

The system could not progress much further in its development, however, as upper-level winds renewed their assault from the north and west. The center once again became exposed later in the day, and the circulation was nearly devoid of thunderstorm activity by early on September 17. This caused Lee to weaken to a tropical depression. Pulses of convection intermittently covered the center over the next day but each was sheared away in turn. This allowed the storm to maintain tropical depression status as it turned west-northwestward. Even this did not last, however. Late on September 18, Lee lost even more organization and degenerated into a remnant low, far away from land.

Wednesday, September 6, 2017

Hurricane Katia (2017)

Storm Active: September 5-9

An area of low pressure formed in the Bay of Campeche on September 1. At first, strong shear prevented the system from doing more than generating shower activity over the region as it moved little. Conditions gradually improved for development, however, and by September 4, the disturbance was producing a large and concentrated area of thunderstorms over water. The next day, Tropical Depression Thirteen formed. There was very little steering the system, so it initially drifted toward the east and then east-southeast overnight. The system strengthened into Tropical Storm Katia early in the morning of September 5.

Later that day, the system developed a very compact inner core, and maximum winds increased rapidly. Just 12 hours after becoming a tropical storm, Katia was already a hurricane. When Katia became a hurricane, Irma and Jose were also hurricanes, making 2017 the first Atlantic season to feature 3 simultaneous hurricanes since 2010. Meanwhile, the system became nearly stationary during the morning of September 7. During the day, hints of an eye were seen, and Katia's winds increased gradually. A developing ridge to the hurricane's north finally set it on a definite heading overnight, this time toward the southwest. The next day, as it approached the coastline, the system reached its peak intensity as a category 2 hurricane with 105 mph winds and a minimum pressure of 972 mb. During the afternoon and evening, however, dry air invaded the circulation, and Katia collapsed weakening rapidly before even hitting land. By the time it made landfall in Mexico, it was down to minimal hurricane strength. The storm's swift demise continued, and it dissipated on September 9. The main impacts of Katia were heavy rain over the mountainous terrain of central Mexico.



The above image shows Katia at peak intensity as a category 2 hurricane. Fortunately, rapid weakening just before landfall reduced impacts in Mexico.



Weak steering currents prevailed during Katia's lifetime in the Bay of Campeche, and the system moved very slowly throughout its existence.

Hurricane Jose (2017)

Storm Active: September 5-

A new tropical wave entered the Atlantic basin right at the end of August and produced disorganized shower activity as it moved westward. Not much organization occurred until September 4, when conditions became more favorable and thunderstorm activity much more concentrated. By early on September 5, the disturbance was producing winds near tropical storm force. Hours later, the center of circulation was organized enough to name the system Tropical Storm Jose. The newly-formed storm was located about halfway between Africa and the Lesser Antilles and was moving west-northwest.

Moist air and low shear allowed Jose to begin strengthening immediately. A predecessor to an eye was already becoming evident during the afternoon of September 6, and the cyclone was a minimal hurricane by the evening. Simultaneously, Irma and Katia were also hurricanes, making 2017 the first Atlantic season to have three hurricanes at once since 2010. Jose's intensification continued well beyond category 1 strength. During the afternoon of September 7, it became another major hurricane as the eye became well-defined on satellite imagery. The next morning, it exploded into strong category 4 intensity. Jose's heading shifted northwest during the day, bringing on a track to just miss the northern Leeward Islands to the northeast. As it approached the islands during the evening, the storm reached its peak intensity of 155 mph winds and a central pressure of 938 mb, just below category 5 strength.

Partially due to the outflow of Irma, upper-level winds became less favorable for Jose overnight, and a weakening trend had begun by the morning of September 9. The hurricane made its closest approach to the northern Leeward Islands before noon. Fortunately for the islands, which had been devastated less than four days prior by Hurricane Irma, the center passed to the northeast, and wind radii were low on the southwest side. Nevertheless, tropical storm conditions did affect some areas for the better part of the day. The system moved northwest away from the Caribbean that evening, and Jose maintained category 4 strength through the morning of September 10. The eye disappeared that day, however, and the system steadily fell through category 3 strength into category 2 overnight. Very deep convection was still present around the center, however. Atmospheric steering currents were also weakening, causing Jose to lose forward speed and veer toward the north into September 11. During the day a developing mid-level ridge began turning the system toward the east, and its heading was due east by early the next morning. Although the hurricane maintained impressive thunderstorm activity during this time, little to no banding could form in the face of strong wind shear. As a result, Jose decayed into a minimal category 1 hurricane by September 12.

At this point, the system stabilized in intensity, and continued its slow clockwise loop over the western Atlantic by moving southeast overnight and into September 13. Warm waters allowed large pulses of deep convection to continue, offsetting the unfavorable upper-level winds and causing some upward fluctuations in intensity. Later that day, Jose turned sharply south and then west as the nearby ridge continued to evolve. The system lost some organization overnight, and weakened a bit on September 14 to a tropical storm. Another factor that inhibited strengthening later that day and early the next is that Jose was completing its loop and crossing over cooler ocean waters left in its wake when it traveled across the region a few days previously. Nevertheless, the storm remained at the brink of hurricane strength into September 15. That day, it recovered some deep convection as it turned northwest, and restrengthened into a hurricane. The storm still struggled some with dry air over the next day, but gradual strengthening occurred. Having reached the western periphery of the steering ridge, Jose also took an overall turn toward the north, although the center wobbled some to the east and west as it did so. On September 17, Jose reached its secondary peak strength of 90 mph winds and a pressure of 967 mb.

By that evening, Jose was beginning to display some characteristics of an extratropical cyclone. As it passed the latitude of North Carolina well offshore, its inner core weakened but its wind field expanded. Nevertheless, it hung on to minimal hurricane strength over the next day as it continued generally northward. Early on September 19, the cyclone's outermost rain bands swept across the mid-Atlantic coast and southern New England. Later in the day, the system turned toward the northeast, away from the coast, though the system was so large that some coastal rains continued. By this time, the center of circulation had moved north of the warm Gulf Stream waters, resulting in weakening. Jose finally lost hurricane status and became a tropical storm. Gradual decay continued into September 20. Meanwhile, the storm turned toward the east and slowed down, coming nearly to a standstill that night southeast of Cape Cod. Rain continued for portions of southern New England through the 21st.

As of 8:00 am EDT on September 21, 2017, Tropical Storm Jose had maximum winds of 60 mph, a minimum central pressure of 982 mb, and was nearly stationary. Please see the National Hurricane Center for current information, watches, and warnings.

Wednesday, August 30, 2017

Hurricane Irma (2017)

Storm Active: August 30-September 12

On August 28, another vigorous tropical wave emerged off of the coast of Africa. Saharan dry air did not hamper it as it had its predecessors, and the wave maintained thunderstorm activity as it passed near the Cape Verde Islands on August 29, bringing locally heavy rain and gusty winds. Before long, its circulation became better-defined and it developed gale-force winds. As a result, advisories were initiated on Tropical Storm Irma during the morning of August 30. Already, the storm had 50 mph sustained winds, and strengthening continued steadily as Irma's inner core became better defined. The system turned a bit toward the west-northwest on August 31, and an eye feature suddenly appeared on satellite imagery. Irma was undergoing extremely rapid intensification, and was upgraded directly from a tropical storm to a category 2 hurricane and then a major hurricane by late afternoon.

The circulation was quite compact, with hurricane-force winds very close to the center. As is often true with small cyclones, Irma was subject to short-term fluctuations in intensity. A few eyewall replacement cycles, in which the eye clouded over temporarily and then reappeared, occurred between August 31 and September 2. This caused Irma to alternate between category 2 and category 3, an impressive intensity as it traversed only marginally warm waters. Meanwhile, the subtropical ridge to its north began to build southward, and the cyclone turned west and even slightly south of west by September 2. Over time, this brought the system toward warmer waters and moister air. By September 3, though Irma's intensity remained in the low-end category 3 range, the cyclone was beginning to grow larger, displaying outer banding features. That evening, Irma's central pressure began to decrease. This trend continued into September 4, when the maximum winds began to strengthen as well.

Meanwhile, Irma began to round the bottom of the subtropical ridge and assume a due westward path near 17° N. This brought it over areas of higher oceanic heat content and even higher atmospheric humidity levels. As a result, intensification once again increased in speed: Irma became a category 4 that afternoon. During the evening, its eye cleared and became quite large in the wake of another eyewall replacement. During the morning of September 5, yet another burst of intensification brought it to category 5 strength, with winds of 175 mph. This was the farthest east such high wind speeds had ever been recorded in the Atlantic. The outer part of Irma's circulation began to affect the northeast Caribbean islands that day. The trend of remarkable deepening continued as the system turned west-northwest, bringing the hurricane to a peak intensity of 185 mph winds and a minimum pressure of 914 mb. These winds were tied for the second-highest ever recorded in an Atlantic hurricane, and the pressure was the lowest known in the Atlantic outside of the Caribbean and Gulf of Mexico. That night, the cyclone passed directly over the northern Leeward Islands.

Despite the continuing evolution of the inner core, Irma did not undergo an eyewall replacement on September 6, and maintained its incredible category 5 intensity, though with some pressure fluctuations. The center passed through the U.S. Virgin Islands and then just north of Puerto Rico that evening. Overnight, the circulation was a bit disrupted from land interaction, and the winds began to slowly decrease as Irma moved west-northwest just north of Hispaniola. That evening, the center of circulation passed among the Turks and Caicos Islands. During the night, the outer eyewall of Irma finally got the better of the inner, weakening the maximum winds down to category 4 strength, but expanding the overall windfield. The system moved west-northwest between Cuba and the Bahamas the morning of the 8th as a strong category 4 hurricane. Late in the afternoon, Irma turned back toward the west and approached the northern coast of central Cuba. Just before making a direct hit on the northern archipelago of Cuba, the system briefly regained category 5 strength, reaching winds of 160 mph and a minimum pressure of 924 mb.

After passing over the northern islands, the center of circulation did not pass inland, but rather turned just north of west and paralleled the coast overnight, slowing down as it did so. Land interaction took a significant toll on the storm for the first time early on September 9, dropping Irma down to high-end category 3 strength. The eye wobbled a great deal along its path during the day, but the overall motion was a turn toward the north-northwest by the evening. Meanwhile, as conditions improved in Cuba, they deteriorated in Florida, as intense outer bands swept across much of the peninsula. These include tropical storm conditions, flooding rains, and several reports of tornadoes. During the night, Irma regained category 4 intensity, reaching a final peak of 130 mph winds and a pressure of 928 mb before passing over the Florida Keys early on September 10. Increasing wind shear and land interaction steadily weakened Irma from then on. It made landfall as a category 3 hurricane in southwestern Florida that afternoon. As with many sheared landfalling systems, Irma became lopsided, with almost all rainfall occurring north of the center, and the northern eyewall much more intense than the southern. The size of the system was such that, located over western Florida, it brought tropical storm force winds from the Florida panhandle to parts of Georgia and even extending well into South Carolina.

On September 11, Irma weakened to a tropical storm while centered over the northwestern Florida Peninsula, having caused more than 6 inches of rain throughout much of the state. By the afternoon, the center had pushed into Georgia and rains spread northwestward as they ended in Florida. Overnight, the system weakened to a tropical depression and then became post-tropical. In addition to those already mentioned, Irma set many other records. Its 3.25 days spent as a category 5 hurricane were tied for the most ever recorded in the Atlantic with the 1932 Cuba hurricane. Its category 5 landfalls in the Leeward Islands and Cuba were among the strongest ever recorded. Finally, Irma maintained 185 mph winds for a period of 37 hours, which was the most ever recorded in the entire world.



This image shows Hurricane Irma at peak intensity on September 6 as it passed directly over the northern Leeward Islands, causing catastrophic damage.



Irma's long track as a powerful hurricane brought devastating impacts to the northern Leeward Islands, the U.S. Virgin Islands, the Turks and Caicos Islands, Cuba, and Florida.

Thursday, August 17, 2017

Hurricane Harvey (2017)

Storm Active: August 17-19, 23-31

On August 13, a large tropical wave entered the Atlantic from the west coast of Africa. As with many of the previous August waves, thunderstorm activity diminished as soon as it was over water. There was some spin associated with the system over the next few days, but the low pressure area remained elongated. The circulation improved greatly on August 15 and 16, leaving limited shower activity as its main barrier to development. Meanwhile, the system was moving due westward at a steady clip toward moister air, and thunderstorm activity increased significantly by the morning of the 17th. That afternoon, aircraft reconnaissance discovered a closed circulation and tropical storm force winds, prompting the naming of Tropical Storm Harvey.

After formation, Harvey moved at around 20 mph toward the west, steered by a ridge to its north. As with many systems moving at such speeds near the Lesser Antilles, the storm had difficulty maintaining a center of circulation and was rather disorganized. Nevertheless, it brought some localized heavy rain and gusty winds as it passed over the Windward Islands during the morning of August 18. Moderate shear also took a toll on the system as it continued quickly westward; during the afternoon of August 19, it was downgraded to a tropical depression. The system's deterioration continued through the evening and aircraft reconnaissance was unable to detect evidence of a closed circulation that evening. Harvey had opened up into a wave and was no longer a tropical cyclone.

The remnants of Harvey continued toward the west, where conditions for development began to improve again. Early on August 20, they passed near the coasts of Nicaragua and Honduras, bringing some rain to the shoreline. Shower activity increased significantly that afternoon. Before a new circulation could fully develop, however, the system began to interact with the Yucatan Peninsula. While Ex-Harvey crossed over land on August 21 and 22, it produced convection mainly over the Gulf waters to the north. Nevertheless, some spin reappeared on satellite imagery. The system became much more vigorous by the morning of the 23rd, once it was back out over warm Gulf waters. Aircraft reconnaissance soon found a well-defined center of circulation and advisories were reinitiated on Tropical Depression Harvey before noon.

During the afternoon, Harvey slowed to a standstill, and a central dense overcast feature appeared, indicative of a developing system. The central pressure began to slowly decline, but the circulation was still rather disorganized. Overnight, the depression was upgraded to a tropical storm. The upper-level low that was causing some shear over Harvey was weakening, meanwhile, leaving the storm in very favorable atmospheric conditions. Early on August 24, the system began a run of rapid intensification, reaching hurricane strength by early in the afternoon! Though the wind speeds leveled out through the evening, the central pressure continued to drop, presaging a corresponding increase of winds. This occurred in the middle of the night, bringing Harvey to category 2 strength. Around this time, a vigorous outer rain band swept across the Texas coastline. During the morning of August 25, it became evident that the hurricane was experiencing an eyewall replacement cycle (EWRC), where the innermost ring of thunderstorms about a powerful hurricane's eye contracts or dissipates, and a second ring (the outer eyewall) takes over. This put a temporary cap on Harvey's winds, but did not stop the central pressure from dropping steadily.

Meanwhile, the system was still moving at a moderate pace toward the northwest and approaching the Texas coastline. Squalls and even tornadoes occurred over land as the more vigorous rain bands swept across the coast. During the afternoon, Harvey's EWRC was completed, and a large eye cleared out on satellite and radar imagery. This was accompanied by another rapid increase in winds, bringing the hurricane to its peak intensity as a category 4 storm; it had maximum winds of 130 mph and a central pressure of 938 mb when it made landfall in Texas. This was first major hurricane landfall in the United States since 2005, the first hurricane landfall in Texas since 2008, and the strongest in the state since 1961. The storm slowed as it moved north-northwestward inland and weakened. By mid-morning on August 26, Harvey was a minimal hurricane, and it weakened to a tropical storm that afternoon. However, as the storm slowed to a standstill, the greatest concern was rain: the counterclockwise spin of the circulation continually brought new moisture from over the Gulf northward over areas east of the center, dumping feet of rain over a wide swath of Texas. Harvey reversed course and began to meander generally southward by the morning of August 27. Later, the direction of drift turned southeastward. Since part of the circulation remained over water, the storm was able to maintain minimal tropical storm strength through the next day. Meanwhile, the main source of rain was a large band wrapping around the northeast side of the circulation down to the Gulf, pulling moisture over eastern Texas and Louisiana. Early on August 28, Harvey's center reemerged over the Gulf of Mexico.

Some intermittent convection rekindled near the center once it touched warm Gulf waters, but the circulation was entraining dry air from western Texas, and wind shear was high. As a result, the inner core could not redevelop, and Harvey resembled an extratropical cyclone more than a tropical one. It had a comma-shaped tail of thunderstorm activity wrapping from north of the center eastward, so that rain continued over eastern Texas and Louisiana. The cyclone traveled first southeast, and then east over the next day. Winds increased modestly during this period to 50 mph in strong rain bands over water. Finally, on the 29th, Harvey turned toward the north and increased in speed somewhat, making its final landfall in western Louisiana early on August 30. The cyclone weakened over land as it moved north, but dealt a final burst of heavy rain to eastern Texas before becoming a tropical depression that evening. Soon, the system became extratropical, but rainfall continued to push northeastward, bringing moderate amounts of rain to the mid-Atlantic and northeast by September 2. A peak rainfall accumulation of 51.88" occurred in Cedar Bayou, Texas, the highest rainfall total every recorded from any tropical cyclone in the continental United States.



The above image shows Harvey shortly before landfall in Texas.



Harvey's unusual slow movement near and over the state of Texas brought unprecedented rains to south and east parts of the state.

Sunday, August 13, 2017

Hurricane Gert (2017)

Storm Active: August 12-17

On August 2, a vigorous tropical wave left Africa and moved westward over the Atlantic Ocean. While environmental conditions seemed conducive for development, the system was unable to consolidate. Dry air interfered with the production of deep convection, and the associated circulation remained highly elongated. Competing vortices on the northeast and southwest sides vying for dominance cost the wave the chance to organize over the next several days. By August 7, conditions had become unfavorable due to the presence of an upper-level low to the northeast. Nevertheless, the system proceeded steadily west-northwestward, passing a bit north of the Lesser Antilles on August 10. Wind shear diminished and the wave encountered more humid air soon after, giving it another chance at development. Convection increased and the circulation became better defined over the next two days, and Tropical Depression Eight finally formed late on August 12.

The system was experiencing some wind shear out of the north, but conditions were otherwise supportive of intensification. August 13 saw the naming of Tropical Storm Gert when the system lay well east of the Florida coastline and was turning toward the north. The inner core structure improved considerably that night and into August 14. The first hints of an eye appeared that afternoon, and Gert was upgraded to a hurricane that night. The cyclone then began to feel the influence of a frontal system moving off of the U.S. east coast, and turned northeast on August 15, accelerating as it did so. Even as it gained latitude, Gert still took advantage of warm Gulf Stream waters to continue strengthening. A compact eye feature became apparent on both visible and satellite imagery by the morning of the 16th. That evening, the system reached its peak intensity as a category 2 hurricane with 105 mph winds and a minimum pressure of 967 mb near 40° N. Cooler waters and deteriorating atmospheric conditions finally caught up with Gert overnight and it weakened, beginning extratropical transition. The system became extratropical on the afternoon of August 17 as it sped east-northeastward over the open ocean.



The above satellite image shows Gert at peak intensity as a category 2 hurricane. Nova Scotia is visible at the top of the image.



A frontal boundary interacting with Gert steered it out to sea, minimizing land impacts.

Monday, August 7, 2017

Hurricane Franklin (2017)

Storm Active: August 6-10

Towards the end of July, a tropical wave tracked westward across the central Atlantic, showing some potential for development as it produced scattered showers and thunderstorms. Dry air and deteriorating atmospheric conditions stifled this potential by the time August had begun. Nevertheless, the tropical wave continued into the Caribbean. Significant convection flared up near the system on August 3 when it was located in the eastern Caribbean, and surface pressures began to slowly decline in the area. For the next day or two, however, it was contending with very high wind shear, and was unable to organize much. This changed early on August 5, when thunderstorm activity concentrated near its nascent circulation. Meanwhile, shear began to decline, allowing the system to take advantage of quite warm sea water. Late on August 6, Tropical Storm Franklin was named northeast of Honduras.

Franklin's environment steered it steadily west-northwest the following day. Its banding features steadily improved, resulting in steady strengthening. By that afternoon, its sustained winds had increased to 60 mph and its pressure had dropped to 999 mb. However, dry air infiltrated the circulation from the south that evening, weakening thunderstorm activity near the center and preventing additional intensification before Franklin made landfall that evening in the Yucatan Peninsula. The cyclone weakened over land into August 8, but the low-lying land did not disrupt the core much, and the system remained well-organized. Late in the afternoon, the center of circulation emerged over the Bay of Campeche and assumed a more westward trajectory. Strong outer bounds quickly formed and Franklin's core also quickly improved over the very warm ocean water. The following day saw the system intensify from a minimal tropical storm to a category 1 hurricane by the afternoon of August 9. It strengthened a bit further to its peak intensity of 85 mph winds and a pressure of 981 mb before making landfall in Mexico. Franklin's decay was swift over the mountainous terrain, and it dissipated by late morning on August 10.

The remnants of Franklin crossed over into the eastern Pacific Ocean over the next day and quickly reorganized over water. Late on August 11, they regenerated into a tropical storm. Since the system dissipated before reforming in another basin, it received a separate name from the Eastern Pacific name list: Jova.



The above image shows Hurricane Franklin at peak intensity just before landfall in Mexico.



Franklin strengthened quickly over the warm waters of the Bay of Campeche.

Monday, July 31, 2017

Tropical Storm Emily (2017)

Storm Active: July 31-August 1 During the last week of July, a cold front extending from Texas to the northeast U.S. pushed south and east, weakening as it did so. By July 30, the southern half of the cold front had moved over the Gulf of Mexico and stalled. A non-tropical low quickly formed along it just south of the Florida panhandle and moved slowly toward the east. Overnight, thunderstorm activity became clustered around the circulation center and the system became organized enough to merit tropical depression status early on July 31. Just two hours after formation, radar indicated that Tropical Depression Six's maximum winds had risen to 45 mph and it was upgraded to Tropical Storm Emily.

The storm moved just south of east through the morning and made landfall near Tampa, Florida before noon. Heavy rain fell even as the system weakened over land, with the heaviest south of the center. By the afternoon, the system had weakened to a depression. It accelerated and turned toward the northeast overnight and emerged over open Atlantic waters east of Florida early on August 1. Emily's grip on tropical cyclone status was quite tenuous by this time: only scattered bursts of disorganized convection remained. Late that night, it was downgraded to a remnant low. This low continued out to sea over the next several days before dissipation.



The above image shows Tropical Storm Emily making landfall in Florida within 12 hours of formation.



Emily was yet another short-lived tropical storm, the fifth of the 2017 season. In fact, the combined ACE (accumulated cyclone energy) of these storms was the lowest on record for the first five of an Atlantic hurricane season.

Monday, July 17, 2017

Tropical Storm Don (2017)

Storm Active: July 17-18

A mid-July tropical wave crossed westward from the coast of Africa to more than half-way across the tropical Atlantic without generating much thunderstorm activity. However, on July 16, the system began to organize, despite the proximity of dry air. A low pressure center formed shortly afterward, even as convection remained quite limited. During the afternoon of July 17, a curved band developed about the center and the circulation became better-defined. As a result, the low was upgraded to Tropical Storm Don about 500 miles east of the Windward Islands.

Over the next day, Don moved quickly toward the west. It strengthened briefly as a central dense overcast appeared, but increasing shear reversed this slight intensification as quickly as it had occurred. By midday on July 18, Don's disorganized thunderstorm activity was moving over the Windward Islands. That evening, before the system passed over the islands, Don lost its circulation center in the face of strong shear and dissipated. Scattered gale force winds and heavy rain did continue, however, as its remnants entered the Caribbean.



Tropical Storm Don was only a small cyclone for its brief existence, forming as it did on the edge of a dry air mass with limited moisture supply.



Don existed for less than two days before succumbing to high wind shear as it entered the Caribbean Sea.