I recently came across the following pair of numbers, quite close to one another, and with similar-looking prime factorizations:
4061 = 31*131
4069 = 13*313
We can explain the proximity of these two numbers by expanding the products as follows:
4061 = (3*10 + 1*1)(1*100 + 3*10 + 1*1) = 3*1000 + 9*100 + 1*100 + 3*10 + 3*10 + 1*1
4069 = (1*10 + 3*1)(3*100 + 1*10 + 3*1) = 3*1000 + 9*100 + 1*100 + 3*10 + 3*10 + 3*3
Notice that only the last terms are different, leading to the difference 3*3 - 1*1 = 8 between the two numbers.
The same sort of argument shows that products of the aba...ba*ba and bab...ab*ab differ only by a*a - b*b, where a and b are any two digits. However, a computer search yields no other examples where all of these numbers are prime, besides the above, up to at least a googol.
Saturday, October 18, 2025
Monday, October 13, 2025
Tropical Storm Lorenzo (2025)
Storm Active: October 13-15
On October 10, a tropical wave entered the Atlantic from Africa. The wave was vigorous and developed fairly quickly, leading to the naming of Tropical Storm Lorenzo on October 13. At the time, it was located around 1000 miles west of Cabo Verde. This was fairly late in the season for a tropical cyclone to form in the "Main Development Region" of the tropical Atlantic between Africa and the Lesser Antilles.
Lorenzo experienced significant shear out of the southwest, preventing it from intensifying much as it moved northwestward. Even after shear lessened the next day, the storm entered an area of dry mid-level air that stifled convective developement. Without moist unstable air to drive its circulation, Lorenzo began to spin down quickly. It curved toward the north-northeast and steadily weakened before dissipating on October 15.
The image above shows Lorenzo on October 14.
Lorenzo did not affect any land areas as a tropical cyclone.
On October 10, a tropical wave entered the Atlantic from Africa. The wave was vigorous and developed fairly quickly, leading to the naming of Tropical Storm Lorenzo on October 13. At the time, it was located around 1000 miles west of Cabo Verde. This was fairly late in the season for a tropical cyclone to form in the "Main Development Region" of the tropical Atlantic between Africa and the Lesser Antilles.
Lorenzo experienced significant shear out of the southwest, preventing it from intensifying much as it moved northwestward. Even after shear lessened the next day, the storm entered an area of dry mid-level air that stifled convective developement. Without moist unstable air to drive its circulation, Lorenzo began to spin down quickly. It curved toward the north-northeast and steadily weakened before dissipating on October 15.
The image above shows Lorenzo on October 14.
Lorenzo did not affect any land areas as a tropical cyclone.
Friday, October 10, 2025
Subtropical Storm Karen (2025)
Storm Active: October 9-10
Around October 8, a non-tropical low pressure system formed well to the northwest of the Azores. The low quickly separated from the surrounding fronts and developed a tiny warm core, embedded in a larger upper-level trough. These characteristics, along with gale force winds, led to the designation of Subtropical Storm Karen late on October 9. This was the northernmost formation by an Atlantic tropical or subtropical cyclone on record, at 44.5°N.
Besides this impressive statistic, Karen did not lead a very notable existence. The small area of convection near the center was snuffed out the following afternoon when the storm moved even farther north over yet colder waters. By that evening, the system was declared post-tropical.
The image above shows Karen as a subtropical storm on October 10.
Karen carved out a warm core inside a larger system and managed to maintain subtropical cyclone status for a day before becoming post-tropical.
Around October 8, a non-tropical low pressure system formed well to the northwest of the Azores. The low quickly separated from the surrounding fronts and developed a tiny warm core, embedded in a larger upper-level trough. These characteristics, along with gale force winds, led to the designation of Subtropical Storm Karen late on October 9. This was the northernmost formation by an Atlantic tropical or subtropical cyclone on record, at 44.5°N.
Besides this impressive statistic, Karen did not lead a very notable existence. The small area of convection near the center was snuffed out the following afternoon when the storm moved even farther north over yet colder waters. By that evening, the system was declared post-tropical.
The image above shows Karen as a subtropical storm on October 10.
Karen carved out a warm core inside a larger system and managed to maintain subtropical cyclone status for a day before becoming post-tropical.
Tropical Storm Jerry (2025)
Storm Active: October 7-11
On October 3, a late season tropical wave entered the Atlantic basin. It moved quickly toward the west-northwest and steadily organized. By October 6, the wave had a very impressive satellite signature, featuring a broad area of spin and concentrated thunderstorm activity. The next day, it was named Tropical Storm Jerry. Jerry was still over a thousand miles east of the Lesser Antilles, but was moving quickly toward the west-northwest. Despite a strong start, the storm actually became less organized after it was named. By the next day, shear opposite to its forward motion had displaced all thunderstorm activity east-southeast of the center. Nevertheless, it managed to strengthen some through the evening of October 8.
Jerry approached the Leeward Islands the next day. The center made its closest approach to land during the evening of the 9th, but the accompanying rains peaked over the islands only overnight and into the next morning, since convection was so removed from the center. The storm wasn't strong, but did cause widespread flooding for the northeasternmost Caribbean islands. Only on the 10th did Jerry lift north away from the Leewards. The cyclone's center was very poorly defined, with a pronounced elongation in the northwest-southeast direction. The cyclone was never able to recover from this poor organization and lost its circulation on October 11, degenerating into a trough of low pressure.
The image above shows Jerry just east of the Leeward Islands on October 9. The center of circulation ultimately missed the islands, but Jerry's passage dragged an area of heavy rain, displaced south and east of the center, across those areas over the following day.
Jerry dissipated shortly after its brush of the Caribbean.
On October 3, a late season tropical wave entered the Atlantic basin. It moved quickly toward the west-northwest and steadily organized. By October 6, the wave had a very impressive satellite signature, featuring a broad area of spin and concentrated thunderstorm activity. The next day, it was named Tropical Storm Jerry. Jerry was still over a thousand miles east of the Lesser Antilles, but was moving quickly toward the west-northwest. Despite a strong start, the storm actually became less organized after it was named. By the next day, shear opposite to its forward motion had displaced all thunderstorm activity east-southeast of the center. Nevertheless, it managed to strengthen some through the evening of October 8.
Jerry approached the Leeward Islands the next day. The center made its closest approach to land during the evening of the 9th, but the accompanying rains peaked over the islands only overnight and into the next morning, since convection was so removed from the center. The storm wasn't strong, but did cause widespread flooding for the northeasternmost Caribbean islands. Only on the 10th did Jerry lift north away from the Leewards. The cyclone's center was very poorly defined, with a pronounced elongation in the northwest-southeast direction. The cyclone was never able to recover from this poor organization and lost its circulation on October 11, degenerating into a trough of low pressure.
The image above shows Jerry just east of the Leeward Islands on October 9. The center of circulation ultimately missed the islands, but Jerry's passage dragged an area of heavy rain, displaced south and east of the center, across those areas over the following day.
Jerry dissipated shortly after its brush of the Caribbean.
Sunday, September 28, 2025
Hurricane Imelda (2025)
Storm Active: September 27-October 2
Around September 16, the first of a pair of tropical waves entered the Atlantic basin from the east. Unlike its successor, which would become Hurricane Humberto, the leading wave did not generate much thunderstorm activity for much of its journey across the tropical Atlantic. It first attracted notice on September 21, when this activity increased markedly as it approached the Leeward Islands. The system remained too disorganized to consolidate into a tropical cyclone, but it brought significant rainfall across the Caribbean. It first impacted the Leewards on the 23rd, Puerto Rico the next day, and the Dominican Republic on the 25th. After that time, the disturbance slowed down and turned toward the north. Less land interaction and favorable atmospheric conditions allowed it to establish a circulation over the next couple of days. Eventually, the system was designated Tropical Depression Nine a little off the northern coast of east Cuba.
Despite achieving tropical cyclone status, the depression was very still broad and disorganized at first, with mid-level spin displaced from the low-level center. It began to build a dense area of convection near the developing center on the 28th. That afternoon, it was upgraded to Tropical Storm Imelda. Around the same time, the center began to move northward through the Bahamas, bringing tropical storm conditions to some of the islands. Imelda deepened steadily over the next few days and winds increased. By the time it exited the Bahamas on September 29, it was a strong tropical storm. It was upgraded to a hurricane during the morning of September 30.
Imelda did not have the traditional appearance of a hurricane on satellite imagery; some dry air was present near the center and convection did not completely surround it. Nevertheless, it continued strengthening. That day it also took a sharp turn toward the east-northeast. This was due to an approaching trough near the U.S. east coastline and a binary interaction with Hurricane Humberto to Imelda's northeast. As the two cyclones approached each other, the Fujiwhara effect caused them to rotate in a counterclockwise direction around the "center of gravity" between the two. This center of gravity was recurving northeast, so Humberto's eastward progress slowed some, while Imelda was yanked quickly eastward out to sea away from land.
Imelda closed off a circular eyewall and continued to intensify. During the morning of October 1, the cyclone reached its peak intensity as a category 2 hurricane with 100 mph winds and a minimum central pressure of 966 mb. After that time, wind shear increased due to the encroaching trough, but Imelda managed to temporarily maintain its strength due to a favorable trough interaction. This meant it was still near peak intensity when the center of circulation passed within a handful of miles of a direct landfall of Bermuda late on October 1. The center's passage just south of the island brought hurricane-force winds to Bermuda for a few hours, before Imelda sped off to the east.
After that, the storm began to weaken and lose its remaining tropical characteristics. During the morning of October 2, Imelda transitioned to a post-tropical cyclone. Its remnants arced northeastward over the open north Atlantic until they dissipated several days later.
The image above shows Imelda on October 1 at peak intensity. The island of Bermuda is visible at right, directly in the hurricane's path.
Imelda took a sharp turn eastward around September 30, preventing it from affected mainland North America. Nevertheless, the storm brought significant impacts to the Bahamas and Bermuda.
Around September 16, the first of a pair of tropical waves entered the Atlantic basin from the east. Unlike its successor, which would become Hurricane Humberto, the leading wave did not generate much thunderstorm activity for much of its journey across the tropical Atlantic. It first attracted notice on September 21, when this activity increased markedly as it approached the Leeward Islands. The system remained too disorganized to consolidate into a tropical cyclone, but it brought significant rainfall across the Caribbean. It first impacted the Leewards on the 23rd, Puerto Rico the next day, and the Dominican Republic on the 25th. After that time, the disturbance slowed down and turned toward the north. Less land interaction and favorable atmospheric conditions allowed it to establish a circulation over the next couple of days. Eventually, the system was designated Tropical Depression Nine a little off the northern coast of east Cuba.
Despite achieving tropical cyclone status, the depression was very still broad and disorganized at first, with mid-level spin displaced from the low-level center. It began to build a dense area of convection near the developing center on the 28th. That afternoon, it was upgraded to Tropical Storm Imelda. Around the same time, the center began to move northward through the Bahamas, bringing tropical storm conditions to some of the islands. Imelda deepened steadily over the next few days and winds increased. By the time it exited the Bahamas on September 29, it was a strong tropical storm. It was upgraded to a hurricane during the morning of September 30.
Imelda did not have the traditional appearance of a hurricane on satellite imagery; some dry air was present near the center and convection did not completely surround it. Nevertheless, it continued strengthening. That day it also took a sharp turn toward the east-northeast. This was due to an approaching trough near the U.S. east coastline and a binary interaction with Hurricane Humberto to Imelda's northeast. As the two cyclones approached each other, the Fujiwhara effect caused them to rotate in a counterclockwise direction around the "center of gravity" between the two. This center of gravity was recurving northeast, so Humberto's eastward progress slowed some, while Imelda was yanked quickly eastward out to sea away from land.
Imelda closed off a circular eyewall and continued to intensify. During the morning of October 1, the cyclone reached its peak intensity as a category 2 hurricane with 100 mph winds and a minimum central pressure of 966 mb. After that time, wind shear increased due to the encroaching trough, but Imelda managed to temporarily maintain its strength due to a favorable trough interaction. This meant it was still near peak intensity when the center of circulation passed within a handful of miles of a direct landfall of Bermuda late on October 1. The center's passage just south of the island brought hurricane-force winds to Bermuda for a few hours, before Imelda sped off to the east.
After that, the storm began to weaken and lose its remaining tropical characteristics. During the morning of October 2, Imelda transitioned to a post-tropical cyclone. Its remnants arced northeastward over the open north Atlantic until they dissipated several days later.
The image above shows Imelda on October 1 at peak intensity. The island of Bermuda is visible at right, directly in the hurricane's path.
Imelda took a sharp turn eastward around September 30, preventing it from affected mainland North America. Nevertheless, the storm brought significant impacts to the Bahamas and Bermuda.
Friday, September 26, 2025
Hurricane Humberto (2025)
Storm Active: September 24-October 1
On September 18, a vigorous tropical wave entered the tropical Atlantic ocean from the west African coastline. It tracked west-northwestward and steadily organized until it was designated Tropical Storm Humberto northeast of the Lesser Antilles on September 24. Despite some wind shear out of the west early on, Humberto steadily strengthened from formation. On the 25th, spiral bands and a central core appeared on satellite imagery. The storm became a hurricane the next morning. Meanwhile, the storm's forward speed slowed significantly due to weak steering currents.
Atmospheric conditions soon improved further over the storm. On September 26, Humberto rapidly intensified. An eye appeared and cleared out extremely quickly; within an 18 hour period, the storm went from a minimal hurricane to a strong category 4 hurricane. Overnight, an eyewall replacement cycle briefly halted strengthening, but the system rebounded surprisingly quickly. September 27 brought an even more symmetric eye surrounded by a larger ring of extremely cold cloud tops. This coincided with Humberto reaching its peak strength as a category 5 hurricane, with maximum sustained winds of 160 mph and a minimum central pressure of 924 mb. Humberto was the second category 5 hurricane of the season, after Hurricane Erin. This made 2025 the second consecutive year with multiple category 5 Atlantic hurricanes, due to the formation of Beryl and Milton in 2024. Such an event only occurred once before on record, during the 1932-1933 seasons.
During this episode of strengthening, Humberto's heading meandered a little, but the subtropical ridge generally pushed it west-northwestward at a slow but steady pace. Although conditions remained favorable a bit longer, another outer eyewall soon formed and disrupted the storm's internal structure, causing it to weaken back to a category 4 by the 28th. The core continued to evolve, but the storm remained a category 4 until the following evening, when shear increased markedly. This shear was associated with an approaching trough and in part due to the increasing proximity between Humberto and Imelda, which was approaching from the southwest. This shear destroyed the hurricane's core and exposed the center, leading to rapid weakening. By the afternoon of September 30, Humberto was down to category 1 strength, though it maintained an area of strong storms northeast of the center.
Meanwhile, the hurricane recurved toward the north and then sharply turned toward the east in the mid-latitue westerly flow. Humberto met a quick demise soon after: its circulation was absorbed into the approaching front during the morning of October 1.
The image above shows the impressive satellite signature of Humberto at its peak intensity as a category 5 hurricane on September 27.
Humberto did not affect any land areas as a tropical cyclone.
On September 18, a vigorous tropical wave entered the tropical Atlantic ocean from the west African coastline. It tracked west-northwestward and steadily organized until it was designated Tropical Storm Humberto northeast of the Lesser Antilles on September 24. Despite some wind shear out of the west early on, Humberto steadily strengthened from formation. On the 25th, spiral bands and a central core appeared on satellite imagery. The storm became a hurricane the next morning. Meanwhile, the storm's forward speed slowed significantly due to weak steering currents.
Atmospheric conditions soon improved further over the storm. On September 26, Humberto rapidly intensified. An eye appeared and cleared out extremely quickly; within an 18 hour period, the storm went from a minimal hurricane to a strong category 4 hurricane. Overnight, an eyewall replacement cycle briefly halted strengthening, but the system rebounded surprisingly quickly. September 27 brought an even more symmetric eye surrounded by a larger ring of extremely cold cloud tops. This coincided with Humberto reaching its peak strength as a category 5 hurricane, with maximum sustained winds of 160 mph and a minimum central pressure of 924 mb. Humberto was the second category 5 hurricane of the season, after Hurricane Erin. This made 2025 the second consecutive year with multiple category 5 Atlantic hurricanes, due to the formation of Beryl and Milton in 2024. Such an event only occurred once before on record, during the 1932-1933 seasons.
During this episode of strengthening, Humberto's heading meandered a little, but the subtropical ridge generally pushed it west-northwestward at a slow but steady pace. Although conditions remained favorable a bit longer, another outer eyewall soon formed and disrupted the storm's internal structure, causing it to weaken back to a category 4 by the 28th. The core continued to evolve, but the storm remained a category 4 until the following evening, when shear increased markedly. This shear was associated with an approaching trough and in part due to the increasing proximity between Humberto and Imelda, which was approaching from the southwest. This shear destroyed the hurricane's core and exposed the center, leading to rapid weakening. By the afternoon of September 30, Humberto was down to category 1 strength, though it maintained an area of strong storms northeast of the center.
Meanwhile, the hurricane recurved toward the north and then sharply turned toward the east in the mid-latitue westerly flow. Humberto met a quick demise soon after: its circulation was absorbed into the approaching front during the morning of October 1.
The image above shows the impressive satellite signature of Humberto at its peak intensity as a category 5 hurricane on September 27.
Humberto did not affect any land areas as a tropical cyclone.
Thursday, September 18, 2025
Hurricane Gabrielle (2025)
Storm Active: September 17-25
A tropical wave entered the Atlantic ocean around September 12 and moved slowly westward over the next several days. It produced a significant amount of thunderstorm activity but remained quite disorganized. The system was eventually designated Tropical Depression Seven on September 17. At the time, it was a little past halfway from Africa to the Windward Islands. Despite achieving tropical depression status, the cyclone was still a mess, with almost all convection displaced east of the center. Furthermore, the center itself was a warring group of vorticies rotating around one another. Later that day, the center reformed further north, coaxed poleward by an upper-level low over the subtropics. The storm's winds also increased enough that it was upgraded to Tropical Storm Gabrielle.
Gabrielle evened out to a more steady west-northwest heading on the 18th and consolidated its circulation, but struggled to produce thunderstorm activity. For most of the day, it was little more than a naked swirl. That evening, it began to put up a better fight against westerly wind shear and storm activity blossomed in the eastern semicircle. Nevertheless, atmospheric conditions remained hostile through the next day. It was only on the 20th that shear lessened and Gabrielle was able to start intensifying again. The storm spent the next few days curving around the western edge of the subtropical ridge, first turning toward the north and toward the east. This path kept it east of Bermuda, too far to cause any direct impacts to the island. This was fortunate, because Gabrielle strengthened significantly.
On the 21st, it was upgraded to a hurricane. Shortly after that, the cyclone's satellite presentation improved markedly. An eye quickly cleared out and became more symmetric. Gabrielle vaulted to major hurricane strength by the morning of September 22. That afternoon it reached its peak intensity as a category 4 hurricane, with maximum winds of 140 mph and a central pressure of 948 mb. The storm accelerated toward the east-northeast and encountered gradually increasing wind shear as well as decreasing ocean heat content. This began a decaying trend, though it remained a significant hurricane.
Gabrielle began to lose tropical characteristics late on September 24 as the central core collapsed and it weakened to a category 1 hurricane. By this time, the storm was speeding eastward toward the central Azores. During the afternoon of September 25, a few hours before arriving at the islands, Gabrielle transitioned to a post-tropical cyclone. This did not prevent the cyclone from bringing strong winds, storm surge, and brief heavy rains to the Azores; during the storm's passage, hurricane-force gusts were recorded at sea level as well as hurricane-force sustained winds at higher elevations. A fully extratropical ex-Gabrielle exited the island chain toward the east by the next morning. Its remnants passed near the coast of Portugal before dissipating days later.
The image above shows Gabrielle as a category 4 hurricane on September 22.
Gabrielle did not directly impact any land areas as a tropical cyclone, but did make a direct hit on the Azores shortly after losing tropical characteristics.
A tropical wave entered the Atlantic ocean around September 12 and moved slowly westward over the next several days. It produced a significant amount of thunderstorm activity but remained quite disorganized. The system was eventually designated Tropical Depression Seven on September 17. At the time, it was a little past halfway from Africa to the Windward Islands. Despite achieving tropical depression status, the cyclone was still a mess, with almost all convection displaced east of the center. Furthermore, the center itself was a warring group of vorticies rotating around one another. Later that day, the center reformed further north, coaxed poleward by an upper-level low over the subtropics. The storm's winds also increased enough that it was upgraded to Tropical Storm Gabrielle.
Gabrielle evened out to a more steady west-northwest heading on the 18th and consolidated its circulation, but struggled to produce thunderstorm activity. For most of the day, it was little more than a naked swirl. That evening, it began to put up a better fight against westerly wind shear and storm activity blossomed in the eastern semicircle. Nevertheless, atmospheric conditions remained hostile through the next day. It was only on the 20th that shear lessened and Gabrielle was able to start intensifying again. The storm spent the next few days curving around the western edge of the subtropical ridge, first turning toward the north and toward the east. This path kept it east of Bermuda, too far to cause any direct impacts to the island. This was fortunate, because Gabrielle strengthened significantly.
On the 21st, it was upgraded to a hurricane. Shortly after that, the cyclone's satellite presentation improved markedly. An eye quickly cleared out and became more symmetric. Gabrielle vaulted to major hurricane strength by the morning of September 22. That afternoon it reached its peak intensity as a category 4 hurricane, with maximum winds of 140 mph and a central pressure of 948 mb. The storm accelerated toward the east-northeast and encountered gradually increasing wind shear as well as decreasing ocean heat content. This began a decaying trend, though it remained a significant hurricane.
Gabrielle began to lose tropical characteristics late on September 24 as the central core collapsed and it weakened to a category 1 hurricane. By this time, the storm was speeding eastward toward the central Azores. During the afternoon of September 25, a few hours before arriving at the islands, Gabrielle transitioned to a post-tropical cyclone. This did not prevent the cyclone from bringing strong winds, storm surge, and brief heavy rains to the Azores; during the storm's passage, hurricane-force gusts were recorded at sea level as well as hurricane-force sustained winds at higher elevations. A fully extratropical ex-Gabrielle exited the island chain toward the east by the next morning. Its remnants passed near the coast of Portugal before dissipating days later.
The image above shows Gabrielle as a category 4 hurricane on September 22.
Gabrielle did not directly impact any land areas as a tropical cyclone, but did make a direct hit on the Azores shortly after losing tropical characteristics.
Sunday, August 24, 2025
Tropical Storm Fernand (2025)
Storm Active: August 23-28
Around August 15, a tropical wave emerged off of the coast of Africa into the tropical Atlantic. During the next week, the modest tropical wave plodded west across the Atlantic. It exhibited some spin on satellite imagery, but never developed a closed circulation. The system veered northwest around the 20th and missed the Lesser Antilles to their northeast. Conditions turned more favorable in the subtropics and the disturbance finally was able to develop into Tropical Storm Fernand on August 23.
The storm battled some mid-level dry air over the next couple of days and moved northward into a weakness in the subtropical ridge, passing well east of Bermuda on the 24th. Fernand found the opportunity to intensify some that day and the next, though it never was a very symmetric tropical storm: the center remained on the northwest edge of the convection and the circulation appeared rather elongated on satellite imagery. Nevertheless, the storm's winds peaked at 60 mph on August 25.
Fernand turned northeast and began to weaken. Its thunderstorm activity evaporated as it moved over cooler water into a drier air mass. On the 26th, it moved over a warm eddy of the Gulf stream and rebounded enough to maintain tropical storm status, jogging eastward. This resurgence was short-lived, however. Soon Fernand crossed into much colder water and completed post-tropical transition early in the morning on August 28. Its remnants dissipated soon afterward.
The image above shows Fernand as a moderately strong tropical storm beset by shear over the subtropical Atlantic.
Fernand did not affect any land areas.
Around August 15, a tropical wave emerged off of the coast of Africa into the tropical Atlantic. During the next week, the modest tropical wave plodded west across the Atlantic. It exhibited some spin on satellite imagery, but never developed a closed circulation. The system veered northwest around the 20th and missed the Lesser Antilles to their northeast. Conditions turned more favorable in the subtropics and the disturbance finally was able to develop into Tropical Storm Fernand on August 23.
The storm battled some mid-level dry air over the next couple of days and moved northward into a weakness in the subtropical ridge, passing well east of Bermuda on the 24th. Fernand found the opportunity to intensify some that day and the next, though it never was a very symmetric tropical storm: the center remained on the northwest edge of the convection and the circulation appeared rather elongated on satellite imagery. Nevertheless, the storm's winds peaked at 60 mph on August 25.
Fernand turned northeast and began to weaken. Its thunderstorm activity evaporated as it moved over cooler water into a drier air mass. On the 26th, it moved over a warm eddy of the Gulf stream and rebounded enough to maintain tropical storm status, jogging eastward. This resurgence was short-lived, however. Soon Fernand crossed into much colder water and completed post-tropical transition early in the morning on August 28. Its remnants dissipated soon afterward.
The image above shows Fernand as a moderately strong tropical storm beset by shear over the subtropical Atlantic.
Fernand did not affect any land areas.
Wednesday, August 13, 2025
Hurricane Erin (2025)
Storm Active: August 11-22
On August 9, a strong tropical wave moved over the eastern Atlantic. The next day, it passed directly over Cabo Verde, bringing stormy conditions to the islands. It moved west-northwest away from the islands and became more organized over the next day. On August 11, the system was designated Tropical Storm Erin.
Erin's path was a little farther north than the deep tropics, putting it in an environment of drier air. This kept thunderstorm activity in check and prevented the storm from intensifying for the next few days. A strong ridge to the system's north steered Erin just south of west at a quick pace. By late on August 13, the storm's path brought it to warmer waters and a more favorable atmospheric environment. The storm began to strengthen and grow in size soon afterward, as well as slow down and turn toward the west-northwest. An inner core really began to take shape on the 15th, with large spiral bands extending well south and west of the center of circulation. That morning, Erin became the first hurricane of the 2025 Atlantic hurricane season.
Thunderstorms from Erin's outer edge reached the northeasternmost Caribbean islands that evening with the center still a few hundred miles distant. Overnight, an eye appeared on satellite imagery and explosive intensification began. Between 0000 UTC and 1200 UTC on August 16, Erin vaulted from a category 1 hurricane all the way to strong category 4 intensity. It also took a westward jog that morning, with the southern portion of the circulation brushing the Lesser Antilles. Fortunately, the center stayed a little more than 100 miles north of the islands, meaning that the worst conditions missed land.
The eye continued to become more symmetric as Erin deepened further. During the afternoon, the storm peaked as a category 5 hurricane, with sustained winds of 160 mph and a minimum central pressure of 915 mb. Erin became the earliest category 5 Atlantic hurricane to form outside the Caribbean and Gulf of Mexico on record. Also, Erin went from a tropical storm to a category 5 hurricane in just 25 hours, an unprecedented feat for an Atlantic hurricane. As is typical with hurricanes of this intensity, the storm experienced eyewall contraction a few hours after as an eyewall replacement began. The inner eye weakened and so did the storm's maximum winds, dropping it to category 3 intensity on August 17. However, Erin's eyewall replacement broadened its windfield signficantly over the following couple of days.
As the inner and outer eyewalls battled for dominance, the storm's forward movement also slowed. The expanding circulation brought rain bands across the Virgin Islands, Puerto Rico, and the Dominican Republic. By August 18, Erin was passing just northeast of the Turks and Caicos, close enough for the islands to experience tropical storm conditions. That same morning, a new, larger eye asserted itself, allowing the storm to deepen and restrengthen to category 4. Shortly after, however, wind shear increased significantly out of the north. This eroded the circulation to the point that the center was nearly exposed on the northern edge of the convection early on August 19. This caused Erin to weaken to a category 2. At the same time, a weakness in the ridge to the storm's north allowed it to turn northwest and then north.
The hurricane's structure changed yet again by August 20: slackening shear let Erin rebuild an inner core, and soon it had a symmetric eye again, surrounded by a compact inner core. Farther out was a massive second eyewall. The east side of the outer eyewall had some of the strongest winds in the system, despite its distance from the center! Because of this sprawling structure, Erin's peak winds did not increase that much and it remained just shy of major hurricane strength. However, it deepened significantly to a secondary minimum pressure of 941 mb on the 20th.
Soon after that, the large hurricane began to accelerate and recurve eastward into the mid-latitude westerlies. Fortunately, this allowed Erin to miss the east coast of the U.S., though rough surf and rip currents affected beaches over thousands of miles of coastline. Increasing shear and an encroaching front soon initiated extratropical transition. By the afternoon of August 22, Erin lost tropical characteristics south of Nova Scotia. The powerful cyclone continued to produce hurricane-force winds over the north Atlantic for the next several days before slowing weakening.
The image above shows Erin at peak intensity as a category 5 hurricane just north of the Leeward Islands on August 16.
This second image shows Erin's secondary pressure minimum of 941 mb on August 20 off of the U.S. east coast. Note how much larger the hurricane is compared to its earlier stages, as well as the concentric eyewall structure.
Erin's track brought it close enough to land to brush the Caribbean islands with gale force conditions. However, the powerful hurricane's core fortunately avoided land during its lifetime.
On August 9, a strong tropical wave moved over the eastern Atlantic. The next day, it passed directly over Cabo Verde, bringing stormy conditions to the islands. It moved west-northwest away from the islands and became more organized over the next day. On August 11, the system was designated Tropical Storm Erin.
Erin's path was a little farther north than the deep tropics, putting it in an environment of drier air. This kept thunderstorm activity in check and prevented the storm from intensifying for the next few days. A strong ridge to the system's north steered Erin just south of west at a quick pace. By late on August 13, the storm's path brought it to warmer waters and a more favorable atmospheric environment. The storm began to strengthen and grow in size soon afterward, as well as slow down and turn toward the west-northwest. An inner core really began to take shape on the 15th, with large spiral bands extending well south and west of the center of circulation. That morning, Erin became the first hurricane of the 2025 Atlantic hurricane season.
Thunderstorms from Erin's outer edge reached the northeasternmost Caribbean islands that evening with the center still a few hundred miles distant. Overnight, an eye appeared on satellite imagery and explosive intensification began. Between 0000 UTC and 1200 UTC on August 16, Erin vaulted from a category 1 hurricane all the way to strong category 4 intensity. It also took a westward jog that morning, with the southern portion of the circulation brushing the Lesser Antilles. Fortunately, the center stayed a little more than 100 miles north of the islands, meaning that the worst conditions missed land.
The eye continued to become more symmetric as Erin deepened further. During the afternoon, the storm peaked as a category 5 hurricane, with sustained winds of 160 mph and a minimum central pressure of 915 mb. Erin became the earliest category 5 Atlantic hurricane to form outside the Caribbean and Gulf of Mexico on record. Also, Erin went from a tropical storm to a category 5 hurricane in just 25 hours, an unprecedented feat for an Atlantic hurricane. As is typical with hurricanes of this intensity, the storm experienced eyewall contraction a few hours after as an eyewall replacement began. The inner eye weakened and so did the storm's maximum winds, dropping it to category 3 intensity on August 17. However, Erin's eyewall replacement broadened its windfield signficantly over the following couple of days.
As the inner and outer eyewalls battled for dominance, the storm's forward movement also slowed. The expanding circulation brought rain bands across the Virgin Islands, Puerto Rico, and the Dominican Republic. By August 18, Erin was passing just northeast of the Turks and Caicos, close enough for the islands to experience tropical storm conditions. That same morning, a new, larger eye asserted itself, allowing the storm to deepen and restrengthen to category 4. Shortly after, however, wind shear increased significantly out of the north. This eroded the circulation to the point that the center was nearly exposed on the northern edge of the convection early on August 19. This caused Erin to weaken to a category 2. At the same time, a weakness in the ridge to the storm's north allowed it to turn northwest and then north.
The hurricane's structure changed yet again by August 20: slackening shear let Erin rebuild an inner core, and soon it had a symmetric eye again, surrounded by a compact inner core. Farther out was a massive second eyewall. The east side of the outer eyewall had some of the strongest winds in the system, despite its distance from the center! Because of this sprawling structure, Erin's peak winds did not increase that much and it remained just shy of major hurricane strength. However, it deepened significantly to a secondary minimum pressure of 941 mb on the 20th.
Soon after that, the large hurricane began to accelerate and recurve eastward into the mid-latitude westerlies. Fortunately, this allowed Erin to miss the east coast of the U.S., though rough surf and rip currents affected beaches over thousands of miles of coastline. Increasing shear and an encroaching front soon initiated extratropical transition. By the afternoon of August 22, Erin lost tropical characteristics south of Nova Scotia. The powerful cyclone continued to produce hurricane-force winds over the north Atlantic for the next several days before slowing weakening.
The image above shows Erin at peak intensity as a category 5 hurricane just north of the Leeward Islands on August 16.
This second image shows Erin's secondary pressure minimum of 941 mb on August 20 off of the U.S. east coast. Note how much larger the hurricane is compared to its earlier stages, as well as the concentric eyewall structure.
Erin's track brought it close enough to land to brush the Caribbean islands with gale force conditions. However, the powerful hurricane's core fortunately avoided land during its lifetime.
Monday, August 4, 2025
Tropical Storm Dexter (2025)
Storm Active: August 3-7
At the beginning of August, a frontal system moved off of the U.S. east coast. A low pressure center formed along the front shortly after, not far from the coast of North Carolina. It moved steadily east-northeast away from land and soon detached from the front. Late on August 3, it had fully shed frontal characteristics, and was already producing gale force winds. Therefore, it was named Tropical Storm Dexter.
From the time of its formation, wind shear out of the west continually increased over Dexter, causing the center to be exposed on the western edge of the convective canopy. The westerly flow northwest of a subtropical ridge over the central Atlantic kept the storm on a steady, but not especially rapid, east-northeast heading. The marginal conditions ensured that Dexter did not strengthen much within the next couple of days. On August 6, the cyclone began to show signs of extratropical transition as shear increased further and the center became elongated. The next day, Dexter became extratropical. The storm actually achieved its peak winds as an extratropical cyclone, with sustained winds approaching hurricane strength as it moved out to sea over the North Atlantic.
Dexter was a sheared storm throughout its short stint as a tropical cyclone.
After forming near land, Dexter moved steadily out to sea.
At the beginning of August, a frontal system moved off of the U.S. east coast. A low pressure center formed along the front shortly after, not far from the coast of North Carolina. It moved steadily east-northeast away from land and soon detached from the front. Late on August 3, it had fully shed frontal characteristics, and was already producing gale force winds. Therefore, it was named Tropical Storm Dexter.
From the time of its formation, wind shear out of the west continually increased over Dexter, causing the center to be exposed on the western edge of the convective canopy. The westerly flow northwest of a subtropical ridge over the central Atlantic kept the storm on a steady, but not especially rapid, east-northeast heading. The marginal conditions ensured that Dexter did not strengthen much within the next couple of days. On August 6, the cyclone began to show signs of extratropical transition as shear increased further and the center became elongated. The next day, Dexter became extratropical. The storm actually achieved its peak winds as an extratropical cyclone, with sustained winds approaching hurricane strength as it moved out to sea over the North Atlantic.
Dexter was a sheared storm throughout its short stint as a tropical cyclone.
After forming near land, Dexter moved steadily out to sea.
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