Hurricane Ashley formed on June 12 while located south of the Hoenn region. The system headed east and was named Tropical Storm Ashley the next day. Ashley steadily strengthened, and reached hurricane strength on June 14. On the 15th, Ashley reached Category 2 intensity and began to rapidly intensify and reached its peak intensity of 150-mph the next morning. It began to slowly weaken until it passed Four Island when it began to rapidly weaken. On June 19, Ashley degenerated into a tropical wave. Four days later, the remnants of Ashley regenerated into a tropical storm while located off the coast of Sinnoh. The storm remained stationary for 18 hours, before turning and making landfall in the Eterna Forest. Ashley became extratropical later that day as it was passing the Battle Frontier. Ashley was the strongest June hurricane recorded in two decades.
Hurricane Brandon
Hurricane Brandon
1
Duration
June 18—June 19
Intensity
80 mph, 985 mbar
Tropical Depression Two formed on June 18, just south of Cianwood City. Three hours later, it was upgraded to Tropical Storm Brandon. Brandon was forecast to cross Cianwood City as a moderate tropical storm with 50-mph winds. Four hours after being upgraded to a tropical storm, radar from Cianwood City indicated that Brandon was a stronger tropical storm with 60-mph. At this point, Brandon was forecast to cross Cianwood City as a 70-mph tropical storm. That night, Brandon became the second hurricane of the season just before moving over Cianwood City. Brandon briefly weakened to a tropical storm over the Whirl Islands. The weakening was only temporary, and Brandon was upgraded to a hurricane again shortly after. Brandon made landfall on Route 47 shortly before noon on June 19. Brandon rapidly weakened and dissipated twelve hours later.
Tropical Storm Claire
Tropical Storm Claire
TS
Duration
June 20—June 21
Intensity
70 mph, 987 mbar
Claire formed from a previously non-tropical low pressure area on June 20, just south of the Orre region. Claire slowly moved north toward Pyrite Town and was forecast to reach the area as a minimal hurricane. Claire made landfall shortly before 6 AM on June 21 just below hurricane strength. Claire dissipated later that day.
Hurricane Dexter
Hurricane Dexter
1
Duration
June 22—June 23
Intensity
85 mph, 985 mbar
Dexter formed on June 22 while located southwest of Fuschia City. The storm quickly strengthened and made landfall the next day with winds of 85-mph just west of Fuschia City.
Hurricane Eliza
Hurricane Eliza
4
Duration
August 31—September 3
Intensity
145 mph, 920 mbar
Eliza was the first storm to form since Dexter over two months prior. Eliza began to explosively strengthen shortly after being designated a tropical storm. Only six hours after forming, Eliza was upgraded to a hurricane. Six hours after that, it was upgraded to a major hurricane. Eliza ended its rapid strengthening after reaching 125-mph. The next morning, Eliza was upgraded to a Category 4 hurricane with 145-mph. Two hours later, Eliza moved over Cinnabar Island. Interaction with the island weakened the storm to a Category 2 hurricane. After moving into the Vermilion Bay, Eliza re-strengthened into a 125-mph hurricane, which it maintained until making landfall near Vermilion City. Eliza dissipated over the northern Kanto region on September 3.
Hurricane Fergus
Hurricane Fergus
5
Duration
September 1—ongoing
Intensity
185 mph, 891 mbar
Fergus formed on September 1 in the Southern Seas far away from land. The system was heavily impacted by wind shear and dissipated that night. The remnant circulation continued on for over a week until it regenerated south of the Hoenn region on September 9. Fergus was in a favorable environment and rapidly intensified, becoming a Category 2 hurricane only 30 hours after reforming. Fergus strengthened even further to a 125-mph Category 3 hurricane as it passed Sootopolis City on September 11. Later that day, Fergus began to rapidly intensify again, and reached Category 5 intensity and made a shift in track and was now threatening Lilycove City. Fergus continued to strengthen on the 12th, and peaked at 185-mph. As of 8 PM EDT, Fergus is a Category 4 hurricane with 145-mph winds and is expected to reach Lilycove City tomorrow night as a Category 3 or 4 hurricane.
Tropical Storm Gina
Tropical Storm Gina
TS
Duration
September 1—September 3
Intensity
50 mph, 1004 mbar
Gina was the last of three systems that formed within 24 hours in late August/early-September (following Eliza and Fergus). Gina was forecast to strike the western Hoenn region, but remained stationary offshore, and dissipated on September 3.
Hurricane Hank
Hurricane Hank
2
Duration
September 10—ongoing
Intensity
100 mph, 984 mbar
Tropical Storm Irma
Tropical Storm Irma
TS
Duration
September 11—September 12
Intensity
60 mph, 1000 mbar
Irma formed on September 11 from a trough of low pressure located south of Azalea Town. Irma moved northeast slowly strengthening to its peak intensity of 60-mph, which it held until landfall in Cherrygrove City on September 12. Irma quickly weakened as it moved inland and was downgraded to a tropical depression only two hours after making landfall.
Tropical Storm Jason
Tropical Storm Jason
TS
Duration
September 12—ongoing
Intensity
60 mph, 991 mbar
Jason formed as a subtropical storm on the evening of September 12 while located south of Almia. Jason quickly gained tropical characteristics later that night and as of 10 PM EDT, it has winds of 60-mph and is expected to reach Almia sometime later tonight. 
Accumulated Cyclone Energy (ACE) Rating
ACE (104kt²) (Source) — Storm:
1
Ashley
20.7
6
Claire
1.44
2
Fergus
18.8
7
Dexter
1.37
3
Eliza
10.5
8
Irma
1.06
4
Hank
2.78
9
Gina
0.607
5
Brandon
1.95
10
Jason
0.250
Total: 59.2
The table on the right shows the ACE for each storm in the season. ACE is, broadly speaking, a measure of the power of the hurricane multiplied by the length of time it existed, so storms that last a long time, as well as particularly strong hurricanes, have high ACEs. ACE is calculated for only full advisories on tropical systems at or exceeding 34 knots (39 mph, 63 km/h) or tropical storm strength. Subtropical cyclones are not included in the ACE, and as a result, Jason's ACE only represents time spent as a tropical cyclone.
Storm names
The following names were used to name storms that formed in 2010. The names not retired from this list will be used again in the 2012 season. Names not assigned are marked in gray.
Ashley
Brandon
Claire
Dexter
Eliza
Fergus (active)
Gina
Hank (active)
Irma
Jason (active)
Kayla (unused)
Lucius (unused)
Marianne (unused)
Nasser (unused)
Orla (unused)
Patrick (unused)
Rachel (unused)
Sylvester (unused)
Tiffany (unused)
Vance (unused)
Wynette (unused)
Retirement
Any retired names will be announced in January 2011.