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Global Tropical Cyclone Activity

2013 Activity Updates

Ryan N. Maue, PhD

Global Tropical Cyclone Activity Update

Active Storms / Invests = 8

BasinNameCurrent Wind Max WindACE

Page decommissioned and moved to WeatherBELL Models Link
Data File: Atlantic ACE per storm (1950-2012) and README
September 12, 2013 : Large monsoon depression at 20N in the West Pac may reach typhoon strength prior to recurving just off the Japanese coast near Tokyo. Another storm will follow but not recurve yet threaten Taiwan and China after 7-days.
September 5, 2013 : TS Gabrielle has fallen apart, lasting 12-hours. To avoid a rare day in early September w/o any Northern Hemisphere tropical cyclone activity, TD 12E has organized off the Mexican coast in the Eastern Pacific. The West Pac looks quiet for next week.
September 2, 2013 : Tropical Storm Kiko nearly became a hurricane but has now quickly degenerated into a remnant low. The only Northern Hemisphere tropical cyclone is currently Tropical Storm Toraji (15W) which seems destined for Kyushu Japan. The tropical wave in the Atlantic (97L) has deteriorated into an elongated trough.
August 28, 2013 : Tropical Storm Juliette forms near tip of Baja California and will drift NW
August 27, 2013 : The North Atlantic season is active with the number of named tropical storms but they are not becoming hurricanes. The ACE of 8 through August 28 is historically pretty slow on par with 2002. 14W Kong-Rey is battling shear but may become a weak typhoon before moving into the midlats.
August 21, 2013 : Typhoon Trami made landfall in China as a 75-knot storm. Invest 94E looks primed to become Hurricane Ivo and travel parallel but west of Baja California.
August 18, 2013 : Pacific got busy. Central Pacific may have a trio evolve out of disturbances well south and SW of Hawaii. Two have been named with Pewa looking like a strong typhoon with well-defined eye (in the West Pac area of responsibility) and TS Unala which looks ragged.
August 15, 2013 : Tropical Storm Erin (05L) formed near the Cape Verdes Islands where it will travel WNW over marginal SSTs. While it may become a small hurricane, it will only bother shipping.
August 11, 2013 : Super Typhoon Utor (11W) may have peaked at 130-140 knots as it approaches Luzon.
August 10, 2013 : Typhoon Utor (11W) has rapidly intensified.
August 8, 2013 : Hurricane Henriette is shrinking but has developed a well-defined eye at 85 knots. Nothing in the Atlantic looks imminent. Next Western Pacific storm well east of the Philippines is consolidating and will move westward where it will likely become a strong tropical storm before landfall in Luzon.
July 31, 2013 : TS Gil & perhaps Henriette join 09W (Jebi) to finish off July
July 29, 2013 : Tropical Storm Flossie is forecast to move over the Big Island of Hawaii and the 13k+ foot peaks of Mauna Loa & Mauna Kea. Even though SSTs increase along the track to the west, there's not going to be much of a coherent circulation left. GFS model shows a series of long-track Eastern Pacific storms in the coming 2-weeks.
July 25, 2013 : TD 06E should become Tropical Storm Flossie and move WNW toward Hawaiian Islands.
July 24, 2013 : Tropical Storm Dorian (04L) has formed -- the second Cape Verdes Island origin storm prior to August. The storm will race westward beneath a strong ridge.
July 17, 2013 : Tropics mostly quiet with only Tropical Depression 08W just passing north of the Philippines.
July 11, 2013 : Typhoon Soulik battling dry air as well as passing over a cold eddy of much less ocean heat content. The typhoon has a very large wind field and will impact Taiwan Friday.
July 7, 2013 : Erick quickly weakening over cooler SSTs near Baja California tip. TD 07W formed with huge area of convection and all signs point to a strong typhon by Thursday nearing Taiwan. An African easterly wave (AEW) racing across the Atlantic is 60% likely to become a depression (95L).
July 5, 2013 : Tropical Storm Erick 05E in East Pac has rapily strengthened near the coast of Mexico and will become a hurricane, perhaps near major strength.
June 29, 2013 : TD 04E is expected to become Tropical Storm Dalila Sunday, June 30th and may become a hurricane as it turns west & away from the Mexican coast.
June 28, 2013 : Tropical Storm Rumbia (06W) developed just prior to landfall in the Philippines.
June 27, 2013 : Cosme has degenerated over cool SSTs into a remnant low. Invest 99W in Western Pacific looks like the next candidate for TC development during the next several days.
June 25, 2013 : Hurricane Cosme may have peaked around 75 knots as it moves west away from land (Baja California)
June 24, 2013 : Convection around center of TS Cosme has exploded. May need to up the maximum intensity estimate if an eyewall can form. Cosme has 36-48 hours over warm SST (>26C) before slowly winding down.
June 23, 2013 : TD-03E in the Eastern Pacific is a large, slowly organizing system that will struggle to become a hurricane. Nothing else in the tropics.
June 21, 2013 : Tropical Storm Bebinca has been upgraded from TD05W in the South China Sea.
June 20, 2013 : Tropical Storm Barry quickly made landfall in Mexico. Active MJO signal over EPAC & Central America should produce one or more tropical cyclones in the EPAC with some models generating binary or multiple vortices coalescing into a strong hurricane. TD 05W was upgraded from 94W and forecast to track into China in 3-days but likely not making typhoon strength.
June 19, 2013 : TD 02L has re-emerged over the Bay of Campeche and is likely to become Tropical Storm Barry. In the Western Pacific, Tropical Storm Leepi (04W) is forecasted to recurve slowly well south of Japan but fail to make Typhoon status (64-knots). Another Invest 94W is slowly organizing in the South China Sea and models develop a depression in two days.
June 17, 2013 : Area of convection east of the Philippines has finally consolidated around a large center of circulation to become Tropical Depression 04W. JTWC guidance brings it to TS status (Leepi) while recurving SE of Japan. Tropical Depression 02L made landfall in Belize and may emerge in the Bay of Campeche although ECMWF guidance keeps circulation over land.

2013 Northern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (ATCF operational intensity estimates, knots)

North Atlantic
2013 Season
Andrea 01L (55 ACE = 1.32)
Barry 02L (40 ACE = 0.565)
Chantal 03L (55 ACE = 2.045)
Dorian 04L (50 ACE = 2.62)
Erin 05L (35 ACE = 1.1025)
Fernand 06L (50 ACE = 0.6975)
Gabrielle 07L (50 ACE = 1.6725)
Eight 08L (30 ACE = 0.0)
Humberto 09L (75 ACE = *)
Ingrid 10L (* ACE = *)
Jerry, Karen, Lorenzo
Melissa, Nestor, Olga, Pablo
Rebekah, Sebastien, Tanya, Van, Wendy
Western North Pacific
2013 Season
Sonamu 01W (45 ACE = 2.59)
Shanshan 02W (25 ACE = 0.0)
Yagi 03W (55 ACE = 2.5825)
Leepi 04W (35 ACE = 1.1025)
Bebinca 05W (35 ACE = 0.49)
Rumbia 06W (65 ACE = 3.67)
Soulik 07W (125 ACE = 19.1925)
Cimaron 08W (40 ACE = 0.885)
Jebi 09W (60 ACE = 2.57)
Mangkhut 10W (40 ACE = 0.65)
Utor 11W (130 ACE = 17.675)
Trami 12W (75 ACE = 5.195)
TD13 13W (30 ACE = 0.0)
Kong-Rey 14W (55 ACE = 2.975)
Toraji 15W (50 ACE = 1.5925)
Man-yi 16W (* ACE = *)
Usagi, Pabuk, Wutip, Sepat
Fitow, Danas, Nari, Wipha
Francisco, Lekima, Krosa, Haiyan
Podul, Lingling, Kajiki, Faxai
Peipah, Tapah, Mitag, Hagibis
Neoguri, Rammasun, Matmo, Halong
East & Central Pacific
2013 Season
Alvin 01E (45 ACE = 1.0925)
Barbara 02E (65 ACE = 1.3475)
Cosme 03E (75 ACE = 4.3025)
Dalila 04E (70 ACE = 6.44)
Erick 05E (70 ACE = 5.135)
Flossie 06E (60 ACE = 4.1275)
Gil 07E (75 ACE = 6.3125)
Henriette 08E (90 ACE = 11.1275)
Pewa 01C (65 ACE = 6.065)
Unala 02C (35 ACE = 0.245)
Ivo 09E (40 ACE = 0.725)
Juliette 10E (45 ACE = 0.6075)
Kiko 11E (60 ACE = 1.7575)
Lorena 12E (40 ACE = 0.9325)
Manuel 13E (* ACE = *)
Narda, Octave, Priscilla
Raymond, Sonia, Tico, Velma
Wallis, Xina, York, Zelda
N. Indian & Arabian Sea
2013 Season
Mahasen 01B (50 ACE = 5.3775)
Phailin, Helen, Lehar
Madi, Na-nauk, Hudhud, Nilofar

2012-13 Southern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (ATCF operational intensity estimates, knots)

South Indian
2012-13 Season
Anais 01S (110 ACE = 12.0275)
Boldwin 02S (55 ACE = 1.785)
Claudia 03S (110 ACE = 16.275)
Dumile 07S (75 ACE = 6.53)
Emang 09S (35 ACE = 2.3275)
Felleng 13S (115 ACE = 16.1925)
Gino 15S (90 ACE = 9.9425)
Haruna 16S (100 ACE = 10.9975)
Imelda 21S (85 ACE = 11.885)
Jamala 24S (45 ACE = 1.94)
Jamala, Kachay, Luciano, Mariam
Njazi, Onias, Pelagie, Quiliro
Richard, Solani, Tamim, Urilia
Vjyane, Wagner, Xusa, Yarona, Zacarias
Australia Region
Mitchell 06S (45 ACE = 1.21 )
Narelle 08S (115 ACE = 18.6375 )
Oswald 11S (35 ACE = 0.3675 )
Peta 12S (35 ACE = 0.6125 )
Rusty 17S (95 ACE = 7.9325* )
Eighteen 18S (40 ACE = 1.375* )
Sandra 19P (115 ACE = 14.0775 )
Tim 20P (55 ACE = 2.8375 )
Victoria 22S (80 ACE = 4.04 )
Zane 23P (60 ACE = 2.19 )
Alessia, Bruce, Christine
Dylan, Edna, Fletcher, Gillian, Hadi
South Pacific
Evan 04P (125 ACE = 25.9075)
Freda 05P (100 ACE = 11.6025)
Garry 10P (85 ACE = 7.955)
Haley 14P (50 ACE = 1.2625)
Ian, June, Kofi, Lusi, Mike
Nute, Odile, Pam, Reuben, Solo
Tuni, Ula, Victor, Winston, Yalo, Zena


2012 Northern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (ATCF operational intensity estimates, knots) 2012 ACE=536

North Atlantic (ACE: 132.6325)
2012 Season (prelim)ACE=131
HURDAT 2012 Official Tracks
May 2012
Alberto (50 ACE = 1.87)
Beryl (60 ACE = 2.49)
June 2012
Chris (75 ACE = 4.085)
Debby (55 ACE = 2.7575)
August 2012
Ernesto (80 ACE = 8.4975)
Florence (50 ACE = 1.5125)
Helene (40 ACE = 0.2825)
Gordon (95 ACE = 8.645)
Isaac (70 ACE = 10.355)
Joyce (35 ACE = 0.245)
Kirk (90 ACE= 7.7425)
Leslie (70 ACE= 16.2825)
Michael (100 ACE = 16.6975)
Nadine (80 ACE = 26.34)
Oscar (45 ACE = 1.455)
Patty (40 ACE = 1.0925)
Rafael (80 ACE = 7.4)
Sandy (100 ACE = 13.6675)
Tony (45 ACE = 1.215)
Valerie, William
Western North Pacific
2012 Season ACE=300.8
JTWC 2012 Official Tracks
March 2012
01W (30 ACE = 0.0)
Parkhar (60 ACE = 3.325)
May 2012
Sanvu (80 ACE = 8.5275)
Mawar (105 ACE = 11.0625)
June 2012
Guchol (130 ACE = 23.3225)
Talim (50 ACE = 1.8275)
Doksuri (40 ACE = 0.97)
July 2012
Khanun (55 ACE = 2.255)
Vicente (115 ACE = 5.14)
Saola (90 ACE = 8.3975)
Damrey (80 ACE = 5.725)
Haikui (65 ACE = 5.705)
Kirogi (45 ACE = 2.595)
Kai-Tak (65 ACE = 5.8125)
Tembin (120ACE = 30.2)
Bolaven (125 ACE = 28.1)
Sanba (155 ACE = 26.505)
Jelawat (140 ACE = 45.96)
Ewiniar (55 ACE = 4.225)
Maliski (45 ACE = 1.8225)
Gaemi (55 ACE = 3.5075)
Prapiroon (105 ACE = 23.19)
Maria (55 ACE = 3.815)
Son-Tinh (110 ACE = 9.59)
25W (30 ACE = 0.0)
Bopha (150 ACE = 38.825)
Wukong (35 ACE = 0.3675)
Shanshan, Yagi, Leepi, Bebinca
Eastern Pacific
2012 Season Best Track ACE=98.5
ATCF real-time ACE: 95.2
May 2012
Aletta (45 ACE = 1.4975)
Bud (100 ACE = 7.9025)
June 2012
Carlotta (95 ACE = 3.5925)
July 2012
Daniel (95 ACE = 11.58)
Emilia (120 ACE = 18.5625)
Fabio (95 ACE = 10.7475)
August 2012
Gilma (70 ACE = 4.825)
Hector (45 ACE = 2.2225)
Ileana (75 ACE = 6.99)
John (40 ACE = 0.81)
Kristy (50 ACE = 3.1325)
Lane (75 ACE = 4.43)
Miriam (105 ACE = 9.7525)
Norman (40 ACE = 0.6875)
Olivia (50 ACE = 1.9375)
Paul (105 ACE = 7.0775)
Rosa (45 ACE = 2.745)
Sergio, Tara, Vicente
Willa, Xavier, Yolanda, Zeke
N. Indian & Arabian Sea
2012 Season ACE=4.135
JTWC 2012 Official Best Tracks
Murjan (35 ACE = 0.6125)
Nilam (55 ACE = 2.1725)
03B (35 ACE = 0.6125)
04A (35 ACE = 0.735)
Mahasen, Phailin
Helen, Leher, Madi, Na-nauk
Hudhud, Nilofar, Priya, Komen

2011-12 Southern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (ATCF operational intensity estimates, knots) ACE = 155.89

JTWC Best Tracks ACE: 148.2625
Australia Region 90o - 160oE
December 2011
03S Grant (60 ACE = 1.2125)
January 2012
06S Heidi (65 ACE = 1.95)
09S Iggy (70 ACE = 9.225)
February 2012
10S Jasmine (115 ACE = 22.055)
March 2012
16S Koji-Joni (75 ACE = 6.19)
17S Lua (95 ACE = 8.1625)
May 2012
19S (30 ACE = 0.0)
Narelle, Oswald, Peta
South Indian 30o - 90oE
December 2011
01S Alenga (95 ACE = 6.38)
02S Two (35 ACE = 0.3675)
04S Benilde (90 ACE = 12.0425)
January 2012
05S Chanda (35 ACE = 0.3675)
Dando (used by Reunion)
07S Ethel (70 ACE=4.6675)
08S Funso (115 ACE=33.3675)
February 2012
12S Giovanna (120 ACE=25.6775)
13S Hilwa (40 ACE = 3.165)
14S Irina (60 ACE=8.1825)
15S (35 ACE=0.49)
June 2012
20S Kuena (55 ACE= 1.33)
South Pacific 160oE - 120oW
February 2012
Cyril (55 ACE = 1.6425)
April 2012
Daphne (55 ACE = 1.5425)
June 2012
21P (35 ACE = 0.245)
Freda, Garry, Heley
Ian, June, Kofi

This page chronicles recent global tropical cyclone activity during the past 5-years and provides historical context for recent and ongoing tropical cyclones -- based upon peer-reviewed research.

Year to Date North Atlantic ACE

Year to Date ACE Matrix for North Atlantic from 1944-2011 -- Data File

August 19, 2012: Northern Hemisphere tropics ramps up considerably during the next several weeks with the Pacific and Atlantic often seeing multiple storms.

August 1, 2012: Graphics updated for July. A total of 8 tropical cyclones occurred all in the Northern Hemisphere, Pacific Ocean.

June 17, 2012: Super Typhoon Guchol likely reached 140 knots and the post-season analysis will adjust accordingly (at least it should). The final ACE will tally around 27 or 28 probably putting Guchol in the top 5 of the year for the Northern Hemisphere. WP92 will be the 6th Western Pacific depression and be named Talim -- in the South China Sea prior to recurvature over Japan.

June 12, 2012: Tropical Storm Guchol (05W) has slowly developed in the Western Pacific and will pass northeast of Yap on its way to Japan post-recurvature. The Eastern Pacific is poised to see maybe one or two storms due to the arriving MJO convective signal.

June 6, 2012: A rather rare June tropical cyclone developed in the Southern Indian Ocean named Kuena. Elsewhere, Typhoon Mawar has transitioned to an extratropical cyclone and likely intensified slightly from its minimum tropical stage pressure when it was 100 knots. Obviously, the background or environmental pressure is much lower in the extratropics, so comparisions are not so applicable.

June 1, 2012: May saw 6 global tropical cyclones including 2 of hurricane strength and Major Hurricane Bud in the Eastern Pacific. The average of the last 42 years is 3 storms and 1 and 2 hurricanes.

May 28, 2012: Beryl made landfall just shy of hurricane strength. An outbound aircraft recon report of 80 knots at 5,000 feet supported hurricane strength but the post-season analysis can hash that out. Many storms have been retroactively upgraded to hurricane strength, e.g. Gaston (2004), after the season is over. Tropics look quiet elsewhere as Sanvu and Bud are gone.

May 26, 2012: May is typically quiet across the entire global tropics, but we have seen several storms. Subtropical Storm Beryl will have trouble dealing with dry air and not strengthen too much in a tropical mode. Major Hurricane Bud made landfall as a weak tropical storm in SE Mexico. Its moisture will spread over Texas Rio Grande and temper the 105F heat only marginally.

May 18, 2012: Aletta has come and gone. Perhaps another storm in the Eastern Pacific. Typically the WestPac is more active, but probably not this year.

May 8, 2012: Updated frequency and ACE graphics for April. The only storm was Daphne in the Southern Hemisphere.

May 7, 2012: TS 19S in the near-equatorial waters of N. Australia did not last very long.

May 3, 2012: Nothing doing anywhere.

April 23, 2012: April is shaping up to be a very quiet month -- as expected. It is the quietest global TC month usually.

April 16, 2012: New normal? Historical context of recent global tropical cyclone inactivity 30th AMS Tropical Meteorology Conference. Abstract and PowerPoint Presentation

April 11, 2012: Tropics all quiet.

12 :|: 6 :|: 3

WeatherBell Analytics North Atlantic Hurricane Forecast

April 5, 2012: North Atlantic Hurricane Season forecasts have been put out by WeatherBell and Colorado State (Drs. Gray and Klotzbach). The idea is that a weak El Nino will limit storm numbers and overall intensity. A total of 10-tropical storms is expected including 5 hurricanes and 2 majors. Seems reasonable but I would hedge towards both more storms and hurricanes simply as a persistence forecast due to the uncertainty in the type of El Nino during the boreal summer and fall.

Figure: Historical North Atlantic tropical storm and major hurricane frequency since 1970 from the HURDAT best-track dataset. Since 1970, there have been 465 tropical storms including 102 major hurricanes (22%). Since 1995, the ratio is slightly higher (26%) or 64 major hurricanes out of a total of 250 storms. Data File

Figure: Historical North Atlantic tropical storm Accumulated Cyclone Energy (ACE) since 1970 from the HURDAT best-track dataset. It is clear from the ACE metric that the active-era since 1995 in the Atlantic is well described with a marked step increase. This is partially due to a preponderance of long-lived Cape Verde origin major hurricanes that have higher intensity and longer duration which means more ACE. ACE is the convolution or sum of the reported wind speed squared (in knots) over the lifetime of the storm. Data File

March 2012: Another record falls... La Nina causes record suppression of global tropical storm numbers ...

The last two calendar years saw a total of 146 global tropical cyclones, the lowest 2-year total in records since at least 1970. In the past 24-months, including ongoing Southern Hemisphere tropical cyclone activity, there have been a total of 141 global tropical storms. This is also a record low.

March 31, 2012: Graphics updated through March 2012.

March 29, 2012: Pakhar has formed in the South China Sea and may reach typhoon strength prior to landfall in Vietnam on April 1

March 27, 2012: Updating the files with JTWC best-tracks. Sarika (WP05) and Banyan (WP23) no longer met the threshold of tropical storm strength and will be dropped from my global frequency statistics. Thus, calendar year 2011 looks to have had 75 storms, subject to the inclusion of the Southern Hemisphere 2011-12 best-tracks. Western Pacific basin ACE for 2011 was 189, which was well below normal for the year -37%

March 26, 2012: Nothing brewing as March comes to an end. Global tropical cyclone frequency remains well below the 30-year average and shows no sign of recovering. Until the Northern Hemisphere cyclone season ramps up in June or July, global TC activity should remain rather quiet.

March 17, 2012: TC Lua made landfall as a 90 knot storm, just below major hurricane intensity. It has since quickly dissipated over the desert regions of W. Australia. The Southern Hemisphere 2011-12 season is quickly waning, with about 20% of the seasonal ACE left to be accounted for, on average. To date, the SH season is slighly below normal in terms of ACE with a total of 17 named tropical cyclones.

March 17, 2012: Proving that even 3 to 5 day forecasts of tropical cyclogenesis or formation are still tricky, nearly-major tropical cyclone Lua (17S) is poised to make landfall as a powerful storm along Australia's NW coast

March 11, 2012: Koji is rapidly spinning down over the central SIO. Elsewhere, no named systems for a while.

February 29, 2012: The Southern Hemisphere saw 5-storms and Madagascar was the focus in the SW Indian Ocean. The previous 12-month total is 74 global tropical cyclones, which is well below the climatological average. March is typically active in the South Pacific, but who knows with the waning La Nina.

February 26, 2012: Total of 4-storms so far for the month, with the likelihood of another couple in the southern Indian Ocean near Madgascar. The SW IO is the focus for 2012...

February 15, 2012: New paper in J. Climate by Jessica Weinkle, Ryan Maue, and Roger Pielke Jr.: "Historical global tropical cyclone landfalls."

In recent decades, economic damage from tropical cyclones (TCs) around the world has increased dramatically. Scientific literature published to date finds that the increase in losses can be explained entirely by societal changes (such as increasing wealth, structures, population, etc) in locations prone to tropical cyclone landfalls, rather than by changes in annual storm frequency or intensity. However, no homogenized dataset of global tropical cyclone landfalls has been created that might serve as a consistency check for such economic normalization studies. Using currently available historical TC best-track records, we have constructed a global database focused on hurricane-force strength landfalls. Our analysis does not indicate significant long-period global or individual basin trends in the frequency or intensity of landfalling TCs of minor or major hurricane strength. This evidence provides strong support for the conclusion that increasing damage around the world during the past several decades can be explained entirely by increasing wealth in locations prone to TC landfalls, which adds confidence to the fidelity of economic normalization analyses.

See more at: Pielke Jr. Blog Write up

February 10, 2012: Giovanna has explosively intensified. Through February 10, 2012: Southern Hemisphere ACE is 74 -- compared to a climatological value of 97 expected during the Southern Hemisphere Tropical Cyclone season to-date (~October to April). Thus, SH ACE is about 25% below normal but within the bounds of one-standard deviation.

February 9, 2012: The Southern Hemisphere is quite active with several storms when the NWP guidance showed nothing substantial a week ago. Giovanna will rapidly intensify at some point and threaten Madagascar as a potent perhaps Category 4+ tropical cyclone on Monday, February 14.

February 7, 2012: Jasmine has indeed reached 105 knots maximum intensity and is a strong Category 3 tropical cyclone.

February 6, 2012: Jasmine and Cyril sprouted in the South Pacific. The former may reach major strength as a nice eyewall has formed at the center of the rather small system. Cyril is nearing much colder water and will not last very long.

February 3, 2012: Tropics very quiet

February 1, 2012: Will update the monthly graphics to include the Southern Hemisphere TC activity during January, which was about average with intense TC Funso accounting for much of the TC ACE during the month. With 09S.IGGY slowly spinning down offshore of Australia, numerical models show a quiet first week of February ahead for global tropical cyclones.

January 25, 2012: Tropical Cyclone Funso is slowly progressing southward through the Mozambique channel. It likely reached a maximum intensity of at least 130-135 knots, even though the operational intensity estimates maxed out at 120 knots. I saw some T-numbers of over 7. SH09 has formed and will quickly strengten. Convective temperatures (cold-cloud tops) went off the color-bar. Very impressive. I think it will be named Iggy since the storm is in the Australian Region. However, landfall as a significant tropical cyclone is unlikely.

January 22, 2012: So far January has seen 4 tropical cyclones putting the last 12-month's total at 74, which is trending downwards. The period January-December 2011 saw 77 tropical cyclones globally, continued quite below normal.

January 19, 2012: Two potentially strong Southern Indian Ocean storms are quickly strengthening: Ethel and Funso. Funso (SH08) will likely meander off the coast of Mozambique for the next 5-days and may make landfall as a very intese tropical cyclone.

January 11, 2012: Chanda and Heidi brought rain and wind but remained tropical storms in the Southern Hemisphere. ECMWF has Chanda taking a westward turn back around Madagascar towards the African coast. SSTs are warm enough to regenerate the cyclone. Little other activity is forecast in the global tropics through 10-days

December 25, 2011: Burst of TC activity on both sides of the equator to end 2011. One cyclone in the Bay of Bengal has the potential to develop into a hurricane-force storm prior to landfall in India. TC Grant in the Gulf of Carpentaria will likely remain disorganized due to proximity to land although the sea-surface is very warm.

December 21, 2011: First day of winter in the NH means the first day of summer in the SH. So far December has been quiet in the Southern Indian and Pacific Ocean basins, which have very warm sea-surface temperatures conducive for strong TC development. A total of 3-storms have been observed globally including Washi, Angela, and 02S. Year end totals for 2011 will be posted next week.

December 6, 2011: The first cyclone of the Southern Hemisphere season was born: Angela. It will remain out to sea and may be joined by Invest 98, unless it's not.

December 1, 2011: The official end of the North Atlantic hurricane season:

Total number of storms was exceptional (19) with 7 hurricanes and 3 major storms. Not so much outside of the Atlantic...

Statement concerning Irene made on August 27, 2011: The mainstream media has wondered in many recent articles if "global warming" is making hurricanes stronger or perhaps made Irene stronger. As Dr. Kerry Emanuel pointed out -- that question is irrelevant. It is the number of intense hurricanes that actually make landfall that is societally important. However, from a scientific point of view, it is a good idea to recognize that the population of "major" global hurricanes has not increased since 1979. Thinking of the Figure as a stock market ticker, there are always ups and downs, recessions and depressions in activity. But, the overall trend is flat proving conclusively that there is NO "overall" global increase in hurricanes, minor or major. Since natural variability such as El Nino and La Nina is the primary driver of global hurricane variability, any discussion of "climate change" impacts on TCs is woefully incomplete without acknowledging the effects of ENSO on global TC activity. The North Atlantic basin is seemingly special -- in that the current "active-period" since about 1995 has not necessarily manifested itself elsewhere -- and scientists are still unsure of why. Tropical cyclone and climate change science is far from settled, and any conjecture about global warming impacts can be argued from both sides of the aisle in a civil manner without resorting to personal, political attacks.

Most Recent Peer-Reviewed Literature

Maue (2011) Recent historically low global tropical cyclone activity: (published June 2011)

Geophys. Res. Lett. (2011, in press PDF )


Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the evolution of the character of observed large-scale climate mechanisms including the El Nino Southern Oscillation and Pacific Decadal Oscillation. In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE.

Historical Tropical Cyclone Activity Graphics

Figure: Global Hurricane Frequency (all & major) -- 12-month running sums. The top time series is the number of global tropical cyclones that reached at least hurricane-force (maximum lifetime wind speed exceeds 64-knots). The bottom time series is the number of global tropical cyclones that reached major hurricane strength (96-knots+). Adapted from Maue (2011) GRL.

Figure: Last 4-decades of Global and Northern Hemisphere Accumulated Cyclone Energy: 24 month running sums. Note that the year indicated represents the value of ACE through the previous 24-months for the Northern Hemisphere (bottom line/gray boxes) and the entire global (top line/blue boxes). The area in between represents the Southern Hemisphere total ACE.
1970- Sept 2012 monthly ACE Data File (Maue, 2010, 2011 GRL) [--] 1970- Sept 2012 global tropical cyclone frequency monthly Data File

Figure: Last 4-decades of Global Tropical Storm and Hurricane frequency -- 12-month running sums. The top time series is the number of TCs that reach at least tropical storm strength (maximum lifetime wind speed exceeds 34-knots). The bottom time series is the number of hurricane strength (64-knots+) TCs.

Global tropical cyclone power dissipation index

Figure: Global and Northern Hemisphere Power Dissipation Index (Emanuel 2005) 1970-2011: 24 month running sums. Note that the year indicated represents the value of PDI through the previous 24-months for the Northern Hemisphere (bottom line/gray boxes) and the entire global (top line/blue boxes). The area in between represents the Southern Hemisphere total PDI. Power dissipation and Accumulated Cyclone Energy are analogous for running-sum time series -- correlation > 0.97
1970-2011 monthly PDI Data File (Maue, 2010 GRL)
2011 Northern Hemisphere Tropical Cyclones

Northern Hemisphere: Calendar Year Totals: 56 Tropical Storms, 28 Hurricane Force, 16 Major Hurricane Force
Global: Calendar Year Totals: 77 Tropical Storms, 39 Hurricane Force, 21 Major Hurricane Force All maximum intensities and ACE values from HURDAT & JTWC best-tracks for 2011.

North Atlantic
June 2011
Arlene (55 ACE = 1.8775)
July 2011
Bret (55 ACE= 3.2775)
Cindy (60 ACE = 2.3125)
Don (45 ACE = 1.62)
August 2011
Emily (45 ACE = 2.3025)
Franklin (40 ACE=0.2825)
Gert (55 ACE = 1.8525)
Harvey (55 ACE=1.5325)
Irene (105 ACE= 18.8125)
TD10 (30 ACE = 0.0)
Jose (40 ACE=0.8475)
Katia (120 ACE = 27.0325)
September 2011
UNNAMED (40 ACE= 0.8475)
Lee (50 ACE=1.785)
Maria (70 ACE=9.98)
Nate (65 ACE=4.3075)
Ophelia (120 ACE=18.6775)
Philippe (80 ACE=15.93)
Rina (100 ACE=10.0875)
Sean (55 ACE=3.7475)
Western North Pacific
May 2011 ---
01W (25 ACE = 0.0)
02W (30 ACE = 0.0)
Aere (50 ACE = 3.4725)
Songda (140 ACE = 26.7775)
June 2011 ---
Sarika (30***ACE = 0.0)
Haima (35 ACE = 0.8575)
Meari (55 ACE = 2.6825)
July 2011 ---
Ma-on (115 ACE=25.4)
Tokage (25 ACE= 0.0)
Nock-ten (65 ACE=4.375)
Muifa (140 ACE=34.54)
August 2011 ---
Merbok (75 ACE= 6.8825)
13W (30 ACE = 0.0)
Nanmadol (140 ACE= 22.005)
Talas (55 ACE = 9.105)
September 2011 ---
Noru (45 ACE= 1.05)
Kulap (45 ACE = 0.6875)
Roke (115 ACE=13.2725)
Sonca (90 ACE=8.1325)
Nesat (115 ACE= 13.1775)
Haitang (35 ACE=0.3675)
Nalgae (130 ACE= 13.5325)
October 2011 ---
Banyan (30*** ACE = 0.0*)
November 2011 ---
24W (30 ACE = 0.0)
25W (25 ACE = 0.0)
26W (30 ACE = 0.0)
December 2011 ---
Washi (50 ACE = 2.84)
N. Indian & Arabian Sea
01A One (35 ACE = 0.3675)
02B Two (35 ACE = 0.245)
November 2011 ---
03A Keila (55 ACE = 1.81)
04A Four (35 ACE = 0.3675)
05A Five (35 ACE = 0.3675)
December 2011 ---
06B Thane (90 ACE=7.245)
Eastern Pacific
June 2011
Adrian (120 ACE = 12.1725)
Beatriz (80 ACE = 3.3025)
Calvin (70 ACE = 2.5475)
July 2011
Dora (135 ACE = 15.4875)
Eugene (115 ACE = 14.67)
August 2011
Fernanda (60 ACE=3.195)
Greg (75 ACE=4.6725)
TD08 (30 ACE=0.00)
September 2011
Hilary (125 ACE=31.1875)
October 2011
Irwin (85 ACE= 8.39)
Jova (110 ACE= 14.4125)
Kenneth (125 ACE = 11.1125)
Lidia, Max

2010 Northern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm

North Atlantic
June 2010
Alex (85 ACE = 7.3725)
July 2010
TD02 (30 ACE = 0.0)
Bonnie (35 ACE = 0.49)
August 2010
Colin (50 ACE = 2.6375)
TD5 (30 ACE = 0.0)
Danielle (115 ACE = 21.805)
Earl (120 ACE = 27.9525)
Fiona (55 ACE = 3.2475)
September 2010
Gaston (35 ACE = 0.3675)
Hermine (55 ACE = 1.3725)
Igor (135 ACE = 42.7975)
Julia (115 ACE = 14.47)
Karl (105 ACE = 6.0375)
Lisa (70 ACE = 4.2)
Matthew (50 ACE = 1.3)
Nicole (35 ACE = 0.1225)
October 2010
Otto (75 ACE = 6.6125)
Paula (85 ACE = 7.0725)
Richard (80 ACE = 4.735)
Shary (65 ACE = 2.4575)
Tomas (85 ACE = 11.835)
Western North Pacific
January 2010
01W (30 ACE = 0.0)
March 2010
Omais (50 ACE = 2.0075)
July 2010
Conson (75 ACE = 8.3225)
Chanthu (75 ACE = 3.5775)
August 2010
Dianmu (55 ACE = 2.4225)
Mindulle (60 ACE = 1.7)
Lionrock (55 ACE = 4.2075)
Kompasu (100 ACE = 11.5325)
Namtheun (40 ACE = 0.6875)
September 2010
Malou (45 ACE = 2.4725)
Meranti (65 ACE = 2.2825)
Fanapi (105 ACE = 13.03)
Malakas (90 ACE = 7.3025)
14W (30 ACE = 0.0)
October 2010
Megi (160 ACE = 42.195)
Chaba (115 ACE = 16.93)
17W (30 ACE = 0.00)
November 2010
18W (30 ACE = 0.00)
N. Indian & Arabian Sea
May 2010
Laila (65 ACE = 4.275)
Bandu (55 ACE = 2.5125)
Phet (125 ACE = 14.7475)
October 2010
Giri (135 ACE = 7.13)
November 2010
Jal (55 ACE = 3.025)
Eastern Pacific
May 2010
Agatha (40 ACE = 0.5275)
TD02 (25 ACE = 0.0)
June 2010
Blas (55 ACE = 2.715)
Celia (140 ACE = 24.09)
Darby (105 ACE = 11.145)
August 2010
Estelle (55 ACE = 2.65)
TD08 (30 ACE = 0.0)
Frank (80 ACE = 8.2225)
TD10 (30 ACE = 0.0)
TD11 (30 ACE = 0.0)
September 2010
Georgette (35 ACE = 0.6125)
December 2010
Omeka (45 ACE = 1.0175)

2010-2011 Southern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (JTWC Best Track Intensity Estimates)

South Indian and South Pacific
October 2010
01S One (35 ACE = 0.6125)
02S Anggrek (55 ACE = 4.0525)
December 2010
03S Abele (80 ACE = 4.4425)
04P Tasha (40 ACE = 0.4425)
January 2011
05P Vania (55*** ACE = 3.1325)
06P Vince (45 ACE = 2.2275)
07P Zelia (95 ACE = 7.655)
08P Wilma (115 ACE = 14.865)
09P Anthony (55 ACE = 2.36)
10S Bianca (95*** ACE = 8.79)
11P Yasi (135 ACE = 16.0775)

February 2011
12P Zaka (45 ACE = 1.2575)
13S Bingiza (100 ACE = 11.3525)
14S Fourteen (35 ACE = 0.1225)
15S Carlos (65 ACE = 7.3925)
16S Dianne (80 ACE = 9.7125)
17P Atu (115 ACE = 15.6725)
March 2011
18S Cherono (45 ACE = 1.9025)
19P Bune (75 ACE = 7.72)
April 2011
20S Twenty (35 ACE = 0.735)
21S Errol (55 ACE = 2.5075)

2009 Northern Hemisphere Tropical Cyclones

Maximum Wind Speed & ACE per storm (HURDAT + JTWC best-tracks)

Western Pacific
Kujira (115 ACE = 12.9375)
Chan-hom (90 ACE = 6.465)
Linfa (75 ACE = 4.915)
Nangka (45 ACE = 2.2975)
Soudelor (35 ACE = 0.1225)
Molave (65 ACE = 2.925)
Goni (45 ACE = 0.9275)
Morakot (85 ACE = 8.4675 )
Etau (40 ACE = 0.895)
Vamco (120 ACE = 26.81)
Krovanh (65 ACE = 4.655)
Dujuan (50 ACE = 3.98)
Mujigae (30 ACE = 0.000 )
Choi-wan (140 ACE = 33.82 )
Koppu (75 ACE = 2.345 )
Ketsana (90 ACE = 6.3375)
18W (30 ACE = 0.00)
Parma (130 ACE = 22.655)
Melor (150 ACE = 40.3325)
Nepartak (55 ACE = 2.7025)
Lupit (140 ACE = 31.435)
Mirinae (90 ACE = 12.94 )
25W (45 ACE = 1.05 )
Nida (155 ACE = 44.58)
27W (30 ACE = 0.0)
28W (35 ACE = 0.245)
Omais Conson Chanthu
Total Tropical Storms+ = 24
Total Typhoons+ = 15
Eastern Pacific
Andres (65 ACE = 2.9475)
Blanca (45 ACE = 1.215)
Carlos (90 ACE = 8.92)
Dolores (45 ACE = 0.8475)
Enrique (50 ACE = 2.205)
Felicia (125 ACE= 19.5875)
Guillermo (110 ACE = 12.2375)
Hilda (55 ACE = 3.5175 )
Ignacio (45 ACE = 1.54 )
Jimena (135 ACE = 24.0175 )
Kevin (45 ACE = 1.135 )
Linda (75 ACE = 5.4425 )
Marty (40 ACE = 1.5725 )
Nora (50 ACE = 1.3425 )
Olaf (40 ACE = 0.9325)
Patricia (50 ACE = 1.7675)
Rick (155 ACE = 21.705)
Sandra Terry Vivian
Waldo Xina York Zelda
Total Tropical Storms+ = 17
Total Hurricanes+ = 7
North Atlantic
TD 01(30 ACE=0.0)
Ana (35 ACE=0.98)
Bill (115 ACE = 26.47)
Claudette (45 ACE = 0.405)
Danny (50 ACE = 2.285)
Erika (50 ACE = 1.4275)
Fred (105 ACE = 10.07)
TD 08 (30 ACE = 0.0)
Grace (55 ACE = 1.4125)
Henri (45 ACE = 1.215)
Ida (90 ACE = 8.2365)
Kate Larry Mindy Nicholas
Odette Peter Rose Sam
Teresa Victor Wanda

Total Tropical Storms+ = 9
Total Hurricanes+ = 3
Central Pacific
Lana (55 ACE = 2.7)
Maka (45 ACE = 1.175 )
Neki (105 ACE = 12.44)
Omeka Pewa
Unala Wali
Total Tropical Storms+ = 3
Total Hurricanes+ = 1
Northern Indian
Bijli (50 ACE=2.4125)
Aila (65 ACE=1.885)
03B (40 ACE = 0.405)
Phyan (50 ACE = 1.395)
Ward (45 ACE = 1.6625 )
Laila Bandu Phet

Total Tropical Storms+ = 5
One Cyclone+

Northern Hemisphere Tropical Storms during Calendar Year 2009 = 58

Northern Hemisphere Hurricanes + during Calendar Year 2009 = 27

The 13 Tropical Cyclones that had an ACE > 10 Account for almost 3/4 of the total Northern Hemisphere ACE. 7 (ACE > 24) account for more than 1/2 of the total NH ACE.

Previous News Items

November 25, 2011: A tropical cyclone will form in the Arabian Sea during the next day and could become rather intense.

November 22, 2011: HWRF deserves credit for rapidly intensifying Kenneth to Category 4 strength, 125 knots.

November 18, 2011: TD13 has formed in the Northeast Pacific and will slowly drift westward reaching hurricane strength in the next few days.

November 11, 2011: Sean has become post-tropical, but added almost 4 ACE points as a tropical storm to the yearly total. Looks like the 2011 hurricane season is winding down. A post season wrap-up will be produced in the coming days.

November 9, 2011: Just a couple weak storms: Sean and TC04A (Arabian Sea)

November 8, 2011: Typically a quiet month in the Northern Hemisphere, yet there are several systems including a Mediterranean tropical storm, TD24W and TC04A in the Arabian Sea. None appear to be strenghtening much past weak tropical storm status but significant enough to get a name. Subtropical Storm Sean in the Atlantic has also formed overnight.

November 2, 2011: Cyclone Keila has formed right on the coast of Yemen. It is providing some rain to the typically arid Arabian peninsula.

October 30, 2011: Graphics and statistics have been compiled through the end of October.

October 28, 2011: Rina has weakened to tropical depression. Tropics are quiet again. End of October updates will show continued below normal activity globally, about 50% of normal

October 25, 2011: Hurricane Rina -- map updates -- Link

October 19, 2011: Nothing happening. Weak short-lived TC-2B in the Bay of Bengal has moved inland.

October 13, 2011: There are currently no tropical storm force tropical cyclones globally. With October nearly half-over, the North Atlantic and North Eastern Pacific hurricane seasons are typically nearing their end. Typical late autumn tropical cyclone activity regions include the Western Pacific, North Indian Ocean, and perhaps in the Southern Hemisphere.

October 12, 2011: Jova has made landfall as a Category 2 hurricane while Irwin is struggling to its west. A weak tropical storm (Banyan 23W) drenched the Philippines and is moving off toward China. It is not expected to become a Typhoon at this time. The North Atlantic is still quiet -- the season is climatologically 85% over with as of October 12.

October 9, 2011: Irwin has been obliterated by vertical wind shear primarily due to the much larger and now stronger Jova to the east. Still looking off east coast of Florida for a weak storm and huge rainmaker for the Southeast USA

October 8, 2011: Irwin and Jova are both at or near hurricane strength.

October 5, 2011: One lonely tropical cyclone in the central North Atlantic: Philippe which will undergo a loop and move north during the next 5 days. It should eventually reach hurricane strength making it the 5th hurricane of the season (Irene, Katia, Maria, Ophelia). During the next 7-days, the GFS model has 2 eastern Pacific storms and possibly a weak development near the Bahamas. The ACE for the year in the Northern Hemisphere is slowly approaching 400.

October 2, 2011: ACE for the Northern Hemisphere has nearly gone over 400 and the North Atlantic has eclipsed 100. Everything is shaping up to be average except in the Northern Indian Ocean, which has not seen much of any tropical activity this year.

Atlantic Update: Long-range forecasts do not indicate any significant tropical development through the first week of October in addition to Opehlia and Philippe, which do not appear to be significant landfall threats. While the number of storms has been high, currently only 3 have become hurricanes. Ophelia is forecast to reach hurricane strength over the open Atlantic. The ACE for the year is mirroring 2007 when many storms were weak and short-lived.

September 29, 2011: There are several named storms in the Northern Hemisphere including two Typhoons, a dissipating Hilary, and Ophelia and Philippe in the North Atlantic.

September 26, 2011: North Atlantic ACE is close to the past 30-year average. With 10-day forecasts not showing any significant tropical Atlantic development, it looks like early October will arrive with below-normal ACE for 2011 year-to-date.

September 26, 2011: Hurricane Hilary will slowly spin down over progressively cooler waters in the EPAC. Nesat will eventually develop into a SuperTyphoon and move west toward the Philippines. In the North Atlantic, Ophelia has weakened again to a depression while Philippe is slowly gaining strength over the central Atlantic

September 23, 2011: Hurricane Hilary has exploded to near-Category 5 intensity as a very small, intense storm. Ophelia has been obliterated by shear. Expect the typhoon to develop in the Western Pacific during the weekend (Nesat)

September 21, 2011: Tropical Storm Ophelia has formed in the central North Atlantic in the Main Development Region (MDR). There is little chance of major intensification during the next 5-days as the enviornment is less than ideal. TD-9 depression has formed in the Eastern North Pacific (Invest 96e) and is expected to develop into a major hurricane.

Spetember 20, 2011: Without any additional ACE since Maria moved into the midlatitudes, the North Atlantic even with its 14-storms has only mustered an ACE of 76. This is about two-days ahead of normal meaning the 2011 season is near-average according to Accumulated Cyclone Energy.

September 20, 2011: Quite the surprise intensity increases for the very small typhoons in the Western North Pacific. Both Sonca and Roke became significantly more powerful: Sonca's maximum intensity was 85 knots (maybe more), and Roke reached 100 knots, or major status. Sonca is rapidly becoming extratropical while Roke is poised to make landfall in Japan during the next 24-36 hours as a typhoon. Expect heavy rain and flooding along the Japanese Alps and coastline.
The North Atlantic and Eastern Pacific each have one area of interest (Invests). Models develop 96e into a powerful hurricane in the EPAC.

September 17, 2011: Roke and Sonca in the Western North Pacific are typical of La Nina years in which the monsoon is displaced generating many weaker, short-lived storms. Maria has become extratropical and finished with an ACE of about 9, which is about average for a Category 1 Atlantic hurricane. This is the statistical peak of the Northern Hemisphere tropical cyclone season. Not very active.

Atlantic Season Update

Half-way point. Sarasota Herald-Tribune article with my thoughts on the Atlantic season: Busy hurricane season, but few pack a punch

September 13, 2011: Very big difference between 2010 and 2011. A year ago, long-lived Igor (ACE=43) and 3 other hurricanes uncorked one of the most active months in recent history. Igor maxed out at 135 knots and was for all purposes a Category 5 hurricane, something the Atlantic has not seen since 2007 (Dean and Felix). It has been 4-years since a Category 5 hurricane has been recorded in the Atlantic.

Spetember 12, 2011: Second half of the North Atlantic season is underway with Maria struggling against wind shear. TD18 has formed in the WPAC and should strengthen into a storm soon. It will be named Roke (18W). ACE stats are up to date for each storm through today.

September 11, 2011: Hurricane Katia has completed extratropical transition and will be nearing the UK soon. Nate is expected to make landfall today as a weak hurricane. Meanwhile, Maria is becoming better organized and will follow the previous track of Katia during the next several days.

September 10, 2011: With September 1/3 over, the month has seen only 5 new tropical storms of minimal strength. The 10-day forecast does not portend much activity in the Pacific and perhaps little in the Atlantic. With the oncoming La Nina, the global tropics may again become very quiet during the fall.

September 3, 2011: Katia and Lee in the North Atlantic are contributing just enough ACE to keep up with climatology. Tropical Storm 16W has formed in the Western Pacific. The Eastern Pacific basin is expectedly quiet due to the chilly waters resulting from the oncoming La Nina.

August 26, 2011: Irene will continue to weaken until extratropical transition. The final ACE will be around 20. The Western Pacific is quite active with the monsoon gyre producing Nanmadol and Talas. Nanmadol is a SuperTyphoon which is undecided on its track at the moment with complex steering currents. Talas is expected to become a Typhoon as well. For the Northern Hemisphere year-to-date, tropical cyclone activity is slightly better than average and balanced across each active basin.

August 20, 2011: Tropical Storm Irene will be a nightmare for forecasters as it will affect many countries at various intensities.

Current paper on tropical cyclones chosen as an AGU journals highlight: Global tropical cyclone activity historically low.

August 19, 2011: Harvey makes the 8th tropical storm in the Atlantic that will fail to reach hurricane strength. This is good.

August 17, 2011: The Northern Hemisphere ACE has reached 200, which is about 4 days sooner than the past 30-year average. So far 2011 can be classified as an average calendar year for each basin as can be seen from the table on the left hand margin

August 12, 2011: "Pacific may hold key to Atlantic hurricanes" Kate Spinner writes about recent paper in GRL (Maue 2011) at the Herald-Tribune

New Paper: Maue (2011) Recent historically low global tropical cyclone activity:

During the past 6-years since Hurricane Katrina, global tropical cyclone frequency and energy have decreased dramatically, and are currently at near-historical record lows. According to a new peer-reviewed research paper accepted to be published, only 69 tropical storms were observed globally during 2010, the fewest in almost 40-years of reliable records.
Furthermore, when each storm's intensity and duration were taken into account, the total global tropical cyclone accumulated energy (ACE) was found to have fallen by half to the lowest level since 1977.

In his new paper, "Recent historically low global tropical cyclone activity", Dr. Ryan Maue, a meteorologist from Florida State University, examined the last 40-years of global hurricane records and found strikingly large variability in both tropical cyclone frequency and energy from year-to-year. Since 2007, global tropical cyclone activity has decreased dramatically and has continued at near-historical low levels. Indeed, only 64 tropical cyclones were observed globally in the 12-months from June 2010 - May 2011, nearly 23-storms below average obliterating the previous record low set in 1977.

On average, the North Atlantic including the Gulf of Mexico and Caribbean Sea accounts for about 1/8 of total global tropical cyclone energy and frequency. However in 2010, the Atlantic saw 19 tropical storms, of which 12 became hurricanes as expected (and forecasted) due to the intense La Nina event and continued positive Atlantic Multidecadal Oscillation (AMO). The Atlantic Ocean's accumulated cyclone energy (ACE) corresponded to about 1/3 of the global calendar year output while the Western North Pacific typhoon season experienced a record few number. Seasonal forecasters of Atlantic hurricanes expect a similar but somewhat tempered outcome for the 2011 season, which has yet to get underway.

While the North Atlantic continued a 16-year period of above-normal activity in 2010, the North Pacific including the warm tropical waters from China to Mexico experienced the quietest tropical cyclone season in at least 40-years of historical records. Similarly, the most recent Southern Hemisphere cyclone season, except for the disastrous impacts of Yasi, was also notably below average. All told through June 27, 2011, overall global accumulated cyclone energy and frequency has settled into a period of record inactivity.

August 4, 2011: With the demise of Emily and the quickly weakening Eugene, focus shifts to landfalling Muifa and tropical transitioining Merbok in the Western Pacific. NCEP GFS is bullish on an African Easterly Wave becoming Franklin over the next week in the far Atlantic with little indications of tropical cyclone development elsewhere. Time for a well-deserved lull in tropical activity after a quite decent burst.

9 tropical cyclones formed during July 2011. This brings the last 12-months total to 73, still well below normal but no longer at "record" lows. The ACE of 80 during July 2011 is a considerable difference to the previous 2-years (2009 and 2010), which only saw an ACE of 15.

Tropical Cyclone ACE for the Northern Hemisphere has made it back to "normal" for year-to-date and will move above normal for the Western North Pacific. July 2011 was quite active for tropical cyclones. Meanwhile, the Eastern North Pacific and North Atlantic are also just about average for this time of year.

July 30, 2011: Super Typhoon Muifa has exploded into a Category 5 monster, with winds at 140 knots according to the JTWC 18z advisory. It will meander northward during the next few days before taking a sharp left turn...maybe.

July 30, 2011: The Western Pacific has become quite active over the past week with a couple new storms and the expectation of third during the upcoming week. Meanwhile, Don in the Gulf of Mexico should be followed by an African Easterly Wave (Invest 91L) that could develop into Emily during the next few days but remain out to sea for the time being. Eugene in the Eastern Pacific is quite likely. July 2011 has been a quite above-average month compared to previous July's. Global tropical cyclone activity is now "normal" in terms of ACE-to-date for the year 2011.

July 18, 2011: Ma-On has started to weaken as it moves toward Japan to later recurve to the NNE. In the North Atlantic, the second storm Bret will likely miss land and remain a tropical storm as it eventually becomes extratropical in a few days. Expect the Invest in the Eastern North Pacific to develop into a hurricane over the next 5-days.

Typhoon Ma-On will be a powerful storm [08W] -- expect it to explode to Category 5 (sub-900 hPa MSLP)

July 11, 2011: Hurricane Calvin developed in the North Eastern Pacific but was a quite small, short-lived storm. The NWP models did not capture the maximum intensity of Calvin well because it was so small. This is typical of the EPAC. Nothing on the horizon for the NATL in the next week, at least. The Western Pacific may produce a Typhoon, though and send it off towards China.

July 5, 2011: Global tropics are dead. While a weak tropical storm may develop during the week, none of the trusted NWP models has a significant tropical cyclone anywhere.

June 30, 2011: Tropical storm Arlene made landfall as a 55-knot storm in Mexico and was the only storm in the Atlantic in June. Elsewhere, Adrian and Beatriz were named in the Eastern Pacific both hurricanes with the former being a major storm. Four additional weak tropical storms were named in the Western Pacific and Arabian Sea region. The total of 7-tropical cyclones brings the 12-month total to 67, which is an improvement of 3 over last month's tally. This is still about 20-TCs below average.

June 28, 2011 -- The Atlantic hurricane season has started with a quite weak storm in the SW Gulf of Mexico: Arlene. It will provide beneficial rain and inject moisture into Northern Mexico and the South Central USA

June 26, 2011 -- With Meari and Haima weakening and dissipating, the global tropics are very quiet. The ECMWF deterministic runs have a couple potential storms, one in the SW Gulf of Mexico and another along 100W in the Eastern Pacific during the next 10-days. Nothing major is on the horizon for the next 10-days, at least.

June 20, 2011 -- So far this June, the Eastern Pacific has produced Adrian and Beatriz, while the North Indian and Western Pacific saw a total of 3 quite weak tropical storms. The total of 5 global tropical storms brings the 12-month running total to 65 . The average should be around 87.

Globally, tropical cyclone frequency has reached uncharted lows -- only 64 storms were counted from June 2010 to May 2011.

June 10, 2011 As expected, Hurricane Adrian developed in the EPAC, but will not threaten land. As an annular storm, it will persist a bit longer or decay a bit slower than a normal major hurricane over colder SSTs. Tropical Storm Sarika in the WPAC has only reached minimal storm status, 35 kts. Arabian Sea TC 01A has similarly failed to exceed the weakest tropical storm strength (35 knots).

June 7, 2011 Global Tropical Cyclone Frequency has fallen to the lowest levels in recorded history. Only 64-tropical cyclones were recorded during the 12-month period from June 2010-May 2011. And, as most have noticed, it is very quiet -- with only one development likely in the Eastern Pacific (Adrian) during the next 10-days.

June 1, 2011 June is usually a quiet month for tropical cyclone activity. The average ACE during the last 30-years during June is about 29: Western Pacific -- 14, Eastern Pacific -- 11, North Atlantic -- 1, North Indian -- 2