F) Tropical cyclones forecasting

F1) What regions around the globe have tropical cyclones and who is responsible for forecasting there?
F2) What are those NWP "numerical weather products" or numerical models that the RSMC La Réunion talks about in the technical warnings and discussions ?
F3) What are the various forecasts that are being issued for seasonal tropical cyclone activity around the world ?
F4) How accurate are the forecasts from the RSMC La Réunion?

Subject F1) What regions around the globe have tropical cyclones and who is responsible for forecasting there?

Contributed by Chris Landsea and Anne-Claire Fontan

There are seven tropical cyclone "basins" where storms occur on a regular basis:

1. Atlantic basin (including the North Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea)
2. Northeast Pacific basin (from Mexico to about the dateline)
3. Northwest Pacific basin (from the dateline to Asia including the South China Sea)
4. North Indian basin (including the Bay of Bengal and the Arabian Sea)
5. Southwest Indian basin (from Africa to about 100E)
6. Southeast Indian/Australian basin (100E to 142E)
7. Australian/Southwest Pacific basin (142E to about 120W)

The 6 WMO recognized Regional Specialized Meteorological Centers (RSMC) for Hurricanes/Typhoons and 6 Tropical Cyclone Warning Centers (TCWC) provide the official tropical cyclone guidance track and intensity forecasts for their designated areas. These are:

1. RSMC Miami. The National Hurricane Center in Miami, Florida, USA has responsibilities for monitoring and forecasting tropical cyclones in the Atlantic and Northeast Pacific basin east of 140W.
2. RSMC Honolulu. The Central Pacific Hurricane Center in Honolulu has responsibilities for the remainder of the Northeast Pacific basin from 140W to 180 degrees longitude.
3. RSMC Tokyo. The Japanese Meteorological Agency Typhoon Center has the responsibility for the northwest Pacific Ocean basin.
4. RSMC New Delhi. The Indian Meteorological Agency Cyclone Center in New Delhi has responsibilities for the North Indian Ocean basin.
5. RSMC La Reunion. The French Meteorological office in La Reunion has responsibilities for the Southwest Indian Ocean basin.
6. RSMC Nadi. The Fijian Meteorological Service office in Nadi, Fiji has the responsibility for the southwest Pacific Ocean.

1. TCWC Perth (Australia) issues advisories for the area 10S-40S/90E-110E
2. TCWC Darwin (Australia) for the area 125E-142E
3. TCWC Brisbane (Australia) for the Coral Sea between 142E and 160E
4. TCWC Wellington (New Zealand) for the southwest Pacific Ocean basin south of 25S
5. TCWC Port-Moresby (Papua New Guinea) for the area 0S-10S/141E-160E
6. TCWC Jakarta (Indonesia) for the area 0S-10S/90E-125E.

• For the Northwest Pacific basin, China, Thailand, Korea, Japan, the Philippines, Hong Kong, China, Macau, China among others,
• For the North Indian Ocean basin, India, Thailand, Pakistan, Bangladesh, Burma, and Sri Lanka among others,
• For the Southwest Indian Ocean basin, Madagascar, Mozambique, Mauritius, and Kenya among others,
• For the southwest Pacific Ocean basin, Papua New Guinea, Vanuatu, and Samoa among others provide tailored forecasts.

Note that on rare occasions, tropical cyclones (or storms that appear to be similar in structure to tropical cyclones) can develop in the Mediterranean Sea. These have been noted to occur in September 1947, September 1969, January 1982, September 1983, and, most recently, during 13 to 17 January, 1995. Some study of these storms has been reported on by Mayengon (1984) and Ernest and Matson (1983), though it has not been demonstrated fully that these storms are the same as those found over tropical waters. It may be that these Mediterranean tropical cyclones are more similar in nature to polar lows.

The recent hurricane that formed in the South Atlantic was handled by the Brazilian weather service. Since tropical cyclones are so rare in this region, the WMO has not designated a forecast center with responsibility for there.

The following are the addresses of tropical cyclone centers listed above that are responsible for issuing advisories and/or warnings on tropical cyclones (thanks to Jack Beven for these):

World Meteorological Organization
WWW:  http://www.wmo.ch/web/www/TCP/rsmcs.html

OAR
Mail: 11691 SW 17th St.
      Miami, FL 33165-2149
      USA
WWW:  http://www.nhc.noaa.gov/index.html


Central Pacific Hurricane Center
Mail: National Weather Service Forecast Office
      Central Pacific Hurricane Center
      2525 Correa Rd. 
      Suite 250
      Honolulu, HI 96822
      USA

WWW:http://www.prh.noaa.gov/cphc


Joint Typhoon Warning Center
Mail: NAVPACMETOCCEN/JTWC
      425 Luapele Rd.
      Pearl Harbor, HI 96860
      USA
WWW:  http://www.npmoc.navy.mil/


Regional Specialized Meteorological Center Tokyo,
Japan - Typhoon Center
Mail: Japanese Meteorological Agency
      1-3-4 Ote-machi, Chiyoda-ku
      Tokyo
      Japan
WWW:  http://www.goin.nasda.go.jp/GOIN/JMA/


Hong Kong Observatory
Mail: 134A Nathan Road
      Kowloon
      Hong Kong
WWW:  
http://www.info.gov.hk/hko/index.htm



Bangkok Tropical Cyclone Warning Center - Thailand

Mail: Director
      Meteorological Department
      4353 Sukumvit Rd.
      Bangkok 10260
      Thailand


Fiji Tropical Cyclone Warning Center
Mail: Director
      Fiji Meteorological Services
      Private Mail Bag
      Nadi Airport
      Fiji


New Zealand Meteorological Service
Mail: Director
      Met Service
      PO Box 722
      Wellington
      New Zealand
WWW:  http://www.metservice.co.nz/index.asp


Port Moresby Tropical Cyclone Warning Center
Mail: Director
      National Weather Service
      PO Box 1240
      Boroko, NCD
      Paupa New Guinea


Brisbane Tropical Cyclone Warning Center
Mail: Regional Director
      Bureau of Meteorology
      GPO Box 413
      Brisbane 4001
      Australia
WWW:  http://www.bom.gov.au/weather/qld


Darwin Tropical Cyclone Warning Center
Mail: Regional Director
      Bureau of Meteorology
      Northern Territory Regional Office
      PO Box 40050, CASUARINA, N.T. 0801
      Australia

WWW:  http://www.bom.gov.au/weather/nt


Perth Tropical Cyclone Warning Center
Mail: Regional Director
      Bureau of Meteorology
      GPO Box 1370
      West Perth,WA 6872
      Australia
WWW:  http://www.bom.gov.au/weather/wa


Jakarta, Indonesia
Mail: Director
      Analysis and Processing Centre
      Jalan Arief Rakhman Hakim 3
      Jakarta
      Indonesia


Regional Specialized Meteorological Centre La Reunion, France - Tropical Cyclones Center
Mail: Director of Meteorological Services
      PO Box 4
      97490 Sainte Clotilde
      La Reunion FRANCE
WWW: http://www.meteo.fr (Le temps/ Outre-mer/ La Reunion)



Sub-Regional Tropical Cyclone Warning Center - Mauritius
Mail: Director of Meteorological Service
      Vacoas
      Mauritius


Sub-Regional Tropical Cyclone Warning Center - Madagascar
Mail: Director of Meteorological Service
      PO Box 1254
      Antananarivo 101
      Madagascar



Nairobi, Kenya
Mail: Director of Meteorological Services
      PO Box 30259
      Nairobi
      Kenya


Maputo, Mozambique
Mail: Director of Meteorology
      PO Box 256
      Maputo
      Mozambique

Philippines:  Manila


China:        Beijing 
              Dalian
              Shanghai
              Guangzhou

Korea:        Seoul

Vietnam:      Hanoi

India:        New Delhi
              Calcutta 
              Bombay

Bangladesh:   Dhaka

Burma:        Rangoon


Sri Lanka:    Colombo

Maldive Islands: Male

Please refer to the section "links" to directly connect to some of the centres.

Subject F2) What are those NWP "numerical weather products" or numerical models that the RSMC La Réunion talks about in the technical warnings and discussions ?

Source Samuel Westrelin.

1. ARPEGE-IFS is a common development between Météo-France and ECMWF. ARPEGE (Action de Recherche Petite Echelle Grande Echelle) is the French name while IFS (Integrated Forecast System) is the name used by ECMWF. It is a global stretched model with no tropical cyclone's initialization. There are 4 runs a day: 00, 06, 12, 18 UTC. 00 UTC run is up to range 102h, 06 UTC up to 72h, 12 UTC up to 84h, and 18 UTC up to 60h. The assimilation runs with a 6-hour cycle, and the analysis method is a four dimensional variational analysis for upper air fields. The time step is 900 seconds. The resolution varies from 15 km over France to 55 km over Reunion Island and 90 km over New-Zealand.


2. ALADIN-Réunion is a model adapted on Southwest Indian ocean at La Réunion by the Cyclone Research Team of Météo-France but developed by 16 euro-mediterranean countries This is a limited area model that covers the [0°-32S] [31.5E – 88.5E] area with a resolution of 10km - horizontal mesh size: 400 (lat) x 648 (lon) points. The initialization of tropical cyclones is a bogus of synthetic wind observations from the surface to 500 hPa deduced from the Holland analytical model, plus the mean sea level pressure at the center. There are 2 runs a day : 00 and 12 UTC, both of them up to 84 hours.


3. The European Centre for Medium-Range Weather Forecasts's global model (ECMWF) runs twice a day, at 00 and 12 UTC, up to 240h (http://www.ecmwf.int).


4. The United Kingdom Meterological Office's global model (UKMET) is utilized for forecasting the track of tropical cyclones around the world (Radford 1994).


5. The GFDL model is a triply-nested movable mesh primitive equation model developed at the Geophysical Fluid Dynamics Laboratory. Position centre (latitude/longitude) and minimal sea level pressure of the tropical cyclones given by this model are received at the RSMC La Réunion since cyclone season 2004-2005.


6. The United States Navy Operational Global Atmospheric Prediction Systems (NOGAPS) is also a global numerical model that shows skill in forecasting tropical cyclone track (Fiorino et al. 1993). Position centre (latitude/longitude) and minimal sea level pressure of the tropical cyclones given by this model are received at the RSMC La Réunion since cyclone season 2004-2005.


7. CONW is not strictly speaking a model but a consensus, i.e. an average of up to 8 models (depending on the availability of the models), computed by the American navy. Position centre (latitude/longitude) and minimal sea level pressure of the tropical cyclones given by this consensus are received at the RSMC La Réunion since cyclone season 2004-2005.

Subject F3) What are the various forecasts that are being issued for seasonal tropical cyclone activity around the world ?

Contributed by Stan Goldenberg

There are a number of different seasonal forecasts currently being issued for various basins. Some of these are fairly new, while the oldest and most well known ( Prof. Bill Gray's forecast from CSU) has been issued for almost two decades.

• North Atlantic Basin:
  1. Prof. Bill Gray, Department of Atmospheric Science, Colorado State University
  2. CPC/HRD/NHC Team, National Oceanic and Atmospheric Administration
  3. Maritza Ballester, Cuban Institute of Meteorology,
  4. Mark Saunders, Tropical Storm Risk, Department of Space and Climate Physics, University College London
  5. Prof. James Elsner, Department of Geography, Florida State University.
• NW Pacific:
  1. Mark Saunders, Tropical Storm Risk, Department of Space and Climate Physics, University College London
  2. Prof. Johnny C. L. Chan, Laboratory for Atmospheric Research, Dept. of Physics & Mat. Sci., City University of Hong Kong
• Australian Basin:
  1. Mark Saunders, Tropical Storm Risk, Department of Space and Climate Physics, University College London
• South China Sea:
  1. Prof. Johnny C. L. Chan, Laboratory for Atmospheric Research, Dept. of Physics & Mat. Sci., City University of Hong Kong

Subject F4) How accurate are the forecasts from the RSMC La Réunion?

Contributed by Anne-Claire Fontan.

The RSMC La Réunion issues an official forecast, every six hours, of the center position, maximum ten-minutes surface (10 meters elevation) wind speed (intensity), radii of the 34 knot, 50 knot, and 64 knot, wind speeds in four quadrants (northeast, southeast, southwest, and northwest) surrounding the system, minimal sea level pressure, system movement etc...
The RSMC La Réunion has been issuing predictions for the forecast periods of 12, 24, and 48 hours since 1990. Forecasts for 36, 60 and 72 hours were first issued in 2004. All official forecast are verified by comparison with the "best track", a set of six-hour center positions, maximum wind speed values, minimal sea level pressure and T/Ci Dvorak numbers, that represents the official RSMC estimate of the location and intensity of a system. A best track is prepared for every system, after the fact, using all available data.

RSMC La Réunion's official track errors have averaged in the last few years about 100 km at 12 hr, 150 km at 24 hr and 300 km at 48 hr. One can see that RSMC La Réunion has even done better than these numbers since 2005. Forecasts are now also issued at 3 lead time. These are average errors so, of course, individual predictions may be substantially better or worse. It is to the researchers community that these predictions have gotten so much better in the last few years, due to a combination of more accurate numerical models, and a better understanding of the physics of hurricane movement.

The improvements in intensity predictions are much slower than in the track predictions. Much work still remains to better understand and predict wind intensity changes in tropical storms and hurricanes.