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Frequently Asked Questions

This FAQ (Frequently Asked Questions) site attempts to address questions regarding hurricanes, typhoons and tropical cyclones that have been posed to hurricane forecasters over the years.

Visit the FAQ from the Atlantic Oceanographic and Meteorological Laboratory's Hurricane Research Division for more questions and answers.


1. Where can I get real-time advisories for tropical cyclones?

Option 1: Get the advisories via the Web. The World Wide Web is a great source for real-time tropical cyclone advisories. There are many sites that provide real-time tropical cyclone information including:

Option 2: Advisories automatically sent to you. Click here for information on receiving tropical cyclone advisories for the Atlantic and East Pacific Basins. You can subscribe to the CPHC mailing list here.

Option 3: Advisories available in RSS format:


2. How can I get hurricane information when I'm not at my computer ?

The National Weather Service offers a variety of services to make sure you stay informed about tropical activity even when you are away from your television or computer. Some of these services are:

  • NOAA Weather Radio
    The easiest way to stay informed is to have an inexpensive portable radio which picks up NOAA Weather Radio. These are available in numerous stores in a host of designs and features.
  • Radio Fax
    For mariners at sea, there are a variety of ways and frequencies that you can use to keep updated on tropical developments.
  • Wireless
    NHC/TPC Tropical Cyclone text advisories, aircraft reconnaissance messages, and Tropical Analysis and Forecasting Branch text forecasts and discussions for the Atlantic Basin are available to Wireless Application Protocol (WAP) capable cellphones and Portable Digital Assistants (PDA). For more information on how to set up your cellphone or PDA go here.
  • E-Mail
    If you can check your email while away from your home computer you might consider subscribing to one of NHC's mailing lists. To see how go here. You can subscribe to the CPHC mailing list here.
  • RSS Feeds
    If your computer has a news aggregator or feed reader you can set it up to receive RSS feeds from CPHC and NHC.

3. What is a super-typhoon? What is a major hurricane ? What is an intense hurricane ?

Major hurricane is a term utilized by the National Hurricane Center and Central Pacific Hurricane Center for hurricanes that reach maximum sustained 1-minute surface winds of at least 96 kt, (50 m/s, 111 mph). This is the equivalent of category 3, 4 and 5 on the Saffir-Simpson scale.

Intense hurricane is an unofficial term, but is often used in the scientific literature. It is the same as major hurricane.


4. When is hurricane season ?

The Atlantic hurricane season is officially from 1 June to 30 November. There is nothing magical in these dates, and hurricanes have occurred outside of these six months, but these dates were selected to encompass over 97% of tropical activity. The Atlantic basin shows a very peaked season from August through October, with 78% of the tropical storm days, 87% of the minor (Saffir-Simpson Scale categories 1 and 2) hurricane days, and 96% of the major (Saffir-Simpson categories 3, 4 and 5) hurricane days occurring then (Landsea 1993). Maximum activity is in early to mid September. Once in a few years there may be a tropical cyclone occurring out of season - primarily in May or December. (For more detailed information, see "What is my chance of having a tropical storm or hurricane strike by each month?")

The Northeast Pacific basin has a broader peak with activity beginning in late May or early June and going until late October or early November with a peak in storminess in late August/early September. The season is officially 15 May 15 through 30 November.

The Central Pacific basin has a very peaked season from August through September. The hurricane season is officially from 1 June to 30 November.

The Northwest Pacific basin has tropical cyclones occurring all year round regularly though there is a distinct minimum in February and the first half of March. The main season goes from July to November with a peak in late August/early September.

The North Indian basin has a double peak of activity in May and November though tropical cyclones are seen from April to December. The severe cyclonic storms (>33 m/s winds [76 mph]) occur almost exclusively from April to June and late September to early December.

The Southwest Indian and Australian/Southeast Indian basins have very similar annual cycles with tropical cyclones beginning in late October/early November, reaching a double peak in activity - one in mid-January and one in mid-February to early March, and then ending in May. The Australian/Southeast Indian basin February lull in activity is a bit more pronounced than the Southwest Indian basin's lull.

The Australian/Southwest Pacific basin begin with tropical cyclone activity in late October/early November, reaches a single peak in late February/early March, and then fades out in early May.

Globally, September is the most active month and May is the least active month. (Neumann 1993)


5. How does El NiƱo-Southern Oscillation affect tropical cyclone activity around the globe?

El Nino/Southern Oscillation (ENSO) - During El Nino events (ENSO warm phase), tropospheric vertical shear is increased inhibiting tropical cyclone genesis and intensification, primarily by causing the 200 mb (12 km or 8 mi) westerly winds to be stronger (Gray 1984). La Nina events (ENSO cold phase) enhances activity. Recently, Tang and Neelin (2004) also identified that changes to the moist static stability can also contribute toward hurricane changes due to ENSO, with a drier, more stable environment present during El Nino events.

Reference: Tang, B. H., and J. D. Neelin, 2004: ENSO Influence on Atlantic hurricanes via tropospheric warming. Geophys. Res. Lett.: Vol 31, L24204. "

The Australian/Southwest Pacific shows a pronounced shift back and forth of tropical cyclone activity with fewer tropical cyclones between 145° and 165°E and more from 165°E eastward across the South Pacific during El Nino (warm ENSO) events. There is also a smaller tendency to have the tropical cyclones originate a bit closer to the equator. The opposite would be true in La Nina (cold ENSO) events. See papers by Nicholls (1979), Revell and Goulter (1986), Dong (1988), and Nicholls (1992).

The Central Pacific basin (140°W to the dateline) appears to experience more tropical cyclone genesis during the El Nino year and more tropical cyclones tracking into the sub-region in the year following an El Nino (Schroeder and Yu 1995) , but this has not been completely documented yet.

The Northwest Pacific basin, similar to the Australian/Southwest Pacific basin, experiences a change in location of tropical cyclones without a total change in frequency. Pan (1981), Chan (1985), and Lander (1994) detailed that west of 160°E there were reduced numbers of tropical cyclone genesis with increased formations from 160°E to the dateline during El Nino events. The opposite occurred during La Nina events. Again there is also the tendency for the tropical cyclones to also form closer to the equator during El Nino events than average.

The eastern portion of the Northeast Pacific, the Southwest Indian, the Southeast Indian/Australian, and the North Indian basins have either shown little or a conflicting ENSO relationship and/or have not been looked at yet in sufficient detail.


6. Where can I get historical data of tropical cyclones?

FREE DATA

  • HURDAT For more detailed information regarding the re-analysis of the Atlantic hurricane database (currently 1851 to 1885) surf to our HURDAT page. To download the actual data go here. Unisys The HURDAT information has be rendered into graphic form by Unisys Corporation and includes a track graphic as well as an ASCII listing for each storm since 1851.
  • NOAA's Coastal Services Center has put together an interactive website that allows the user to search the HURDAT data base by location. You may select a major city or latitude and longitude and find how many storms of a particular strength and over particular ranges of time and proximity have approached that point.

NOT-FREE DATA

  • World Weather Disc: Monthly temp, precip, pressure, sunshine data for about 2000 world stations for period of record. Daily weather data at hundreds of US stations. Data for some stations on temp, precip, freeze, drought, soil moisture, wind, storms. Frequency and movement of tropical cyclones. Contact:
    Cliff Mass
    Dept. of Atmos. Sci. (AK40)
    University of Washington
    Seattle, WA 98195 USA
    (206)685-0910
  • Global Tropical and Extratropical Cyclone Climatic Atlas (GTECCA) 2.0 CD-ROM: This single volume CD-ROM contains global historic tropical storm track data for five tropical storm basins. Period of record vary for each basin, beginning as early as the 1870's, with 1995 as the latest year. Northern hemispheric extratropical storm track data are included from 1965 to 1995. Tropical track data includes time, position, storm stage (maximum wind, central pressure when available). The user has the capability to display tracks, and to track data for any basin or user-selected geographic area. The user is also able to select storm tracks passing within a user-defined radius of any point. Narratives for all tropical storms for the 1980-1995 period are included along with basin-wide tropical storm statistics.
    Contact:
    National Climatic Data Center
    Federal Building
    Asheville, NC 28801 USA
    (704)271-4800
    email ncdc.orders@noaa.gov

HISTORICAL DATA ON-LINE


7. Which tropical cyclone lasted the longest?

Hurricane/Typhoon John lasted 31 days as it traveled both the Northeast and Northwest Pacific basins during August and September 1994. (It formed in the Northeast Pacific, reached hurricane force there, moved across the dateline and was renamed Typhoon John, and then finally recurved back across the dateline and renamed Hurricane John again.) Hurricane Ginger was a tropical cyclone for 28 days in the North Atlantic Ocean in 1971.

It should be noted that prior to the weather satellite era (1961) many tropical cyclone life cycles could be underestimated.

Longest lasting Atlantic Hurricanes
RANK No. of DAYS NAME and YEAR
1 27.25 GINGER 1971
2 24.75 INGA 1969
3 22 KYLE 2002
4 20.75 CARRIE 1957
STORM 9 OF 1893
6 20.25 INEZ 1966
7 19.75 ALBERTO 2000
8 19.50 STORM 4 OF 1926
9 18.50 STORM 6 OF 1893
10 18.00 STORM 2 OF 1930
11 17.75 STORM 2 OF 1899
12 17.50 BEULAH 1967
STORM 3 OF 1906

(From James Franklin and Eric Blake, NHC)

Longest lasting Central Pacific Hurricanes
RANK No. of DAYS NAME and YEAR
1 12.5 FICO 1978
2 11.5 ULEKI 1988
3 11.25 KATE 1976
4 10.75 KEONI 1993

8. What hurricanes have been at Category Five status the longest ?

Here are lists of the longest lived Category 5 storms for three basins since the start of the reconnaissance era (1944). These times are based on the six hourly advisories issued by NHC or JTWC.

Atlantic
Storm and Year Days as Category 5
ALLEN (1980) 3.00 days
DOG (1950) 2.50 days
ISABEL (2003) 1.75 days
DAVID (1979) 1.75 days
MITCH (1998) 1.75 days
East Pacific
Storm and Year Days as Category 5
PAKA (1997) 2.50 days
JOHN (1994) 1.75 days
OLIWA (1997) 1.75 days
LINDA (1997) 1.75 days
GUILLERMO (1997) 1.00 days
AVA (1973) 1.00 days
Central Pacific
Storm and Year Days as Category 5
EMILIA (1994) 0.75 days
GILMA (1994) 0.50 days
JOHN (1994) 1.75 days
West Pacific
Storm and Year Days as Category 5
NANCY (1961) 5.50 days
KAREN (1962) 4.25 days
SALLY (1954) 4.00 days
DINAH (1959) 3.75 days
NINA (1953) 3.50 days

9. How many tropical cyclones have there been in the Central Pacific Basin each year? What years were the greatest and fewest seen?

The average number of tropical cyclones (depressions, storms, and hurricanes) in the Central Pacific Basin is 4 to 5 each year.

The most active years on record were 1992 and 1994 with 11 systems each.

The least active, with 0 systems, were 1977, 1969, 1964, and 1960.
1992 had 4 tropical depressions, 5 tropical storms, and 2 hurricanes.
1994 had 3 tropical depressions, 3 tropical storms, and 5 hurricanes.


10. How many hurricanes have there been in each month?

Tropical Cyclone Systems in the Central Pacific Basin by Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

2

0

1

1

0

1

42

64

32

17

2

1

 

 

Bar graph of tropical cyclones per month in the Central Pacific basin from 1971 to 2008


11. What was the largest number of tropical cyclones in the Central Pacific at the same time?

August 27 and 28, 2002, 3 cyclones, TD remnants of Alika, developing Tropical Storm Ele, and dissipating Tropical Storm Fausto.
August 28, 1978, Tropical Storm John, TD remnants of Kristy, and Tropical Storm Mariam.