Inmeteorology, aninvest (short for "investigative area")[1] is a designated area of disturbed weather that is monitored for potentialtropical cyclone (TC) development. Invests are designated by three separateUnited States forecast centers: theNational Hurricane Center, theCentral Pacific Hurricane Center, and theJoint Typhoon Warning Center.
Invests (also calledareas of interest) are designated by three separate forecast centers located in the United States: theNational Hurricane Center inMiami,Florida, overseeing theNorth Atlantic andNorth Eastern Pacificbasins (east of the 140°W meridian); theCentral Pacific Hurricane Center inHonolulu,Hawaii, monitoring theNorth Central Pacific basin (between theInternational Date Line and the 140°W meridian); and the militaryJoint Typhoon Warning Center inPearl Harbor, Hawaii (formerly located in the island ofGuam), serving U.S. government interests elsewhere (i.e. theNorth Western Pacific basin west of the International Date Line). The designation of a system as an invest does not necessarily correspond to any particular likelihood of development of the system into a tropical cyclone (tropical depression, tropical storm, or hurricane/typhoon).
| Basin(s) | Warning Center | Suffix | Rolling numbers |
|---|---|---|---|
| N Atlantic | NHC | L | from Invest-90L to Invest-99L |
| NE Pacific (E of 140°W) | E | from Invest-90E to Invest-99E | |
| NC Pacific (E of IDL, W of 140°W) | CPHC | C | from Invest-90C to Invest-99C |
| NW Pacific (W ofIDL) | JTWC | W | from Invest-90W to Invest-99W |
| N Indian O. (Bay of Bengal) | JTWC (unoff.) | B | from Invest-90B to Invest-99B |
| N Indian O. (Arabian Sea) | A | from Invest-90A to Invest-99A | |
| SW Indian O. &Australian reg. (W of 135°E) | S | from Invest-90S to Invest-99S | |
| Australian reg. &S Pacific (E of 135°E) | P | from Invest-90P to Invest-99P | |
| S Atlantic | NRL,NHC (unoff.) | Q | from Invest-90Q to Invest-99Q |
| Mediterranean | SAB (unoff.) | M | from Invest-90M to Invest-99M |
Invests are numbered from 90 to 99, followed by a suffix letter "L" in the North Atlantic basin, "E" and "C" in the Eastern and Central Pacific basins (respectively), or "W" in the Western Pacific basin.[2]
TheJoint Typhoon Warning Center also issues unofficial warnings for U.S. government interests (predominantly military) in the Southern Hemisphere, designating tropical invests with the "S" suffix when they form west of 135°E (this spans the whole SouthIndian Ocean, including theSouth-Western Indian Ocean basin and the western half of theAustralian-region basin), and the "P" suffix when they form east of 135°E (spans both the eastern half of the Australian region and theSouth Pacific basin). In addition, invests in theNorth Indian Ocean cyclone basin are also labelled by the JTWC, and are suffixed with "A" if they form in theArabian Sea and with "B" if they form in theBay of Bengal.
TheNaval Research Laboratory's Marine Meteorology Division also uses the "Q" suffix to designate invests which form in theSouth Atlantic Ocean,[3][4] even though it is not recognized as an official tropical cyclone basin by theWorld Meteorological Organization.
These suffix letters (with the usual exception of "L") are also used with thetropical cyclone numbers (TC numbers for short) assigned to tropical and subtropical depressions (and potential tropical cyclones) monitored by the NHC & CPHC (North Atlantic systems are usually designated by TC numbers without a suffix letter; the "L" is still used, however, by the NRL for this basin) and all tropical, subtropical, and potential tropical cyclones tracked by the JTWC.[5]
Numbers are rotated within the season and are re-used as necessary (the next invest after 99 would be numbered 90). In contrast, TC numbers start each year/season with 01 and run upwards, usually up to 30 in NHC and CPHC-monitored basins.[6] The hard-coded limit imposed by theAutomated Tropical Cyclone Forecasting System is 49. TC numbers assigned to proper cyclones (tropical, subtropical, and potential tropical) are not recycled until the following year/season. If the invest system develops into a (sub)tropical cyclone, it is reclassified as the next name/number on the list. This is a TC number if evolving into a depression or JTWC cyclone; or a name if evolving quickly into a tropical or subtropical storm, bypassing the depression stage). The NHC also numbers cyclones based on previous seasons.
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