Invests have numbers from 90 to 99 , with a L in the Atlantic , E and C in the East and Central Pacific in that order , or W in the West Pacific after the number . Invests are numbered from 90 to 99 , followed by L in the Atlantic , E and C in the East and Central Pacific respectively , or W in the West Pacific ; the Joint Typhoon Warning Center also issues unofficial warnings for the Australian cyclone region , designating tropical invests with the `` S '' suffix when they form west of 135 Â E , and the `` P '' suffix when they form east of 135 Â E. Invests in the North Indian Ocean cyclone basin are also labeled by the JTWC , and are suffixed with `` A '' if they form in the Arabian Sea and with `` B '' if they form in the Bay of Bengal . Numbers are rotated within the season and are re-used as necessary ( the next invest after 99 would be numbered 90 ) .