NOUS40KWBC 191420 FOS/NOAAPORT NOTICE NO. 1790 AUGUST 19... 2000 ATTENTION FAMILY OF SERVICES SUBSCRIBERS/NOAAPORT USERS SUBJECT NOTICE OF INTENT TO CHANGE AVN MOS GUIDANCE EFFECTIVE WITH THE 1200 UTC FORECAST CYCLE ON SEPTEMBER 19... 2000 GUIDANCE FOR THE PROBABILITY OF THUNDERSTORMS... THE CONDITIONAL PROBABILITY OF SEVERE THUNDERSTORMS... AND THE PROBABILITY OF PRECIPITATION /POP/ WILL BE ADDED TO THE NEW AVN MOS MESSAGES. THESE MESSAGES ARE IDENTIFIED WITH WMO HEADERS FOPA20... FOUS21-FOUS26... AND FOAK37-FOAK39... AND ARE STORED AS MAV PRODUCTS IN THE AWIPS TEXT DATA BASE. PROBABILITIES FOR BOTH 6- AND 12-H PERIODS WILL BE DISPLAYED ON THE MESSAGES. FOR THE POP... THE 6-H PROBABILITIES WILL BE VALID EVERY 6 HOURS FROM 6-12... 12-18... AND 66-72 HOURS AFTER 0000 OR 1200 UTC. THESE PROBABILITIES ARE GIVEN ON THE LINE LABELED P06. EXCEPT FOR THE HAWAII STATIONS GIVEN IN THE FOPA20 MESSAGE... THE POP FOR 12-H PERIODS WILL BE VALID EVERY 12 HOURS FROM 12-24... 24-36.... AND 60-72 HOURS AFTER 0000 OR 1200 UTC. FOR THE HAWAIIAN SITES THE 12-H POPS ARE VALID FROM 6-18... 18-30 ... AND 54-66 HOURS AFTER 0000 OR 1200 UTC. ALL THE 12-H POP FORECASTS ARE DISPLAYED ON THE LINE LABELED P12. BECAUSE OF THE DATABASE USED IN DEVELOPMENT... THE THUNDERSTORM AND SEVERE THUNDERSTORM PROBABILITIES ARE AVAILABLE ONLY FOR STATIONS IN THE CONTIGUOUS U.S. AS WITH POP... THUNDERSTORM PROBABILITIES AND CONDITIONAL /UPON THUNDERSTORMS OCCURRING/ SEVERE THUNDERSTORM PROBABILITIES ARE VALID FOR 6-H PERIODS FROM 6-12... 12-18... AND 66-72 HOURS AFTER 0000 AND 1200 UTC. THE GUIDANCE FOR THE 6-H PERIODS IS AVAILABLE ON THE LINE LABELED T06 ...WITH THE THUNDERSTORM PROBABILITY TO THE LEFT OF THE SLASH... AND THE SEVERE THUNDERSTORM PROBABILITY FOR THE SAME PERIOD TO THE RIGHT OF THE SLASH. THUNDERSTORM PROBABILITIES AND CONDITIONAL SEVERE THUNDERSTORM PROBABILITIES ARE ALSO AVAILABLE FOR 12-H PERIODS FROM 6-18.. 18-30.. 30-42.. 42-54..AND 54-66 HOURS AFTER 0000 AND 1200 UTC. THE GUIDANCE FOR THE 12-H PERIODS IS SHOWN ON THE LINE LABELED T12... WITH THE THUNDERSTORM PROBABILITY TO THE LEFT OF THE SLASH... AND THE SEVERE THUNDERSTORM PROBABILITY FOR THE SAME PERIOD TO THE RIGHT OF THE SLASH. MORE DETAILS ON THE NEW GUIDANCE MAY BE FOUND AT THE FOLLOWING HTTP//WWW.NWS.NOAA.GOV/TDL/SYNOP/MOS2000.HTM HTTP//WWW.NWS.NOAA.GOV/OM/TPB/463.PDF END NNNN