JTWC 升評Medium

THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 20.2S
165.5W, IS NOW LOCATED NEAR 20.5S 167.7W, APPROXIMATELY 405 NM SOUTH-
SOUTHEAST OF PAGO PAGO, AMERICAN SAMOA. ANIMATED INFRARED SATELLITE
IMAGERY REVEALS A WELL DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH PERSISTENT CENTRAL CONVECTION AND BROKEN CONVECTIVE BANDING
ALONG THE SOUTHERN SEMI-CIRCLE. A 220912Z AMSU-B MICROWAVE IMAGE
REVEALS A BROAD CIRCULATION WITH A SMALL AREA OF SHEARED DEEP
CONVECTION TO THE NORTHWEST. A 220913Z ASCAT PASS SHOWS A HIGHLY
ASYMMETRIC WIND FIELD WITH SOME 25 TO 30 KNOT WINDS DISPLACED FROM
THE LLCC. UPPER LEVEL ANALYSIS REVEALS A POOR ENVIRONMENT AS AN
UPPER-LEVEL LOW IS POSITIONED OVER THE LLCC ALL WHILE MODERATE (15-
25 KNOTS) VERTICAL WIND SHEAR CONTINUES TO ACT UPON THE SYSTEM.
ANIMATED WATER VAPOR IMAGERY, HOWEVER, IS STARTING TO SHOW THE LOW
IS BEGINNING TO FILL WHICH WOULD ALLOW FOR A MORE FAVORABLE
ENVIRONMENT. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO
30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1001
MB. DUE TO THE IMPROVING UPPER LEVEL ENVIRONMENT, WHICH IS ALLOWING
THIS SYSTEM TO BECOME TROPICAL IN NATURE, THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO MEDIUM.