Tropical Storm OCTAVE

ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM OCTAVE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP152013
200 PM PDT SUN OCT 13 2013
 
DURING THE PAST 6 HOURS...OUTER BAND CONVECTION HAS DISSIPATED WHILE
INNER CORE CONVECTION HAS MADE SOMEWHAT OF A COMEBACK.  THE INNER
CORE CONVECTION NOW CONSISTS OF A SMALL RING OF CONVECTION ABOUT
100 NMI IN DIAMETER WITH A 25 NMI DIAMETER EYE FEATURE EMBEDDED
NEARLY IN THE CENTER OF THE CONVECTIVE RING.  HOWEVER...SEVERAL
PASSIVE MICROWAVE IMAGES INDICATE THAT THE MID-/UPPER-LEVEL EYE
FEATURE IS TILTED MORE THAN 20 NMI TO THE NORTH OF THE LOW-LEVEL
CENTER. SATELLITE INTENSITY ESTIMATES HAVE JUMPED SHARPLY TO
T4.0/65 KT FROM TAFB AND T3.5/55 KT FROM SAB SINCE THE PREVIOUS
ADVISORY...BUT A 1639Z ASCAT-B OVERPASS ONLY REVEALED 35-40 KT
WINDS WITHIN 20 NMI EAST OF THE CENTER...AND A 1725Z ASCAT-A
OVERPASS ONLY INDICATED 45 KT IN THE EASTERN EYEWALL. THIS SUGGESTS
THAT OCTAVE MIGHT NOT BE AS STRONG AS THE SATELLITE SIGNATURES
INDICATE. THE INITIAL INTENSITY BLENDS THESE ESTIMATES AND IS
GENEROUSLY SET TO 55 KT. UW-CIMSS SHEAR ANALYSES INDICATE THAT
OCTAVE IS EXPERIENCING 15-20 KT OF SOUTHERLY MID-LEVEL SHEAR THAT
IS UNDERCUTTING THE OTHERWISE FAVORABLE 6 KT OF 850-200 MB SHEAR...
WHICH EXPLAINS THE NORTHWARD TILT OF THE EYE FEATURE. SOME
ADDITIONAL STRENGTHENING IS POSSIBLE DURING THE NEXT 12 HOURS OR
SO...BUT THE TILTED EYE FEATURE...ALONG WITH THE RATHER COMPACT
SIZE OF THE CYCLONE...MEANS THE OCTAVE SHOULD QUICKLY WEAKEN ONCE
IT MOVES OVER MUCH COOLER WATERS IN ABOUT 18-24 HOURS. AFTER
THAT...STEADILY INCREASING SOUTHWESTERLY SHEAR SHOULD DECOUPLE THE
LOW- AND UPPER-LEVEL CIRCULATIONS...RESULTING IN OCTAVE BECOMING A
REMNANT LOW BY 96 HOURS...IF NOT SOONER.
 
THE INITIAL MOTION ESTIMATE IS 335/11 KT. OCTAVE SHOULD CONTINUE TO
MOVE AROUND THE WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE
THROUGHOUT THE FORECAST PERIOD. THE CYCLONE SHOULD GRADUALLY SLOW
DOWN AND TURN NORTHWARD BY MONDAY AND TOWARD THE NORTH-NORTHEAST
AND NORTHEAST ON TUESDAY. BY WEDNESDAY...A VERTICALLY SHALLOW AND
WEAK OCTAVE COULD BECOME NEARLY STATIONARY AS IT APPROACHES THE
SOUTHWESTERN COAST OF THE BAJA CALIFORNIA AND COMPLETELY DECOUPLES.
THE MID-/UPPER-LEVEL CIRCULATIONS AND THE ASSOCIATED MOISTURE
PLUME...HOWEVER...SHOULD CONTINUE TO MOVE NORTHEASTWARD AND SPREAD
LOCALLY HEAVY RAINS ACROSS BAJA AND NORTHERN MEXICO AND INTO THE
SOUTHWESTERN U.S.  THE NHC FORECAST TRACK IS SIMILAR TO THE
PREVIOUS TRACK...AND IS CLOSE TO A BLEND OF THE TCVE AND FSSE
MODELS.
 
DESPITE THE RECENT STRENGTHENING OF OCTAVE...THE CURRENT TRACK
AND INTENSITY FORECASTS...PLUS AVAILABLE INTENSITY GUIDANCE...DOES
NOT WARRANT ANY TROPICAL STORM WATCHES OR WARNINGS FOR THE BAJA
CALIFORNIA PENINSULA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/2100Z 19.2N 112.7W   55 KT  65 MPH
 12H  14/0600Z 20.6N 113.5W   55 KT  65 MPH
 24H  14/1800Z 22.3N 113.7W   45 KT  50 MPH
 36H  15/0600Z 23.7N 113.6W   35 KT  40 MPH
 48H  15/1800Z 24.6N 113.2W   30 KT  35 MPH
 72H  16/1800Z 25.1N 113.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  17/1800Z 26.0N 112.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  18/1800Z...DISSIPATED
 
$$
FORECASTER STEWART
 
NNNN