Tropical Storm SURIGAE Advisory Thu Apr 22

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 035//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 378 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT 04 KNOTS
OVER THE PAST SIX HOURS. TY SURIGAE CROSSED A SIGNIFICANT CHECKPOINT
DURING THE PAST TWELVE HOURS AND BEGAN A NORTH-NORTHEASTERLY
DIRECTION TOWARDS THE MID-LATITUDES. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) SHOWS THE EYE HAS CONSTRICTED SLIGHTLY AND
IS BEGINNING TO BECOME CLOUD-FILLED. MSI STILL SHOWS A VIGOROUS AND
WELL-ORGANIZED SYSTEM WITH A 45NM EYE WHICH LENDS HIGH CONFIDENCE IN
THE INITIAL POSITION. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS WARMING CLOUD TOPS AND AN EXPANDING CLOUD SHIELD THAT
IS BEGINNING TO STRETCH TO THE NORTHEAST AS SURIGAE FEELS THE
EFFECTS OF VIGOROUS UPPER LEVEL WESTERLIES. BASED ON THE SATELLITE
IMAGERY, THE SYSTEM IS ON A CLEAR WEAKENING TREND. BOTH SUBJECTIVE
AND AUTOMATED DVORAK ASSESSMENTS ARE IN GOOD AGREEMENT (PGTW T5.5,
RCTP T5.0, RJTD T5.5, KNES T5.0), LENDING HIGH CONFIDENCE IN THE 100
KTS INITIAL INTENSITY.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY SURIGAE WILL CONTINUE ON A NORTHEASTERLY BEARING AND WEAKEN
STEADILY DURING THE NEXT 48 HOURS, WITH THE EYE FILLING AND THE
CLOUD SHIELD STRETCHING AS IT DOES SO. ANALYSIS OF STORM CROSS
SECTIONS INDICATE THE BEGINNING OF DRY AIR ENTRAINMENT INTO THE
WESTERN FLANK OF THE SYSTEM WHICH WILL LEAD TO FURTHER WEAKENING IN
THE NEAR TERM. TWO MID-LATITUDE TROUGHS MOVING OFF THE ASIA
CONTINENT WILL AFFECT THE SYSTEM DURING THE NEXT 72 HOURS.  THE
FIRST WILL BE A NEAR MISS AS SURIGAE TRACKS SOUTH OF OKINAWA. IT
WILL STRETCH AND WEAKEN THE SYSTEM BUT NOT PICK IT UP AND CARRY IT
INTO THE MID-LATITUDES.  AS A SHORT WAVE RIDGE BUILDS IN BEHIND THE
FIRST TROUGH IT WILL NUDGE THE SYSTEM SOUTHEASTWARD BETWEEN TAU 48
AND 72. A SECOND, DEEPER SHORT WAVE TROUGH THAT IS CURRENTLY
TRACKING OVER THE GOBI DESERT WILL PICK UP THE SYSTEM NEAR TAU 72
AND LEAD TO THE INITIATION OF EXTRA-TROPICAL TRANSITION (ETT). TRACK
GUIDANCE IS TIGHT THROUGH TAU 72 (NEAR THE 135TH MERIDIAN), THEN
BEGINS TO SPREAD AND VARY IN ALONG-TRACK SPEEDS DURING THE PROCESS
OF ABSORPTION INTO THE THICKNESS RIBBON (BAROCLINIC ZONE).
INTENSITY GUIDANCE HAS CONTINUED TO CONSOLIDATE IN THE LATEST MODEL
RUNS AND LENDS HIGH CONFIDENCE IN A STEADY AND LINEAR DECLINE IN
INTENSITY THROUGH THE FIRST 72 HOURS. DESPITE GOOD CONFIDENCE IN
BOTH TRACK AND INTENSITY FORECAST THROUGH THE FIRST 72 HOURS THE
LACK OF RECENT SCATTEROMETRY AND THE COMING STRETCHING OF THE
WINDFIELDS BY THE UPPER LEVEL TROUGHS MAKE FOR CONSIDERABLY LESS
CONFIDENCE IN THE WIND RADII.
   C. GUIDANCE HAS CRYSTALLIZED REGARDING TY SURIGAE?S TRANSITION TO
AN EXTRA TROPICAL CYCLONE SHORTLY PAST TAU 120. THE GFS SOLUTION
CONTINUES TO DEPICT A DECAPITATION SCENARIO, HOWEVER, AS THE SYSTEM
TRACKS UNDER THE WESTERLIES AND RESULTS IN A MEANDERING LOW LEVEL
VORTEX. THIS SCENARIO CONTINUES TO BE A MODEL OUTLIER. A MORE
STANDARD CASE OF ABSORPTION INTO THE BAROCLINIC ZONE AND TRANSITION
TO A MID-LATITUDE LOW IS BECOMING MORE CONVINCING. ASIDE FROM GFS,
PHASE-BASED GUIDANCE IS UNANIMOUS IN SHOWING THE TRANSITION TO A
COLD CORE. BASED ON THE PREPONDERANCE OF GUIDANCE, THE JTWC FORECAST
IS BASED ON THE EXTRA TROPICAL TRANSITION SCENARIO, ALBEIT WITH
LOWER CONFIDENCE THAN DESIRED GIVEN THE RECENT OUTSTANDING
PERFORMANCE OF THE GFS MODEL. THE HEARTENING NEWS IS THAT EVEN IF
THE GFS SOLUTION DOES MANIFEST, THE LEFTOVER LOW LEVEL VORTEX WILL
BE SO WEAK AND FAR FROM LAND AS TO BE INCONSEQUENTIAL. THE JTWC
TRACK STAYS VERY TIGHT WITH CONSENSUS THROUGH TAU 72, THEN IS HEDGED
A LITTLE EQUATORWARD OF CONSENSUS TOWARDS THE ECMWF AND JGSM
SOLUTIONS. THE JTWC FORECAST REMAINS THAT OF A TEXT-BOOK MID-
LATITUDE TRANSITION AND IS SUPPORTED BY ALL OTHER GUIDANCE.
BEGINNING NEAR TAU 72 (25/00Z) THE EXTRA-TROPICAL TRANSITION PROCESS
WILL BEGIN IN EARNEST AND THE SYSTEM WILL ACCELERATE TO THE
NORTHEAST WHILE BECOMING ABSORBED INTO THE BAROCLINIC ZONE. THE
INTENSITY FORECAST REMAINS IN THE MIDDLE OF THE ENVELOPE ON
INTENSITY GUIDANCE THROUGHOUT THE FORECAST. A BRIEF BUMP IN
INTENSITY WILL OCCUR AS IT FUSES WITH THE BAROCLINIC ZONE AND
BECOMES A VIGOROUS STORM FORCE LOW WHILE TRACKING TO THE SOUTHEAST
OF IWO TO.//
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