This is one of the most interesting weather updates I have had the pleasure to read, especially since it concerns the fate of a system which used to be a menacing typhoon, and then a collapsing tropical storm, and is at the time of this writing, a mere tropical depression. From reading the series of these updates, I get the feeling that there has been lively debate (possibly with thrown crockery) at the Joint Typhoon Warning Center, which uniformly turns in a great product. I reproduce it here in full, and will likely refer back to this post from a more informed future post.
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL DEPRESSION 08W (MA-ON) WARNING NR 040
DOWNGRADED FROM TROPICAL STORM 08W
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
—
WARNING POSITION:
210600Z — NEAR 30.4N 140.8E
MOVEMENT PAST SIX HOURS – 125 DEGREES AT 14 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS – 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 30.4N 140.8E
—
FORECASTS:
12 HRS, VALID AT:
211800Z — 30.2N 142.5E
MAX SUSTAINED WINDS – 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 24 HR POSIT: 060 DEG/ 08 KTS
—
24 HRS, VALID AT:
220600Z — 31.0N 144.0E
MAX SUSTAINED WINDS – 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 36 HR POSIT: 035 DEG/ 10 KTS
—
36 HRS, VALID AT:
221800Z — 32.7N 145.3E
MAX SUSTAINED WINDS – 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 48 HR POSIT: 030 DEG/ 17 KTS
—
EXTENDED OUTLOOK:
48 HRS, VALID AT:
230600Z — 35.6N 147.3E
MAX SUSTAINED WINDS – 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
VECTOR TO 72 HR POSIT: 030 DEG/ 17 KTS
—
72 HRS, VALID AT:
240600Z — 41.4N 151.9E
MAX SUSTAINED WINDS – 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
—
REMARKS:
210900Z POSITION NEAR 30.4N 141.2E.
TROPICAL DEPRESSION 08W (MA-ON), LOCATED APPROXIMATELY 300 NM
SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED SOUTHEASTWARD AT 14 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A FILLING, PARTIALLY-EXPOSED AND CLOUD-FREE LOW-LEVEL
CIRCULATION CENTER (LLCC). MSI ANIMATION ALSO SHOWS AN EXTENSIVE
FIELD OF COLD AIR STRATOCUMULUS FLOWING DOWN THE KANTO AND INTO THE
SYSTEM. A 202349Z ASCAT IMAGE SHOWS THE HIGHEST WINDS ASSOCIATED
WITH THE SYSTEM ARE DISPLACED AWAY FROM THE LLCC, IN THE
NORTHEASTERLIES OFF-SHORE OF TOKYO AND IN THE CONVERGENT
SOUTHWESTERLIES SOUTH OF THE SYSTEM. THE SOUTHERN SEMICIRCLE IS THE
ONLY AREA OF DEEP CONVECTION, AND THAT IS DUE TO STRAIGHT-LINE
CONVERGENCE WITHIN THE GRADIENT FLOW.
[pullquote]NOT SO FAST![/pullquote]
BOTH A 201637Z AMSRE AND A
202333Z SSMI MICROWAVE SERIES SHOWS A BROAD, OPEN LLCC WITH NO DEEP
CONVECTION ANYWHERE NEAR THE CORE. ATSUGI AND YOKOTA ARE REPORTING
TEMPERATURE FALLS OF 20 DEGREES FAHRENHEIT FROM THEIR PRE-08W
CONDITIONS. THE MOISTURE FRONT LIES BETWEEN HANEDA AIRPORT (RJTT)
AND HACHIOJIMA (RJTH), AS THERE IS AN EIGHT DEGREE CELSIUS DEW POINT
CONTRAST BETWEEN THE TWO STATIONS, AND HACHIOJIMA IS STILL IN THE
TROPICAL AIR. THE COLD AIR STRATOCUMULUS AND FALLING TEMPERATURES
OVER THE KANTO COMBINED WITH THE MERGE OF THE SYSTEM WITH AN
EXTENSIVE FRONTAL BOUNDARY THAT STRETCHES OVER THE WESTERN PACIFIC
FROM OFF-SHORE OF JAPAN INTO THE GULF OF ALASKA GIVE TD 08W THE
SIGNATURE OF A SYSTEM THAT IS UNDERGOING EXTRA-TROPICAL TRANSITION
AND FORMING A WAVE ALONG THE BAROCLINIC BOUNDARY. NOT SO FAST,
HOWEVER. HI-RES VISUAL IMAGERY SHOWS THE LLCC IS SEPARATED SLIGHTLY
FROM THE BAROCLINIC BOUNDARY, AND AMSU TEMPERATURE PROFILES STILL
SHOW MID-LEVEL WARM ANOMALIES TYPICAL OF A MATURE TROPICAL SYSTEM.
500 MB HEIGHT VALUES ARE ALSO TROPICAL. FURTHERMORE, THE
SOUTHEASTWARD COURSE OF THE SYSTEM WILL ALSO ALLOW IT TO OPEN SOME
MORE SEPARATION FROM THE BAROCLINIC ZONE.
VERTICAL WIND SHEAR IS
STILL LESS THAN 20 KNOTS, NOT TYPICAL OF A SYSTEM UNDERGOING NORMAL
EXTRATROPICAL TRANSITION, AND VALUES ARE EXPECTED TO DECREASE AS THE
SYSTEM TRACKS SOUTHEASTWARD. THE PGTW 210000Z UPPER LEVEL STREAMLINE
ANALYSIS REVEALS THAT TD 08W EXISTS IN A MODERATELY DIFFLUENT REGION
VERY CLOSE TO THE SUBTROPICAL RIDGE AXIS. WATER VAPOR ANIMATION
SHOWS THAT THE POLAR FRONT JET IS WELL EAST OF THE LLCC, DIVING DOWN
ALONG THE 150TH MERIDIAN DUE TO A BLOCKING PATTERN OVER THE NORTHERN
SEA OF JAPAN. WATER VAPOR IMAGERY AND 200MB ANALYSIS REVEAL THAT THE
NORTHWESTERLIES FLOWING OVER THE TOHOKU REGION AND TOWARDS TD 08W
ARE ACTUALLY A FINGER OF THE SUBTROPICAL JET, WHICH HAS BEEN
DISPLACED POLEWARD DUE TO THE UPSTREAM RIDGE. ALL IN ALL THEN, TD
08W EXISTS IN AN EXTREMELY COMPLEX, ATYPICAL ENVIRONMENT AND IS
LIKEWISE SHOWING ATYPICAL BEHAVIORS.
[pullquote]DIFFICULT TO VIEW WITHOUT SKEPTICISM[/pullquote]
MODEL GUIDANCE DID FAIRLY WELL
TO PREDICT THE SOUTHEASTWARD TURN IN THE TRACK, AT LEAST FROM INSIDE
72, BUT ARE STRUGGLING WITH THE EXTRATROPICAL TRANSITION PROCESS AND
THE INTENSITY DURING THAT PHASE. MOST INDICATE THAT TD 08W WILL
UNDERGO AN EXTREMELY SLOW EXTRA-TROPICAL TRANSITION AND DEVELOP
SUBTROPICAL CHARACTERISTICS AS IT IS FORCED POLEWARD ALONG THE
WESTERN BOUNDARY OF A THE BLOCKING RIDGE BEGINNING TO FORM OVER THE
WESTERN PACIFIC. MANY ALSO PREDICT TD 08W WILL MAINTAIN TROPICAL
HEIGHT VALUES AT 500 MB AS FAR POLEWARD AS THE KURILS, WHICH IS
DIFFICULT TO VIEW WITHOUT SKEPTICISM.
[pullquote]CONSENSUS IS BEING DISTORTED BY AN INCOHERENT GFDN TRACK[/pullquote]
SEA SURFACE TEMPERATURES ARE
FAVORABLE FOR DEVELOPMENT AND MAINTENANCE OF WARM CORE
CHARACTERISTICS ONLY THROUGH 35N (APPROXIMATELY TAU 48). GIVEN THAT
THE LLCC IS MOVING UNDER A REGION OF DECREASING VERTICAL WIND SHEAR
AND INCREASING DIVERGENCE, MILD RE-INTENSIFICATION DURING THE NEXT
48 HOURS IS PLAUSIBLE. AFTER TAU 48, THE SHARP DROP-OFF IN SEA
SURFACE TEMPERATURE WILL WEAKEN WHAT IS LEFT OF THE SYSTEM
REGARDLESS OF THE UPPER LEVEL ENVIRONMENT. THE TRACK FORECAST IS
BETWEEN ECMWF AND JGSM, AS CONSENSUS IS BEING DISTORTED BY AN
INCOHERENT GFDN TRACK.NEXT WARNINGS AT 211500Z, 212100Z, 220300Z AND
220900Z.//
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