WPAC: OMAIS - Post-Tropical

[Subtrop]

16W SIXTEEN 210810 1200 12.2N 179.0E WPAC 25 1007

[Hayabusa]

First warning

WDPN31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 12.2N 179.0E
INITIAL INTENSITY: 25 KTS
GEOGRAPHIC REFERENCE: 553 NM NORTHEAST OF MAJURO
MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAPIDLY CONSOLIDATING SYSTEM, WITH DEVELOPING SPIRAL BANDS AND DEEP
FLARING CONVECTION, WITH OCCASIONAL OVERSHOOTING TOPS, NEAR THE
ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). THERE HAS BEEN A LACK
OF RECENT MICROWAVE IMAGERY AND ASCAT PASSES, THUS ANALYSIS OF THE
VISIBLE OUTER BANDS IN THE SHORTWAVE INFRARED (SWIR) BANDS, AND THE
AGENCY FIX POSITIONS, LEND ONLY MEDIUM CONFIDENCE TO THE INITIAL
POSITION. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES, ALONG WITH A
SERIES OF SCATTEROMETER PASSES BETWEEN THE 0600Z-0730Z HOURS WHICH
INDICATED 25-30 KNOT WINDS IN THE EASTERN HEMISPHERE AND 20-25
KNOTS IN THE WESTERN HEMISPHERE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: LOW TO MID-LEVEL SUBTROPICAL RIDGE
(STR) COMPLEX TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T1.5 - 25 KTS
KNES: T1.5 - 25 KTS
PHFO: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 5-10 KTS
SST: 28-29 CELSIUS
OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
INITIAL POSITION: MEDIUM
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL DEPRESSION 16W (SIXTEEN) HAS RAPIDLY
CONSOLIDATED OVER THE PAST 12 HOURS AS IT CROSSED THE DATELINE.
MID-LEVEL DRY AIR AND SOME SHEAR ON THE WESTERN PERIPHERY HAD
CONSTRAINED CONVECTIVE DEVELOPMENT AND HELD THE CONVECTION OFF TO
THE EAST OF THE LLCC DURING THE DAY. AN INFLUX OF MOISTURE AND A
RELAXATION AND REORIENTATION OF THE SHEAR VECTOR, HAS ALLOWED THE
CONVECTION TO EXPAND WESTWARD OVER THE LLCC OVER THE PAST SIX
HOURS. IN THE UPPER LEVELS, CIMSS ANALYSIS AND JTWC 200MB ANALYSIS
REVEALS A SMALL POINT SOURCE OVER TOP OF TD 16W, WHILE A TUTT CELL
LIES ABOUT 700 NM TO THE NW, PROVIDING MODERATE TO STRONG POLEWARD
OUTFLOW ALONG THE EASTERN SIDE OF THE TUTT. THE SYSTEM HAS SLOWED
IN FORWARD SPEED OVER THE PAST TWELVE HOURS AS IT HAS MOVED INTO A
SLIGHTLY WEAKER STEERING ENVIRONMENT IN THE WEAK GRADIENT BETWEEN
LOW TO MID-LEVEL STR CENTER NW OF KAUAI AND ANOTHER LARGER STR
CENTER NEAR 30N 150E. FOR THE DURATION OF THE FORECAST PERIOD, TD
16W IS EXPECTED TO CONTINUE TRACKING GENERALLY WESTWARD, ALONG A
SHALLOW SINE-WAVE TRACK WITH MINOR DEVIATIONS NORTH AND SOUTH OF
DUE WEST, ALONG THE BASE OF THE STR TO THE NORTH. TD 16W IS
FORECAST TO INTENSIFY TO 35 KNOTS WITHIN THE NEXT 12 HOURS, AS THE
TUTT CELL TO THE NORTHWEST MOVES WEST AHEAD OF TD 16W AND REMAINS
IN A FAVORABLE POSITION TO SUPPORT CONTINUED STRONG POLEWARD
OUTFLOW. BY TAU 36 THE TUTT MOVES OUT OF THE AREA AND IS REPLACED
BY RIDGING ALOFT, PUSHING NORTHEASTERLY FLOW OVER TOP OF TD 16W AND
WEAKENING THE OUTFLOW. WHILE THE SYSTEM WILL REMAIN IN RELATIVELY
LOW SHEAR AND OVER VERY WARM WATERS, THE LACK OF OUTFLOW WILL
INHIBIT DEVELOPMENT, LEADING TO WEAKENING THROUGH TAU 72.
THEREAFTER, WEAK EQUATORWARD OUTFLOW WILL OFFSET LOW TO MODERATE
VWS AND WARM SSTS, WITH TD 16W MAINTAINING WEAK MINIMAL TROPICAL
DEPRESSION STRENGTH THROUGH THE REMAINDER OF THE FORECAST.

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE IS IN GOOD AGREEMENT,
WITH THE MAJORITY OF AVAILABLE TRACKERS CLUSTERED WITHIN A 60 NM
ENVELOPE AT TAU 48, INCREASING TO 135 NM AT TAU 120. NAVGEM IS THE
SOLE OUTLIER, THAT WHILE FOLLOWING THE SAME TRACK SHAPE, IS
DISPLACED WELL NORTH OF THE OTHER TRACKERS. THE JTWC FORECAST LIES
SOUTH OF THE MULTI-MODEL CONSENSUS, AND CLOSELY TRACKS THE GFS
ENSEMBLE WITH HIGH CONFIDENCE. THE INTENSITY GUIDANCE IS MIXED,
WITH THE DECAY SHIPS (GFS AND NAVGEM) INDICATE SIGNIFICANT
STRENGTHENING AFTER TAU 72, WHILE THE COAMPS-TC AND HWRF MODELS
INDICATING MORE MODERATE NEAR-TERM INTENSIFICATION AND A FLAT
TRAJECTORY THEREAFTER. ANALYSIS OF THE SHIPS GUIDANCE INDICATES THE
SHARP INTENSIFICATION IS DUE PRIMARILY TO SST POTENTIAL AND SAMPLE
CHANGE VICE ENVIRONMENTAL PARAMETERS, WHILE THE HWRF AND OTHER
MODELS SEEM TO BE TRACKING THE CHANGES IN THE ENVIRONMENT AND ARE
MORE REALISTIC IN THEIR IMPACTS. HENCE THE JTWC FORECAST TRACKS
CLOSE TO THE CONSENSUS THROUGH TAU 48 WITH MEDIUM CONFIDENCE, AND
BELOW THE CONSENSUS THROUGH THE REMAINDER WITH LOW CONFIDENCE.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
TRACK 72-120 HR: HIGH
INTENSITY 0 - 72 HR: MEDIUM
INTENSITY 72-120 HR: LOW//
NNNN

[Sciencerocks]

[InfernoFlameCat]

https://imagizer.imageshack.com/img922/788/oe91DC.gif

Oh man the cpac failed hard

[Sciencerocks]

[Yellow Evan]

[Kingarabian]

Still sorta exposed to the west but looks better than what's currently in the EPAC so far.

[Hayabusa]

Here are the TCs that peaked during the month of August, originated at least 160E and tracked at least 40 degrees of lon

[Sciencerocks]

[Hayabusa]

Unless 16W intensifies more than what the models expect, seems after crossing the Marianas that some models like ICON really start to intensify it.

[Kingarabian]

Here are the TCs that peaked during the month of August, originated at least 160E and tracked at least 40 degrees of lon
https://i.imgur.com/zzHHOQS.png

Pretty ominous signal then that this could become a significant TC down the line.

[Sciencerocks]

[Hayabusa]

I like this latest discussion of how's and why's of 16W, also noted possible favorable development in the later taus

WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN)
WARNING NR 007//
FORECAST DISCUSSION: TROPICAL DEPRESSION 16W IS A WEST RUNNER. THE
SUBTROPICAL RIDGE WILL STEER THE SYSTEM STEADILY ALONG TRACK NEAR
THE 12TH LATITUDE AND IT WILL INCREASE IN SPEED ONLY SLIGHTLY FROM
ITS CURRENT 10 KNOTS TO 14 KNOTS NEAR TAU 120. THE ACTIVE PHASE OF
THE MADDEN JULIAN OSCIALLATION (MJO) THAT WREAKED HAVOC WITH THE
UPPER AIR PATTERN OVER THE WESTERN PACIFIC BASIN AND CAUSED
INCREASED TROPICAL CYCLONE ACTIVITY OVER THE PREVIOUS TWO WEEKS HAS
PASSED DOWNSTEAM AND PRONOUNCED CONVERGENCE NOW EXISTS OVER THE
BASIN, SUPPRESSING TC FORMATION AND DEVELOPMENT. STREAMLINE
ANALYSIS CONFIRMS THAT THE MONSOON TROF HAS BEEN WIPED OUT, FORCING
SYSTEMS TO STRUGGLE TO DEVELOP WITHIN THE DEEP EASTERLIES. ONE OF
THE FEW FACTORS IN FAVOR OF SYSTEM SUSTAINMENT IS THAT IT IS AUGUST
IN THE WESTERN PACIFIC. OTHERWISE, ENVIRONMENTAL CONDITIONS ARE
UNFAVORABLE FOR INTENSIFICATION IN A VARIETY OF WAYS. BOTH AMERICAN
AND EUROPEAN 850MB VORTICITY MODELS SUPPORT SUSTAINMENT OF A
MARGINAL VORTEX THROUGH TAU 120, AND IF THE SYSTEM MANAGES TO STAY
INTACT, IT WILL ENCOUNTER MORE FAVORABLE CONDITIONS IN THE
PHILIPPINE SEA. UNTIL THEN, THE SYSTEM IS EXPECTED TO STRUGGLE IN
THE 25-30 KT RANGE AND FLUCTUATE ONLY DIRUNALLY. THE SUPPRESSIVE
PHASE OF THE MJO IS EXPECTED TO PEAK THIS WEEK, ALLOWING FOR A
GRADUAL RETURN OF TO MORE SEASONABLE CONDITIONS.

MODEL DISCUSSION: TRACK GUIDANCE IS IN OUTSTANDING AGREEMENT, EVEN
FOR A WEST RUNNER. ALONG TRACK SPEEDS ARE REMARKABLY CONSISTENT.
INTENSITY GUIDANCE IS SKEPTICAL OF ANY INTENSIFICATION THROUGH TAU
120 WITH THE EXCEPTION OF SHIPS GUIDANCE, WHICH IS DISMISSED
BECAUSE IT IS GROSSLY UNDERESTIMATING THE CURRENT LEVEL OF SHEAR.
THE GFS ENSEMBLE IS NEARLY UNAMIMOUS IN MAINTAINING A FLAT
INTENISTY THROUGH TAU 120, WHILE NEARLY HALF OF THE ECMWF ENSEMBLE
MEMBERS LOSE THE VORTEX UPSTREAM OF GUAM. THE JTWC FORECAST LEANS
TOWARDS THE MAJORITY OF ENSEMBLE GUIDANCE AND SUSTAINS A MARGINAL
SYSTEM THROUGH TAU 120.

[Hayabusa]

Latest GFS has a TS just before passing the Marianas

[dexterlabio]

MSLP forecast maps from the Euro show a discernable closed low, albeit weak, tracking towards Luzon strait in 10 days. I don't know if this is just the Euro being Euro with its very conservative forecasts but I consider this as a development that 16W is something to watch out for.


EDIT: Apparently CMC, NAVGEM, and ICON also develop 16W further into typhoon category but real consolidation will start in 5 days.

[Sciencerocks]

[mrbagyo]

[Hayabusa]

Upgraded to TS

16W SIXTEEN 210813 0000 12.7N 168.6E WPAC 35 1007

[mrbagyo]

Upgraded to TS

16W SIXTEEN 210813 0000 12.7N 168.6E WPAC 35 1007

just over 200 nautical miles ENE from Spongebob and company

[mrbagyo]