WPAC: TEMBIN - Post-Tropical

[euro6208]

Downgraded to LOW earlier in the day...

THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED
NEAR 6.9N 142.9E, IS NOW LOCATED NEAR 7.9N 140.8E, APPROXIMATELY
364 NM EAST OF PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND
A 172353Z AMSU METOP-B 89GHZ IMAGE DEPICT A DISORGANIZED LOW LEVEL
CIRCULATION (LLC). A RECENT ASCAT PASS SHOWS AN ILL-DEFINED AND
ELONGATED LLC WITH WINDS 10-15 KNOTS LOCATED TO THE WEST OF THE
LLC. OVER THE LAST 24 HOURS UPPER LEVEL ANALYSIS SHOWS THE
DISTURBANCE REMAINING IN AN AREA OF LOW TO MODERATE (10-15 KNOTS)
VERTICAL WIND SHEAR, OFFSET BY WEAK DIFFLUENCE ALOFT. THE SYSTEM
RESTS IN AN AREA OF WARM SSTS (30-31 CELSIUS), SUPPORTING THE
DISTURBANCES FUELING PROCESS. GLOBAL MODELS REMAIN MIXED SHOWING
DIFFERENCES IN CONSOLIDATION WITH NO AGREEMENT ON TRACK MOTION.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS REMAINS LOW.

[xtyphooncyclonex]

Taiwan's CWB has a TD



Also, here's why I'm not entirely skeptical of development within this week... be 97W or its successor

[1900hurricane]

Here's a reason why I am: dry air. That shear map above actually shows the location of the monsoon trough pretty well since surface westerlies on the south side of the monsoon trough will oppose the easterlies aloft and show up as shear. However, a little to the north of the monsoon trough in the surging trades lies a much drier airmass. PWs were less than 2" at Guam in the 12Z sounding with significant dry layers. This airmass extends across much of the Tropical Western Pacific, and will remain with 97W until it at least crosses the Philippines as the trades continue to surge on the north side of the monsoon trough.







97W may have a little more luck in the South China Sea since it doesn't appear that a surface high will be dropping south from Siberia into China, but at the moment, I remain skeptical.

[1900hurricane]

And if you think that 12Z sounding from PGAC is dry, you should see the 00Z soundings from both PGAC and PTKK. PWs in those soundings barely squeak over an inch!

[euro6208]

THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED
NEAR 7.9N 140.8E, IS NOW LOCATED NEAR 8.2N 138.8E, APPROXIMATELY 255
NM EAST-NORTHEAST OF PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
AND AN 182142Z SSMIS 91GHZ PARTIAL MICROWAVE IMAGE DEPICT AN
ELONGATED AND DISORGANIZED LOW LEVEL CIRCULATION (LLC). THE SYSTEM
IS CURRENTLY LOCATED IN AN AREA OF GOOD UPPER LEVEL DIVERGENCE, LOW
TO MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR, AND VERY WARM SSTS
(30-31 CELSIUS). GLOBAL MODELS ARE IN MODERATE AGREEMENT THAT THE
DISTURBANCE WILL TRACK WESTWARD OVER THE NEXT SEVERAL DAYS BUT ARE
SPLIT AS TO IF AND WHEN THE SYSTEM WILL INTENSIFY. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1010 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS REMAINS LOW.

[Digital-TC-Chaser]

real earth wind map tool shows a surface circulation upto 500mb.



tpw dryer air also on the south side


lots of white cloud the dryer air in the mix.

[euro6208]

THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED
NEAR 8.2N 138.8E, IS NOW LOCATED NEAR 7.5N 138.0E, APPROXIMATELY 200
NM EAST OF PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
AN ELONGATED AND DISORGANIZED LOW LEVEL CIRCULATION (LLC). THE
SYSTEM IS CURRENTLY LOCATED IN AN AREA OF GOOD UPPER LEVEL
DIVERGENCE, LOW TO MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR, AND
VERY WARM SSTS (30-31 CELSIUS). GLOBAL MODELS ARE IN MODERATE
AGREEMENT THAT THE DISTURBANCE WILL TRACK WESTWARD OVER THE NEXT
SEVERAL DAYS BUT ARE SPLIT AS TO IF AND WHEN THE SYSTEM WILL
INTENSIFY. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1010 MB.
THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS REMAINS LOW.

[xtyphooncyclonex]

I sense a Jangmi repeat..... possibly weaker/stronger but relatively similar and the storm is an excellent analog. Similar track, time of year (off by several days), favorable environment with high SSTs, OHC & low vertical wind shear alongside decent model support. Models were backing off the intense typhoon scenario and went for a weaker (albeit still deadly) storm striking close to Cebu and unleashing copious amounts of rainfall over the Visayas/Mindanao area. What would happen after traversing the archipelago depends on conditions, but like Jangmi models saw potential and were bullish. Another significant rain event may unfold within the next few days.

[xtyphooncyclonex]

The GFS is now cranking this up 976 mb in 2 days' time! That's thanks to increasingly favorable conditions. 97W needs to get its act together pretty quickly for this run to actually come into fruition, but as we all know the West Pacific can pull off surprises... I'm somewhat skeptical on the 976 mb scenario though, but we could see relatively significant development for the next 48 hours.

[1900hurricane]

The 00Z PTYA (Yap) sounding will give a good idea how much dry air remains on the north side of the monsoon trough.

[Digital-TC-Chaser]

GFS 18z had saturation



Some intense rain on sat.

[1900hurricane]

The Yap sounding I've been waiting for is now available (below), and while I'd still like to see a more moist profile in the vicinity of 97W, it could certainly be far worse. Perhaps the biggest plus for 97W can be seen with the low and mid level wind trajectories, which have a southerly component. This may help shield the invest from the bone dry airmass not too far to the northeast (seen as PWs <1" in the Guam sounding I also have below). Given the apparent low level vorticity on visible imagery, we may get a weak tropical cyclone out of 97W yet.

[1900hurricane]

And just for fun, here's the 00Z Palau sounding, which is very near the center of 97W.

[cycloneye]

JMA once again upgrades 97W to TD.

TROPICAL DEPRESSION 1006 HPA AT 08N 136E WEST SLOWLY.

[euro6208]

084
WWPQ80 PGUM 192309
SPSPQ

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TIYAN GU
908 AM ChST Wed Dec 20 2017

PMZ161-171-210000-
KOROR PALAU-YAP-
908 AM ChST Wed Dec 20 2017

...TROPICAL DISTURBANCE PASSING BY KOROR...

A TROPICAL DISTURBANCE IS CENTERED NEAR KOROR AT 7N135E...OR
ABOUT 50 MILES SOUTHEAST OF KOROR...AND MOVING SLOWLY WESTWARD.
HEAVY SHOWERS AND THUNDERSTORMS ARE DEVELOPING OVER KOROR AND TO
THE EAST AND NORTH OF KOROR ACROSS WESTERN OF YAP STATE.

THE DISTURBANCE IS EXPECTED TO DRIFT TOWARD THE WEST OR WEST-
NORTHWEST. IT WILL CONTINUE TO SPREAD SHOWERS OVER WESTERN YAP
STATE AND OVER NORTHERN PARTS OF THE REPUBLIC OF PALAU THROUGH
TODAY. THE DISTURBANCE SHOULD BE CENTERED WEST OF KOROR BY THIS
EVENING AND WEATHER CONDITIONS SHOULD BE IMPROVING OVER THE AREA
BY THURSDAY.

WINDS AND SEA CONDITIONS ARE HAZARDOUS FOR SMALL CRAFT NEAR THE
DISTURBANCE AND NORTHWARD OVER YAP STATE. WINDS OF 15 TO 25 MPH
WITH GUSTS TO 35 MPH NEAR SHOWERS AND COMBINED SEAS OF 7 TO 10
FEET ARE EXPECTED FOR YAP STATE AND NORTHERN PARTS OF PALAU TODAY.
RAINFALL AMOUNTS OF 3 TO 5 INCHES ARE LIKELY IN THE HEAVIER
SHOWERS.

IF YOU ARE OPERATING SMALL BOATS OR PLANNING INTER-ISLAND TRAVEL
OR OUTDOOR ACTIVITY...BE AWARE OF THE CURRENT MARINE AND WEATHER
CONDITIONS. INTER-ISLAND TRAVEL IS NOT RECOMMENDED. STAY INFORMED
ON THE LATEST FORECASTS AND ADVISORIES ISSUED BY THE NATIONAL
WEATHER SERVICE AND YOUR LOCAL WEATHER SERVICE AND EMERGENCY
MANAGEMENT OFFICES.

PRODUCTS ISSUED BY THE NATIONAL WEATHER SERVICE ARE POSTED ON THE
WFO GUAM WEB PAGE AT WWW.PRH.NOAA.GOV/GUAM/.

$$

SIMPSON

[1900hurricane]

ASCAT data has the center almost directly over Palau.

[Digital-TC-Chaser]

With good shear conditions over the storm it appears to be looking a bit better organised and not greatly affected by the dry-air atm.

[euro6208]

WTPN21 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
165 NM EITHER SIDE OF A LINE FROM 7.1N 133.7E TO 8.0N 127.9E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AND SYNOPTIC DATA AT 200830Z INDICATE THAT A CIRCULATION
CENTER IS LOCATED NEAR 7.2N 133.5E. THE SYSTEM IS MOVING WEST-
NORTHWESTWARD AT 04 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED
NEAR 7.1N 133.9E IS NOW LOCATED NEAR 7.2N 133.5E, APPROXIMATELY 65NM
WEST OF PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A
200416Z AMSR2 MICROWAVE IMAGE SHOW FORMATIVE CONVECTIVE BANDING
WRAPPING INTO A CONSOLIDATING THOUGH STILL ELONGATED LOW LEVEL
CIRCULATION CENTER. VERTICAL WIND SHEAR REMAINS IN THE LOW TO
MODERATE RANGE (10-20 KNOTS) ALTHOUGH THE REGION OF FAVORABLE SHEAR
IS SHRINKING. HOWEVER THIS IS OFFSET BY VERY STRONG UPPER LEVEL
DIVERGENCE AND A NEARLY RADIAL OUTFLOW PATTERN AS SEEN IN THE MSI
LOOP. SEA SURFACE TEMPERATURES REMAIN FAVORABLE (28-29 CELSIUS) FOR
THE WATERS EAST OF MINDANAO, PHILIPPINES. GLOBAL DYNAMIC MODELS ARE
IN GOOD AGREEMENT THAT 97W WILL DEVELOP BEFORE TAU 24 AS IT TRACKS
WESTWARD PRIOR TO MAKING LANDFALL IN MINDANAO. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
210900Z.//
NNNN

[xtyphooncyclonex]

That look already.... impressive outflow and banding

[dexterlabio]

Mindanao trackers, whether weak or intense, have been known troublemakers in the Philippines. The already saturated ground due to Kai-tak would only make things worse.