WPAC: Invest 91W - Post-Tropical

[Nancy Smar]

91W.INVEST.15kts.1006mb.17N.117.8E

[Hayabusa]

And that makes the 2nd invest that spawned from Danas

[Hayabusa]

[Nancy Smar]

THERE IS LITTLE TO NO CONVECTION NEAR THE LLCC BUT THERE ARE TWO
AREAS OF DEEP CONVECTION (90W TO THE EAST, 91W WEST OF THE
PHILIPPINES) ALONG THE PERIPHERY OF THE CIRCULATION. PREVIOUS ASCAT
PASSES AND MICROWAVE IMAGERY REVEAL THAT NEITHER INVEST HAS A
DEFINED LLCC ALTHOUGH BOTH BEAR MONITORING.

[Nancy Smar]

AN AREA OF CONVECTION (INVEST 91W) HAS PERSISTED NEAR 17.2N 117.2E, APPROXIMATELY 275 NM NORTHWEST OF MANILA, PHILIPPINES. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 171042Z 91GHZ SSMIS MICROWAVE IMAGE DEPICT A LARGE AREA OF CONVECTION ABOVE A DEVELOPING LLC. TWO DISTINCT BANDS OF CONVECTION PERSIST TO THE NORTH AND SOUTH BUT SHOW LITTLE EVIDENCE OF WRAPPING INTO THE LLC. HIGH (25-40KT) VERTICAL WIND SHEAR REMAINS A LIMITING FACTOR FOR FURTHER DEVELOPMENT, WITH STRONG UPPER LEVEL OUTFLOW AND WARM (30-32C) SSTS SUSTAINING CONVECTION. GLOBAL MODELS ARE SPLIT BETWEEN TWO DISTINCT SOLUTIONS, WITH GFS AND ECMWF MAINTAINING 91W AS AN INDEPENDENT SYSTEM AND TRACKING TO THE NORTHEAST BEHIND TS 06W. NAVGEM, UKMO, AND JGSM INSTEAD PREDICT THAT 91W WILL BE ABSORBED INTO 06W BY TAU 24. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 995 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS MEDIUM.

[wxman57]

ScatSat data overnight indicated a well-defined closed surface low with 35-40 kt winds. Looks like it is a tropical storm. JMA has now identified it as a TD.

[Nancy Smar]

THE CONVECTION TO THE WEST (INVEST 91W) NOW
APPEARS LIKELY TO BREAK AWAY FROM 06W, POSSIBLY FORMING A DISTINCT
TROPICAL CYCLONE IN THE NEXT 24 TO 48 HOURS.

[NotoSans]

This system forms under the deep convection originally associated with Danas and is a typical example showing how interaction with Luzon can mess things up. Seems to have consolidated quickly and I actually think this is a TS already. JMA just classifies it as a TD at 12Z while JTWC thinks it has a medium chance to develop into a TC within the next day - both are likely too conservative here.

[1900hurricane]

 https://twitter.com/pppapin/status/1151655278372216833

[euro6208]

WTPN21 PGTW 180230
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
130 NM EITHER SIDE OF A LINE FROM 18.9N 119.2E TO 22.8N 121.6E
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 18 TO 23 KNOTS. METSAT
IMAGERY AT 180000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 19.4N 119.3E. THE SYSTEM IS MOVING NORTH-NORTHEASTWARD AT 11
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED
NEAR 17.2N 117.2E, IS NOW LOCATED NEAR 19.4N 119.3E APPROXIMATELY
628 NM SOUTHWEST OF KADENA AB, OKINAWA, JAPAN. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY AND A 172316Z 91GHZ SSMIS MICROWAVE IMAGE
DEPICT A LARGE AREA OF DEEP CONVECTION SHEARED 60 NM SOUTHWARD OF A
CONSOLIDATING LLC. UPPER LEVEL ANALYSIS SHOWS 91W IS NOW IN AN AREA
OF MODERATE (15-20KT) VERTICAL WIND SHEAR OFFSET BY STRONG POLEWARD
UPPER LEVEL OUTFLOW. SSTS ARE FAVORABLE FOR DEVELOPMENT AT 30-32C.
GLOBAL MODELS SHOW 91W TRACKING NORTHWARD AND TRAILING TS DANAS(06W)
AS AN ELONGATED DISTURBANCE WITH LINEAR CONVECTION. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 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
190230Z.//
NNNN

[euro6208]

91W INVEST
As of 18:00 UTC Jul 18, 2019:

Location: 22.5°N 120.5°E
Maximum Winds: 20 kt
Minimum Central Pressure: 997 mb

[euro6208]

Possibly a missed TS. ASCAT was impressive.

[euro6208]

WTPN21 PGTW 190230
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91W) CANCELLATION//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/180221Z JUL 19//
AMPN/REF A IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PGTW 180230)//
RMKS/
1. REMARKS: THIS CANCELS REF A (WTPN21 PGTW 180230). THE AREA OF
CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 19.4N 119.3E, IS NOW
LOCATED NEAR 21.8N 119.9E APPROXIMATELY 439 NM WEST-SOUTHWEST OF
KADENA AB, OKINAWA, JAPAN. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY AND A 182302Z 91GHZ SSMIS MICROWAVE IMAGE DEPICT A LARGE
AREA OF DEEP CONVECTION SHEARED OVER A WEAK ELONGATED CIRCULATION.
UPPER LEVEL ANALYSIS SHOWS 91W IS NOW IN AN AREA OF LOW TO MODERATE
(10-20KT) VERTICAL WIND SHEAR WITH UPPER LEVEL OUTFLOW. 9IW IS
CURRENTLY OVER LAND BUT SSTS IN THE SURROUNDING WATERS ARE FAVORABLE
AT 28-29C. GLOBAL MODELS SHOW 91W TRACKING NORTHWARD AND TRAILING TS
DANAS(06W) AS AN ELONGATED DISTURBANCE WITH LINEAR CONVECTION.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 0 TO 0 KNOTS AND A
HIGHLY ASYMETIRC WIND FIELD. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 997 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS DOWNGRADED
TO MEDIUM.
//
NNNN

[euro6208]

91W INVEST
As of 12:00 UTC Jul 19, 2019:

Location: 24.6°N 123.0°E
Maximum Winds: 20 kt
Minimum Central Pressure: 995 mb