Invest

Western Pacific Invest · WP992026

16.6°N, 161.5°E

Moving NW at 9 mph

Max Winds

25 mph

Pressure

1007 mb

Forecast Points

Summary

Invest 99W currently has maximum sustained winds around 25 mph and is moving north-northwest at about 9 mph. It is located about 330 nautical miles southwest of Wake Island, with disorganized bursts of thunderstorms covering a loosely defined low-level circulation. The Joint Typhoon Warning Center says formation of a significant tropical cyclone is possible within the next 12 to 24 hours, and rates the potential for development within 24 hours as high. The environment is favorable for strengthening, with low vertical wind shear, warm ocean waters, abundant deep-layer moisture, and strong outflow aloft. Forecast guidance described by JTWC suggests gradual to steady development over the next 24 to 36 hours as the system moves generally northward. For now, the available data does not support issuing numbered tropical cyclone warnings.

Key messages

Invest 99W has 25 mph winds and is moving north-northwest, located southwest of Wake Island.
JTWC says the chance of development into a significant tropical cyclone within 24 hours is high, with formation possible in 12 to 24 hours.
Models support gradual to steady strengthening over the next 24 to 36 hours as the system moves generally northward.

Satellite Imagery (IR)

CIRA/RAMMB · 26 Aug 04:40 UTC

JTWC Warning 25 Aug 18:00 UTC

WTPN21 PGTW 252330
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
085 NM EITHER SIDE OF A LINE FROM 16.0N 161.9E TO 18.1N 163.7E
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 25 KNOTS. METSAT
IMAGERY AT 251800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 16.0N 162.0E. THE SYSTEM IS MOVING NORTH-NORTHWESTWARD AT 08
KNOTS.
2. REMARKS:THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED NEAR 
15.3N 162.3E IS NOW LOCATED NEAR 16.0N 162.0E, APPROXIMATELY 330 NM 
SOUTHWEST OF WAKE ISLAND. ANIMATED ENHANCED INFRARED IMAGERY (EIR) 
DEPICTS DISORGANIZED BURSTS OF DEEP CONVECTION FULLY OBSCURING A LOOSELY 
DEFINED LOW-LEVEL CIRCULATION CENTER. THE 251441Z AMSR2 WINDSPEED 
PRODUCT REVEALED A COMPACT, ASYMMETRIC, AND WEAK WIND FIELD, WITH 15-20 
KT WINDS CONFINED TO BENEATH THE DEEP CONVECTION. THE 251807Z SSMIS 91 
GHZ DATA REVEALS FAINT LOW LEVEL CLOUD BANDING WRAPPING INTO THE CENTRAL 
DEPP CONVECTIVE PLUME. ENVIRONMENTAL ANALYSIS IS CONDUCIVE FOR 
DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (10-15 KTS), WARM SEA SURFACE 
TEMPERATURES (29-30 C), ABUNDANT DEEPLAYER MOISTURE, AND STRONG POLEWARD 
OUTFLOW ALOFT. GLOBAL DETERMINISTIC AND ENSEMBLE MODELS ILLUSTRATE 
GRADUAL TO STEADY DEVELOPMENT OVER THE NEXT 24-36 HOURS AS THE SYSTEM 
TRANSITS GENERALLY NORTHWARD. MAXIMUM SUSTAINED SURFACE WINDS ARE 
ESTIMATED AT 18 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 
262330Z.
//
NNNN

Products not available for West Pacific storms

NEXRAD radar — no radar coverage over the open West Pacific.
Storm-surge inundation — no public storm-surge model for this basin.
Wind-speed probabilities — JTWC does not publish them.
Watches and warnings — issued by local agencies (PAGASA, JMA, CWA), not JTWC.
Reconnaissance aircraft — no routine aircraft reconnaissance in the West Pacific.
Rapid-intensification and shear diagnostics — SHIPS-based guidance is not published for this basin.

These are data-availability limits for the West Pacific basin, not omissions.

Source: U.S. Navy/Air Force Joint Typhoon Warning Center (JTWC), via the UCAR Tropical Cyclone Guidance Project. JTWC data is in the public domain. · Updated 2026-08-26 02:05 UTC · JMA analysis: Source: Japan Meteorological Agency (10-minute average winds). Satellite imagery: CIRA/RAMMB.