Eighteen

Western Pacific Tropical Depression · WP182026

20.1°N, 108.4°E

Moving WNW at 9 mph

Max Winds

30 mph

Pressure

995 mb

Forecast Points

Summary

Tropical Depression 18W is currently a tropical depression with maximum sustained winds of 30 mph. It is located about 150 nautical miles east-southeast of Hanoi, Vietnam, and has been moving west-northwest. JTWC expects the system to become nearly stationary in the Gulf of Tonkin and then drift very slowly, mainly northward, because steering winds are weak. Forecast positions keep it in roughly the same area through the next five days. The environment is only marginally favorable, and moderate to high wind shear is expected to persist. As a result, the depression is not expected to strengthen beyond about 35 mph (30 knots) and may ease back to about 30 mph (25 knots) late in the forecast, although heavy convection and precipitation have been noted southwest of the center.

Key messages

Tropical Depression 18W has 30 mph sustained winds and is expected to stay a tropical depression.
The system is forecast to move very slowly and may become nearly stationary in the Gulf of Tonkin, with a slow northward drift.
Despite limited strengthening potential, the storm’s convection is described as potent, with the heaviest precipitation displaced to the southwest of the center.

Forecast intensity

JTWC forecast maximum sustained winds (mph) by hour.

Satellite Imagery (IR)

CIRA/RAMMB · 20 Aug 21:50 UTC

JTWC Warning #1 20 Aug 18:00 UTC

WTPN32 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL DEPRESSION 18W (EIGHTEEN) WARNING NR 001//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/200551ZAUG2026//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. TROPICAL DEPRESSION 18W (EIGHTEEN) WARNING NR 001    
   02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   201800Z --- NEAR 20.1N 108.4E
     MOVEMENT PAST SIX HOURS - 290 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 030 NM
     POSITION BASED ON CENTER LOCATED BY RADAR
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   REPEAT POSIT: 20.1N 108.4E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   210600Z --- 20.2N 108.3E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 24 HR POSIT: 360 DEG/ 01 KTS
    ---
   24 HRS, VALID AT:
   211800Z --- 20.4N 108.3E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 36 HR POSIT: 360 DEG/ 01 KTS
    ---
   36 HRS, VALID AT:
   220600Z --- 20.6N 108.3E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 48 HR POSIT: 025 DEG/ 01 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   221800Z --- 20.8N 108.4E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 60 HR POSIT: 025 DEG/ 01 KTS
    ---
   60 HRS, VALID AT:
   230600Z --- 21.0N 108.5E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 72 HR POSIT: 025 DEG/ 01 KTS
    ---
   72 HRS, VALID AT:
   231800Z --- 21.2N 108.6E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 96 HR POSIT: 025 DEG/ 01 KTS
    ---
   LONG RANGE OUTLOOK:
    ---
   96 HRS, VALID AT:
   241800Z --- 21.4N 108.7E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 120 HR POSIT: 060 DEG/ 01 KTS
    ---
   120 HRS, VALID AT:
   251800Z --- 21.5N 108.9E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
REMARKS:
202100Z POSITION NEAR 20.1N 108.4E.
20AUG26. TROPICAL DEPRESSION 18W (EIGHTEEN), LOCATED
APPROXIMATELY 150 NM EAST-SOUTHEAST OF HANOI, VIETNAM, HAS
TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS.
MINIMUM CENTRAL PRESSURE AT 201800Z IS 995 MB.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 201800Z IS 9 FEET.
NEXT WARNINGS AT 210300Z, 210900Z, 211500Z AND 212100Z.
REFER TO TROPICAL STORM 17W (SAUDEL) WARNINGS (WTPN31 PGTW)
FOR SIX-HOURLY UPDATES.
2. THIS CANCELS AND SUPERSEDES REF A (WTPN21 PGTW 200600).//
NNNN

Forecast Reasoning 20 Aug 21:00 UTC

WDPN32 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1N 108.4E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 150 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 9 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS POORLY
ORGANIZED DEEP CONVECTION DISPLACED TO THE SOUTHWEST OF THE
ASSESSED CENTER LOCATION DUE TO APPARENT PRESSURE FROM
NORTHEASTERLY SHEAR. ANIMATED RADAR IMAGERY DEPICTS A LOOSELY
DEFINED CYCLONIC ROTATION IN THE GULF OF TONKIN WITH THE HEAVIEST
PRECIPITATION DISPLACED TO THE SOUTHWEST UNDER THE CONVECTION. THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE
ROTATION IN ANIMATED RADAR. THE INITIAL INTENSITY OF 25 KTS IS
ASSESSED WITH LOW CONFIDENCE BASED ON EARLIER SCATTEROMETRY DATA
AND T1.0-1.5 AGENCY DVORAK FIXES. THE ENVIRONMENT IS CHARACTERIZED
AS MARGINALLY FAVORABLE, WITH WARM SEA SURFACE TEMPERATURES AND
MODERATE EQUATORWARD OUTFLOW BEING MITIGATED BY MODERATE-HIGH
VERTICAL WIND SHEAR (VWS).

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

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 18W HAS TRAVERSED
WESTWARD OFF THE COAST OF HAINAN OVER THE PAST 6 HOURS AND APPEARS
TO BE TAKING UP A QUASI-STATIONARY POSITION IN THE GULF OF TONKIN.
THE SYSTEM IS EXPECTED TO MIGRATE VERY SLOWLY THROUGH THE GULF OF
TONKIN WITH A PRIMARILY NORTHWARD COMPONENT AS THERE ARE NO
SYNOPTIC FEATURES PRESENT TO DICTATE A STEERING REGIME. THE SYSTEM
IS NOT EXPECTED TO INTENSIFY BEYOND 30 KTS BASED ON THE INITIAL
PROGNOSIS OF THE ENVIRONMENT, WITH MODERATE-HIGH SHEAR EXPECTED TO
PERSIST OVER THE GULF OF TONKIN THROUGHOUT THE FORECAST PERIOD.
THAT SAID, THE ASSOCIATED CONVECTION IS QUITE POTENT AND SHOULD BE 
ABLE TO SUSTAIN TROPICAL DEPRESSION INTENSITY.

MODEL DISCUSSION: MODEL TRACK GUIDANCE SOLUTIONS ALL DEPICT SOME
VERSION OF QUASI-STATIONARY MOTION WITHIN THE GULF OF TONKIN,
HOWEVER, THERE IS NO CONSENSUS ON A SPECIFIED TRACK. THE GENERAL
TREND OF GUIDANCE AND GLOBAL MODEL FIELDS SUGGESTS A SLOW NORTHWARD
MIGRATION WITH A SMALL EASTWARD COMPONENT. THE JTWC FORECAST IS
REPRESENTATIVE OF THIS TREND BUT IS PLACED WITH VERY LOW
CONFIDENCE. MODEL INTENSITY GUIDANCE ALL REMAINS BELOW 35 KTS FOR
THE ENTIRE FORECAST PERIOD, WITH THE EXCEPTION OF GFS-BASED
COAMPS-TC, WHICH DEPICTS AN UNREALISTIC PEAK NEAR 50 KTS.
CONSIDERING THE VWS ENVIRONMENT, THE JTWC INTENSITY FORECAST IS
PLACED ON THE UPPER END OF THE REMAINING GUIDANCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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 2026-08-20 21:49 UTC · JMA analysis: Source: Japan Meteorological Agency (10-minute average winds). Satellite imagery: CIRA/RAMMB.