Tropical Storm Mun (04W) - Tropical Cyclone Advisory #5, 1200 UTC 7/3/25

…Mun continues to strengthen and could become a typhoon on Friday…

Current storm information:

• Position: 28.3°N 145.4°E

• Movement: N at 7 knots (10 km/h)

• Intensity [1-min]: 60 knots (110 km/h)

• Intensity [10-min]: 40 knots (75 km/h)

• Central pressure: 982 hPa

Trend:

• Some additional strengthening is forecast during the next 24 hours, and Mun could become a typhoon on Friday.

Watches and warnings:

• There are no land-based watches or warnings in effect.

Hazards affecting land:

• None.

Discussion:

Although its convection has decreased significantly in coverage, Mun has clearly continued to strengthen since the previous advisory. The small central dense overcast feature continues to exhibit well defined spiral banding, with an eye feature intermittently visible on satellite imagery. The system continues to be co-located with an upper-level low pressure area just to the southwest, and as a result Mun still has some subtropical characteristics, namely an asymmetric wind field with the strongest winds located north and east of the center. Although Dvorak-based intensity estimates are not particularly impressed with the system and are within the 40-45 kt range (and JMA in fact shows an intensity of 40 kts, 10-minute), a RCM-3 Synthetic Aperture Radar image from around 0830 UTC suggests the winds are significantly stronger, even finding winds of 73 kts in the northeastern quadrant. This may be a bit too high, but given winds of 60-65 kts found in other quadrants, the intensity is increased to a potentially conservative 60 kts.

There are no significant changes to the forecast, other than Mun’s higher starting intensity. Mun is forecast to continue on a relatively slow and erratic northward track between the upper-level low to the west and a strong ridge to the northeast. A trough will move quickly off the coast of Japan on Friday, which will cause Mun to turn sharply northeastward. This trough will leave Mun behind and allow the ridge to build back in, which will turn Mun back northward again. Some short-term strengthening appears likely as Mun remains over warm waters, and Mun will likely become a typhoon on Friday. By late Saturday or early Sunday, Mun’s erratic track will take it over steadily cooling waters, which will result in steady weakening. Mun is expected to become a post-tropical cyclone by Monday as it loses its convection. The post-tropical cyclone could turn toward Japan by the end of the forecast period, but it appears likely to dissipate before it gets there.

Forecast positions and maximum winds

• 00 hrs: 28.3°N 145.4°E – 60 kts

• 12 hrs: 29.6°N 145.0°E – 65 kts

• 24 hrs: 30.4°N 145.5°E – 65 kts

• 48 hrs: 31.6°N 148.0°E – 60 kts

• 72 hrs: 33.6°N 149.6°E – 45 kts

• 96 hrs: 36.6°N 149.3°E – 35 kts Post-tropical

• 120 hrs: 40.0°N 152.9°E – 30 kts Post-tropical/remnant low