Yutu（T1826）
RSMC Tokyo - Typhoon Center
Japan Meteorological Agency

Outline of Yutu（T1826）• Yutu (T1826) formed over the sea
around the Marshall Islands andmoved westward, causing severe
damage to the Philippines.
Violent TY• Its duration sustaining TS intensity
or higher was 11.25 days, which
was the longest in 2018.
• It was also the most developed TCin 2018, with the same intensity of
115kt and 900hPa as Kong-rey(T1825).

Track and atmospheric conditions• Yutu could not move northward due to strong Pacific throughout the period.
Geopotential height at 500hPa (color) and relative vorticity
at 850 hPa(contour (>=3.0x10-5 s-1)) 20 Oct.-2 Nov. 2018

Intensity changes
LandfallVelocity (kt)Wind area (nm)Maximum velocity≥ 30 kt wind area
≥ 50 kt wind area
Date (MM/DD)• As a result of rapid intensificationsuch as the maximum velocity
increased by 80 kt in 60 hours at
the beginning of the occurrence, thepeak intensity reached 115 kt and900 hPa.
• After the weakening to 95kt, it
developed again to 105kt.
• After that, the weakness and redevelopment were repeated twice.

Atmospheric and ocean conditions• Upper-level divergence was suitable for thedevelopment of tropical cyclones throughout
the period, and vertical shear was also
suitable mainly in the first half of the period.

Vertical Wind Shear

SST

Maximum
Velocity

SST（℃)

Upper-level
Divergence

TCHP
Divergence(*10e-6/s)
Velocity (kt) and TCHP(KJ/cm2)

Velocity and shear(kt)Maximum
Velocity• Both SST and TCHP were suitable for thedevelopment of tropical cyclones except
for the end stage.

Atmospheric and ocean conditions• The middle layer humidity during a period of rapid intensification was high.
Maximum Potential Index (MPI) was high throughout the period.

MaximumVelocity

Middle layer
humidity

Humidity（%)

Velocity (kt) and MPIMPIFeatures of rapid intensification at the beginning of the occurrence
10/21 23UTC T2.0

10/23 00UTC T4.0

10/23 23UTC T7.0

Features of 1st weakening
The eastern part of wall cloud became thinner. It seems to have been influenced by the
middle-level dry air.
10/24 07:22UTC
T7.5

10/24 16:07UTC
T7.5⇒7.0

10/24 19:58UTC
T7.0⇒6.5

10/25 09:01UTC
T6.0⇒5.0

10/25 21:36UTC
T5.0⇒5.5

T number indicates the closest time value of the best track.

Features of re-development and second weakening
In the second weakening, the eastern part of wall cloud became thinner.
It also seems to have been influenced by the middle-level dry air.
10/25 21:36UTC
T5.0⇒5.5

10/26 8:40UTC
T6.5⇒6.0

10/26 21:14UTC
T7.0⇒6.5

10/27 4:26UTC
T6.5

10/27 8:28UTC
T6.5

10/27 16:38UTC
T6.5⇒6.0

Track and Intensity forecast• Accuracy of track forecast for Yutu was higher than the average forecast accuracy of all named TCsin 2018.
• However, that of intensity forecast was lower, because we could not fully predict the rapid
intensification and repeated development and weakening.
Accuracy of track forecast

Accuracy of intensity forecast

Forecast on rapid intensification
2018/10/24/00UTC
Track forecast
Maximum wind (kt)Intensity forecast
LandfallBest Track
RSMCTIFS

Date (MM/DD)•Best Track
RSMC
ECMWF
JMANCEP
UKMO
EJNU

•

The intensity forecast guidance TIFS was not able tofollow the rapid development in analysis and could
not fully predict the subsequent rapid intensificationand the following intensity change.
In the RSMC forecast, as a result of raising theintensity predicted by TIFS according to the intensity
in analysis, the peak intensity could be forecasted
roughly, but the trend of intensity change could not
be fully forecasted.

Forecast on 1st weakening
2018/10/24/12UTC
Track forecast
Maximum wind (kt)Intensity forecast
LandfallBest Track
RSMC
TIFS

Date (MM/DD)Best Track
RSMC
ECMWF
JMANCEPUKMO
EJNU• TIFS was not able to catch up the rapid
intensification in the analysis continuously, but
predicted the subsequent weakening trend.
• The RSMC forecast did not adopt the TIFS
forecast that could not catch up the intensity ofanalysis, and as a result, the forecast was forfurther development.

Forecast on re-development
2018/10/25/18UTC
Track forecast
Maximum wind (kt)Intensity forecast
LandfallBest Track
RSMC
TIFS

Date (MM/DD)Best Track
RSMC
ECMWF
JMANCEPUKMO
EJNU• TIFS could not predict re-development well andcould not predict subsequent weakening.
• As a result of adopting TIFS, the RSMC forecast
has almost same value and tendency as the TIFS
prediction.

Forecast on 2nd weakening
2018/10/28/00UTCTrack forecast
Maximum wind (kt)Intensity forecast
LandfallBest Track
RSMC
TIFS

Date (MM/DD)Best Track
RSMC
ECMWF
JMANCEPUKMO
EJNU• The TIFS prediction showed a weakening trend,
but it were not able to make sufficientquantitative prediction.
• As a result of adopting TIFS, the RSMC forecast
has almost same value and tendency as the TIFS
prediction.