T1909 LEKIMARSMC Tokyo – Typhoon Center
And
Meteorological Research Institute, JMA

Track & Intensity of LEKIMA- LEKIMA formed as a TS to theeast of Luzon and continued ona northwestward track.
- Intensified by 55kt within 60
hours starting at 00UTC Aug. 6- Peaked at 105kt at 12UTC Aug. 8- Most intensified in 2019, tying
with T1902 WUTIP
9Best track intensity(kt)
87655kt

Peaked at 105kt
at 12UTC Aug. 85
Aug. 4

Aug. 4 5 6 7 8 9 10 11 12

Track & Intensity of LEKIMALEKIMA is one of two TCs that havereached 100kt intensity in 2019.

TC nameLifetime
Maximum
intensity (kt)(1)PABUK

45(2)WUTIP

105(3)SEPAT40(4)MUN

35(5)DANAS

45(6)NARI

35(7)WIPHA

45(8)FRANCISCO

70(9)LEKIMA

105(10)KROSA

75(11)BAILU

50(12)PODUL

40(13) LINGLING

90(14)KAJIKI

35(15)FAXAI

85(16)PEIPAH

35(17)TAPAH

65(18)MITAG75HIMAWARI-8 IR images
East China Sea
Okinawa
TaiwanPhilippines

Genesis of LEKIMA and S.W. monsoon activity
Southwest Asian monsoon activity index
Monsoon surge
early August

Kinetic energy of rotational component of windvectors at 850hPa averaged over the Asia
monsoon region (red box in the inset figure)Stream function anomalies at 850hPa& OLR anomalies for early August

Deep monsoontrough- Genesis of LEKIMA wasassociated with enhanced
SW monsoon and a deep
monsoon troughAtmospheric conditions- Mid-level atmosphere was wetter than normal over much of the western Pacific- In early August, the subtropical jet stream flowed in the distant north andvertical wind shear was weak around LEKIMA- These atmospheric conditions were favorable for LEKIMA’s intensification
Dew-point depression (T-Td) anomalies
at 600hPa averaged for 4 to 8 Aug.

Wind vector and zonal wind speed at200hPa averaged for 4 to 8 Aug.

Subtropical jet
LEKIMA’spath

WETDRYm/sOcean conditions- Ocean conditions were moderately favorable with SSTs at 29-30oC
and TCHP above 50 along the LEKIMA’s track

TIFS (intensity forecast guidance) results- JMA forecasters primarily depend on Typhoon Intensity Forecast
Scheme based on SHIPS (TIFS) for forecast guidance- TIFS struggles with forecasting quick intensity changes, because it isa linear multiple regression statistical model.
(kt)
(kt)

Intensity

TIFS initial time:
00UTC Aug. 6Best track
TIFS guidance
Official forecast
Forecast timeWhat is TIFS ?
- TIFS predicts intensity changes
exploiting statistical relationshipbtw TC intensity changes andenvironmental conditions.
- TIFS originates from SHIPS,
adapted for the western North
Pacific. (Many thanks to Dr.
DeMaria)

FT=120FT=18
FT=12
FT=6 FT=0

Atmosphere & ocean
conditions averaged over thevicinity of a typhoon forevery 6-hr step

Explanatory factors for TIFS
(not exhaustive)
VariablenameDescription

PERSISTENCE

Change in max sustained wind during the last
12 hours

SHEAR

Vertical wind shear between 200 and 850hPa
levelsPOTENTIAL

Difference between the latest TC intensity andits maximum potential intensity

TANGENTIAL

Tangential wind speed around the TC at
850hPa level

MAXWIND

The latest max sustained wind

TEMP200,
TEMP250

Temperature at 200 and 250hPa

MID_RH

Relative humidity in the mid-troposphere

VOR850Vorticity at 850hPa

DIV200

Divergent at 200hPa

MOTION

Zonal component of translation speed of theTC

OHC

Ocean heat contentIRPortion of cloud area with infrared irradiancebelow -30oC

TIFS by contribution factors

NegativePositive(kt)- For early forecast time (FT=30hrs), the largest
negative contribution comes from
SST_POTENTIAL^2- This factor works as a restraint when SSTs arehigh but a TC is weak, because that suggests theTC lacks something needed to intensify.
- In hindsight, disregarding this factor andadjusting upward, if possible, would have led to abetter intensity forecast

Doppler-Radar derived winds at 2km- Post analysis using Ishigaki radar data
- During this period, Lekima had strong winds greater than 70 m/s at 2-km altitudeand had concentric eyewalls.
(m/s)(mm/h)

Doppler-Radar derived tangential winds at 2km

1800

1600

Time (UTC)- The radius of maximum
wind is located at about
12km from the center- The inner eyewall was very
compact- The maximum tangential
wind speed reached 65m/s- The secondary eyewall
developed and contracted
between 60 and 90 km
from the storm center

2000

1400

1200

1000

0800
08 AUG
0700

Radius from center(m s-1)(km)

Doppler-radar derived maximum sustained winds- 6-hourly Dvorak analysis gives constant CI numbers of 7.0 throughthe peak intensity period- Doppler-radar provides information on intensity with hightemporal resolution.
(m/s)
CI=7.0CI=7.010090

Maximum winds at 2km

80
70*0.88*0.88

60

Maximum 10-min sustained winds at the surface

50
40time (UTC, dhhmm)

82000

81900

81800

81700

81600

81500

81400

81300

81200

81100

81000

80900

80800

80700

30