FITOW and 23W…

IR 2013-10-03 1301Z (from NOAA)

IR 2013-10-03 1301Z (from NOAA)

Severe Tropical Storm FITOW (T1323/22W) has strengthened slightly during the past 24 hours… Spiral rainbands have increased… They are wrapping nicely into the centre from the southeast… At 12 UTC / 20 HKT… convection wraps 1.0 deg.. giving a DT of 3.5… The storm looks more symmetric now… The maximum sustained wind speed is estimated to be 110 km/h (60 kts)…

A divergence source is providing good ventilation to FITOW… The storm will intensify into a Typhoon tomorrow… Further strengthening is expected due to nice outflow and weak to moderate vertical wind shear… FITOW should reach Severe Typhoon strength in the weekend…

A major upper level trough is located over Japan… FITOW is drifting to the north along the western periphery of a steering ridge located quite far away from the storm… This poleward motion should continue in the next 24 hours… The ridge will re-build gradually over Japan 24 hours later as the trough propagates northeast… FITOW should make a left turn later tomorrow or on Saturday… The storm will affect Yaeyama Islands late Saturday… and also on Sunday…

Models are in poor agreement regarding the strength of the ridge… ECMWF expects a steady northwestward movement and a landfall close to Shanghai… GFS and NAVGEM turn FITOW more to the west-northwest… JGSM, UKMET and CMC form another group that predict a sharp turn to the west/west-southwest towards Taiwan/Luzon Strait… and eventually move the storm into the South China Sea…

Based on latest observations… I would draw my forecast track closer to equatorward cluster… or in other words… to the south of official forecasts from JTWC, JMA and the ECMWF guidance… The forecast confidence is very low… The Japanese solution looks rather unrealistic… but of course… we will closely monitor the movement of FITOW in the coming few days… Let’s wait and see if it slows down and make a westward turn tomorrow…

Japanese Ensemble Tracks 06Z

Japanese Ensemble Tracks 06Z

ECMWF Ensemble Tracks 00Z (from ECMWF)

ECMWF Ensemble Tracks 00Z (from ECMWF)

The track of FITOW may be complicated because of uncertainties in the strengths of the steering ridge… upper level trough… northeast monsoon… and perhaps also the influence from another developing storm currently located near the Marianas (TD 23W)…

Residents in southern Ryukyus should prepare for Typhoon conditions as soon as possible… Friends in Taiwan, southeastern China and remaining parts of Okinawa should also pay extra attention to FITOW…

At 13 UTC / 21 HKT / 22 JST…
Shimojishima 下地島 reported north-northeasterly winds of 57 km/h (31 kts)…

IR 2013-10-03 1301Z (from NOAA)

IR 2013-10-03 1301Z (from NOAA)

Tropical Depression 23W (former 97W) is moving to the west over the Marianas… OSCAT image taken earlier today showed a weak low level circulation centre with stronger winds in the northern semicircle… Disorganized convection starts to build and consolidate around the centre…TD 23W will develop gradually as it moves west-northwest during the weekend… It will be named DANAS within 48 hours…

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