FLHurricane.com: TS Chanchu

Yes it is interesting that it is so large...attached a more recent microwave that clearly shows the ERC in progress. Notice the lack of strong convection north of 18N (cooler water). This is hidden pretty well under the CDO.

The timing of this ERC, with such a large outer band of convection, will definitely help to weaken the storm. This structure is interesting considering the transition to ET will start to occur just before landfall (the latest JTWC prog is below). The RMW could be quite large. However the JTWC forecast appears to show the wind radii contracting, so the thought must be that the ERC will start towards completion. But since the strong convection is south of 18N over the next 24 hours significant weakening is likely to occur and it is unclear if this will be able to happen. If it can, this may help the TC maintain more intensity than it would otherwise.

It appears that Hong Kong will start to get some stormy weather from the outer band of convection along the outflow channel before too long, and depending on the track, may remain under that band of convection for some time.

There is very good agreement with both track and intensity models, with all intensity models forecasting weakening to around 90-100 kts in 24 hours.

JTWC warning #31 drops the winds down to 110 kts and weakening at the same rate as in the previous warning.

As the storm approaches tomorrow it can be observed on Hong Kong radar:

http://www.hko.gov.hk/wxinfo/radars/radar.htm

Excepts from the most recent JTWC prog (a lot of good info in this one):

B. TY 02W IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A MID-LEVEL STEERING RIDGE CENTERED EAST OF TAIWAN. UPSTREAM MID-LATITUDE TROUGHING IS FORECAST TO AMPLIFY SLIGHTLY AS A SERIES OF SMALLER PERTURBATIONS TRACK OVER THE NORTHERN BAY OF BENGAL AND NORTHERN INDOCHINA. ADDITIONALLY, A WESTWARD EXTENSION OF THE STEERING RIDGE SHOULD REMAIN IN PLACE TO THE NORTHEAST OF TY 02W THROUGH TAU 24. THE RESULTING FLOW WILL INDUCE A NORTHWARD TRACK INITIALLY, FOLLOWED BY A SHIFT TOWARD THE NORTH-NORTHEAST AFTER TAU 24 AS THE TROUGH MOVES EASTWARD AND RIDGING EAST OF TY 02W WEAKENS. THE STORM WILL BECOME EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES BY TAU 36 AND BEGIN EXTRATROPICAL TRANSITION (XT) WHILE APPROACHING THE COAST OF SOUTHERN CHINA. THE SYSTEM IS EXPECTED TO MAKE LANDFALL EAST OF HONG KONG AROUND TAU 36 AND COMPLETE XT BY TAU 72. WITH THE EXCEPTION OF AN EASTERN (COAMPS) AND WESTERN (TCLAPS) OUTLIER, THE REMAINING DYNAMIC AIDS CONSISTING OF NOGAPS, GFDN, AFWA MM5, NCEP GFS, JGSM, JTYM, EGGR, AND WBAR ARE IN GOOD AGREEMENT WITH THIS SCENARIO.

C. ALTHOUGH TY 02W REMAINS OVER FAVORABLE SEA SURFACE TEMPERATURES AND MAINTAINS GOOD ANTICYCLONIC OUTFLOW, THE SYSTEM IS EXPECTED TO WEAKEN AS MORE STABLE LOW LEVEL AIR IS FUNNELED THROUGH THE TAIWAN STRAIT AND INTO THE NORTHERN SOUTH CHINA SEA. THE STORM WILL WEAKEN RAPIDLY AFTER TAU 24 AS IT TRAVERSES LOWER SEA SURFACE TEMPERATURES, INTERACTS WITH LAND, AND UNDERGOES XT.

D. CURRENT WIND RADII ARE BASED ON A 152234Z QUIKSCAT PASS. FORECAST WIND RADII ARE BASED UPON CLIMATOLOGY FOR AN AVERGE- TO LARGE-SIZED SYSTEM, WITH SOME MODIFICATION FOR XT AT TAU 36.

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