western pacific Typhoon Tapah

[Vorticity0123]

A new tropical depression has formed in the western Pacific, just to the southeast of Guam. The JMA (Japan Meteorological Agency) has started issuing advisories on the system, without classifying it as of yet. The JTWC has issued a tropical cyclone formation alert on the system, and that agency currently has designated the system as 99W.

 

Current structure

 

Over the last few hours (as of 11:00 UTC), inner convection has weakened markedly, with a circular area of convection rapidly weakening into a weakly defined banding structure. The weakening of the inner convection can be seen below:

 

DVORAK satellite imagery loop of 99W (courtesy: NOAA)

 

Despite the apparent disorganization of the convection, a clear circulation is apparent near 146.5E, 10.5N. This circulation has become better defined over the last day or so.

 

Forecast

 

Currently, the system is moving northeastward. The JMA forecasts a slow curve back toward the northwest with some slight intensification. Meanwhile, the GFS forecasts a track directly northward without any strengthening. However, it appears as if the GFS has badly initialized the system, which indicates that this track forecast might not be very reliable. The track forecast from GFS is indicated below:

 

 

 

 

Once the system becomes better defined, a more clear picture of the track of 99W will become apparent.

 

Sources:

http://www.usno.navy.mil/JTWC/

http://www.jma.go.jp/en/typh/

http://www.ssd.noaa.gov/PS/TROP/floaters/99W/99W_floater.html

http://www.nrlmry.navy.mil/TC.html

Edited May 1, 2014 by Vorticity0123

[Somerset Squall]

JTWC have upgraded the system to a tropical depression, with winds of 25kts. TD 06W is moving northwards along the western flank of a subtropical ridge to the east. Shear is low, and outflow good, so 06W should strengthen and become a tropical storm over the next couple days, before eventually weakening as the system reaches cooler water and higher shear with increasing lattitude.

[Somerset Squall]

Winds are up to 30kts now. Currently some very deep convection over LLCC:

 

 

 

 

[Somerset Squall]

Tropical Depression 06W hs rapidly strengthened overnight and has become Tropical Storm Tapah, with winds of 50kts according to JTWC. Tapah has a soild central dense overcast, with an eye rapidly forming. Tapah should become a typhoon in the next 12hrs, the second of this active start to the season.  sign of things to come? Last year, we had only one tropical storm and one tropical depression by this point. This year, we have had four tropical storms, one typhoon (soon to be two by the looks of things) and one tropical depression.

 

[Somerset Squall]

Tapah remains a well organised system, though the rapid strengthening episode has ceased. Winds are up to 55kts according to JTWC. Tapah retains a well established central dense overcast flanked by banding, and the occasional glimpses of an eye-like feature. Tapah is still expected to become a typhoon as it moves northwards over the next 24hrs. A building ridge to the north should temporarily steer Tapah northwestwards beyond 24hs, until the storm gets picked up by a trough and sent northeastwards out of the tropics.

Edited April 28, 2014 by Somerset Squall

[Somerset Squall]

Tapah has become a typhoon this morning, with winds of 65kts according to JTWC. Tapah remains a compact system with a solid central dense overcast and tightly wrapped banding. Tapah has another 12-24hrs to strengthen before it runs into higher shear and cooler waters aloing track.

[Vorticity0123]

Tapah has most likely reached its peak intensity as a minimal typhoon a few hours ago (as of 20:00 UTC). The system has since weakened to a strong tropical storm (60 kt). Convection seems to be sheared toward the northeast, but the centre is still under the convective canopy. Furthermore, banding has become somewhat better established to the northeast of the system (instead of a sheared pattern). The organizational trends can be seen in the visible loop below:

 

Visible satellite loop of Tapah (courtesy: NOAA)

 

As mentioned by Somerset Squall, Tapah is currently very close to a sharp gradient in wind shear. Shear values in excess of 80 kt are present far to the north of the system, while just to the south shear is only 10 kt. This shear gradient can be seen below:

 

Shear values and tendency as analysed by CIMSS. The colours indicate shear values, while the contour lines indicate shear tendency (which is not important in this situation). The position of Tapah is indicated by the cyclone symbol just southwest of 20N, 150E. 

 

Concluding, despite the seemingly positive organizational trends in the last few satellite frames (as of 20:00 UTC), weakening seems imminent.

 

Sources:

http://www.ssd.noaa.gov/PS/TROP/floaters/06W/06W_floater.html

http://www.usno.navy.mil/JTWC/

http://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=westpac&sat=wgms∏=shr&zoom=&time=

Edited April 29, 2014 by Vorticity0123

[Somerset Squall]

Tapah has gone, and JTWC have issued their last advisory.

[Vorticity0123]

Tapah has gone, and JTWC have issued their last advisory.

 

Indeed, though the LLCC (low level circulation center) is still clearly apparent. It will most likely take some time before the LLCC dissipates completely. Given the fact that no convection is currently present anywhere close to the LLCC (as of 20:54 UTC), and that Tapah is currently located in a harsh environment (with high shear values and SSTS below 26*C), regeneration appears extremely unlikely.

 

Below a satellite image of the remnants of Tapah:

 

Satellite image of the remnants of Tapah (note: the image automatically updates itself)

 

Sources:

http://www.ssd.noaa.gov/PS/TROP/floaters/06W/

http://moe.met.fsu.edu/cyclonephase/gfs/fcst/archive/14050112/4.html

Edited May 1, 2014 by Vorticity0123

[Somerset Squall]

Certainly an active start to the season, and with the developing El Nino, it could be an active season overall.