west pacific Tropical Storm Peipah

[Somerset Squall]

The fifth tropical depression of the season has formed well to the east of the basin, at around 144E, and only about 2 degrees north of the equator. Intensity is 30kts. Convection is already building nicely over the LLCC, with banding features also evident. Shear is low, and waters warm, which should allow at least steady intensification over the next few days. A west-northwest track is expected, with 05W approaching the Philippines by day 5. It could be a typhoon by this stage, so it needs closely monitoring.

Edited April 5, 2014 by Somerset Squall

[Somerset Squall]

TD 05W has been under higher than forecast shear over the last couple of days. Nevertheless, it is now Tropical Storm Peipah, the fourth named storm of the season, with winds of 35kts. Easterly shear is displacing the bulk of the convection to the west of the LLCC, and this shear is expected to persist. It shouldn't be strong enough to prevent intensification, but it will slow it. Peipah should be a high end tropical storm on landfall on the Philippines.

[Somerset Squall]

Peipah has succumbed to the shear, and has weakened to a 25kt tropical depression. Convection is well displaced to the northwest of the entirely exposed LLCC. Shear could ease a little as Peipah approaches the Philippines, but significant re-itensification before landfall appears unlikely, with dissipation expected over the southern islands.

[Vorticity0123]

The JTWC seems to be having a hard time resolving the future track and intensity forecasts for Peipah. Last few advisory packages have swung from a forecasted typhoon to no intensification and back to a 40 kt tropical storm. The uncertainty is reflected in the prognostic reasoning bulletin from JTWC:

 

 

 

DUE TO THE UNCERTAINTY
IN THE INITIAL POSITION AS WELL AS MAJOR TRACK AND TRACK SPEED
DIFFERENCES BETWEEN THE DYNAMIC MODELS, THERE IS LOW CONFIDENCE IN
THE JTWC TRACK FORECAST.

 

Meanwhile, convection continues to pulsate vigorously around and to the north(east) of the system. This convection is sheared immediately off to the west, giving Peipah no chance to become better organized. The center appears to be located on the southern flank of the weakening convection in the southwestern corner (as of 20:32 UTC). A visible image loop of Peipah can be seen below:

 

 

Sources:

http://tropic.ssec.wisc.edu/#

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp0514prog.txt

http://www.ssd.noaa.gov/PS/TROP/floaters/05W/05W_floater.html

Edited April 7, 2014 by Vorticity0123

[Somerset Squall]

Peipah continues to be pumelled by strong southeasterly shear. Winds have fluctuated between 25 and 30kts over the past two days, but are currently only at 25kts. The depression has continued to limp towards the Philippines on a very slow west-northwesterly track. There have been multiple LLCC's popping up in various locations around the persistant but disorganised convection. This is a sign of a system losing the battle against the shear. Peipah may well dissipate before reaching the Philippines, but JTWC forecast Peipah to hang on in there until landfall. Currently, convection is on the decrease, and the centre of circulation is very poorly defined, so Peipah could be on the way out.