central pacific Tropical Storm Unala

[Somerset Squall]

Tropical Storm Unala has formed in the far west of the Central Pacific, from Invest 90C. I actually suspect this was a tropical storm yesterday, if not a day or so before, and it seems like CPHC are admitting they were late upgrading it based on some of the words of their first advisory. Unala has a small area of deep convection near the LLCC, and an intensity of 35kts. Unala is not in a very favourable environment, as shear is moderate to strong. This is in part due to Tropical Storm Pewa to it's west. Therefore, it is likely Unala is at it's peak and will begin to weaken very soon. In fact, CPHC have just issued a special advisory indicating Unala dissipating in the next 24hrs, as even stronger shear awaits it as it approaches the international dateline. It should however, make it into the West Pacific before dissipation.

[Coast]

 

3 p.m. Monday, Aug. 19, Japan time: A possible new worry popped onto the tropical cyclone grid this afternoon in the form of Tropical Storm Unala, which appears to be following somewhat in Tropical Storm Pewa’s footsteps. Joint Typhoon Warning Center’s latest forecast has Unala tracking 125 miles northeast of the Wake Island group around 5 p.m. Wednesday, but packing a relatively light punch, 40-mph sustained winds and 52-mph gusts at its center. PST will keep a close eye on it to see if it intensifies as it approaches and crosses the International Date Line sometime this evening.

 

 

 

http://www.stripes.com/blogs/pacific-storm-tracker/pacific-storm-tracker-1.106563/tropical-storm-12w-trami-6-tropical-storms-01c-02c-pewa-unala-4-1.236084

[Somerset Squall]

Unala is racing westward and is crossing the dateline into the West Pacific. Unala has moved much closer to Typhoon Pewa, and Pewa is now inflicting strong shear over Unala. As a result, Unala's convection has been stripped from the LLCC. Unala is forecast to be absorbed by Typhoon Pewa within the next 24hrs as the weaker system gets dragged into Pewa's circulation.

Edited August 19, 2013 by Somerset Squall

[Somerset Squall]

Unala is no longer identifiable on satellite imagery as it has been absorbed by Tropical Storm Pewa. Therefore, the last advisory has been issued.

[Coast]

 

NASA's Aqua satellite has been busy capturing temperature data from developing tropical cyclones around the world. Aqua captured an image of Tropical Storm Unala in the central Pacific Ocean where it formed early today, Aug. 19. Over several hours, Unala moved into the northwestern Pacific where it quickly weakened to a depression. NASA's Aqua satellite caught Unala in the same image as Typhoon Storm Pewa, which is responsible for Unala's quick weakening. The two tropical cyclones are just 184 nautical miles apart and are expected to be just 60 miles from each other later today (Aug. 19).

 

The Atmospheric Infrared Sounder or AIRS instrument captures infrared data and scientists are able to measure cloud top temperatures of storms, and surrounding sea surface temperatures: two factors that are important in understanding what's happening or will happen with tropical cyclones.Tropical cyclones need sea surface temperatures of at least 26.6C/80F to survive and thrive, and temperatures in the vicinity of Tropical Depression Unala are at least that warm. Cloud top temperatures in the thunderstorms that make up tropical cyclones tell scientists how high the cloud tops are in the troposphere, and the higher the storm, the colder it is, and the stronger it is.

 

Cloud top temperatures in thunderstorms circling Unala's center early on Aug. 19 were around -63F/-52C, indicating there were some strong storms with heavy rain potential, but those cloud tops warmed later in the day, indicating weakening. Storms in nearby Pewa showed colder temperatures, and Pewa has since become a typhoon. At 1500 UTC/11 a.m. EDT on Aug. 19, Tropical Depression Unala had maximum sustained winds near 30 knots/34.5 mph/55.5 kph, after peaking earlier in the day at 40 mph/65 kph. The center of Unala was located near latitude 17.3 north, longitude 178.1 west, about 705 nautical miles east of Wake Island. The estimated minimum central pressure is 1008 millibars. Unala was moving toward the west near 20 mph/32 kph, and this general motion is expected to continue for the next day. 

 

Forecasters at the Central Pacific Hurricane Center noted that the interaction between Unala and Typhoon Pewa is expected to cause Unala to weaken more and dissipate within 24 hours.

 

http://phys.org/news/2013-08-nasa-tropical-storm-unala-weaken.html