1200UTC/192000PST, August 11, 2012
THINGS QUIET DOWN A BIT AFTER AN EVENTFUL TWO WEEKS!
After two weeks of dealing with multiple tropical systems in the WESPAC, along with destructive rains in the Philippines from the HAIKUI-enhanced southwest monsoon, this week finds things a little quieter. But, we are not totally out of the woods, as another player has taken the stage, ready to deal a blow of death and destruction to some unwilling participants in the tropical WESPAC region at some point in the future.
ON THE BOARD…
The season is off to a rather average start, although at times it has seemed like the tropical activity would take over ALL of the western Pacific Ocean. At one time last week, we had 3 named systems (SAOLA, DAMREY, and HAIKUI) and one INVEST area (90W) to track and forecast. The aforementioned named systems have all moved into China at this point, and the INVEST area became a storm called KIROGI, but has since started to dissipate and is no longer being considered a threat to the tropical WESPAC region. But, one organized system bears watching in the tropical WESPAC region. This system is called…
93W INVEST has formed in recent days, and much unlike the other 5 previous systems, this one appears to be a little more “normal”. What I mean by that is, many of the storms that have formed this season have been born out of DEEP tropical air masses, with TUTTs helping to generate the initial convergence that gets over the warm waters of the Pacific, forms convection, and then starts to spin and then…well, you know what happens next. 93W is a slightly different animal; however, latest data shows it may be morphing into more of the kind of system we have been seeing. For right now, here are the latest figures on 93W INVEST:
|Location:||1222km (759mi) ENE of Viga, Catanduanes, Philippines|
|Movement:||W at 14 knots (estimated)|
|Max. Winds:||15 knots|
Source: NRL (0900UTC/1700PST)
This system has been moving quite a bit faster than expected over the past 12-24 hours. And I even notice a bit of a WSW shift in movement this morning, but that may have been just an optical illusion. In any case, the system is getting better organized and is expected to become a significant tropical system in the next 1 to 3 days. This slower development curve gives me a reason for pause, as it indicates this system may also be another monsoon-depression type system. The typical life span of these storms includes…
1. Slow initial formation with an elongated trough that slowly consolidates into a LLCC (Low-Level Circulation Center)
2. Numerous “ghost” vortices…swirls in the clouds that make it hard to pinpoint the real center of the action
3. Propensity to change the upper-level air dynamics in favor of development, primarily in the form of lowering vertical wind shear values in, and around, the LLCC.
4. Fast initial movement, followed by 3 or 4 days of very slow forward progression and slow strengthening, and then a rapid increase in forward speed and storm strength within 36 hours of landfall.
5. Large southwest-oriented “feeder” feature, which enhances the southwest monsoon for near- continental regions during the storm’s life cycle.
Not all of these features are in place with 93W INVEST, but there have been multiple vortices spotted and the upper-level dynamics are forming in such a way as to indicate this may be one of those systems. VWS speeds were at 20-30 knots on Friday, but have fallen off to less than 5 knots now in the immediate area of the supposed circulation center.
The prognostic factors are as follows:
A, Upper-level divergence, the dynamic that helps the storm evacuate excess moisture and energy (simplified), is rather high, especially on the SW quadrant of the storm.
B. Low-level convergence, the surface dynamic that indicates the level of surface instability, lift, and flow into the system (simplified), is also quite high on the southeast quadrant of the system.
C. 850mb vorticity, the dynamic that indicates general instability and cyclonic airflow, is at moderate levels at this time at the location of the supposed circulation center.
D. VWS (Vertical Wind Shear- a storm-killer if there ever was one) is virtually non-existent in the immediate area of the storm’s given center location.
E. SST’s (Sea-Surface Temperatures) are quite high at 27-29 C.
All of these factors add up to a moderate risk of tropical storm development within the next 24-48 hours.
Computer models are taking this system north of the Philippines in the general direction of Taiwan. I am watching this system very closely, because in July of 2010, there was a system called CONSON (Basyang), and this system was forecast to take a similar track to 93W’s forecasted path. However, the STR set up rather unexpectedly, and kept CONSON on a mostly westward track, where it crossed the island of Luzon and passed just south of the Metro Manila area. I hold out the slight suspicion that this system may behave similarly, but I have no scientific evidence to prove it. Call it a hunch. In any case, everyone from the Philippines to Japan needs to keep their eyes on this one.
AREAS OF INTEREST
The first area of interest is an area of disturbed weather located to the SW of a TUTT cell in the central WESPAC. This system is located near 17N, 148E. The system appears to be moving SSE at this time, as a result of the NNW flow around the TUTT. I can already see a bit of rotation, but that could be an optical illusion. At this time, computer models are not making much out of this area showing it being swallowed up inside the circulation of 93W as it strengthens and moves to the NW.
The next area of interest in an area of disturbed weather embedded in the ITCZ. This system is located near 5N, 151E. This system is moving WNW in the overall ITCZ flow. It would appear some vorticity is taking place here as well, but it could also be an illusion. Computer models are taking this storm to the NW near 142E, and situating it west of Guam at the end of the model run.
The final area of interest is also embedded in the weak part of the ITCZ far to the east. This system is located near 10N, 171E. This disturbance appears to be moving mostly west. Models are showing nothing with this system at this time.
AROUND THE NEIGHBORHOOD…
We are entering a dry phase of the MJO (Madden-Julian Oscillation). What this means is, traditionally, less moisture is available for convective development during the dry phase, with the opposite being true for the wet phase. This condition oscillates, as the name suggests, which means we are exiting a wet phase, indicated by the NUMEROUS tropical systems and copious moisture that has been in place for the past 3 weeks. As we enter the dry phase, convective activity is decreasing across the WESPAC. This should continue for a week or two, before we start to shift back to a wet phase sometime in September.
I’ve been talking a lot about TUTT (Tropical Upper-Tropospheric Trough) cells this tropical season, but today, we only have one and it is located far to the east near 27N, 165E. This TUTT appears to be drifting slowly to the WSW at this time. AOI081112-A is associated with this TUTT, much the same way that KHANUN, VICENTE, DAMREY, SAOLA, HAUKUI, and KIROGI all have been with various similar systems over the past weeks.
Once again the crystal ball paints a rather muddy picture for us but…oh…wait…let me wipe the mud off from the NEARLY 1000mm of rain that has fallen here in the past 2 weeks!!! Sheesh! Much better. But I still can’t tell you much about what is in store. 93W is expected to form within the next 2 days and move to the NW toward Taiwan. That’s about all I can give you. There is potential for other systems to organize, but for now, we just have to keep looking out to the east.
Earlier this week, the Philippines suffered an enormous tragedy, as wave after wave of southwest monsoonal rain poured over the central and northern parts of the island of Luzon. Figures are still not official but it is safe to say that between July 27 and August 10, nearly 1200mm of precipitation fell in various parts of the area. Rivers are still swollen and over a million people have been displaced from their homes. Here at Westernpacificweather.com, we have set up a way for you to help in the relief efforts, by forwarding ALL proceeds from ads and donations to the website this week to The Philippine Red Cross to assist in flooding relief efforts there. We appreciate your generosity.
While we are at it, let’s hold out hope and prayers for the people in eastern China as well. They have taken the brunt of no less than 4 tropical cyclones so far this year. Millions have lost their homes, thousands have died, and there is a good possibility that they will suffer more before the season is done.
Michael Williams Sr.