1000UTC/1800PST, July 14, 2012
90W GOES AWAY, KINDA, AND 91W FORMS AS THINGS PICK UP IN THE TROPICAL WESPAC…
Things have been rather quiet for the past 7 days or so, but now it would appear the hints of a busier time ahead are starting to appear on the horizon in the tropical WESPAC. Although things should stay relatively quiet for the next 7 days, I think we might have some action in the short-term. What, do you say, is happening?? Please continue…
ON THE BOARD…
In the Mid-Week report, I mentioned a TUTT cell located near 19N, 142E. Well, it seems that the atmospheric conditions have come together in such a way as to allow a tropical disturbance to form there. The situation is very complicated, but I will attempt to explain it a bit later. Here are the latest official numbers for the system:
Coordinates: NRL- 19.4N, 143.7E
JTWC- 18.9N, 144.1E
Location: NRL- 217km (135mi) WNW of Agrihan Island
JTWC- 165km (103mi) WNW of Agrihan Island
Movement: NRL- N/A
JTWC- SW (based on JTWC positioning)
Max. Winds: NRL- 15-20 knots (estimated)
JTWC- 12-17 knots (based on 0600 JTWC ABPW10 bulletin)
Min. Pressure: NRL- 1008mb (estimated)
JTWC- 1008mb (based on 0600 JTWC ABPW10 bulletin)
The situation, as mentioned earlier, is quite complex. First, the very fact that a surface system has formed so close to an upper level TUTT cell is rare enough. The fact that the tropical WESPAC is conspicuously littered with these upper-level systems is also a bit of an oddity. Nevertheless, a surface system has indeed formed in this area. SST’s (Sea-Surface Temperatures) are very high in the expected path of this system, ranging between 30 and 32 degrees Celsius. Wind shear speeds are quite low in the vicinity of the system’s center, but values increase a bit in the expected path. The aforementioned expected path is to be west-southwest, then west, and the system is expected to intensify somewhat. The NOGAPS and GFS 00z runs are showing a quite complicated monsoon gyre-type system, with a great deal of scattered vorticity in and near the projected center of circulation. The NOGAPS model shows more of a consolidation of the system by 21 July, and located to the ENE of the northern Philippines. The JTWC ABPW10 bulletin issued at 0600UTC (1400PST) listed the 24-hour formation potential of this system as MEDIUM. This system is definitely one worth watching.
AROUND THE NEIGHBORHOOD…
Elsewhere, it’s mostly quiet in the tropical WESPAC. Earlier in the report, I had mentioned that 90W INVEST had mostly dissipated. Well, that is because the remnants of that system have moved over the island of Mindanao in the Philippines, and a LLCC is clearly evident over the landmass at this time. I believe this system will emerge in the warm waters of the SCS (29-30 degrees Celsius) and could most likely become 92W INVEST and form into a marginal tropical threat for Southeast Asia. Otherwise, it’s all upper-level action that is happening out there. There are three areas of upper level low pressure, or TUTT’s (Tropical Upper-Level Tropospheric Trough)’s. Two are located quite close to the newly-born 91W INVEST. A rather elongated TUTT is located at 16N, 134E, while another, more focused TUTT cell is found at 25N, 145E. These systems are somehow working together to make the upper-level dynamics a bit more favorable for 91W’s development. Another, much larger TUTT, is located near 21N, 163E, and it contains several smaller areas of upper-level vorticity, which further complicates the possibilities when trying to forecast these systems. The look around the neighborhood ends with a check of the rather active ITCZ, and the Mei-Yu baroclinic zone, which has sent an impulse or two into the northern fringes of the tropical region, and helped stir things up a bit over the past 2 or 3 days. The Mei-Yu zone is responsible for record-setting rainfall in parts of Japan from Wednesday until Friday. Numerous deaths were reported due to flooding and landslides. Please check the earlier postings on the website for more detailed information.
All in all, the crystal ball seems cloudy and muddled today. If 91W INVEST were just a simple area of low pressure with a chance to develop in a more typical atmospheric setup, then it might be easier. In this case, it is quite difficult. NOGAPS is showing 91W strengthening a bit and consolidating before positioning itself just east of the Philippines on July 21st. The model is also showing a possible low pressure area forming along the ITCZ near 10N, 150E by July 21st. The GFS model is much more scattered and undecided, showing no real potential for organized development through the model run, ending July 21st. I think we will have to watch 91W, and prepare for an upswing in the activity as we head into next weekend.
Michael Williams Sr.