Average 20 year old weather nerd. Plymouth State University Meteorology, Class of 2018. Interning this summer at NWS Boston.
By: MAweatherboy1 , 12:20 AM GMT on November 26, 2012
Finally some interesting tropical weather to blog on tonight! The action center tonight is the West Pacific, as Invest 91W has organized enough to be classified as Tropical Depression 26W according to the Joint Typhoon Warning Center. As of the first JTWC warning on the system, 26W is located about 285 nautical miles SE of Chuuk, and is moving WNW at 8kts. Maximum 1 minute sustained winds in the system are estimated at 25kts, or about 30mph. This is based mainly off of Dvorak classifications, as well as satellite appearance. It should be noted the system's current Raw T#, which is useful in determining short term intensity changes, is a 2.3, which would suggest the system is closing in on tropical storm status, which is generally indicated by a 2.5.
Forecast For 26W
The official intensity forecast from JTWC strengthens 26W, bringing it to an intensity of 90kts in 5 days, which would make it a Category 2 equivalent on the Saffir Simpson Scale. 26W is in a favorable environment, with warm waters, moist air, and very little shear. The two main factors working against it are its low latitude and the fact that it is a broad system. The low latitude (3.6N as of the first JTWC advisory) will make it difficult for the system to get enough spin going to strengthen significantly. This problem will slowly abate as the system moves WNW. Having a large, broad circulation means the system will take time to consolidate. The two major models I'm looking at, the GFS and ECMWF, show fairly different intensity solutions. The GFS has been consistent in forecasting 26W to organize quickly and strengthen significantly. The ECWMF had been showing little development until yesterday, and has steadily been trending towards the GFS since then, though it still shows a weaker and more compact system. Due to its consistency, I am heavily basing my intensity forecast off the aggressive GFS, and I forecast a peak intensity of 100kts in 5 days. If 26W forms a strong inner core, which current microwave imagery does not show happening, then rapid intensification could occur and my 100kts 5 day prediction could be too low. If the system struggles to consolidate 100kts could be too high. There is certainly potential for 26W to strengthen beyond the 5 day timeframe, but that is as far as I'll go in this blog. The main steering influence for 26W will be a large ridge which will keep the system on a generally WNW heading for the next 5 days. Because it shows a weaker storm, the ECMWF is farther south than the more aggressive GFS, and it is also a little slower. Since my intensity forecast is mostly based off the GFS, my track forecast will also favor this model's solution. Larger differences occur farther out, as the GFS has been consistently recurving the system while the ECMWF's 12z run today showed possible impacts for the Philippines in 10 days or so. The ECMWF is struggling with this system, and I feel that it is trying to come in line with the GFS, so I feel a recurve will eventually be the fate of this system. Nonetheless, residents of the Philippines should keep an eye on the system. In the shorter term, there are some small islands in 26W's path, but no major population centers. Though I expect a more northerly track than what JTWC is showing, I do not feel 26W poses any significant threat to Guam, which is on the northern edge of the forecast cone.
Figure 1: Official JTWC forecast of 26W, showing an acceleration in a day or so as it moves out from its current weak steering environment and into the influence of a large ridge. Its heading should remain fairly steady throughout the next 5 days.
Figure 2: TD 26W. The system is currently broad and disorganized, but with favorable conditions in its path it is likely to consolidate and strengthen, possibly at a rapid pace at times.
Not too much else to speak of in the global tropics tonight. Tropical Cyclone Boldwin weakened quickly and dissipated in the South Indian basin today. The Atlantic and East Pacific are quiet, with no areas currently being watched and nothing showing up on the models. The seasons for these two basins are more than likely over, and the official climatological end of the season is only a few days away.
Thank you as always for reading! I'll be releasing my end of season Atlantic recap either Friday night or Saturday. Have a great week!
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