Trosum (tropical summary) -- Wednesday October 10, 2012

By: Stu Ostro , 8:36 PM GMT on October 10, 2012

Been a while since I have posted anything -- was traveling in the weather (flying, and drove through a healthy MCS) and also for a while was under the weather -- but hope to start blogging more regularly. Also, there hasn't been as much to talk about in the tropics, but there's a lotta stuff going on at the moment (I've bolded in the entry below the elements most interesting to me), so I thought I'd post this version of the trosum.


[Source of all images in this entry is NOAA]

- There have been a number of tropical cyclones and wannabes with interesting and/or long histories this season, including Debby, whose potential for development models predicted weeks in advance, and whose track forecast entailed extreme differences between models; Isaac, whose remnants circled all the way back to the Gulf Coast and tried to redevelop; Nadine, which was one of the longest-lived tropical storms on record; and now Invest 97L.

- 97L's spin and moisture can be traced all the way back to the disturbance in the Caribbean which brought flash flooding to Jamaica at the end of September. It got sucked up to the north ahead of the system that produced flash flooding in Midland, Texas, to a position just off the Delmarva coast, then rotated clockwise around a ridge of high pressure to near the Bahamas, when it started trying to take on characteristics of a tropical cyclone.

- A part of it got strung out (and this system wasn't officially still designated as Invest 97L after yesterday morning until it was again this afternoon), but a portion continues to be quite resilient. In fact, it arguably has enough characteristics of a tropical cyclone to be designated as one. It'd be interesting to see what aircraft recon would find if there was one investigating. The only thing missing is that there are have been multiple centers of circulation at multiple levels, though the most recent satellite imagery suggests that even they seem to be consolidating.

- Strong upper-level winds, hostile to tropical cyclone development, continue to be strong just to the northwest, but are lighter overhead, which has enabled its survival, and given this system's resiliency, it is likely to hang on into tomorrow. Then models are suggesting a scenario in which the upper-level winds will become stronger across the whole system, finally discombobulating it Friday and Saturday, its top getting blown to the northeast while its lower portion detaches to the southwest toward Cuba. And in the meantime, its rain and wind are offshore, with its history and today's goings-on being a meteorological curiosity rather than this being a system which is having a significant impact.


- Invest 98L still does not possess enough organization to be close to tropical depression status, but it still has many days left to continue to try. As Dr. Masters noted in his blog today, the most likely time for that to happen is late in the weekend or early next week just north of the Caribbean islands. Regardless of the extent to which 98L takes on more characteristics of a tropical cyclone, as we head toward and into the weekend it'll bring gusty showers to the Leeward Islands. Looking ahead to next week, models have been consistent in showing a steering flow pattern that'll turn the system to the north and northeast, and keep it away from the U.S.


- A disorganized area of thunderstorms extending west from Central America within the "monsoon trough" of low pressure has been designated Invest 97E. Slow development into a tropical cyclone is possible as the system moves farther out to sea.


- Typhoon Prapiroon is drifting slowly, in an area of the ocean far from the Philippines, Okinawa and Iwo To (Iwo Jima), and is not in a hurry to travel very far anytime soon. In the longer range, i.e. early next week, Prapiroon is likely to accelerate toward the north and northeast, the question being whether it reaches or stays east of Japan.

- As indicated by the model forecast below for Sunday afternoon which shows a green plume of high "precipitable water," some of the typhoon's moisture will get carried by winds aloft all the way to the Pacific Northwest of the United States and contribute to heavy rainfall that will be ending the dry pattern there.


- An area of convection and spin -- associated with the remnants of Tropical Storm Gaemi, which made landfall in Vietnam a few days ago -- moved off the coast of Myanmar and entered the Bay of Bengal from the east, regenerated into Invest 94B (and arguably is a tropical cyclone), and is now making landfall on the coast of Bangladesh with heavy rain and onshore winds which are likely near tropical storm force.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Proud to be a weather-obsessed weather geek! \m/ Senior meteorologist at The Weather Channel. If not a meteorologist, would be a DJ ♫

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