- Center of western Gulf system has moved onshore (made landfall); characteristics of a tropical depression but not officially one - Second disturbance is over south-central Gulf, headed for TX/LA coast tomorrow into Saturday; limited time to organize but will bring surge of moisture - Cristobal non-tropical remnant to merge with another system and track over or near Iceland, something which would be an infrequent event - Combination of a disturbance near the coast of South America and what used to be Invest 97L in the tropical Atlantic expected to join and move across the western Caribbean, Central America and southeast Mexico, and maybe the southwest Gulf - Imminent development of the tropical wave coming off Africa not expected; possible eventually; models have become not as certain that it’ll curve out to sea - Ocean waves past peak on Pacific and Atlantic coasts, but still up, along with rip current risk, in some places - Unnamed tropical system bringing heavy rain to Southeast Asia GULF OF MEXICO The system we’ve been tracking since thunderstorm clusters came off the AL/FL coast a couple days ago continued to organize today, and seemed to have acquired the characteristics of a tropical depression. The surface center appeared to be well-defined, e.g. with northwest winds at Brownsville all day leading up to landfall. Something which is subjective in such assessments is the extent to which the deep convection (rain clouds & thunderstorms) is sufficiently present and organized. Though not in as big a burst as early this morning, it has been repeatedly firing east of the center, and radar imagery indicates it’s deep (>40K feet high) in the cells even to the west and south, and has been structured in spiral bands. (Yet as this increased organization since yesterday has occurred, the official probability of becoming a tropical depression was lowered to near zero.) The center looks like it has moved onshore and that should end the organization/development process, unless it were to do something goofy like stall and move back offshore. The slow movement of the system could lead to locally heavy rain amounts depending on what those bands of tropical showers do. Then a second disturbance is taking shape on schedule over the south-central Gulf. The bands of showers and thunderstorms sorta look like they’re part of a larger feature that includes Invest 98L on the Texas coast, and models say there will be a relationship between the two. That second thing will bring a surge of moisture and locally heavy rain to the west-central Gulf Coast, and tropical moisture will subsequently flow directly into the U.S. system bringing wet weather to many during the holiday weekend. (It’s not directly part of a subsequent system that’ll be bringing the severe thunderstorms to the northern Plains on Sunday.) The rip current risk on the Gulf Coast continues too. Analysis of the lower part of the atmosphere show a combo of a piece of ex-97L that came in from the east and new spin coming off of South America. And convection has flared up today. All this stuff could further organize in the western Caribbean during the next couple of days or in the southwest Gulf early next week, if it is able to emerge off land that far north. Model forecasts keep this one south of the U.S. CRISTOBAL It is on its way to combine with a high-latitude system aloft, and absorb that other system in the lower levels, and then head toward Iceland. Models aren’t in total agreement whether the center will go over Iceland or slide just to the south and east. Either way, there’ll be wind, rain, and high surf, though there’d be less with a track of the center sufficiently away from the island. It will become a non-tropical storm before then, but as it approaches Iceland, models are indicating it could regain a warm core (a characteristic of tropical cyclones) by a process known as a warm seclusion, which is at it says — the warm air aloft gets secluded in the storm’s core, surrounded by colder air. It wouldn’t be a tropical storm again, but would have some aspects of a hybrid, as intense winter cyclones can have. The historical record shows very few ex-tropical cyclones have gone over or close to Iceland. Not unprecedented, but infrequent. (With not only the usual caveats, but also if, say, ex-Cristobal were to not be included in the ex-tropical storm record that far north because it merges with another system, one wonders whether there have been other cases of that.) ELSEWHERE Imminent development of the tropical wave coming off Africa is not expected; it’s possible eventually; whereas previously models were consistently showing it to curve far out to sea, more recent runs open the door to a farther-west track. Ocean waves are past peak on U.S. Pacific and Atlantic coasts, but still up, along with rip current risk, in some places, i.e. buoys offshore of San Diego and Florida show the wave heights have been slow to come down, while farther north on each coast that has happened more quickly. Like with 98L on the Texas coast, curiously a system with swirling tropical rainbands (satellite loop below) moving into Vietnam was, as best as I can find, not classified by either the Joint Typhoon Warning Center or the Japan Meteorological Agency as a tropical depression. Now it is moving well inland, and is bringing heavy rain from that country to Laos and Thailand.
Posted on: Fri, 29 Aug 2014 11:59:57 +0000
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