Published: August 22,2014
- Invest 96L: A fascinating system meteorologically, and one whose potential future track scenarios and model forecast trends have significant implications and still warrant close attention
- In the meantime, it has brought flooding to Puerto Rico and the Virgin Islands; rain is increasing on the vulnerable island of Hispaniola (Haiti & Dominican Republic) - As NASA put it below, triple tropical tempests -- Karina, Lowell & Marie -- are in the eastern Pacific; surf's up in SoCalATLANTIC
Invest 96L
Still a squirrelly one. Significant run-to-run and model-to-model track forecast differences continue. Just when it looks like they might all be converging, they diverge.
There are two primary reasons for this system's future prospects being so vexing this week.
(MORE: What's an Invest?)
One, there's a particularly sharp fork in the road. That's the big trough -- southward dip in the jet stream -- we've been talking about which will be digging in over the western Atlantic. The right fork is for the system to get scooped up like a shovel by the digging trough and flung northeast and way out to sea; the left fork is if it gets missed by the jet stream dip and continues west toward the U.S. That's a very big difference in outcomes and impacts.
Two, rather than there being a clearly defined, tight, single center of circulation which the models can latch onto with precision and accuracy to start off ("initialize") their forecasts, a couple lobes of a broad circulation have been twirling around in the lower-middle part of the atmosphere, plus there still isn't yet, per aircraft reconnaissance today, a center of circulation anywhere at the surface.
And just as a small difference in location on a highway -- one lane -- can make the difference between which fork is taken, same thing with just a short distance difference in where this tropical weather system and its true center are when they come to the fork in the atmosphere in a couple days.
The amount of convection (deep rain clouds and thunderstorms) continues to increase, and with aircraft reconnaissance again having found tropical storm force winds, all it'd take is an identifiable center of circulation for 96L to be designated a tropical storm. Like the track story, the intensity one is also tricky and complicated, but the upshot is a likelihood of this to become Cristobal and then strengthen at least some more.
So the bottom line message for the U.S. mainland remains the same, until such time that the out-to-sea-track is the one and the all-clear could be given: Stay tuned, keep abreast of the latest information.
What is changing is that as the days pass, there are fewer before a potential encounter with this system as it gets closer and closer. As the satellite image below shows, it's not super-far away anymore. The speed of movement is expected to slow down some after having raced quickly, but nevertheless if it were to take the left fork it'd be approaching the coast by Monday or Tuesday.
The most likely location for an initial destination in the U.S. mainland would be Florida. (The European model, which for a couple runs showed an in-between-the-forks scenario in which the trough and the tropical system merge, the result being a track more toward North Carolina, no longer shows that, though at this point it wouldn't be shocking if that reappears as an option.)
In the meantime, per other emails today there have been impacts from heavy rain in Puerto Rico and the Virgin Islands; satellite images show rainfall on the increase in Hispaniola, which is vulnerable to flash flooding and mudslides, and in the Turks and Caicos, and heading toward the southeast Bahamas and eastern Cuba. Along with rain there'll be gusty winds and choppy seas.
(MORE: Detailed Forecast)
EASTERN PACIFIC
Some moisture from large Lowell with its large eye circulation reached into the southwest U.S.
No significant changes to previous days' expectations of a steering interaction between Lowell and smaller Karina.
Karina is a hurricane again; Lowell is back down to a tropical storm but still large; and Marie is on its way to being a hurricane and probably an intense one as well as being large.
No change to the expectation of ongoing elevated surf and rip current risk in SoCal.
(MORE: Glossary of Tropical Terms | New NHC Storm Surge Maps)
WESTERN PACIFIC
Still a nice lull.
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