Weather Nerd

92L still toying with forecasters

The “Joker” has struck again! More than 18 hours after I declared its development “imminent,” Invest 92L is still refusing to organize. The National Hurricane Center’s 8:00 AM EDT Tropical Weather Outlook states:

THUNDERSTORM ACTIVITY HAS INCREASED THIS MORNING IN ASSOCIATION WITH THE AREA OF LOW PRESSURE LOCATED OVER PUERTO RICO. WHILE THIS SYSTEM CONTINUES TO SHOW SIGNS OF ORGANIZATION…IT DOES NOT YET APPEAR TO HAVE A WELL-DEFINED CENTER OF CIRCULATION AT THE SURFACE.

The Outlook adds that “upper-level winds are favorable for development,” and “a tropical depression could form at any time the the next day or so” — but, where have I heard that before? Proto-Fay is now officially rivaling proto-Dolly for 2008’s “stubborn refusal to gets its act together” record!

More interestingly, the Outlook notes:

WHEN AND WHERE A DEPRESSION MIGHT FORM IS UNCERTAIN…IN PART DUE TO POTENTIAL INTERACTIONS WITH THE LAND MASS OF HISPANIOLA.

You can see 92L’s proximity to both Hispaniola and Puerto Rico on the satellite view:

fay-rgb.jpg

Weatherblogger Alan Sullivan picks up this theme, writing that “land interaction is preventing further organization” already. He predicts:

It’s possible that a more focused circulation could form over the Mona Passage [between Puerto Rico and Hispaniola -ed.] today, or along the NE coast of the Dominican Republic tonight, but on its present path, the circulation may be too disrupted to close off as a tropical depression until it extricates itself from land and drifts past the Turks and Caicos.

Sullivan, who is himself in South Florida, foresees a greater threat to his area because of this track, but adds: “It still seems most probable to remain a Bahamian storm. At present I expect a category one hurricane about a hundred miles east of Hollywood Beach on Tuesday.” Several of the computer models expect something similar:

That said, it’s still way too early to put much stock in exact computer-model tracks, particularly given that the storm hasn’t even formed yet. Once proto-Fay becomes an actual tropical cyclone, and has been such for about 24 hours, then we can start trusting the models a bit more. For now, everybody from the Gulf up the East Coast should keep an eye on it — two eyes in Florida.

UPDATE: Dr. Jeff Masters says of 92L, “I don’t recall ever seeing a system that looked this good on satellite imagery not technically qualify as a tropical depression.” He adds that 92L — or “The Joker,” as he calls it — is “certainly worthy of having a full set of advisories issued for it, given is possible impacts, even if it doesn’t technically qualify as a tropical depression.” Masters suggests that, in the future, “perhaps NHC should consider an extension to their ‘Special Tropical Disturbance Statement’ that includes a set of forecast tracks, marine forecast, discussion, etc.”

Masters also clarifies why 92L isn’t technically a T.D. or T.S. yet, even though satellite intensity estimates say it has 40 mph winds:

Last night’s Hurricane Hunter mission did find that 92L had a vigorous circulation at mid levels of the atmosphere, but this circulation did not extend down to the surface. Even when the center of 92L was over northwestern Puerto Rico, I couldn’t find any winds out of the west on the island, suggesting that 92L did not have a closed surface circulation. However, the latest QuikSCAT pass from 5:52 am EDT shows that 92L had a large area of west winds south of the island. However, this data was not enough for NHC to upgrade 92L to a tropical depression or tropical storm this morning, presumably because the QuikSCAT data was contaminated by rain and not deemed trustworthy.

On satellite, 92L appears on satellite as “a well-organized system with a steadily increasing area of heavy thunderstorms” and “fair” outflow on three sides. Wind shear is almost literally nonexistent (1 knot), and 92L is sitting under an upper-level high pressure system, allowing for good outflow. “This favorable upper-level wind environment is expected to last at least through Sunday. Beyond then, increasing shear may be a problem for the storm.”

As for the storm’s eventual track, Masters notes that the computer models are still all over the place, but no model is calling for 92L to recurve harmlessly out to sea. The current predictions are:

GFDL, HWRF: parallel to the east coast of Florida, 50-100 miles offshore, eventually threatening South Carolina
UKMET: Through South Florida
NOGAPS: Through the Florida Keys, into South Florida
ECMWF: Through the Bahamas and into North Carolina
GFS: Through the Bahamas, then west across central Florida in the Gulf of Mexico
Canadian: Across Cuba and through the Cayman Islands, then north in the Gulf of Mexico