From Watts Up With That?

Brief News Note by Kip Hansen

Just in time to beat the “hurricane season peak  deadline”, NOAA’s National Hurricane Center declared the Potential Tropical Storm Six to be Tropical Storm Francine:

10:00 AM CDT Mon Sep 9

Location: 23.0°N 94.9°W

Moving: NNW at 5 mph

Min pressure: 1002 mb

Max sustained: 50 mph

From the Discussion section: 

“Tropical Storm Francine Discussion Number   4

NWS National Hurricane Center Miami FL       AL062024

1000 AM CDT Mon Sep 09 2024

The structure of the system on satellite imagery has improved this

morning, with a large circular region of cold convection between -70

to -85 near the estimated center. An Air-Force Reconnaissance

Aircraft is sampling the system this morning and earlier found a

cyclonic wind shift from southeasterly to northwesterly flow near

the center of the mass of deep convection. This data provides enough

evidence that a well-defined circulation now exists, and thus PTC

Six has become Tropical Storm Francine with sustained winds of   

45 kt this advisory.

The estimated motion is still tricky given the center only recently

formed but is estimated still off to the north-northwest at    340/4

kt. The system is expected to gradually turn northward and then

north-northeastward as it moves between a mid-level ridge centered

over Cuba and a broad mid- to upper-level trough located to its

northwest over Texas. The guidance this cycle has shifted a little

eastward and faster, and the NHC track forecast was once again

nudged in that direction. The current track splits the difference

between HCCA and TVCN and still shows Francine moving ashore of

Louisiana sometime on Wednesday evening. There remains a decent

amount of track uncertainty with the GEFS and EPS ensembles showing

along-track spread implying some speed differences near landfall.

While the system is now a tropical storm, the inner core wind field

per reconnaissance observations is still broad and in the organizing

stage, and initial intensification will be gradual. However, after

an inner-core becomes established, and assuming the cyclone’s

vertical structure becomes aligned, a period of more significant

intensification is possible while storm is embedded in a low shear,

high mid-level moisture, and over very warm 30-31 C sea-surface

temperatures.  The SHIPS rapid intensification (RI) indices are

pretty elevated, and a period of RI could also occur between   24-48

h. For now, the NHC intensity forecast will not explicitly forecast

RI, but is higher than the previous cycle and shows a 75 kt peak in

48 h, in good agreement with the intensity consensus aids. After

that period, southwesterly vertical wind shear quickly increases

from 10 kt to more than 30 kt and the intensity could plateau as it

approaches the northwestern U.S. Gulf coastline, though the system

is forecast to remain a hurricane at landfall. The NHC intensity

forecast continues to be in good agreement with the consensus aids,

but is a bit under the HAFS-A/B and COAMPS-TC models.

Given the latest forecast, a Hurricane Watch has been issued for

the Louisiana coastline from Cameron to Grand Isle, and a Storm

Surge Watch has been issued from High Island, TX eastward to the

Mississippi/Alabama Border.”

Thus, for the season to date we now have this:

# # # # #

Author’s Comment:

Compared to the historical record, the 2024 Hurricane season is running at a little less than 50%.

The Two-Day and Seven-Day forecasts show a couple of things in the pipeline – which may develop into tropical storms.

And that’s the news.

# # # # #