Saturday Melissa advisories and more (about to get stronger)

[nitpicked]

5. and the discussion (bolding mine)

https://www.nhc.noaa.gov/text/refresh/MIATCDAT3+shtml/250843.shtml

(snip)
Melissa is very nearly a hurricane. Data from both the Air Force
Reserve Hurricane Hunters indicate the storm has become better
organized, with a 20 n mi eyewall that has been coming an going.
This structure has also been seen on radar images out of Kingston,
Jamaica. Compared to last night, Tail Doppler Radar (TDR) data
indicates the tropical cyclone is much better aligned vertically,
though some residual eastward tilt with height exists in the
mid-levels. The peak flight level winds at 700 mb were up to 68 kt.
Using a standard 0.9 adjustment factor to surface winds yields an
intensity of 60 kt, but Melissa could become a hurricane at any
time, as other satellite intensity estimates already support a
higher value.

The initial motion is crawling along to the west-northwest,
estimated between aircraft fixes to be 285/1 kt. Now that the
tropical cyclone has become better aligned vertically, it should
increasingly feel the deep-layer steering, which has a slight south
of due-west component from the latest ECMWF steering diagnostics.
The spread in the model solutions even in the next 12-36 hours is
higher than usual, with the AI models, Google DeepMind ensemble
mean (GDMI) and ECMWF-AI (AIFS) on the south and western end of the
guidance envelope showing a westward or even west-southwestward
motion in the short-term, while the traditional dynamical aids
(ECMWF, HAFS-A/B) show more of a west-northwestward drift
towards Jamaica over the next 24-36 hours. Still though, nearly all
of the reliable track guidance (discounting the GFS which has been
an eastward outlier since the storm formed) shows Melissa making
landfall in Jamaica sometime in the 60-72 hour time frame. During
this time, a digging mid-latitude trough in the southeastern United
States is expected to create a new weakness to the north of
Melissa, which should result in the cyclone taking a sharp turn to
the northeast. While the guidance is in good agreement on this
general turn with relatively small across-track spread, there
remains high along-track spread in the solutions, best highlighted
by the Google DeepMind ensemble which shows a spread in possible
locations in 96 h from still inland over Jamaica to northeast
of Cuba in the southwestern Atlantic. The NHC track forecast is a
touch south of the prior track for the first 24-48 hours, but
converges on the prior track forecast thereafter. This is a little
on the eastern side of the track guidance envelope, giving credence
to the AI model solutions (GDMI, ECAI) which to date are the best
preforming track guidance this hurricane season.

Melissa seems to be shaking off the negative effects of westerly
shear now that the storm is becoming better vertically aligned.
Thus, it appears likely that a period of rapid intensification
will occur as the storm moves slowly over very warm ocean waters
(30-31C sea-surface temperatures) which is also over the highest
oceanic heat content in the entire Atlantic basin, which will limit
initial ocean upwelling under the slow moving storm. Similar to the
previous cycles, roughly 40/50 Google DeepMind ensemble members show
Melissa becoming a Category 5. While I am not ready to forecast that
intensity yet given the track uncertainty, that remains a
possibility. After 48 h, inner core processes (such as eyewall
replacement cycles) could cause fluctuations in intensity, but
Melissa is still expected to make landfall in Jamaica as an
upper-end Category 4 hurricane, which could be the strongest direct
landfall for the island in since tropical cyclone record keeping has
been made in the Atlantic Basin. Weakening is expected as Melissa
moves over the high terrain of Jamaica and eastern Cuba, with
further weakening expected thereafter as southwesterly vertical wind
shear increases. The NHC intensity forecast remains on the high end
of the guidance, but closest too the Google DeepMind ensemble mean,
which has also been on of our best intensity guidance performers
this year.


Key Messages:

1. Jamaica: Melissa’s slow movement will bring a multi-day period
of damaging winds and heavy rainfall beginning tonight, likely
causing catastrophic flash flooding, numerous landslides, extensive
infrastructural damage, long-duration power and communication
outages, and potentially prolonged isolation of communities. A
life-threatening storm surge is also likely along portions of the
southern coast early next week. All preparations should be completed
today.

2. Haiti: Catastrophic and life-threatening flash flooding and
landslides are expected across southwestern Haiti into early next
week, likely causing extensive infrastructural damage and
potentially prolonged isolation of communities. Strong winds could
also potentially last for a day or more over the Tiburon peninsula.

3. Dominican Republic: Heavy rainfall could produce potentially
catastrophic flash flooding and numerous landslides in southern
regions.

4. Eastern Cuba, Southeast Bahamas, and the Turks and Caicos:
Monitor Melissa closely. There is an increasing risk of a
significant storm surge, damaging winds, and heavy rainfall by the
middle of next week. In eastern Cuba, the risk of life-threatening
flash flooding and landslides is increasing.
(snip)