AXNT20 KNHC 222108
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sat Sep 23 2023
Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.
Based on 1800 UTC surface analysis and satellite imagery through
Tropical Storm Ophelia is centered near 32.9N 76.3W at 22/2100
UTC or 100 nm SE of Cape Fear North Carolina, moving NNW at 11
kt. Estimated minimum central pressure is 986 mb. Maximum
sustained wind speed is 60 kt with gusts to 75 kt. Scattered
moderate and isolated strong convection is noted within 150 nm in
the W quadrant of Ophelia. Peak seas are currently around 23 ft SE
of Cape Fear, North Carolina, per the Ocean Prediction Center
based on nearby observations from NDBC buoys. On the forecast
track, the center of Ophelia will approach the coast of North
Carolina tonight, and then move across eastern North Carolina,
southeastern Virginia, and the Delmarva Peninsula Saturday and
Sunday. Little change in strength is forecast before landfall
along the coast of North Carolina. Weakening is expected after
landfall through the rest of the weekend. Swells generated by
this system will affect much of the U.S. east coast through the
weekend, likely causing life-threatening surf and rip currents.
Heavy rainfall from this system could produce locally considerable
flash, and urban flooding impacts across portions of the Mid-
Atlantic states from North Carolina to New Jersey through Sunday.
Please read the latest HIGH SEAS FORECAST issued by the National
Hurricane Center at website -
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest
Ophelia NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.
Invest 90L in the Central Tropical Atlantic: The axis of a
tropical wave is analyzed along 35W with a 1009 mb low centered
at 14N35W, or several hundred nautical miles west of the Cabo
Verde Islands. Maximum winds are currently 25 kt and peak seas
are up to 10-11 ft. Shower and thunderstorm activity associated
with this area of low pressure has decreased slightly over the
last few hours, however, further development is still expected.
Scattered moderate convection is noted within about 420 nm in the
NW semicircle of the low. A tropical depression is likely to
form during the next couple of days while the system moves
generally westward at 10 to 15 kt. The system is then expected to
turn west-northwestward early next week as it moves over the
central tropical Atlantic. The formation chance through 48 hours
is high. Please see the latest Tropical Weather Outlook at
www.hurricanes.gov for more information.
Please see the Special Features Section for details on the
tropical wave (Invest 90L) along 35W.
A tropical N Atlantic tropical wave has its axis along 58W, south
of 22N, moving westward around 10 kt. Scattered moderate
convection is noted from 08N to 15N between 56W and 64W, including
over inland portions of NE South America.
The monsoon trough reaches the Atlantic through the coast of
Senegal near 14N17W and continues westward to the aforementioned
low pressure near 14N35W, before terminating near 09N47W. No ITCZ
is evident in the tropical Atlantic at this time. Scattered
moderate convection is noted from 12N to 19N between 43W and 47W.
GULF OF MEXICO...
A weak surface trough is analyzed from 26N90W to 23N85W. Scattered
showers and thunderstorms are noted between 60 nm and 180 nm NE of
the trough. Moderate NE-E winds and 3-4 ft seas are NE of the
trough. Otherwise, weak high pressure over the lower Mississippi
Valley is supporting only light to gentle NE to E breezes and
slight seas across the remainder of the basin this afternoon,
along with 1-3 ft seas.
For the forecast, weak high pressure over the lower Mississippi
Valley extending across the northern Gulf will control the weather
pattern across basin through early next week. This will support
mostly gentle to moderate winds and slight seas, except for
moderate winds pulsing to fresh winds offshore the western Yucatan
Peninsula in the evenings.
Weak surface ridging north of the Caribbean is forcing only
gentle trades N of a line from the SW tip of Haiti to central
Jamaica to the border of Nicaragua and Honduras, where seas are
mainly 2-3 ft. Moderate to fresh trades prevail SE of there,
highest in the central Caribbean with the pressure gradient is
relatively tight, along with 3-6 ft seas, locally 7 ft near
11.5N76.5W. No deep convection is noted today over the Caribbean.
For the forecast, moderate to fresh trade winds in the central
Caribbean will change little through Sat. Winds across central
portions will increase modestly Sun through Mon as high pressure
strengthens across the region. Fresh to strong trade winds will
pulse offshore of northern Colombia and northwest Venezuela during
mainly the overnight and early morning hours into early next
week. Looking ahead, seas will build in mixed NE and E swell
across waters east of the Leeward Islands starting early Mon,
ahead of low pressure moving westward across the tropical
Atlantic, possibly as the next tropical cyclone.
Please see the Special Features section section above for
information on Tropical Storm Ophelia and Invest 90L.
A mid-level trough extends from 31N73W to near Key Largo, Florida.
Scattered showers and thunderstorms are noted within 120 nm SE of
this feature, with similar activity from 22N to 27N between 67W
and 72W. A weak surface trough is analyzed from 31N28.5W to
29.5N35W to 30N40W with a parent front just N of 31N. Elsewhere,
ridging extends across the Atlantic along roughly 30N/31N. Between
the ridge and the monsoon trough/ITCZ, the trades are gentle to
moderate with seas 5-8 ft. Winds and seas are higher in the
vicinity of Ophelia extending S into our area to 29N, and also
near Invest 90L. Isolated to widely scattered moderate convection
is noted from 19N to 28N between 45W and 59W in association with
an upper-level trough.
For the forecast west of 55W, Ophelia will move further northward and
inland across coastal North Carolina on Sat. Large northerly swell
will move through the waters W of 70W tonight through early Sun
before fading. A weak ridge will build in the wake of Ophelia off
Florida through early next week, although a trough will persist
across the Bahamas through Mon. Looking ahead, seas will build in
mixed NE and E swell across waters northeast of the Leeward
Islands starting Mon, ahead of low pressure moving westward across
the tropical Atlantic, possibly as the next tropical cyclone.