BULLETIN
Tropical Depression Four Advisory Number 1
NWS National Hurricane Center Miami FL AL042021
1100 AM EDT Mon Jun 28 2021
...NEW TROPICAL DEPRESSION FORMS OFF THE COAST OF SOUTH CAROLINA...
...TROPICAL STORM WARNING ISSUED FOR PORTIONS OF THE SOUTH
CAROLINA COAST...
SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...31.9N 78.3W
ABOUT 145 MI...235 KM ESE OF BEAUFORT SOUTH CAROLINA
ABOUT 110 MI...180 KM ESE OF CHARLESTON SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1013 MB...29.92 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
A Tropical Storm Warning has been issued for a portion of the coast
of South Carolina from Edisto Beach northeastward to South Santee
River.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Edisto Beach to South Santee River South Carolina
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 12 hours.
For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.
DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Depression Four
was located near latitude 31.9 North, longitude 78.3 West. The
depression is moving toward the west-northwest near 16 mph (26 km/h)
and this general motion is expected to continue for the next couple
of days. On the forecast track, the center of the tropical cyclone
should make landfall along coast of South Carolina in the warning
area later this evening.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some slight strengthening is expected today, and the depression is
forecast to become a tropical storm before it makes landfall. Rapid
weakening is forecast after landfall occurs.
The estimated minimum central pressure is 1013 mb (29.92 inches).
HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Depression Four can be found in the
Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header
WTNT44 KNHC and on the web at
http://www.hurricanes.gov/graphics_at4. ... y_messages.
WIND: Tropical storm conditions are expected to first reach
the coast within the warning area by late this afternoon, making
outside preparations difficult or dangerous.
RAINFALL: The depression could produce 1 to 3 inches of rainfall
with locally higher amounts along the immediate coasts of Georgia
and southern South Carolina. This region has been dry, limiting
potential widespread flooding impacts, however, local flooding
impacts, especially in urban areas along the southern South Carolina
and Georgia coasts, cannot be ruled out at this time.
Farther inland, 1 to 2 inches of rainfall is possible across Upstate
South Carolina, the Piedmont of Georgia, and into northeastern
Alabama.
STORM SURGE: The combination of storm surge and the tide will cause
normally dry areas near the coast to be flooded by rising waters
moving inland from the shoreline. The water could reach the
following heights above ground somewhere in the indicated areas if
the peak surge occurs at the time of high tide...
Port Royal Sound, SC to South Santee River, SC...1 to 3 ft
Surge-related flooding depends on the relative timing of the surge
and the tidal cycle, and can vary greatly over short distances. For
information specific to your area, please see products issued by
your local National Weather Service forecast office.
NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.
$$
Forecaster Stewart
Tropical Depression Four Discussion Number 1
NWS National Hurricane Center Miami FL AL042021
1100 AM EDT Mon Jun 28 2021
The area of disturbed weather and associated low pressure system
that the NHC has been tracking the past couple of days has developed
into a tropical depression off the coast of South Carolina this
morning. The inner-core cloud structure noted in high-resolution
visible satellite imagery has continued to tighten up and deep
convection with cloud top temperatures of -60 deg C have persisted
northwest through southwest of the center, yielding a Dvorak shear
pattern intensity estimate of 30 kt. This intensity estimate is
consistent with overnight scatterometer surface wind data of 31-32
kt just north of the well-defined center.
The initial motion estimate is 300/14 kt. The small tropical cyclone
is expected to maintain a west-northwestward to northwestward motion
for the next couple of days, resulting in landfall along the
south-central coast of South Carolina later this evening. The small
cyclone is expected to dissipate by 48 hours, if not sooner, when
the system will be located over the southern Appalachian Mountains.
The NHC track forecast lies close to the tightly packed GFS- and
ECMWF-based Beta-Advection models due to the lack of any significant
inner-core convection, which is allowing the cyclone to be steered
more by the low-level flow rather than the deep-layer flow as
depicted by the global and regional models.
There is a narrow window of opportunity this afternoon for the
depression to strengthen into a tropical storm before landfall
occurs. During the next few hours, the small cyclone will be passing
over the warmer Gulf Stream where sea-surface temperatures are
around 28 deg C. In addition, as the outer wind field begins to
interact with land, low-level frictional convergence along and just
offshore should help to generate deep convection just prior to
landfall, helping to spin up the wind field. The NHC forecast shows
the system becoming a tropical storm before landfall, and as a
result a tropical storm warning has been issued for a portion of
the South Carolina coast.
An Air Force Reserve Unit reconnaissance aircraft will investigate
the system this afternoon beginning around 1800 UTC, providing more
detailed information on the cyclone's intensity.
Key Messages:
1. Heavy rainfall is possible from coastal southern South Carolina
and Georgia, inland across the Piedmont of Georgia into northeast
Alabama. Isolated flooding is possible across urban areas of the
southern South Carolina and Georgia coasts.
2. Tropical-storm-force winds are expected across portions of
the South Carolina coast late this afternoon and tonight where a
Tropical Storm Warning is in effect.
3. Swells generated by the depression are expected to affect
portions of the South Carolina coast this afternoon and tonight.
These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS
INIT 28/1500Z 31.9N 78.3W 30 KT 35 MPH
12H 29/0000Z 32.8N 80.6W 35 KT 40 MPH...INLAND
24H 29/1200Z 34.2N 83.3W 20 KT 25 MPH...POST-TROP/INLAND
36H 30/0000Z 35.2N 85.6W 15 KT 15 MPH...POST-TROP/INLAND
48H 30/1200Z...DISSIPATED INLAND
$$
Forecaster Stewart
Tropical Depression Four Advisory Number 1
NWS National Hurricane Center Miami FL AL042021
1100 AM EDT Mon Jun 28 2021
...NEW TROPICAL DEPRESSION FORMS OFF THE COAST OF SOUTH CAROLINA...
...TROPICAL STORM WARNING ISSUED FOR PORTIONS OF THE SOUTH
CAROLINA COAST...
SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...31.9N 78.3W
ABOUT 145 MI...235 KM ESE OF BEAUFORT SOUTH CAROLINA
ABOUT 110 MI...180 KM ESE OF CHARLESTON SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1013 MB...29.92 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
A Tropical Storm Warning has been issued for a portion of the coast
of South Carolina from Edisto Beach northeastward to South Santee
River.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Edisto Beach to South Santee River South Carolina
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 12 hours.
For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.
DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Depression Four
was located near latitude 31.9 North, longitude 78.3 West. The
depression is moving toward the west-northwest near 16 mph (26 km/h)
and this general motion is expected to continue for the next couple
of days. On the forecast track, the center of the tropical cyclone
should make landfall along coast of South Carolina in the warning
area later this evening.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some slight strengthening is expected today, and the depression is
forecast to become a tropical storm before it makes landfall. Rapid
weakening is forecast after landfall occurs.
The estimated minimum central pressure is 1013 mb (29.92 inches).
HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Depression Four can be found in the
Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header
WTNT44 KNHC and on the web at
http://www.hurricanes.gov/graphics_at4. ... y_messages.
WIND: Tropical storm conditions are expected to first reach
the coast within the warning area by late this afternoon, making
outside preparations difficult or dangerous.
RAINFALL: The depression could produce 1 to 3 inches of rainfall
with locally higher amounts along the immediate coasts of Georgia
and southern South Carolina. This region has been dry, limiting
potential widespread flooding impacts, however, local flooding
impacts, especially in urban areas along the southern South Carolina
and Georgia coasts, cannot be ruled out at this time.
Farther inland, 1 to 2 inches of rainfall is possible across Upstate
South Carolina, the Piedmont of Georgia, and into northeastern
Alabama.
STORM SURGE: The combination of storm surge and the tide will cause
normally dry areas near the coast to be flooded by rising waters
moving inland from the shoreline. The water could reach the
following heights above ground somewhere in the indicated areas if
the peak surge occurs at the time of high tide...
Port Royal Sound, SC to South Santee River, SC...1 to 3 ft
Surge-related flooding depends on the relative timing of the surge
and the tidal cycle, and can vary greatly over short distances. For
information specific to your area, please see products issued by
your local National Weather Service forecast office.
NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.
$$
Forecaster Stewart
Tropical Depression Four Discussion Number 1
NWS National Hurricane Center Miami FL AL042021
1100 AM EDT Mon Jun 28 2021
The area of disturbed weather and associated low pressure system
that the NHC has been tracking the past couple of days has developed
into a tropical depression off the coast of South Carolina this
morning. The inner-core cloud structure noted in high-resolution
visible satellite imagery has continued to tighten up and deep
convection with cloud top temperatures of -60 deg C have persisted
northwest through southwest of the center, yielding a Dvorak shear
pattern intensity estimate of 30 kt. This intensity estimate is
consistent with overnight scatterometer surface wind data of 31-32
kt just north of the well-defined center.
The initial motion estimate is 300/14 kt. The small tropical cyclone
is expected to maintain a west-northwestward to northwestward motion
for the next couple of days, resulting in landfall along the
south-central coast of South Carolina later this evening. The small
cyclone is expected to dissipate by 48 hours, if not sooner, when
the system will be located over the southern Appalachian Mountains.
The NHC track forecast lies close to the tightly packed GFS- and
ECMWF-based Beta-Advection models due to the lack of any significant
inner-core convection, which is allowing the cyclone to be steered
more by the low-level flow rather than the deep-layer flow as
depicted by the global and regional models.
There is a narrow window of opportunity this afternoon for the
depression to strengthen into a tropical storm before landfall
occurs. During the next few hours, the small cyclone will be passing
over the warmer Gulf Stream where sea-surface temperatures are
around 28 deg C. In addition, as the outer wind field begins to
interact with land, low-level frictional convergence along and just
offshore should help to generate deep convection just prior to
landfall, helping to spin up the wind field. The NHC forecast shows
the system becoming a tropical storm before landfall, and as a
result a tropical storm warning has been issued for a portion of
the South Carolina coast.
An Air Force Reserve Unit reconnaissance aircraft will investigate
the system this afternoon beginning around 1800 UTC, providing more
detailed information on the cyclone's intensity.
Key Messages:
1. Heavy rainfall is possible from coastal southern South Carolina
and Georgia, inland across the Piedmont of Georgia into northeast
Alabama. Isolated flooding is possible across urban areas of the
southern South Carolina and Georgia coasts.
2. Tropical-storm-force winds are expected across portions of
the South Carolina coast late this afternoon and tonight where a
Tropical Storm Warning is in effect.
3. Swells generated by the depression are expected to affect
portions of the South Carolina coast this afternoon and tonight.
These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS
INIT 28/1500Z 31.9N 78.3W 30 KT 35 MPH
12H 29/0000Z 32.8N 80.6W 35 KT 40 MPH...INLAND
24H 29/1200Z 34.2N 83.3W 20 KT 25 MPH...POST-TROP/INLAND
36H 30/0000Z 35.2N 85.6W 15 KT 15 MPH...POST-TROP/INLAND
48H 30/1200Z...DISSIPATED INLAND
$$
Forecaster Stewart