BULLETIN
Subtropical Depression Four Advisory Number 1
NWS National Hurricane Center Miami FL AL042020
500 PM AST Mon Jun 22 2020
...SUBTROPICAL DEPRESSION FORMS WELL OFFSHORE OF THE U.S. EAST
COAST...
...FORECAST TO MOVE AWAY FROM LAND...
SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...38.2N 65.7W
ABOUT 310 MI...495 KM SE OF NANTUCKET MASSACHUSETTS
ABOUT 455 MI...730 KM SSW OF HALIFAX NOVA SCOTIA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...ENE OR 75 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES
WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.
DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Subtropical Depression Four
was located near latitude 38.2 North, longitude 65.7 West. The
subtropical depression is moving toward the east-northeast near 9
mph (15 km/h) and this motion is forecast to continue through
tonight. A motion toward the northeast is expected on Tuesday and
Wednesday.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some slight strengthening is possible tonight and early Tuesday,
and the subtropical depression could briefly become a subtropical
storm. Slow weakening is expected to begin by Tuesday afternoon or
evening.
The estimated minimum central pressure is 1009 mb (29.80 inches).
HAZARDS AFFECTING LAND
----------------------
None.
NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.
$$
Forecaster Stewart
Subtropical Depression Four Discussion Number 1
NWS National Hurricane Center Miami FL AL042020
500 PM AST Mon Jun 22 2020
The non-tropical low pressure system that the National Hurricane
Center has been following for the past couple of days off of the
U.S. east coast has developed enough organized convection near the
center to be classified as subtropical depression. The subtropical
status is due to the low-level circulation center being co-located
beneath an upper-level cold low as seen in water vapor imagery. The
initial intensity of 30 kt is based on earlier ASCAT wind data
indicating numerous surface wind vectors of 26-28 kt in the
southern semicircle, along with a TAFB subtropical satellite
classification of ST1.5/25-30 kt.
The initial motion estimate is 075/08 kt. Subtropical Depression
Four is located north of a deep-layer ridge and is being influenced
by weak westerly mid- to upper-level flow. The cyclone is forecast
by all of the global and regional models to move east-northeastward
tonight and then turn northeastward on Tuesday. A northeastward
motion at a faster forward speed is expected Tuesday night through
Thursday when the system is forecast to be located over the cold
waters of the far north Atlantic. The cyclone should be absorbed by
a larger extratropical low or dissipate on Thursday. The NHC track
forecast is close to a blend of the simple consensus aids TVCN and
GFEX and the NOAA-HCCA corrected consensus.
The cyclone is beginning to move over a ridge of higher SSTs of
26.0-26.5 deg C in the northern extent of the Gulf Stream. The
forecast track takes the subtropical depression down the length of
the axis of warmer water during the next 12-18 h, so there is the
potential for the cyclone to become a subtropical storm during that
time, especially given the large pool of cold air aloft, with 200-mb
temperatures of near -58 deg C and 500-mb temperatures of about -10
deg C which is creating a lot of instability. After the system moves
off of the warm ridge and into sharply cooler water around 36 hours
or so, gradual weakening is expected, with transition to an
extratropical cyclone forecast by 48 hours. The NHC intensity
forecast closely follows a blend of the consensus models ICON, IVCN,
and HCCA.
FORECAST POSITIONS AND MAX WINDS
INIT 22/2100Z 38.2N 65.7W 30 KT 35 MPH
12H 23/0600Z 38.5N 64.0W 35 KT 40 MPH
24H 23/1800Z 39.0N 62.0W 30 KT 35 MPH
36H 24/0600Z 40.5N 59.3W 30 KT 35 MPH
48H 24/1800Z 42.5N 56.7W 30 KT 35 MPH...POST-TROP/EXTRATROP
60H 25/0600Z 45.0N 53.3W 30 KT 35 MPH...POST-TROP/EXTRATROP
72H 25/1800Z 47.8N 50.4W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 26/1800Z...DISSIPATED
$$
Forecaster Stewart
Subtropical Depression Four Advisory Number 1
NWS National Hurricane Center Miami FL AL042020
500 PM AST Mon Jun 22 2020
...SUBTROPICAL DEPRESSION FORMS WELL OFFSHORE OF THE U.S. EAST
COAST...
...FORECAST TO MOVE AWAY FROM LAND...
SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...38.2N 65.7W
ABOUT 310 MI...495 KM SE OF NANTUCKET MASSACHUSETTS
ABOUT 455 MI...730 KM SSW OF HALIFAX NOVA SCOTIA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...ENE OR 75 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES
WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.
DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Subtropical Depression Four
was located near latitude 38.2 North, longitude 65.7 West. The
subtropical depression is moving toward the east-northeast near 9
mph (15 km/h) and this motion is forecast to continue through
tonight. A motion toward the northeast is expected on Tuesday and
Wednesday.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some slight strengthening is possible tonight and early Tuesday,
and the subtropical depression could briefly become a subtropical
storm. Slow weakening is expected to begin by Tuesday afternoon or
evening.
The estimated minimum central pressure is 1009 mb (29.80 inches).
HAZARDS AFFECTING LAND
----------------------
None.
NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.
$$
Forecaster Stewart
Subtropical Depression Four Discussion Number 1
NWS National Hurricane Center Miami FL AL042020
500 PM AST Mon Jun 22 2020
The non-tropical low pressure system that the National Hurricane
Center has been following for the past couple of days off of the
U.S. east coast has developed enough organized convection near the
center to be classified as subtropical depression. The subtropical
status is due to the low-level circulation center being co-located
beneath an upper-level cold low as seen in water vapor imagery. The
initial intensity of 30 kt is based on earlier ASCAT wind data
indicating numerous surface wind vectors of 26-28 kt in the
southern semicircle, along with a TAFB subtropical satellite
classification of ST1.5/25-30 kt.
The initial motion estimate is 075/08 kt. Subtropical Depression
Four is located north of a deep-layer ridge and is being influenced
by weak westerly mid- to upper-level flow. The cyclone is forecast
by all of the global and regional models to move east-northeastward
tonight and then turn northeastward on Tuesday. A northeastward
motion at a faster forward speed is expected Tuesday night through
Thursday when the system is forecast to be located over the cold
waters of the far north Atlantic. The cyclone should be absorbed by
a larger extratropical low or dissipate on Thursday. The NHC track
forecast is close to a blend of the simple consensus aids TVCN and
GFEX and the NOAA-HCCA corrected consensus.
The cyclone is beginning to move over a ridge of higher SSTs of
26.0-26.5 deg C in the northern extent of the Gulf Stream. The
forecast track takes the subtropical depression down the length of
the axis of warmer water during the next 12-18 h, so there is the
potential for the cyclone to become a subtropical storm during that
time, especially given the large pool of cold air aloft, with 200-mb
temperatures of near -58 deg C and 500-mb temperatures of about -10
deg C which is creating a lot of instability. After the system moves
off of the warm ridge and into sharply cooler water around 36 hours
or so, gradual weakening is expected, with transition to an
extratropical cyclone forecast by 48 hours. The NHC intensity
forecast closely follows a blend of the consensus models ICON, IVCN,
and HCCA.
FORECAST POSITIONS AND MAX WINDS
INIT 22/2100Z 38.2N 65.7W 30 KT 35 MPH
12H 23/0600Z 38.5N 64.0W 35 KT 40 MPH
24H 23/1800Z 39.0N 62.0W 30 KT 35 MPH
36H 24/0600Z 40.5N 59.3W 30 KT 35 MPH
48H 24/1800Z 42.5N 56.7W 30 KT 35 MPH...POST-TROP/EXTRATROP
60H 25/0600Z 45.0N 53.3W 30 KT 35 MPH...POST-TROP/EXTRATROP
72H 25/1800Z 47.8N 50.4W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 26/1800Z...DISSIPATED
$$
Forecaster Stewart