000
WTNT41 KNHC 191431
TCDAT1
Subtropical Depression One Discussion Number 1
NWS National Hurricane Center Miami FL AL012017
1100 AM AST Wed Apr 19 2017
The non-tropical low over the north central Atlantic which has
been tracked by NHC for the past few days has developed organized
convection mainly in a curved band southeast of the center. The
system is still embedded within an upper-low, the outflow is minimal
and the strongest winds are removed from the center of circulation.
Consequently, the low is being classified as a subtropical
depression with an initial intensity of 30 kt. These winds are based
on recent ASCAT data. It is anticipated that shear and cold waters
will not allow intensification, and the subtropical depression is
expected to become absorbed by a large extratropical cyclone in
about 36 hours or sooner.
The subtropical depression is moving toward the north-northeast at
about 10 kt. A gradual turn to the north and north-northwest
around the approaching extratropical low is forecast for the next
24 hours or so.
FORECAST POSITIONS AND MAX WINDS
INIT 19/1500Z 31.9N 40.9W 30 KT 35 MPH
12H 20/0000Z 32.8N 40.2W 30 KT 35 MPH
24H 20/1200Z 35.0N 40.5W 30 KT 35 MPH
36H 21/0000Z...DISSIPATED
$$
Forecaster Avila
Animación de #One en el #Atlántico de las últimas 5 horas(https://lh3.googleusercontent.com/Fnsj4G2bhMuAcZAFnuYlWgjcskMlLc3IOkCIiLVso3CdPVXS-iUS1h5zQUqtM3yK7jV3lr-akOrSug=w1366-h768-no)
000
WTNT41 KNHC 201442
TCDAT1
Tropical Depression One Discussion Number 5
NWS National Hurricane Center Miami FL AL012017
1100 AM AST Thu Apr 20 2017
Conventional satellite imagery indicate that the convection,
although not very deep, has become more symmetric around the center,
suggesting that the subtropical cyclone has transitioned into a
tropical depression. This is supported by AMSU data this morning
that shows that the system has developed a weak, but warm core. This
transition is a common process, and does not change the previous
intensity or track forecasts that call for the depression to
become a remnant low later today, and become absorbed by a larger
low tonight or early Friday. It is estimated that the depression is
producing winds of 30 kt within some convective bands. Since the
circulation is already becoming elongated, a weakening trend is
likely to begin soon.
The depression is moving toward the northwest at 12 kt, and this
general motion with a gradual increase in forward speed is expected
to continue until dissipation.
FORECAST POSITIONS AND MAX WINDS
INIT 20/1500Z 36.1N 40.0W 30 KT 35 MPH
12H 21/0000Z 38.0N 43.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 21/1200Z...DISSIPATED
$$
Forecaster Avila
000
WTNT41 KNHC 210237
TCDAT1
Tropical Storm Arlene Discussion Number 7
NWS National Hurricane Center Miami FL AL012017
1100 PM AST Thu Apr 20 2017
Despite increasing involvement with a frontal zone, Arlene
continues to produce organized convection in infrared imagery and to
show good low-level organization in microwave imagery. A partial
ASCAT overpass showed a few 40 kt vectors well to the northeast of
the center, and based on this the initial intensity is increased to
45 kt. Unfortunately, the scatterometer data did not cover the
central core and could not answer the question of whether the storm
still has a closed circulation. Based on the available data, Arlene
remains a tropical storm for this advisory. However, it could
become extratropical, lose convection and become post-tropical, or
degenerate into a trough at any time during the next 12 to 24 hours.
The official forecast has the system degenerating to a post-tropical
low in 12 hours and then dissipating as it is absorbed into a
baroclinic low.
The initial motion is 305/24. Arlene is being steered by the
aforementioned deep-layer baroclinic low centered near 36N 48W, and
the tropical cyclone, or its remnants, is expected to move in a
cyclonic loop around this low for the next few days.
Tropical storms in April are rare and Arlene is only the second
one observed in this month during the satellite era. It should be
noted, however, that this type of storm was practically impossible
to detect prior to the weather satellite era.
FORECAST POSITIONS AND MAX WINDS
INIT 21/0300Z 39.4N 44.2W 45 KT 50 MPH
12H 21/1200Z 40.0N 48.0W 40 KT 45 MPH...POST-TROPICAL
24H 22/0000Z...DISSIPATED
$$
Forecaster Beven