老農民版夜神月

  熱帶風暴  
編號：02 L
名稱：Bill

  基本資料  
擾動編號日期：2021 年 06 月 14 日 13 時
命名日期　　：2021 年 06 月 15 日 11 時
撤編日期　　：2021 年 06 月 16 日 08 時
登陸地點　　：無

  巔峰時期資料  
近中心最強風速 ：50  kt ( TS )
海平面最低氣壓 ：998 百帕

  擾動編號資料  
93L.INVEST.20kts.1008mb.32.3N.77.1W

  NHC：10%

2. A non-tropical area of low pressure is located about 150 miles
south-southeast of Wilmington, North Carolina and is producing
disorganized showers and thunderstorms.  This system is forecast to
move northeastward for the next few days near the Gulf Stream
waters,  which could allow for some tropical development to occur
while it moves away from the United States.  The low should be over
cold waters south of Nova Scotia by midweek, ending its development
chances.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

以上資料來自：NHC、颱風論壇整理製作

dom

NHC展望提升至Medium

1. Updated:  A well-defined, non-tropical low pressure system is
located about 120 miles south of Cape Hatteras, North Carolina.  
Satellite and radar data indicate that thunderstorm activity has
continued to increase and become more concentrated near the center
of the low early this morning, and environmental conditions are
expected to be at least marginally conducive for tropical cyclone
formation. If this recent development trend continues, then a
short-lived tropical depression or tropical storm could form later
today while the system moves northeastward away from the United
States. The low will move over colder waters south of Nova Scotia
on Wednesday, ending any opportunity for further development.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.

dom

NHC展望提升至High

1. Satellite, radar and surface observations indicate that a
well-defined low pressure system located about 90 miles southeast of
Cape Hatteras, North Carolina, is acquiring more tropical
characteristics.  Environmental conditions appear conducive for
further development, and a tropical depression or tropical storm is
likely to form later today or tonight.  This system is expected to
move northeastward away from the United States and move over colder
waters south of Nova Scotia on Wednesday, ending any opportunity for
further development by midweek.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...70 percent.

dom

FWC-N1200Z發佈TCFA

SUBJ/TROPICAL CYCLONE FORMATION ALERT (93L)//
WTNT21 KNGU 141200
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 32.8N 76.1W TO 35.7N 73.2W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 140600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 32.7N 76.1W. THE SYSTEM IS MOVING NORTHEASTWARD AT 9 KNOTS.
2. REMARKS: MOREHEAD CITY, NC DOPPLER RADAR AND MARINE SURFACE
OBSERVATIONS INDICATE THAT A SMALL, WELL DEFINED LOW PRESSURE
SYSTEM HAS FORMED ABOUT 120 NM SOUTH OF CAPE HATTERAS, NC. SURFACE
WINDS IN STRONG THUNDERSTORMS WELL OFFSHORE AND EAST OF THE
CIRCULATION CENTER ARE SOUTHEASTERLY AT 26-28 KT WITH HIGHER GUSTS.
ENVIRONMENTAL CONDITIONS ARE ONLY MARGINALLY CONDUCIVE FOR FURTHER
DEVELOPMENT. HOWEVER, IF CONVECTIVE TRENDS CONTINUE TO IMPROVE, A
SHORT LIVED DEPRESSION OR TROPICAL STORM COULD FORM TODAY OR TONIGHT
AS THE SYSTEM MOVES NORTHEASTWARD, WELL OFFSHORE OFF THE
MID-ATLANTIC COAST.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR
CANCELLED BY 151200Z.//
BT
#0001
NNNN

老農民版夜神月

NHC升格TD02L

000
WTNT42 KNHC 141442
TCDAT2

Tropical Depression Two Discussion Number   1
NWS National Hurricane Center Miami FL       AL022021
1100 AM EDT Mon Jun 14 2021

Satellite and radar images show that the low pressure area that NHC
has been following since yesterday off the coast of North Carolina
has become better organized, with a small central dense overcast
over the center and more prominent banding features.  The low also
has advanced ahead of a nearby diffuse stationary front, with that
boundary lying northwest of the center.  Considering the small core
of the low, ample deep convection, satellite pattern, and that the
low is feeding off of the thunderstorm activity (and not the front)
-- it is now classified as a tropical depression.  The initial
intensity is set to 30 kt, which is our best estimate assuming
strengthening from the 20-25 kt overnight ASCAT and surface
observations.

The depression is moving northeastward at about 18 kt.  A large
mid-latitude trough digging across eastern North America should
cause the cyclone to continue moving generally northeastward, but
faster, over the next couple of days.  In about 48 hours, the system
is forecast to dissipate near Newfoundland as it is absorbed by a
larger extratropical low.  Model guidance is in very good agreement
on this scenario, and the NHC forecast lies near the track
consensus.

The depression has about 24 hours over marginally warm waters in
low-to-moderate shear to strengthen before it moves north of the
Gulf Stream and decays.  Almost all of the intensity guidance shows
the system becoming a tropical storm tonight, and considering the
healthy initial structure, the official forecast follows that
guidance.  The low should lose tropical characteristics in about 36
hours due to very cold waters and dissipate near Newfoundland in
about 2 days.  

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 35.0N  73.7W   30 KT  35 MPH
12H  15/0000Z 36.6N  70.9W   40 KT  45 MPH
24H  15/1200Z 39.8N  65.3W   45 KT  50 MPH
36H  16/0000Z 43.6N  59.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
48H  16/1200Z...DISSIPATED

$$
Forecaster Blake

老農民版夜神月

底層看上去還不差,NHC持續上望45節

000
WTNT42 KNHC 142035
TCDAT2

Tropical Depression Two Discussion Number   2
NWS National Hurricane Center Miami FL       AL022021
500 PM EDT Mon Jun 14 2021

Deep convection has weakened some this afternoon near the center of
the depression, and the cloud pattern definitely is showing signs of
shear.  However, visible satellite imagery still indicates that it
has a tight circulation, and past experience suggests with that kind
of low-level structure, the depression is close to becoming a
tropical storm.  None of the conventional intensity estimates,
however, show the system as a storm yet, and since scatterometer
data also totally missed this morning, 30 kt will stay as the
initial wind speed. No change is made to the intensity forecast from
the last advisory, with the system having about 24 hours of time
over marginally warm water to intensify.  Afterwards, the cyclone
should quickly lose convection and transition into an extratropical
low, and dissipate near Newfoundland.  This forecast is somewhat
higher than the the guidance consensus on this cycle, but given that
I was on the low side on the first forecast compared to guidance, I
decided to hold steady and not waffle like the models are prone to
doing.

The depression is moving northeastward at about 16 kt, a little
slower than before.  Model guidance is in excellent agreement on
large trough over eastern North America causing the depression to
accelerate quite a bit in that general direction during the next
day or two.  The northeastward track is forecast to continue until
the system dissipates near Newfoundland on Wednesday while it is
absorbed by a larger extratropical low.  The model guidance has
shifted a little south of the previous advisory, and the NHC track
prediction is shifted in that direction.


FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 35.5N  72.0W   30 KT  35 MPH
12H  15/0600Z 37.5N  68.3W   40 KT  45 MPH
24H  15/1800Z 40.9N  62.5W   45 KT  50 MPH
36H  16/0600Z 45.0N  57.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
48H  16/1800Z...DISSIPATED

$$
Forecaster Blake

dom

NHC03Z命名Bill

000
WTNT42 KNHC 150238
TCDAT2

Tropical Storm Bill Discussion Number   3
NWS National Hurricane Center Miami FL       AL022021
1100 PM AST Mon Jun 14 2021

Deep convection has increased in a cluster to the northeast of the
estimated center.  Scatterometer measurements showed a couple of
40-41 kt vectors over the southeastern quadrant of the cyclone.  On
this basis, the estimated intensity is increased to 40 kt, which
makes this the second tropical storm of the season, albeit a rather
high-latitude one.  The system is in an environment of fairly
strong southwesterly shear, but the diffluent upper-level flow has
apparently contributed to some strengthening in a seemingly hostile
environment.  Some additional short-term strengthening could occur
but by 36 hours, the cyclone should merge with a baroclinic zone
while approaching Newfoundland and become extratropical.  This
transition is also shown by the FSU cyclone phase analyses of the
GFS model fields.

Bill is moving fairly swiftly northeastward, or 055/20 kt.  The
track forecast appears to be straightforward.  The flow ahead of a
large mid-tropospheric trough near the United States east coast
should accelerate the system northeastward for the next day or two,
and until the system dissipates.  The NHC track forecast is similar
to the previous one and not far from the model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 36.7N  69.8W   40 KT  45 MPH
12H  15/1200Z 38.9N  65.1W   45 KT  50 MPH
24H  16/0000Z 42.6N  59.6W   40 KT  45 MPH
36H  16/1200Z 46.5N  54.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
48H  17/0000Z...DISSIPATED

$$
Forecaster Pasch

老農民版夜神月

NHC預測將於12H內轉化為溫帶氣旋

417
WTNT42 KNHC 152035
TCDAT2

Tropical Storm Bill Discussion Number   6
NWS National Hurricane Center Miami FL       AL022021
500 PM AST Tue Jun 15 2021

Bill is well on its way to becoming an extratropical cyclone.  The
convective pattern has become quite asymmetric with the center
exposed to the southwest of the weakening thunderstorms.  The
center itself has become stretched, and in fact, surrounding
observations suggest that the surface center may no longer
be closed.  In addition, a warm front appears to be forming on
the storm's southeast side.  Based on these trends, it seems very
likely that Bill won't be around for long as a tropical storm. The
initial intensity is held at 50 kt based on the earlier ASCAT data,
but that could be a little generous.

The initial motion remains a very fast 055/31 kt.  A continued fast
east-northeast to northeast motion in the mid-latitude jet stream
is expected until the cyclone dissipates within the next 12-24
hours near Atlantic Canada.  Some weakening seems likely prior to
dissipation due to the cyclone moving over much colder SSTs while
remaining in a strong wind shear environment.

Due to the system's fast forward speed, the strong winds will
remain confined to the south and east sides of the cyclone.

FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 41.6N  59.6W   50 KT  60 MPH
12H  16/0600Z 44.7N  55.9W   45 KT  50 MPH...POST-TROP/EXTRATROP
24H  16/1800Z...DISSIPATED

$$
Forecaster Cangialosi