老農民版夜神月

  熱帶風暴  
編號：30 L
名稱：Theta

  基本資料  
擾動編號日期：2020 年 11 月 09 日 02 時
命名日期　　：2020 年 11 月 10 日 11 時
撤編日期　　：2020 年 11 月 15 日 20 時
登陸地點　　：無

  巔峰時期資料  
近中心最強風速 ：60  kt ( TS )
海平面最低氣壓 ：989 百帕

  擾動編號資料  
97L.INVEST.25kts-1010mb-28.5N-47W


  NHC：10%  

1. Recent satellite-derived wind data confirm that a low pressure
system has developed several hundred miles southwest of the Azores.
Shower and thunderstorm activity associated with this system is
currently disorganized. However, the low could slowly develop
tropical or subtropical characteristics during the next several days
while it moves eastward or east-northeastward over the northeastern
Atlantic Ocean.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

以上資料來自：NHC、颱風論壇整理製作

dom

提升至medium

1. Shower activity associated with a non-tropical low pressure system
located several hundred miles southwest of the Azores is showing
some signs of organization.  This system will likely gradually
acquire subtropical or tropical characteristics this week, and a
tropical or subtropical storm could develop within a few days while
this system moves eastward or east-northeastward over the
northeastern Atlantic Ocean.
* Formation chance through 48 hours...medum...40 percent.
* Formation chance through 5 days...medium...60 percent.

老農民版夜神月

數值普遍支持97L的發展,就看最後是會成為TS還是SS了

老農民版夜神月

NHC評級提升至High,70%/80%

1. Shower and thunderstorm activity associated with a low pressure
system located several hundred miles southwest of the Azores has
increased and become better organized during the past several hours.
Satellite-derived wind data earlier this morning suggested that the
system had not yet become distinct from a frontal boundary in the
area, however, it will likely become non-frontal soon. The satellite
data also indicated that the system is already producing gale-force
winds. Additional development is expected, and a tropical or
subtropical storm will likely form during the next day or two while
the system moves eastward or east-northeastward over the
northeastern Atlantic Ocean.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...80 percent.

老農民版夜神月

FWC-N2000Z發布TCFA

WTNT21 KNGU 092000
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 28.7N 44.8W TO 29.2N 37.8W
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 35 TO 45 KNOTS. METSAT
IMAGERY AT 091800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 28.6N 44.9W.
2.REMARKS:
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 989 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS HIGH. AN AREA OF OF LOW PRESSURE
ASSOCIATED WITH A FRONTAL BOUNDARY IS LOCATED OVER THE CENTRAL
ATLANTIC WELL SOUTHWEST OF THE AZORES. SHOWERS AND THUNDERSTORMS
PRODUCED BY THIS SYSTEM HAVE INCREASED IN AREAL EXTENT AND ARE
GRADUALLY BECOMING BETTER ORGANIZED. THE LOW IS EXPECTED TO
SEPARATE FROM THE FRONTAL ZONE DURING THE NEXT 24 HOURS AFTER
WHICH IT COULD BECOME A SUBTROPICAL OR TROPICAL STORM WHILE
MOVING GENERALLY EAST-NORTHEASTWARD TOWARD THE NORTHEASTERN
ATLANTIC.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 102000Z.
BT
#0001
NNNN

dom

命名THETA，為SS性質，巔峰上望50KT

065
WTNT45 KNHC 100259
TCDAT5

Subtropical Storm Theta Discussion Number   1
NWS National Hurricane Center Miami FL       AL302020
300 AM GMT Tue Nov 10 2020

Over the past 12 h convection has slowly consolidated near the
center of a non-tropical area of low pressure over the far
northeast Atlantic. Earlier, there was a 2325 UTC ASCAT-B pass that
showed that the low-level circulation had become more detached
from the warm frontal boundary located to its northeast. In
addition, the ASCAT pass showed that winds have increased to near 45
kt on the southeast portion of the circulation near where coldest
convective cloud tops were located. Both a 2137 UTC SSMIS and 2324
UTC AMSU microwave pass showed convective banding under the cirrus
canopy near where the highest winds were observed. However, water
vapor satellite imagery still shows the presence of a broad
upper-level low tangled up with the low-level circulation embedded
in the convection. Therefore, Theta has been designated as a
subtropical storm with maximum wind of 45 kt.

Theta has been on a near due east heading over the last 12 h at
90/13 kt. Currently the cyclone is located south of a broad
deep-layer longwave trough. This trough is expected to bypass the
cyclone to the east and Theta will primarily be steered by
southwesterly flow on the northern periphery of a mid-level ridge
centered over the Cape Verde islands. This flow will steer Theta
slowly to the east-northeast over the next 3-5 days. The track
guidance is in good agreement with this solution, with only minor
differences in across-track spread. There are somewhat larger
differences in the along-track spread related to different forward
motion, but the latest NHC track forecast elected to stay close to
the track consensus at this time.

Thetas structure has evolved from a frontal cyclone to a
subtropical cyclone, though a frontal boundary remains nearby on the
northeast side of the circulation. This boundary is expected to
gradually dissipate and Theta is expected to fully transition to a
tropical storm in 24 h as convection erodes the upper-level cyclonic
flow overhead. The maximum sustained winds were increased slightly
in the first 12 h of the forecast but are kept at 50 kt through 120
h which is on the high end of the intensity guidance.

Theta is the 29th named storm in the record-breaking 2020 Atlantic
Hurricane Season, breaking the previous record of 28th named storms
in 2005.


FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 28.8N  40.3W   45 KT  50 MPH...SUBTROPICAL STORM
12H  10/1200Z 29.0N  38.6W   50 KT  60 MPH...SUBTROPICAL STORM
24H  11/0000Z 29.1N  36.3W   50 KT  60 MPH...TROPICAL STORM
36H  11/1200Z 29.5N  34.3W   50 KT  60 MPH
48H  12/0000Z 30.0N  32.6W   50 KT  60 MPH
60H  12/1200Z 30.5N  30.7W   50 KT  60 MPH
72H  13/0000Z 31.0N  28.7W   50 KT  60 MPH
96H  14/0000Z 32.2N  24.3W   50 KT  60 MPH
120H  15/0000Z 33.3N  20.6W   50 KT  60 MPH

$$
Forecaster Papin/Brown

老農民版夜神月

NHC定強來到60KT,並預測當下便是巔峰

894
WTNT45 KNHC 101452
TCDAT5

Subtropical Storm Theta Discussion Number   3
NWS National Hurricane Center Miami FL       AL302020
300 PM GMT Tue Nov 10 2020

Theta continues to exhibit a mix of tropical and subtropical
characteristics. The cyclone has a fairly compact radius of maximum
winds with a central dense overcast over the northern portion of the
circulation. However, there is a strong subtropical jet located just
to the south of Theta, and strong upper-level winds in the
surrounding environment in the presence of an upper trough. Based on
this inconclusive data, Theta is being maintained as a subtropical
storm for this advisory. An ASCAT-B overpass this morning revealed
50-kt winds in the northwest and southwest quadrants, with several
55-60 kt wind vectors, some of those vectors outside of the deep
convection making them more believable. Based on this, the initial
advisory intensity has been set to 60 kt.

The storm is moving just north of due east, or 085/13 kt. Theta
should continue to be steered eastward to east-northeastward during
the next several days on the north side of a mid-level ridge.  This
motion should take the cyclone across the subtropical eastern
Atlantic throughout the forecast period.  The latest model guidance
is a little faster and slightly north of the previous forecast
track, and so the latest NHC forecast has been adjusted slightly as
well.

Theta is still expected to transition to a tropical storm later
today as it separates from the upper-level trough.  Although Theta
will be tracking over progressively cooler SSTs and within moderate
wind shear conditions, the air mass is expected to remain unstable
for the next couple of days, which should be supportive of deep
convection. Therefore, little change is strength is indicated during
that time. Some weakening is anticipated later in the forecast
period as the airmass becomes more stable. The NHC intensity
forecast is higher than the previous one primarily due to the higher
initial intensity, and is near the IVCN and HCCA consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 29.0N  37.4W   60 KT  70 MPH
12H  11/0000Z 29.1N  35.7W   60 KT  70 MPH
24H  11/1200Z 29.7N  33.4W   60 KT  70 MPH
36H  12/0000Z 30.4N  31.3W   55 KT  65 MPH
48H  12/1200Z 31.1N  28.7W   55 KT  65 MPH
60H  13/0000Z 31.7N  26.0W   50 KT  60 MPH
72H  13/1200Z 32.2N  23.7W   45 KT  50 MPH
96H  14/1200Z 33.0N  19.5W   40 KT  45 MPH
120H  15/1200Z 34.3N  17.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto

老農民版夜神月

21Z判定已由SS轉為TS,定強維持60KT

000
WTNT45 KNHC 102037
TCDAT5

Tropical Storm Theta Discussion Number   4
NWS National Hurricane Center Miami FL       AL302020
900 PM GMT Tue Nov 10 2020

A central dense overcast has persisted near the center of Theta
since yesterday, and although the clouds tops have warmed over the
past several hours there remains a distinct curved band feature
over the northern portion of the circulation. Water vapor imagery
shows the mid- upper-level trough that was over the Azores is
beginning to leave the cyclone behind. Based on these factors, and
the earlier indications of a compact radius of maximum winds, it
appears that Theta has completed a transition to a tropical
cyclone. Even though the clouds tops have recently warmed, the
overall structure of Theta has not degraded by much since the
previous advisory. Therefore, the initial intensity is being held
at 60 kt.

The storm is moving 075/12 kt around the north side of a mid-level
ridge. This feature should continue to steer Theta in a generally
east-northeastward motion for the next few days. Late in the
forecast period, the ridge will begin to weaken as another trough
approaches from the northwest. This should cause the cyclone to slow
its forward motion and begin to turn to the northeast. The latest
model guidance has once again slowed down and the new NHC track
forecast now lies between the previous one and the various consensus
models.

Although Theta will be moving over progressively cooler SSTs and
within moderate wind shear conditions, the air mass is expected to
remain unstable for the next day or so, which should be supportive
of deep convection. Therefore, little change is strength is
indicated during that time. Some weakening is anticipated later in
the forecast period as the airmass becomes more stable. By the end
of the 5-day forecast period, the combination of the cooler waters
and an approaching trough should result in extratropical transition.
The NHC intensity forecast has changed little from the previous one
and remains near the IVCN and HCCA consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 29.4N  36.2W   60 KT  70 MPH
12H  11/0600Z 29.8N  34.7W   60 KT  70 MPH
24H  11/1800Z 30.3N  32.8W   55 KT  65 MPH
36H  12/0600Z 30.8N  30.5W   55 KT  65 MPH
48H  12/1800Z 31.5N  28.0W   50 KT  60 MPH
60H  13/0600Z 32.1N  25.7W   50 KT  60 MPH
72H  13/1800Z 32.6N  23.8W   45 KT  50 MPH
96H  14/1800Z 33.2N  20.5W   40 KT  45 MPH
120H  15/1800Z 34.4N  19.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto