老農民版夜神月

  熱帶風暴  
編號：20 L
名稱：Victor

  基本資料  
擾動編號日期：2021 年 09 月 27 日 20 時
命名日期　　：2021 年 09 月 30 日 03 時
撤編日期　　：2021 年 10 月 05 日 19 時
登陸地點　　：無

  巔峰時期資料  
近中心最強風速 ：40  kt ( TS )
海平面最低氣壓 ：1004 百帕

  擾動編號資料  
90L.INVEST.15kts.1006mb.10N.23W

  NHC：40%

3. A tropical wave is moving offshore the west coast of Africa and
into the far eastern tropical Atlantic.  Upper-level winds are
forecast to be conducive for gradual development, and a tropical
depression is likely to form in a few days while the system moves
westward to west-northwestward at 10 to 15 mph over the far eastern
tropical Atlantic.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...high...80 percent.

以上資料來自：NHC、颱風論壇整理製作

霧峰追風者

NHC:70%

king111807

NHC展望提升至80%

2. Showers and thunderstorms are showing signs of organization in
association with a tropical wave and broad area of low pressure
located over the far eastern tropical Atlantic.  Environmental
conditions are conducive for development, and a tropical depression
is likely to form in a day or two while the disturbance moves
west-northwestward at 10 to 15 mph over the eastern tropical
Atlantic.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

老農民版夜神月

FWC-N發布TCFA

SUBJ/TROPICAL CYCLONE FORMATION ALERT (90L)//
WTNT21 KNGU 282000
RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE
WITHIN 100 NM EITHER SIDE OF A LINE FROM 6.8N 21.2W TO 8.3N 26.2W
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 25 TO 30 KNOTS. METSAT IMAGERY AT
281800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 6.8N
21.2W. THE SYSTEM IS MOVING WEST-NORTHWEST AT 8-12 KNOTS.
2. REMARKS: A BROAD AREA OF LOW PRESSURE LOCATED OVER THE FAR
EASTERN ATLANTIC, SEVERAL HUNDRED MILES SOUTH-SOUTHEAST OF THE CABO
VERDE ISLANDS, IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS. THIS SHOWER ACTIVITY IS GRADUALLY BECOMING BETTER
ORGANIZED AND A TROPICAL DEPRESSION IS EXPECTED TO FORM IN THE NEXT
24 HOURS.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR
CANCELLED BY 292000Z.//
BT

king111807

NHC展望提升至90%

1. Recent satellite-derived surface wind data indicate that the low
pressure system located over the far eastern tropical Atlantic
several hundred miles south of the Cabo Verde Islands is gradually
becoming better defined. The associated showers and thunderstorms
are showing signs of organization, and a tropical depression is
expected to form during the next day or so while the disturbance
moves west-northwestward at 10 to 15 mph over the eastern tropical
Atlantic.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

king111807

NHC升格TD20L

000
WTNT45 KNHC 291436
TCDAT5

Tropical Depression Twenty Discussion Number   1
NWS National Hurricane Center Miami FL       AL202021
200 PM CVT Wed Sep 29 2021

The area of low pressure located over the far eastern tropical
Atlantic that NHC has been monitoring has now become a tropical
depression, the twentieth tropical cyclone of the 2021 Atlantic
hurricane season. Satellite images indicate that the system is
producing a large area of showers and thunderstorms that have become
fairly well organized around the center.  An ASCAT-A pass from a  
few hours ago indicated that the system now has a well-defined
circulation and that the radius of maximum wind is 30-40 n mi north
of the center.  The initial intensity is set at 30 kt based on the
ASCAT data and the T2.0/30 kt Dvorak classifications from TAFB and
SAB.  The minimum pressure of 1007 mb is partially based on data
from a ship report that passed near the depression.

Based on satellite fixes, the depression appears to be moving
west-northwestward at about 12 kt.  The system is currently located
on the south side of a deep-layer ridge, and that feature should
keep the cyclone on a west-northwest track during the next couple of
days.  After that time, the models show a mid- to upper-level low
developing over the central tropical Atlantic, which erodes the
western portion of the ridge.  This change in the steering flow
should cause the system to turn northwestward on Friday and then
northward toward the end of the forecast period.  Although the
models generally agree on the evolution of the large-scale pattern,
there are notable differences in the details, which leads to a fair
amount of spread concerning when and where the turn to the north
occurs.  The GFS is farthest east while the ECMWF shows the
westernmost solution.  The NHC track forecast lies between those
models and is near the TVCA multi-model consensus.  

The depression is expected to remain in conducive environmental
conditions for strengthening during the next 2 or 3 days.  During
that time period, the storm is forecast to move over 28-29 deg C
waters while embedded within an airmass of high mid-level moisture
and very low wind shear (less than 10 kt).  Therefore, steady
strengthening seems likely, and the NHC forecast brings the system
to a tropical storm by tonight and a hurricane in a couple of days.  
Beyond a few days, however, the models show a pronounced increase
in southwesterly shear and a notably drier atmosphere. These
unfavorable conditions should end the opportunity for strengthening
and promote a weakening trend.  The NHC intensity forecast is a near
a blend of the HCCA, IVCN, and IVDR consensus models.  


FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z  8.3N  24.6W   30 KT  35 MPH
12H  30/0000Z  8.8N  25.8W   35 KT  40 MPH
24H  30/1200Z  9.5N  27.6W   45 KT  50 MPH
36H  01/0000Z 10.3N  29.9W   55 KT  65 MPH
48H  01/1200Z 11.2N  31.9W   65 KT  75 MPH
60H  02/0000Z 12.4N  33.7W   70 KT  80 MPH
72H  02/1200Z 14.0N  35.4W   70 KT  80 MPH
96H  03/1200Z 18.4N  38.8W   55 KT  65 MPH
120H  04/1200Z 24.3N  40.9W   45 KT  50 MPH

$$
Forecaster Cangialosi

king111807

NHC升格TS，命名Victor

095
WTNT45 KNHC 300247
TCDAT5

Tropical Storm Victor Discussion Number   3
NWS National Hurricane Center Miami FL       AL202021
200 AM CVT Thu Sep 30 2021

Victor has changed little in organization since the last advisory,
with a large circulation and a complex of convective bands mainly in
the northern semicircle.  Satellite intensity estimates from TAFB
and SAB remain at or near 35 kt, as do other objective intensity
estimates.  Thus, the initial intensity is still 35 kt, although the
most recent ASCAT-A data suggests the possibility that this is a
little generous.

The center has moved or re-formed a bit to the west during the past
several hours, although the longer-term motion still seems to be to
the west-northwest at 290/11 kt.  Other than the more westerly
initial position, there is little change to the forecast philosophy
or the forecast track since the last advisory.  Victor is forecast
to move west-northwestward for the next 36 h or so as it is steered
by the flow on the south side of a deep-layer ridge.  By 48 h, the
global models forecast the western periphery of the ridge to get
eroded by to a mid- to upper-level low over the subtropical central
Atlantic. This evolution should cause the cyclone to turn
northwestward at that time, followed by a northward turn by the end
of the forecast period.  There remains a fair amount of spread in
the timing and location of the northward turn with the GFS and HWRF
still on the right side of the guidance envelope and the ECMWF
showing the slowest and westernmost solution. The new forecast track
is in the center of the guidance envelope and lies very close to the
various consensus models.

For the next 36-48 h, Victor is expected to remain in an environment
of warm sea surface temperatures and light vertical wind shear.  
This should allow steady strengthening, and rapid strengthening
cannot be ruled out if the storm develops a better defined inner
core.  Based on a steady strengthening scenario, the new intensity
forecast is identical to the previous one, taking Victor to
hurricane intensity in 36 h with a peak intensity of 70 kt in 48 h.  
After that time, the aforementioned upper-level low is expected to
cause significant shear over Victor while the cyclone moves into a
drier air mass.  This combination should cause the cyclone to
weaken, and it is possible Victor could weaken faster than currently
forecast after 60 hours.  The new official intensity forecast lies
near the upper edge of the intensity guidance.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z  8.4N  26.7W   35 KT  40 MPH
12H  30/1200Z  8.9N  28.3W   45 KT  50 MPH
24H  01/0000Z  9.7N  30.2W   55 KT  65 MPH
36H  01/1200Z 10.6N  32.0W   65 KT  75 MPH
48H  02/0000Z 11.8N  33.5W   70 KT  80 MPH
60H  02/1200Z 13.4N  35.1W   70 KT  80 MPH
72H  03/0000Z 15.5N  36.7W   60 KT  70 MPH
96H  04/0000Z 20.5N  39.5W   45 KT  50 MPH
120H  05/0000Z 26.0N  41.0W   40 KT  45 MPH

$$
Forecaster Beven

老農民版夜神月

發展未如預期,NHC已降格TD

000
WTNT45 KNHC 022039
TCDAT5

Tropical Depression Victor Discussion Number  14
NWS National Hurricane Center Miami FL       AL202021
500 PM AST Sat Oct 02 2021

Victor was about out of time as a tropical cyclone, but a recent
burst of deep convection about 60 n mi northeast of its center saved
it from being declared a remnant low this afternoon. The cyclone
continues to struggle with dry air and strong southwesterly shear.
Scatterometer overpasses missed Victor today, so the initial
advisory intensity of 30 kt is based on the latest CI-value from the
TAFB Dvorak estimate.

The depression is moving northwest, or 310/12 kt in the flow to the
southwest of a subtropical ridge. This general motion is forecast to
continue until Victor dissipates in a few days. The latest NHC track
forecast is little changed from the previous one, and is near the
various multimodel track consensus solutions.

Victor refused to succumb to the strong shear and dry air over the
past 24 h. However, these hostile conditions are not forecast to
abate over the cyclone for the foreseeable future.  Therefore, the
depression should struggle to maintain persistent deep convection,
and the cyclone could degenerate to a remnant low at any time over
the next couple of days. The global model guidance is in good
agreement that Victor should gradually weaken early this week, and
open into a tough of low pressure by Tuesday. The latest NHC
intensity forecast is unchanged from the previous one, except for
the timing of the system becoming a remnant low.


FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 13.7N  38.0W   30 KT  35 MPH
12H  03/0600Z 14.9N  39.5W   30 KT  35 MPH
24H  03/1800Z 16.8N  41.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
36H  04/0600Z 18.9N  43.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
48H  04/1800Z 20.7N  45.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
60H  05/0600Z 22.5N  47.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
72H  05/1800Z...DISSIPATED

$$
Forecaster Latto