NHC21Z降格TD,並預測24H後將減弱為殘餘低氣壓

243
WTNT45 KNHC 022038
TCDAT5

Tropical Depression Omar Discussion Number   9
NWS National Hurricane Center Miami FL       AL152020
500 PM AST Wed Sep 02 2020

Conventional satellite imagery shows that Omar's cloud pattern is
rapidly deteriorating, and the surface circulation center has
become quite ill-defined.  This morning's METOP-A/B scatterometer
passes revealed only a few 33 kt winds well to the southeast of
the center and it's reasonable to determine that those winds are no
longer present.  Therefore, the initial intensity is lowered to 30
kt for this advisory and is further supported by the subjective
satellite intensity T-numbers from TAFB and SAB.  The latest global
model runs agree with the depression degenerating to a remnant
low in 24 hours, or less, and the NHC intensity forecast follows
suit.  Dissipation of the remnant low should occur no later than
Saturday evening.

Omar's initial motion is estimated to be due east, or 090/13 kt,
within the mid-latitude westerlies north of a subtropical ridge
stretching east to west over the central Atlantic.  Omar should
continue moving eastward through Friday, although a couple of the
global models are showing a track a bit more east-southeastward.  
Around the 60 hour period, the remnant low is expected to reduce in
forward speed, and turn toward the east-northeast in response to an
approaching baroclinic system entering the northwest Atlantic.  The
NHC forecast is nudged just a little to the right of the previous
one, and lies close to the HCCA and TVCA consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 36.1N  65.7W   30 KT  35 MPH
12H  03/0600Z 36.1N  63.6W   30 KT  35 MPH
24H  03/1800Z 36.0N  61.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
36H  04/0600Z 35.7N  59.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
48H  04/1800Z 35.7N  57.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
60H  05/0600Z 35.9N  56.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
72H  05/1800Z...DISSIPATED

$$
Forecaster Roberts

請問『有紀錄以來最早前15個命名風暴』意思是大西洋有紀錄以來，最早形成的第15號颶風嗎？

NHC21Z升格TD15L

1. 000
   
2. WTNT45 KNHC 312044
   
3. TCDAT5
   
4. 
   
5. Tropical Depression Fifteen Discussion Number   1
   
6. NWS National Hurricane Center Miami FL       AL152020
   
7. 500 PM EDT Mon Aug 31 2020
   
8. 
   
9. Satellite images indicate that the area of low pressure offshore of
   
10. the Carolinas has had convection organized in bands since before
    
11. dawn, and scatterometer plus an Air Force Reserve Hurricane
    
12. Hunter mission data confirm that the circulation is closed.  Thus,
    
13. this is now a tropical depression, and the initial wind speed is
    
14. set to 30 kt in accordance with 25-30 kt ASCAT-A data plus buoy
    
15. 42001 readings which earlier had an adjusted 10-m peak of 30 kt.
    
16. 
    
17. The depression is moving northeastward at about 10 kt.  The system
    
18. should gradually turn toward the east-northeast by Wednesday due to
    
19. it moving around the northwest side of the subtropical ridge, then
    
20. move eastward in a few days around the flat ridge.  By late week,
    
21. the cyclone could slow and eventually turn back toward the northeast
    
22. around a rather strong mid-latitude high pressure system over the
    
23. northeast Atlantic.  There is considerable spread in the guidance,
    
24. which really seems to depend upon whether the system stays coherent,
    
25. like the official forecast, or would become a shallow low-level
    
26. swirl by 120h and end up slower and south of forecast track. This
    
27. forecast is near the corrected-consensus guidance, leaning toward
    
28. the ECMWF-based models, and it should be considered of low
    
29. confidence.
    
30. 
    
31. Gradual strengthening is expected over the next day or so while the
    
32. depression remains in a low-to-moderate shear environment. Although
    
33. the depression is expected to be traversing the warm Gulf Stream for
    
34. the next several days, wind shear is expected to greatly increase by
    
35. Wednesday, which should limit intensification.  In fact there's
    
36. some chance the system could decay and lose any deep convection in
    
37. rather strong shear in a few days. However, since it likely will be
    
38. moving near the Gulf Stream, I suspect it will continue to pulse
    
39. thunderstorm activity and stay alive throughout the period. The NHC
    
40. intensity forecast is near or just above the model consensus on
    
41. that reasoning, closest to the HWRF model.  The cyclone could
    
42. become extratropical (or a remnant low) by the end of the forecast,
    
43. but this is very uncertain.
    
44. 
    
45. 
    
46. FORECAST POSITIONS AND MAX WINDS
    
47. 
    
48. INIT  31/2100Z 32.6N  76.5W   30 KT  35 MPH
    
49. 12H  01/0600Z 33.8N  75.0W   35 KT  40 MPH
    
50. 24H  01/1800Z 34.9N  72.4W   40 KT  45 MPH
    
51. 36H  02/0600Z 35.8N  69.7W   40 KT  45 MPH
    
52. 48H  02/1800Z 36.7N  67.0W   40 KT  45 MPH
    
53. 60H  03/0600Z 37.6N  63.7W   35 KT  40 MPH
    
54. 72H  03/1800Z 38.2N  60.5W   35 KT  40 MPH
    
55. 96H  04/1800Z 39.0N  55.0W   35 KT  40 MPH
    
56. 120H  05/1800Z 41.5N  49.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
    
57. 
    
58. $
    
59. Forecaster Blake
    

複製代碼

FWC-N發布TCFA

WTNT22 KNGU 311300
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
REF/A/FLEWEACEN NORFOLK VA/301900Z AUG 20//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTNT21 KNGU 301900)//
RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 30.4N 78.4W TO 32.8N 74.6W
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 311300Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 31.6N 77.4W. THE SYSTEM IS MOVING NORTHEASTWARD AT 10
KNOTS.
2. REMARKS: A BROAD AREA OF LOW PRESSURE IS LOCATED ABOUT 150 MILES
SOUTH-SOUTHEAST OF WILMINGTON, NORTH CAROLINA. THE SURFACE
CIRCULATION HAS BECOME A LITTLE BETTER DEFINED THIS MORNING AND THE
ASSOCIATED SHOWERS AND THUNDERSTORMS HAVE EXPANDED IN COVERAGE.
SUBSEQUENTLY, A TROPICAL DEPRESSION IS LIKEY TO DEVELOP DURING THE
NEXT 24 HOURS AS IT MOVES GENERALLY NORTHEASTWARD WELL OFFSHORE OF
THE SOUTHEASTERN AND MID-ATLANTIC COAST OF THE UNITED STATES.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
011300Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 12.6N 64.0W.//
BT
#0001
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