Meow

  一級颶風  
編號：01L
名稱：Alex


  基本資料  
形成日期：2016 年 01 月 07 日 08 時
命名日期：2016 年 01 月 14 日 05 時
轉化日期：2016 年 01 月 16 日 05 時
撤編日期：2016 年 01 月 17 日 03 時
登陸地點：葡萄牙 亞速自治區特塞拉島

  巔峰時期資料  
近中心最強風速： 75 kt ( Cat.1 )
海平面最低氣壓： 981 百帕

  過去路徑圖  


  討論帖圖片  
90L.INVEST.45kts.990mb.24.8N.37.9W



NHC:40%

1. A non-tropical low pressure system located over the central Atlantic
Ocean about 900 miles southwest of the Azores is producing a large
area of gale-force winds with maximum winds near 60 mph.  Shower
activity is currently limited near the center, but this low could
gradually acquire some subtropical or tropical characteristics
during the next couple of days while it moves southeastward and then
eastward into the eastern subtropical Atlantic.  Regardless of
subtropical or tropical cyclone formation, this system is expected
to produce hazardous marine conditions over portions of the central
and eastern Atlantic for the next few days.  For additional
information, see High Seas Forecasts issued by the National Weather
Service. The next Special Tropical Weather Outlook on this system
will be issued by 2 PM EST Tuesday.
* Formation chance through 48 hours...medium...40 percent
* Formation chance through 5 days...medium...40 percent

以上資料來自：NHC、颱風論壇整理製作

alu

這個颶風應該是我追風以來最奇特的一個熱帶風暴:P;P也是第一個看見從溫帶氣旋轉變成颶風

Meow

1月14日Suomi NPP截取颶風Alex巔峰。


https://commons.wikimedia.org/wiki/File:Alex_2016-01-14_1435Z.jpg

krichard2011

對於這個颶風 我請教了一下鄭主任
他給我的回覆是 這個系統的上方有很強的冷空氣
導致那裏的環境不穩定 對流高度發展
原本就有的底層環流加強 因而建構出眼形結構
但因為海溫極低 理論上這種情形不會維持太久

簡單說這是一個結合種種巧合所孕育出來的奇葩

krichard2011

正式破紀錄 大西洋史上最強的一月當月生成颶風
文中提到此颶風所在的海溫只有 20 度左右
而雲頂溫度甚至達到 -60度左右 雲層發展高度甚至比熱帶對流層頂高度為高
算是個相當特別的案例
後期上看 80 KT 有機會與 1955 年 Alice 颶風並列 一月史上最強
目前是一月 自1955 以來最強颶風

000
WTNT41 KNHC 141434
TCDAT1

HURRICANE ALEX DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012016
1100 AM AST THU JAN 14 2016

Remarkably, Alex has undergone the transformation into a hurricane.
A distinct eye is present, embedded within a fairly symmetric mass
of deep convection.  Water vapor imagery shows that the upper-level
trough is now west of the cyclone, with divergent flow over the
center - indicative of a tropical transition. It is very unusual to
have a hurricane over waters that are near 20 deg C, but the
upper-tropospheric temperatures are estimated to be around -60 deg
C, which is significantly colder than the tropical mean. The
resulting instability is likely the main factor contributing to the
tropical transition and intensification of Alex.  With these
changes, the government of the Azores has issued warnings for most
of the Azores islands.

The initial intensity is set to 75 kt in accordance with the
analyzed Dvorak T-number of 4.5.  Only slight additional
intensification seems possible since the system will be passing
over even colder waters during the next day or two.  In 36 hours,
the global models suggest that the cyclone will become
extratropical as it begins to merge with a large low pressure area
at high latitude.  The post-tropical cyclone is then likely to lose
its identity after 48 hours.

The initial motion is north-northeastward or 020/17 kt.  Alex is
being steered by a shortwave mid-level trough that is rotating
around a larger trough to the northwest.  This should cause the
cyclone to turn northward and north-northwestward and accelerate
over the next couple of days.  The official track forecast is very
similar to the previous one and also quite close to the consensus
of the tightly-packed dynamical model forecast tracks.

Alex is the first hurricane to form in the month of January since
1938, and the first hurricane to occur in this month since Alice of
1955.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 31.5N  28.4W   75 KT  85 MPH
12H  15/0000Z 34.3N  27.7W   80 KT  90 MPH
24H  15/1200Z 38.9N  27.7W   75 KT  85 MPH
36H  16/0000Z 45.3N  28.6W   60 KT  70 MPH...POST-TROP/EXTRATROP
48H  16/1200Z 53.0N  31.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
72H  17/1200Z...DISSIPATED

$$
Forecaster Pasch

krichard2011

這個型態 這個風眼 說他是副熱帶風暴什麼的我才不信 = =
紅外線衛星雲圖對流弱弱的
從可見光來看完全是另外一回事
但該處超低的海溫甚只有20度C左右的確符合副熱帶氣旋的環境
難以想像 太神啦




補充:
稍早 NHC 速報升格颶風

AL, 01, 2016011412,   , BEST,   0, 308N,  287W,  75,  981, HU,  34, NEQ,  120,  130,  100,   30, 1012,  300,  15,   0,   0,   L,   0,    ,   0,   0,       ALEX, D,
AL, 01, 2016011412,   , BEST,   0, 308N,  287W,  75,  981, HU,  50, NEQ,   30,   30,    0,    0, 1012,  300,  15,   0,   0,   L,   0,    ,   0,   0,       ALEX, D,
AL, 01, 2016011412,   , BEST,   0, 308N,  287W,  75,  981, HU,  64, NEQ,   20,   20,    0,    0, 1012,  300,  15,   0,   0,   L,   0,    ,   0,   0,       ALEX, D,

krichard2011

副熱帶風暴能有這種型態
有點讓人難以置信 = =

Meow

這結構和對流對於副熱帶風暴而言實在太好了。