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Subtropical Storm ALEX


500 AM AST THU JAN 14 2016

Since the previous advisory, the convective structure of Alex has
continued to improve with a 15-nmi clear eye now embedded within a
solid cloud shield of tops colder than -50C, with a ring of cloud
tops near -60C surrounding the eye in the northern semicircle. The
intensity of Alex is difficult to ascertain due to its subtropical
characteristics, and satellite intensity estimates range from
ST3.5/55 kt from TAFB to a tropical T4.5/77 kt from SAB. NHC AODT
intensity estimates range from T4.0/65 kt to T4.5/77 kt using a
tropical pattern and various eye scenes. Since the overall cloud
pattern of Alex has improved markedly since the earlier 50-kt
ASCAT-B scatterometer wind data, and a clear and distinct eye
feature is now evident, the intensity is being raised to 60 kt.

Alex continues to gradually turn toward the left and the initial
motion is now 020/16 kt.  The cyclone is forecast to turn northward
during the next 12 hours or so as it is steered by deep southerly
flow between a large extratropical low centered over the northwest
Atlantic and a subtropical ridge over northwestern Africa. A general
northward motion is expected to continue through at least 36 hours,
which should bring the center of Alex through the central Azores in
about 30 hours or 1200 UTC 15 January. By 48 hours, Alex should
start to turn more toward the northwest and west as it moves closer
to the center of a larger extratropical low forecast to be south of
Greenland on days 3 and 4. The new forecast track is essentially
just an update of the previous advisory track through 36 hours, and
lies close to the consensus model TVCA.

Global and regional models, plus geostationary and microwave
satellite data, indicate that Alex remains a vertically stacked
low pressure system up to the 200 mb level, suggesting that the
cyclone is still primarily a subtropical storm. However, water vapor
imagery during the past few hours has been hinting that some weak
upper-level outflow might be trying to develop. GFS and NAM model
forecast soundings indicate that the current inner-core region of
Alex with Lifted Indices (LI) of -2 and CAPE values of 400-500 are
only expected to decrease to LI of -1 and CAPE near 300 as the
cyclone nears the Azores islands in 24-30 hours. In addition, the
inner-core region is forecast to remain saturated up to the 200 mb
level, along with precipitable water values around 1.60 inches. This
would suggest that Alex could remain as a subtropical cyclone by
the time it reaches the Azores, and some slight strengthening is
even possible as 300 mb temperatures are forecast to decrease from
-40C to around -42C in the inner core. The official intensity has
been nudged upward and is similar to a blend of the ECMWF and HRWF
model intensity forecasts.

Gale- and storm-force winds, as well as locally heavy rains, are
likely to affect portions of the Azores beginning tonight and
continuing into early Friday. Recent communications with the Azores
Meteorological Office indicate that wind gusts to a least 70 kt (130
km/h) are forecast to occur across portions of the central and
eastern Azores islands. However, stronger gusts will be possible at
higher elevations, especially over mountain tops and ridges.
Interests in the Azores should closely monitor the progress of Alex
and official forecasts issued by the Azores weather office.


INIT  14/0900Z 30.1N  29.3W   60 KT  70 MPH
 12H  14/1800Z 32.4N  28.3W   60 KT  70 MPH
 24H  15/0600Z 36.4N  27.6W   60 KT  70 MPH
 36H  15/1800Z 42.0N  28.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  16/0600Z 49.1N  29.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  17/0600Z 60.0N  40.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

Forecaster Stewart