Último boletín de discusión...

Se hace referencia a que el ojo de OPHELIA se ha hecho más definido en las últimas 6 horas, y aunque los topes nubosos cerca del núcleo del huracán son más cálidas que hace 24 horas, un anillo de temperaturas de -50ºC o más frías todavía rodea al ojo.

La intensidad se mantiene en 85 KT.

Muy interesante la útima parte que destaco en fuente grande y negrita, y es la posibilidad de que la inestabilidad baroclina provoque un último pico de intensidad en OPHELIA antes de extratropicalizarse. Justo lo que ven varios modelos esta noche, como el GFS o el HWRF...

Hurricane Ophelia Discussion Number  19
NWS National Hurricane Center Miami FL       AL172017
500 PM AST Fri Oct 13 2017

Ophelia's eye has become better defined over the past 6 hours.
Although cloud tops near the inner core of the hurricane are warmer
than 24 hours ago, a ring of -50 deg C or colder cloud tops still
surrounds the eye.  Dvorak current intensity estimates have not
changed substantially, and a blend of objective and subjective
classifications still supports an initial intensity of 85 kt.

Little change in strength is expected while Ophelia remains a
hurricane, since the relatively cool SSTs along the hurricane's path
will likely be offset by low shear and cold upper-level temperatures
for the next 36 h.  Extratropical transition will likely begin
shortly after that time, as Ophelia begins to interact with a large
upper-level trough approaching from the west.  The dynamical
guidance suggests that Ophelia will deepen in response to the
trough, and although the forecast does not explicitly show it, I can
not rule out that Ophelia will briefly intensify as it undergoes
extratropical transition.  By 72 hours, the cyclone is expected to
occlude and begin weakening, though the expansion of the wind field
will result in impacts over portions of the British Isles,
regardless of its exact location or strength.  By 96 hours,
continued weakening and interaction with land will likely cause the
surface circulation to become ill-defined, and dissipation is
expected shortly thereafter.

Ophelia is beginning to accelerate toward the east-northeast and the
initial motion estimate is 060/11 kt.  Very little change has been
made to the official track forecast.  Ophelia is still expected to
continue picking up speed on an east-northeast heading while passing
south of the Azores during the next 24 to 36 hours.  By 48 hours,
interaction with the aforementioned upper-level trough will cause
Ophelia to turn toward the northeast and approach Ireland and the
western UK in about 72 h.  The track guidance is tightly clustered,
especially through 72 h, and the new NHC track forecast is close to
the various multi-model consensus aids.  Although the center of
Ophelia is not expected to reach Ireland or the UK until about day
3, wind and rain effects will arrive well in advance of the cyclone
center.  Individuals in those locations should consult products from
their local meteorological service for more information on local
impacts.

Tropical-storm-force winds are possible throughout the Azores
beginning late Saturday or Saturday night due to an approaching cold
front.  Any deviation to the left of Ophelia's forecast track could
bring stronger winds to the islands.  Interests in the Azores should
refer to products issued by the Azores Weather Forecast and Watch
Center.

KEY MESSAGES:

1. Ophelia is expected to become a hurricane-force post-tropical
cyclone by Monday before it moves near Ireland and the United
Kingdom. Direct impacts from wind and heavy rain in portions of
these areas are likely, along with dangerous marine conditions. For
more details on the magnitude, timing, and location of impacts from
post-tropical Ophelia, residents in Ireland should refer to products
issued by Met Eireann, and residents in the United Kingdom should
refer to products issued by the Met Office.

FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 32.3N  31.8W   85 KT 100 MPH
 12H  14/0600Z 33.4N  29.5W   80 KT  90 MPH
 24H  14/1800Z 35.2N  25.4W   80 KT  90 MPH
 36H  15/0600Z 38.2N  20.3W   80 KT  90 MPH
 48H  15/1800Z 43.1N  16.0W   80 KT  90 MPH
 72H  16/1800Z 53.2N  10.4W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  17/1800Z 60.5N   2.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  18/1800Z...DISSIPATED

$$
Forecaster Zelinsky

Vista en perspectiva de OPHELIA, conservando su ojo a estas horas, y a poco menos de 2000 km. de Lisboa...



Sin cambios significativos en las previsiones...

Hurricane Ophelia Discussion Number  20
NWS National Hurricane Center Miami FL       AL172017
1100 PM AST Fri Oct 13 2017

The eye of Hurricane Ophelia continues to be remarkably distinct on
satellite and remains surrounded by a ring of deep convection. An
average of objective and subjective Dvorak numbers still support an
initial intensity of 85 kt. The hurricane has managed to move
through an area of relatively low shear and maintain its intensity
so far. This is about to change in a day or so when a cold front
reaches the circulation of the hurricane and the shear increases
substantially. By then, any increase in intensity should be
triggered by baroclinic forces as the cyclone becomes extratropical.
The NHC forecast calls for Ophelia to become extratropical in about
48 hours and dissipate or absorbed by another large low beyond 4
days.

Given that the cyclone is forecast to become extratropical, the wind
field should expand, resulting in impacts over portions of the
British Isles regardless of its exact location or strength.  By 96
hours, Ophelia should have weakened due to the interaction with
land, causing the surface circulation to become ill-defined, and
dissipation is expected shortly thereafter.

Now that the cyclone is well embedded in the mid-latitude
westerlies, it is moving faster toward the east-northeast or 060
degrees at 17 kt.  An additional increase in forward speed is
anticipated as a large high-latitude trough accelerates the westerly
flow. Track models are in very good agreement and this increases the
confidence in the NHC forecast which is in the middle of the tight
guidance envelope.

Although the center of Ophelia is not expected to reach Ireland or
the UK for another 2-3 days, wind and rain effects will arrive
well in advance of the cyclone center. Individuals in those
locations should consult products from their local meteorological
service for more information on local impacts.

Tropical-storm-force winds are possible throughout the Azores
beginning Saturday night primarily due to an approaching cold front.
However, any track deviation to the left could bring stronger winds
associated with Ophelia's circulation to the islands. Interests in
the Azores should refer to products issued by the Azores Weather
Forecast and Watch Center.

KEY MESSAGES:

1. Ophelia is expected to become a hurricane-force post-tropical
cyclone by Monday before it moves near Ireland and the United
Kingdom. Direct impacts from wind and heavy rain in portions of
these areas are likely, along with dangerous marine conditions. For
more details on the magnitude, timing, and location of impacts from
post-tropical Ophelia, residents in Ireland should refer to products
issued by Met Eireann, and residents in the United Kingdom should
refer to products issued by the Met Office.


FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 33.0N  30.6W   85 KT 100 MPH
 12H  14/1200Z 34.3N  27.9W   80 KT  90 MPH
 24H  15/0000Z 36.5N  23.2W   80 KT  90 MPH
 36H  15/1200Z 40.3N  17.7W   75 KT  85 MPH
 48H  16/0000Z 46.0N  14.0W   75 KT  85 MPH...POST-TROP/EXTRATROP
 72H  17/0000Z 56.0N   7.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  18/0000Z 62.0N   1.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  19/0000Z...DISSIPATED

$$
Forecaster Avila

Nueva simulación de imágenes IR+RGB del modelo HWRF, de las 00 UTC de hoy, y que permite observar que OPHELIA aguantaría como huracán, sin terminar de perder sus características, hasta estar bastante cerca de la Península. El seguimiento seguirá siendo muy interesante durante todo el fin de semana.

Impresionante como dice Pedro verla tan cerca. Sigue en categoría 2.

El #HuracanOphelia continua en #Cat2 y vientos de 155 Km/h a 480 Km al SSW de las #Azores

Magnífico e interesantísimo movimiento para una situación que no se ve todos los días, ni todos los años.

Las imágenes satelitales que nos está mostrando este Huracán tan cerca de la Península son para enmarcar y guardar a buen recaudo. Ahora a estar atentos a este proceso de extratropicalización, a ver como le sienta, y como acaba la cosa. Pero en Irlanda se van a comer un buen bichaco.

En la animación de imágenes IR+RGB se observa que el ojo de OPHELIA ha crecido en tamaño pero, lo más importante, que la convección que estructura su pared del ojo es más intensa y con los topes más fríos Esto para mi significa intensificación, aunque sea momentánea y gracias a inestabilidad baroclina y aire más frío en altura, así como gran velocidad de traslación que hace que se neutralice en cierta forma la componente de la cizalladura vertical del viento.

En la actualización del aviso se pone de manifiesto lo que yo he comentado en otros posts, incluso el hecho de que las SST estén como 2ºC por encima de lo normal por donde se va a mover OPHELIA

Hurricane Ophelia Discussion Number  21
NWS National Hurricane Center Miami FL       AL172017
500 AM AST Sat Oct 14 2017

Ophelia's 20-nmi-diameter eye has continued to become more distinct
and cloud-free, with the eye temperature now reaching 15 deg C.
Satellite intensity estimates range from T4.5/77 kt from TAFB to
T5.0/90 kt from SAB and T5.5/102 kt from UW-CIMSS ADT. For now, the
initial intensity will remain at 85 kt, which is an average of the
available intensity estimates.

The initial motion estimate is 060/21 kt. Ophelia is embedded within
deep-layer southwesterly flow on the east side of a broad
mid-latitude trough. The global and regional models remain in
excellent agreement on the trough amplifying over the next 3-4 days,
which will cause the hurricane to accelerate toward the northeast at
forward speeds near 30 kt by 48 hours. The tight clustering of the
NHC model guidance, which shows very little cross-track or
along-track spread, increases the confidence in the official track.
As a result, no significant changes were made to the previous
advisory, and the new forecast track remains near the middle of the
guidance envelope, close to the HCCA and TVCX consensus models.

Ophelia is expected to remain in relatively low vertical wind shear
environment for the next 12 hours or so, which should help the
hurricane retain much of its current intensity during that time,
even though SSTs are only going to be 24-25C. However, upper-level
temperatures that are still about 2 deg C cooler than normal, which
will help to create sufficient instability to continue to drive the
development of inner-core convection. By 36 hours or so, the shear
is forecast to increase to 30-40 kt and the troposphere is expected
to become stable as sea-surface temperatures decrease to less than
20 deg C. However, even those SST values are about 2 deg C warmer
than normal for this time of the year. Those above-average ocean
temperatures are forecast to combine with strong baroclinic energy
associated with a potent, negatively tilted, upper-level trough,
causing Ophelia to transition into a powerful extratropical low
pressure system. By 48 hours, the post-tropical cyclone is forecast
to maintain sustained hurricane-force winds as it approaches
Ireland, with stronger winds expected over higher terrain.

Given that Ophelia is forecast to become extratropical, the wind
field should expand, resulting in impacts over portions of the
British Isles regardless of its exact location or strength.  By 96
hours, Ophelia should have weakened due to the interaction with
land, causing the surface circulation to become ill-defined, and
dissipation is expected shortly thereafter.

Although the center of Ophelia is not forecast to reach Ireland or
the UK for another 48-60 hours, wind and rain effects will arrive
well in advance of the cyclone center. Individuals in those
locations should consult products from their local meteorological
service for more information on local impacts.

Tropical-storm-force winds are possible throughout the Azores
beginning tonight, primarily due to an approaching cold front.
However, any track deviation to the west could bring stronger winds
associated with Ophelia's circulation to those islands. Interests
in the Azores should refer to products issued by the Azores Weather
Forecast and Watch Center.

KEY MESSAGES:

1. Ophelia is expected to become a hurricane-force post-tropical
cyclone by Monday before it moves near Ireland and the United
Kingdom.  Direct impacts from wind and heavy rain in portions of
these areas are likely, along with dangerous marine conditions. For
more details on the magnitude, timing, and location of impacts from
post-tropical Ophelia, residents in Ireland should refer to products
issued by Met Eireann, and residents in the United Kingdom should
refer to products issued by the Met Office.


FORECAST POSITIONS AND MAX WINDS

INIT  14/0900Z 33.9N  28.6W   85 KT 100 MPH
 12H  14/1800Z 35.3N  25.4W   80 KT  90 MPH
 24H  15/0600Z 38.3N  20.4W   80 KT  90 MPH
 36H  15/1800Z 43.0N  16.0W   75 KT  85 MPH...POST-TROP/EXTRATROP
 48H  16/0600Z 48.4N  12.5W   75 KT  85 MPH...POST-TROP/EXTRATROP
 72H  17/0600Z 57.4N   6.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  18/0600Z 63.1N    .5W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  19/0600Z...DISSIPATED

$$
Forecaster Stewart

Y otra cosita desde el punto de vista de un aficionado, llegará a Irlanda como una bestia parda


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