Buenísima esa imagen. A ver si finalmente el ECMWF no exageraba y vemos el primer cat.5 de la temporada...

Una pregunta con miga, Santi: ¿sabes de algún categoría 5 que se haya formado fuera del GOM o del Caribe? Yo es que no recuerdo ningún caso...

Yo tampoco recordaba ningún caso de cat.5 en la MDR... gracias deltaforce  beer

Por cierto, en mi opinión la estimación de intensidad actual de 40 kts me parece muy conservadora. ¡Si ya tiene aspecto de cat.1 mínimo!  

De todas maneras, esa presentación tan buena, redondeada, con bandas espirales y con el impresionante outflow de cirros engaña un poco... Luego cargas la imagen de microondas y ves el tema por dentro..., aunque la imagen ya está algo desfasada. Sin embargo, la afirmación de que será huracán para el domingo, creo que también es conservadora. Yo diría que con este ritmo que lleva, mañana por la tarde podríamos verlo ya como huracán evil

En el último aviso, el CNH dice que IGOR sigue viéndose afectado por algo de cizalladura en niveles medios y aire seco, pero que las condiciones se van a ir haciendo cada vez más favorables para su intensificación. Adjunto el aviso:

000
WTNT41 KNHC 102044
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST FRI SEP 10 2010

THE UPPER-LEVEL SHEAR THAT HAS BEEN PLAGUING IGOR FOR THE PAST
SEVERAL DAYS HAS FINALLY STARTED TO ABATE AND CIRRUS OUTFLOW HAS
NOW BECOME PRONOUNCED IN ALL QUADRANTS. HOWEVER...SOME MID-LEVEL
SHEAR AND DRY AIR ENTRAINMENT IS STILL AFFECTING THE CYCLONE...
WHICH HAS RESULTED IN A VERY ASYMMETRIC CONVECTIVE CLOUD PATTERN
WITH THE LOW-LEVEL CENTER DISPLACED AT LEAST 30 NMI TO THE EAST OF
THE COLDEST CLOUD TOPS. INTENSITY ESTIMATES ARE 30 KT FROM SAB...55
KT FROM TAFB...AND UW-CIMSS 3-HR AVERAGE ADT VALUES OF 49 KT AND
AMSU ESTIMATES OF 53 KT. THE INITIAL INTENSITY HAS BEEN
CONSERVATIVELY INCREASED TO 40 KT...WHICH WILL BE TOO LOW IF THE
LOW-LEVEL CENTER IS ACTUALLY CLOSER TO THE DEEP CONVECTION.

THE INITIAL MOTION IS 280/18. THERE IS NO CHANGE TO THE PREVIOUS
TRACK FORECAST OR REASONING. IGOR IS EXPECTED TO MOVE WESTWARD...
ACCOMPANIED BY A GRADUAL DECREASE IN FORWARD SPEED...FOR THE NEXT 96
HOURS AS THE CYCLONE MOVES ALONG THE SOUTHERN PERIPHERY OF A LARGE
AND STRONG SUBTROPICAL RIDGE SITUATED TO THE NORTH. BY DAY 5...A
BROAD LONGWAVE TROUGH IS FORECAST TO MOVE OFF THE U.S. EAST COAST
AND CREATE A WEAKNESS IN THE RIDGE TO THE NORTHEAST OF THE LESSER
ANTILLES. THIS SHOULD CAUSE THE STEERING FLOW TO WEAKEN AND ALLOW
WHAT IS EXPECTED TO BE A LARGE HURRICANE IGOR AT THAT TIME TO
GRADUALLY TURN WEST-NORTHWESTWARD. THE LATEST MODEL GUIDANCE IS
MORE TIGHTLY PACKED AROUND THE PREVIOUS NHC TRACK...ESPECIALLY AT
DAYS 4 AND 5.  IN PARTICULAR...THE GFDL AND ECMWF SHOW LESS OF A
NORTHWARD TURN THAT MIGHT BE RELATED TO A FLATTER LONGWAVE TROUGH
IN THE LATEST GLOBAL RUNS.  THE OFFICIAL FORECAST TRACK REQUIRES
LITTLE CHANGE AND IS AN EXTENSION OF THE PREVIOUS ADVISORY.

THE VERTICAL SHEAR IS EXPECTED TO CONTINUE TO DECREASE TO 5 TO 10 KT
FOR THE NEXT 5 DAYS. THIS FAVORABLE UPPER-LEVEL ENVIRONMENT...IN
CONJUNCTION WITH SSTS INCREASING TO 29C BY THE END OF THE FORECAST
PERIOD...SHOULD RESULT IN STEADY INTENSIFICATION. IGOR IS EXPECTED
TO REACH HURRICANE STATUS BY SUNDAY AND MAJOR HURRICANE STATUS BY
DAYS 4 OR 5. THIS SCENARIO IS SUPPORTED BY THE SHIPS...LGEM...
HWRF...AND GFDL MODELS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      10/2100Z 16.7N  33.3W    40 KT
 12HR VT     11/0600Z 16.8N  35.4W    45 KT
 24HR VT     11/1800Z 17.1N  38.4W    50 KT
 36HR VT     12/0600Z 17.2N  41.0W    60 KT
 48HR VT     12/1800Z 17.3N  43.4W    70 KT
 72HR VT     13/1800Z 17.7N  47.8W    80 KT
 96HR VT     14/1800Z 18.7N  51.6W    90 KT
120HR VT     15/1800Z 20.0N  55.0W   105 KT

$$
FORECASTER STEWART

Cierta tu apreciación sobre esa animación... Pareciera que en ella ha bajado de latitud aunque no sabemos si su centro siguió el mismo camino!

Sea como fuere, el CNH confirma que IGOR se encuentra cerca del estatus de huracán

000
WTNT41 KNHC 110835
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST SAT SEP 11 2010


IGOR IS STRENGTHENING AND IN FACT...THERE WAS A PERIOD FOR ABOUT TWO
HOURS...BETWEEN 04 AND 06 UTC THAT A SMALL EYE-LIKE FEATURE BECAME
APPARENT ON SATELLITE. HOWEVER...SINCE THEN...SUCH FEATURE HAS
BECOME INTERMITTENT...OTHERWISE I COULD HAVE DECLARED IGOR A
HURRICANE. ALTHOUGH THE CLOUD PATTERN IS BETTER ORGANIZED...THE
OVERALL CONVECTION HAS DECREASED A LITTLE AND NOW CONSISTS OF TWO
WELL-DEFINED CYCLONICALLY CURVED BANDS LOCATED PRIMARILY TO THE
SOUTH OF THE CENTER. THE OUTFLOW HAS BECOME ESTABLISHED IN ALL
QUADRANTS. BASED ON A BLEND OF T-NUMBERS FROM TAFB AND SAB WHICH
ARE 4.0 AND 3.5 ON THE DVORAK SCALE...THE INITIAL INTENSITY HAS
BEEN INCREASED TO 60 KNOTS. GIVEN THE CURRENT INTENSITY TREND...THE
CYCLONE WILL LIKELY BECOME A HURRICANE LATER TODAY. ALL OF THE
ENVIRONMENTAL PARAMETERS APPEAR TO BE FAVORABLE FOR IGOR TO
INTENSIFY...AND THE FORECAST CALLS FOR IGOR TO BE AN INTENSE
HURRICANE IN ABOUT 3 DAYS. GLOBAL MODELS SUGGEST THAT IGOR COULD
ALSO BECOME LARGE.   

IGOR IS MOVING TOWARD TOWARD THE WEST OR 270 DEGREES AT 18 KNOTS.
THIS IS BASED ON THE MOTION OF THE EYE-LIKE FEATURE AND CONTINUITY.
THE CYCLONE IS BEING STEERED BY A BUILDING SUBTROPICAL RIDGE OVER
THE EASTERN ATLANTIC...AND THIS PATTERN IS FORECAST BY GLOBAL
MODELS TO PERSIST. ON THIS BASIS...THE OFFICIAL FORECAST CALLS FOR
A GENERAL WESTWARD MOTION FOR THE NEXT 3 DAYS OR SO. BY THEN...IGOR
WILL BE REACHING THE SOUTHWESTERN EDGE OF THE SUBTROPICAL HIGH
WHERE THE STEERING CURRENTS ARE WEAKER...AND BEGIN TO APPROACH A
BROAD TROUGH OVER THE WESTERN ATLANTIC. THIS PATTERN SHOULD FORCE
IGOR TO SLOW DOWN AND BEGIN TO TURN MORE TO THE WEST-NORTHWEST AND
NORTHWEST. THE TRACK FORECAST IS VERY CLOSE TO THE CONSENSUS AND
BIASED TO THE ECMWF AND THE GFS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      11/0900Z 17.1N  37.8W    60 KT
 12HR VT     11/1800Z 17.1N  40.2W    70 KT
 24HR VT     12/0600Z 17.2N  43.1W    75 KT
 36HR VT     12/1800Z 17.4N  46.0W    80 KT
 48HR VT     13/0600Z 17.5N  48.5W    90 KT
 72HR VT     14/0600Z 17.5N  52.5W   100 KT
 96HR VT     15/0600Z 18.5N  55.5W   100 KT
120HR VT     16/0600Z 20.5N  59.0W   100 KT

$$
FORECASTER AVILA

A estas horas, su presentación a través del satélite, es un poco desgarrada, extraña... Quizá no tan bonito como en tu animación, Eric. Adjunto la imagen:

Está claro que si está temporada no está siendo explosiva es por culpa del aire seco, verdadero handicap este año... ¿Qué factores harán que esté más o menos presente a lo largo de una temporada? Se supone que una parte del aire seco es el que va asociado al SAL. Pero también aire seco de origen estratosférico, que quizá pueda colarse en la troposfera debido a las turbulencias que generan las borrascas, sea cual sea el nivel que ocupen (borrascas que ocupen todo el perfil troposférico, o sólo las que ocupan parcelas superiores, como las DANAs). Si hay una gran actividad ciclónica extratropical en una cuenca, a lo mejor hay más aire seco de origen estratosférico dando por saco... ¿Cómo lo ves?

Es curioso que no haya aviso intermedio sobre IGOR........... ¿Me huelo a que los meteorólogos del CNH se han llevado una sorpresita con el aire seco?

Está claro que si está temporada no está siendo explosiva es por culpa del aire seco, verdadero handicap este año... ¿Qué factores harán que esté más o menos presente a lo largo de una temporada? Se supone que una parte del aire seco es el que va asociado al SAL. Pero también aire seco de origen estratosférico, que quizá pueda colarse en la troposfera debido a las turbulencias que generan las borrascas, sea cual sea el nivel que ocupen (borrascas que ocupen todo el perfil troposférico, o sólo las que ocupan parcelas superiores, como las DANAs). Si hay una gran actividad ciclónica extratropical en una cuenca, a lo mejor hay más aire seco de origen estratosférico dando por saco... ¿Cómo lo ves?

Pues esa pregunta me la he hecho yo esta mañana, y me han contestado que es debido a las altas presiones que dominan desde hace dos semanas el Atlántico Central, supongo que por un efecto de subsidencia que hace que descienda aire frío y seco desde las capas altas a las capas medias. Porque viendo los mapas del CIMSS, está claro que SAL no es.
Claro que tu explicación de las DANASs también suena razonable... porque una DANA arrastraría aire seco y frío a capas más bajas, ¿no? pero no sé si provocaría aire seco en una extensión tan enorme como la que ha ocupado en el Atlántico Central en las últimas semanas... no sé, a ver si alguien nos aclara esto, tengo muchas dudas.

Esto es lo que pone en la página del CIMSS.

Lo que dice el CIMSS al respecto es:

SAL:

Background:   This imagery is created by differencing the 12.0 and 10.8µm infrared channels on the Meteosat-8 satellite. The algorithm is sensitive to the presence of dry and/or dusty air in the lower atmosphere (~600-850 hPa or ~4,500-1,500 m) and is denoted by the yellow to red shading.
 
Uses: This imagery is useful for monitoring the position and movement of dry air masses such as the Saharan Air Layer (SAL). Animations of the imagery are useful for tracking these features and can also help identify the source of the dry and/or dusty air that is indicated in the imagery.
 
Notes:
• Dry air and suspended aerosols (e.g. mineral dust) both contribute to a positive "SAL" signal in this imagery, but the relative contribution of each cannot be determined from this imagery alone.
• Polar air originating from the mid-latitudes produces a positive signal in this imagery that is similar to that of the SAL. This is because both air masses contain substantial dry air in the lower to middle troposphere. The JAVA movie is a useful tool for determining which type of air mass is being indicated in the imagery.

http://cimss.ssec.wisc.edu/tropic2/misc/sal/info.sal.m8split.html

-------------------------------------------------------------------------------------------------------

VAPOR DE AGUA EN NIVELES MEDIOS:

Background:   This product uses the 7.3µm channel on the Meteosat-8 satellite, which is sensitive to moisture in the lower to middle levels of the atmosphere.
 
Uses: The 7.3µm channel is useful for detecting moisture in the lower to middle troposphere and is typically most sensitive to moisture at ~600 hPa or ~4,500 m.
 
Notes:
• This channel is more effective than the upper-level water vapor imagery for tracking the Saharan Air Layer (SAL) because it detects moisture (or lack of) more effectively at levels where the SAL is typically found (~500-850 hPa or 6,000-1,500 m).
• Since this channel is able to detect the lower atmosphere more effectively, caution should be taken in interpreting the imagery, particularly in extremely dry areas over land (e.g. the Sahara Desert). In these regions, rapid heating during the day and cooling at night can affect the satellite retrievals in this channel. Specifically, if the lower to middle atmosphere is extremely dry, this channel "sees" more effectively down to the Earth's surface. Therefore, strong surface heating can produce an enhanced false "dry" signal and surface cooling can produce an enhanced false "moist" signal. However, although this effect can be significant over land areas, it is negligible over the ocean.

http://cimss.ssec.wisc.edu/tropic2/misc/sal/info.sal.wvlower.html

---------------------------------------------------------------------------------------------------------

VAPOR DE AGUA EN NIVELES ALTOS

Background:   This product uses the 6.2µm channel on the Meteosat-8 satellite, which is sensitive to moisture in the middle to upper levels of the atmosphere.
 
Uses: The 6.2µm channel is useful for detecting moisture in the middle to upper troposphere and is typically most sensitive to moisture at ~400 hPa or ~7,500 m.
 
Notes:
• This channel is often not effective for tracking the Saharan Air Layer (SAL) because it detects moisture (or lack of) more effectively at levels above where the SAL is typically found (~500-850 hPa or 6,000-1,500 m).

http://cimss.ssec.wisc.edu/tropic2/misc/sal/info.sal.wvupper.html