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EPAC Tropical Action 2011


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This storm is defiantly not annular, and I'd suspect we are already in the beginning stages of the next eyewall replacement cycle. The definition of an annual hurricane is pretty strict.

An annular hurricane is identified if the hurricane persists for at least 3 h in an axisymmetric state defined by the following: 1) the hurricane has a normal-to-large-sized circular eye surrounded by a single band of deep convection containing the inner-core region and 2) the hurricane has little or no convective activity beyond this annulus of convection. The use of digital IR data also allows for the development of an objective technique of identifying storms with these characteristics, which will be addressed in section 4. Note that a hurricane is considered an annular hurricane only when these conditions are met; before and after the annular phase, the hurricane is considered an asymmetric storm.

Fore more reading go here... its a pretty easy to follow paper for those not in the field.

http://journals.amet...AH%3E2.0.CO%3B2

Microwave certainly shows plenty of outside rain-bands from the inner core of the storm, one if which is likely the beginning of a secondary wind maxima.

2n1coxy.jpg

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This storm is defiantly not annular, and I'd suspect we are already in the beginning stages of the next eyewall replacement cycle. The definition of an annual hurricane is pretty strict.

Fore more reading go here... its a pretty easy to follow paper for those not in the field.

http://journals.amet...AH%3E2.0.CO%3B2

Microwave certainly shows plenty of outside rain-bands from the inner core of the storm, one if which is likely the beginning on the secondary wind maxima.

2n1coxy.jpg

Yeah, I noticed in the animation in 645 it has banding features. I thought (but could be wrong) there was an SST value above which canes don't usually become annular.

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Wow-- the EPAC is just on fire this season. It's only mid-July, and we've already had a handful of high-quality cyclones.

Perhaps a sign of things to come in the ATL. These EPAC systems spin up in less water and are stronger than Atlantic systems, pretty impressive.

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Yeah, I noticed in the animation in 645 it has banding features. I thought (but could be wrong) there was an SST value above which canes don't usually become annular.

It is thought that Annual storms are more common where SSTs are lower but favorable atmospheric conditions persist otherwise. However, warm SSTs certainly don't necessarily prevent annual hurricanes from developing. If you read the paper, you will find some other examples of Annular storms that were under pretty warm SSTs during their existence.

This is from the paper I cited above... these are the observed characteristics that were found in common with the storms analyzed in the study. Note the percentage. This tells how the percentage that each particular threshold existed for all tropical cyclones in that basin. Note that the "cool" SSTs threshold is only common in 64% of tropical cyclones in the Atlantic, and only 51% of storms in the EPAC. The enhanced IR images for each storm are also posted for a visual representation.

30rv7f6.jpg

1zmpa3t.png

EDIT: I reread the study, and the percentages actually are representative of ALL tropical cyclones that occurred in each basin. Still, if you look at the storms observed, SSTs don't necessarily limit a storms "annular characteristics"

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So close you can almost touch it...

SATELLITE IMAGES INDICATE THAT CONVECTION IN THE EYEWALL OF DORA HAS

BECOME MORE INTENSE DURING THE LAST SEVERAL HOURS...WITH THE EYE

STAYING MOSTLY CLEAR. VISIBLE PICTURES ARE RATHER SPECTACULAR WITH

MESOVORTICES NOTED WITHIN THE DISTINCT EYE. DVORAK ESTIMATES ARE

BETWEEN 127-140 KT...AND THE INITIAL INTENSITY IS SET TO 135 KT.

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Understanding how fish in the EPAC spin down wouldnt be my top priority

It is one of the priorities of the NHC since there's little direct observational data of storms spinning down in the east pac, so their forecasts of spin down are basically guesses. It's important for shipping interests to get the right forecast.

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