Rare late-season Eastern Pacific hurricane forms
Tropical Storm Kenneth formed over the weekend in the Eastern Pacific, and intensified into a hurricane late this morning. We are well past the date for the usual formation of the season's last storm, since the African waves spawned by the African monsoon, which serve as low pressure "seeds" to get the atmosphere spinning and trigger formation of more than half of the Eastern Pacific's storms, are rare this time of year. Kenneth formed from some unusual wave-like motions in the atmosphere over the Eastern Pacific that were not associated with African tropical waves. Since 1949, here have been just three Eastern Pacific named storms that formed after November 18. These three storms were an unnamed tropical storm on November 27, 1951; Tropical Storm Sharon on November 27, 1971; and Hurricane Winnie on December 5, 1983. None of these storms hit land, though the 1951 storm grazed the Baja. If Kenneth grows stronger than a 90 mph hurricane, it will surpass Hurricane Winnie of 1983 as the strongest Eastern Pacific storm so late in the season. Kenneth is moving westwards out to sea, and should not be a threat to land.
Figure 1. Morning satellite image of Tropical Storm Kenneth taken at 7 am EST November 21, 2011. Image credit: NASA/GSFC.
Atlantic's Invest 99L could become Subtropical Storm Tammy
In the Atlantic, Invest 99L, an extratropical storm in the middle Atlantic that is generating tropical storm-force winds, has the potential to transition into a subtropical storm over the next day or two. The storm currently lacks a well-defined surface circulation. If it develops one, 99L would be called Subtropical Storm Tammy. The storm is over waters of 26°C, and these waters will cool to 24°C by Tuesday, as 99L moves northeastwards out to sea. These water temperatures are near the limit of where a subtropical or tropical storm can form. The storm is not a threat to any land areas.
Jeff Masters
Reader Comments
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No.
November 22nd?
2011 season suddenly gains a hurricane and a storm
Yeah I figured they would name that one. I believe that was 94L back in early Sept.
D:
I was thinking the same thing. He wants to be, but I'm not sure if he is. The proof will be once he hits cold water, if he weakens rapidly, then not annular.
Also, rip 99L and 2011 Atlantic season. There were a few interesting storms, and i finally got to experience one again (irene). Being in the northeast that doesn't happen too often. Last one (not including remnants) was 1997's Danny.
I have a question... Why the lack of gulf of Mexico storms in the past 6 years? In 2005 storm after storm got in there and blew up. Since then, only a few, and the ones that did make it stayed south into Mexico and didn't have much time to intensify. Don't get me wrong, It's a good thing, but growing up I remember the gulf as a hotspot, now It's not.
So, 19+ storms for the fourth time in sixteen years.
This season is now just one behind the Typhoon season of the west Pacific. Last year,the Atlantic beat it. Will it do so again? Probably not, but to be so close is impressive.
its not like the gulf is not a hotspot. since 2009 there has been persistent east coast troughing up to today so anything that came off africa usually went north of the islands. if something went into the carribean it had a chance to develop but didnt becuase last year there were no oppertunities to hit the US Gulf coast thanks to the Texas Ridge however in late august the ridge weakened and no storm took advantage
There is also a site for determining the "Annular" status of all cyclones.
JOHN A. KNAFF
NOAA/NESDIS/Center for Satellite Applications and Research, Fort Collins, Colorado
ABSTRACT
Annular hurricanes are a subset of intense tropical cyclones that have been shown in previous work to be
significantly stronger, to maintain their peak intensities longer, and to weaken more slowly than average tropical cyclones.
Because of these characteristics, they represent a significant forecasting challenge. This
paper updates the list of annular hurricanes to encompass the years 1995–2006 in both the North Atlantic and eastern–central North Pacific tropical cyclone basins.
Because annular hurricanes have a unique appearance in infrared satellite imagery, and form in a specific set of environmental conditions, an objective real-time method of identifying these hurricanes is developed.
However, since the occurrence of annular hurricanes is rare (4% of all hurricanes), a special algorithm to detect annular hurricanes is developed that employs two steps to identify the candidates: 1) prescreening the data and 2) applying a linear discriminant
analysis. This algorithm is trained using a dependent dataset (1995–2003) that includes 11 annular hurricanes.
The resulting algorithm is then independently tested using datasets from the years 2004–06, which contained an additional three annular hurricanes. Results indicate that the algorithm is able to discriminate
annular hurricanes from tropical cyclones with intensities greater than 84 kt (43.2 m s1).
The probability of detection or hit rate produced by this scheme is shown to be 96% with a false alarm rate of 6%, based on 1363 six-hour time periods with a tropical cyclone with an intensity greater than 84 kt (1995–2006).
FOUR HURRICANE...STRONGEST LATE SEASON EASTERN NORTH PACIFIC HURRICANE ON RECORD...
7:00 AM PST Tue Nov 22
Location: 12.7°N 113.9°W
Max sustained: 145 mph
Moving: W at 13 mph
Min pressure: 943 mb
One theory is that the Atlantic track system has shifted to a 1950 type set-up (possibly related to PDO shift, but hard to say) which favours recurvature or east coast hits as opposed to Gulf coast storms.
That is not to say Gulf storms won't happen or they won't be dangerous. Audrey, for example, still formed in 1957.
Other aspects might be other cycles. QBO may have an influence, but that would only explain a two year period of non-activity within a certain area at best due to its fluctuations.
NAO would also be a factor and it's largely been negative or neutral the last two years (also is a factor why Europe's last two winters were so cold).
Maybe it's just natural variation.
Have to see how it plays out to see if it's a trend or just a blip. Just some thoughts to throw out there.
Storm Relative 1km Geostationary Visible Imagery
WHOA!
Look at the eye!
Another historic weather extreme! It has been quite a year! I wonder what December has in store for us?
maybe Tammy is waiting for December lol
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 895
NWS STORM PREDICTION CENTER NORMAN OK
1200 PM CST TUE NOV 22 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
WESTERN AND CENTRAL ALABAMA
EASTERN MISSISSIPPI
EFFECTIVE THIS TUESDAY AFTERNOON FROM NOON UNTIL 500 PM CST.
TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES NORTH NORTHWEST OF
PINE BELT MISSISSIPPI TO 35 MILES EAST NORTHEAST OF SELMA
ALABAMA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.
DISCUSSION...A LINE OF THUNDERSTORMS OVER CENTRAL MS HAS INTENSIFIED
AND ACCELERATED DURING THE PAST HOUR...AND WILL TRACK ACROSS THE
WATCH AREA DURING THE NEXT FEW HOURS. STRONG WINDS ALOFT AND
MESOSCALE ORGANIZATION OF LINE WILL POSE A THREAT OF DAMAGING WINDS.
ALSO...ISOLATED DISCRETE CELLS FORMING AHEAD OF THE LINE MAY BECOME
SUPERCELLULAR WITH A RISK OF DAMAGING WINDS OR ISOLATED TORNADOES.
I ended with .51" yesterday, had .05" so far today..
Actually it is marginally annular.. I've seen them declared Annular when AHI=1 & for Kenneth that has been the case since 12:45am...
Here's the latest run..
## ANNULAR HURRICANE INDEX (AHI) EP132011 KENNETH 11/22/11 18 UTC ##
## PASSED SCREENING STEP, MIGHT BE ANNULAR, CALCULATE AHI FROM DISCRIMINANT ANALYSIS ##
## AHI= 1 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
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