I'm flabbergasted. So are the forecasters. These are their words, and they should be read in their entirety:
THERE HAS BEEN RAPID STRENGTHENING OF THE HURRICANE TODAY. FELIX HAS A SPECTACULAR PRESENTATION ON SATELLITE IMAGES WITH A WELL-
DEFINED EYE EMBEDDED IN A CIRCULAR CENTRAL DENSE OVERCAST. THE HURRICANE HUNTER CREW REPORTED A STADIUM EFFECT IN THE EYE AND THAT
THE EYE DIAMETER HAD SHRUNK TO 12 N MI. THE AIR FORCE PLANE ALSO MEASURED A PEAK 700 MB FLIGHT LEVEL WIND OF 132 KT AND...FOR A SYSTEM OF SUCH CONVECTIVE VIGOR...THE 90 PER CENT RATIO OF SURFACE TO FLIGHT LEVEL WINDS SHOULD CERTAINLY APPLY HERE. THIS WOULD EQUATE TO PEAK SURFACE WINDS OF ABOUT 120 KT. A GPS DROPSONDE IN THE NORTHERN EYEWALL MEASURED A SURFACE WIND OF 128 KT BUT THIS IS A SPOT WIND THAT IS NOT NECESSARILY REPRESENTATIVE OF A 1-MINUTE AVERAGE. THUS THE CURRENT INTENSITY IS SET AT 120 KT. A CENTRAL PRESSURE OF 957 MB WAS MEASURED BY DROPSONDE...WITH 15 KT WINDS AT THE SURFACE. SO THE MINIMUM PRESSURE IS ESTIMATED TO BE SLIGHTLY LOWER OR 956 MB. THIS CORRESPONDS TO A FALL IN CENTRAL PRESSURE AT A RATE OF 3.4 MB PER HOUR OVER THE PAST 7 HOURS OR SO...WHICH IS ONE OF THE MORE RAPID DEEPENING RATES WE HAVE OBSERVED. FELIX WILL REMAIN IN A VERY LOW SHEAR TROPOSPHERIC ENVIRONMENT AND WILL BE PASSING OVER WATERS OF EXTREMELY HIGH OCEANIC HEAT CONTENT OVER THE
NEXT COUPLE OF DAYS. IN ADDITION...TO EXACERBATE THE SITUATION...THERE IS A WARM EDDY OVER THE CENTRAL CARIBBEAN THAT FELIX IS PROJECTED TO MOVE OVER IN 12 HOURS OR SO. THE OFFICIAL INTENSITY FORECAST COULD BE CONSERVATIVE AND THERE IS CERTAINLY THE POTENTIAL FOR US TO HAVE ANOTHER CATEGORY FIVE HURRICANE ON OUR HANDS BEFORE ALL IS SAID AND DONE.
Wow...
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Chris: What's up with the forward speed? Dean marched across at what, 17mph?
We mere citizens have always been told that faster forward progress impedes strengthening.
My understanding (as an amateur) is that high forward speed raises the following issues which typically work against the cyclone:
(a) It can make the surface inflow less symmetric.
(b) It can move the cyclone out of favorable conditions before it has time to strengthen.
(c) In the Atlantic and the NW Pacific, high forward speed generally brings a cyclone toward land sooner, again reducing the time it has to strengthen.
(d) In the low tropics, cyclones tend to move west or northwest, while upper-level winds tend to blow west to east, so high forward speed tends to be associated with higher shear.
It is also associated with two other issues that can work in a cyclone's favor:
(e) It can move a cyclone toward more favorable conditions. In both the Atlantic and the NW Pacific, strong permanent high-pressure systems in the northeast of the basin push the warm water to the west, where it gathers into large deep pools - that's why the ocean in the Caribbean and the Gulf of Mexico is warmer than at the same latitude off the coast of Africa. This means that a fast west-moving cyclone (like Dean or Felix) is generally moving toward more favorable conditions.
(f) It can move a cyclone to fresh warm waters before it uses up all the available heat, or before the cyclone's strong winds cause the upwelling of cold deep water that can cause a slow-moving cyclone to chill itself out, and weaken.
(a) is mostly a problem when a cyclone's max surface winds are only 2-3 times the cyclone's speed. So 17 mph doesn't introduce much asymmetry into a cyclone with 140 mph max surface winds (like Felix or Dean).
(b) is not problem for Felix (nor was it for Dean) because Felix has been moving west toward warmer waters (as Dean did), and therefor (e) applies instead.
(c) was not a problem for Dean, and has not been a problem for Felix because both cyclones strengthened relatively rapidly.
(d) was not a problem for Dean, and has not been a problem for Felix because both traveled under strong upper-level highs, resulting in the unusual direction of the upper-level winds, and low shear.
(f) may have helped Felix a bit, but the warm water under Felix has been quite deep, so high forward speed may not have been needed here.
In any case, fast-moving major hurricanes are a normal feature of a La Nina episode, and conditions in the tropical Pacific have been very near La Nina conditions for months.
As of the 8 PM EDT 2 September advisory , Felix is a category 5 hurricane, the 9th in the last 10 years (more than twice the 1951-2000 average of 3.4 category 5 Atlantic hurricanes every 10 years), the 2nd in the 2007 season (only 3 previous seasons, 1960, 1961, and 2005, had 2 or more category 5 hurricanes), coming only 13 days after Dean reached category 5 strength.
Well it's a category Five now:
http://www.nhc.noaa.gov/text/refresh/MIATCPAT1+shtml/022359.shtml
REPORTS FROM A NOAA HURRICANE HUNTER AIRCRAFT INDICATE THAT FELIX
HAS INTENSIFIED AND IS NOW A CATEGORY FIVE HURRICANE. THE AIRCRAFT
REPORTED PEAK FLIGHT-LEVEL WINDS OF 152 KT...WITH PEAK SFMR WINDS
OF 142 KT IN THE SOUTHWEST QUADRANT. HIGHER SFMR WINDS WERE FOUND
IN THE NORTHEAST QUADRANT...UP TO 163 KT...BUT THESE MAY HAVE BEEN
CONTAMINATED BY GROUPEL. A DROPSONDE RELEASED IN THE SOUTHWEST
QUADRANT LANDED IN THE NORTHEAST QUADRANT...AND THIS DROP YIELDED A
SURFACE ESTIMATE OF 139 KT BASED ON THE LOWEST 150 M LAYER AVERAGE.
BASED ON THESE DATA...THE PEAK SURFACE WINDS ARE ESTIMATED TO BE AT
LEAST 145 KT. AN EYE SONDE MEASURED A SURFACE PRESSURE OF 936 MB
WITH SURFACE WINDS OF 24 KT. BECAUSE OF THE EXTREME TURBULENCE AND
GROUPEL THAT THE AIRCRAFT EXPERIENCED...THE MISSION IS BEING
ABORTED AND THE AIRCRAFT IS RETURNING TO ST. CROIX.
Yeah, so sad when you post it one hour and it's now old news the next hour.
Scenario: Felix hits Honduras as a category 5 storm, crosses the country and reaches the Eastern Pacific as a tropical storm. Strengthens to Category 5 again in the Eastern Pacific and heads off on a long, meandering journey that ends with Felix heading up the Gulf of California, across the Mexican state of Baja California Norte and becoming the very first Atlantic Hurricane to hit the city of San Diego CA.
And you know what, this is the sort of thing that could happen in real life. :)
Latest;
SINCE THE TIME OF THE LAST RECONNAISSANCE PENETRATION OF FELIX AT
23Z...THE SATELLITE PRESENTATION HAS NOT CHANGED APPRECIABLY...WITH
THE HIGHEST OBJECTIVE DVORAK RAW T NUMBERS REACHING T7.3 AROUND
00Z. GIVEN NO NET TREND IN THE SATELLITE PRESENTATION SINCE THE
TIME OF THE LAST FIX...THE INITIAL INTENSITY IS HELD AT 145 KT.
THE OUTFLOW PATTERN REMAINS IMPRESSIVE...AND FELIX HAS YET TO PASS
OVER THE VERY HIGH HEAT CONTENT WATERS OF THE WESTERN CARIBBEAN.
LATEST MICROWAVE IMAGERY DOES NOT SHOW CONCENTRIC EYEWALL
STRUCTURE...SO THERE COULD BE A LITTLE MORE SHORT-TERM
INTENSIFICATION. THERE DO NOT APPEAR TO BE ANY LARGE-SCALE FACTORS
TO CAUSE APPRECIABLE WEAKENING UNTIL THE HURRICANE INTERACTS WITH
THE LAND MASS OF CENTRAL AMERICA.