Wayward meteorology student on a journey back to the promise land. Aggie. Extreme Weather Junkie. Precipitation Snob. Catholic. Musician. Texan. Nerd.
By: 1900hurricane , 12:18 AM GMT on September 17, 2010
Hurricane Karl held his structure together amazingly well while crossing the Yucatan, and now that he is over open water, intensification has resumed. However, the big question is how much stronger Karl will get before landfall. The NHC is calling for a Category 2 Hurricane by landfall. I'm predicting slightly higher, a Category 3 Major Hurricane. Here's why:
As I mentioned earlier, Karl had very good structure coming off of the Yucatan, and it has only improved since then. The latest Microwave pass reveals that Karl has developed a very well defined and tight core, and with the favorable conditions that Karl is currently experiencing, steady and possible rapid intensification should continue up to the point of landfall. Recently, the small eye has started to become decreeable on visible imagery, which is another possible sign of rapid intensification.
The only limiting factor that can be seen in Karl's future at the moment is landfall. From an academic standpoint, it will be quite interesting to see how strong Karl can manage to get before landfall.
The same story cannot be said about Major Hurricane Igor. After completing a pretty radical Eyewall Replacement Cycle and reaching a tertiary peak intensity at 125 kt (145 mph), the behemoth has begun to encounter some southwesterly wind shear, which has caused a portion of the eyewall to erode and subsequently weakened the giant. Below will be a time series of Igor's eyewall erosion as seen by 85GHz Microwave imagery:
By 0255Z September 16th, Igor completes his ERC. His very large eye then begins to clear out and once again, he begins to strengthen.
By 0928Z, Igor reaches his tertiary peak intensity of 125 kts. At this point, wind shear starts to impact him and strengthening ends. The effects of the shear can be seen in Igor's southwest quadrant, where the brightness returns are much weaker than in the rest of the eyewall.
A couple of hours later, at 1224Z, the shear/dry air combo continues to take its toll on Igor, and it can easily be seen that the SW eyewall has been eroded away. By this time, Igor has begun to weaken again and is down to 120 kt (140 mph) by the time of this pass. Since then, Igor has weakened even more, down to a 110 kt (125 mph) category 3 hurricane. However, the National Hurricane Center states this in their forecast discussion:
HURRICANE IGOR DISCUSSION NUMBER 35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST THU SEP 16 2010
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REACHED THE CENTER OF
IGOR AROUND 1600 UTC. THE HURRICANE HUNTERS MEASURED A MINIMUM
PRESSURE OF 940 MB AND MAXIMUM FLIGHT-LEVEL AND SFMR WINDS OF 130
AND 98 KT...RESPECTIVELY. SINCE THAT TIME..THE CLOUD PATTERN
ASSOCIATED WITH IGOR HAS CHANGED LITTLE IN ORGANIZATION...AND
DVORAK T-NUMBERS REMAIN AT 5.5 FROM SAB AND TAFB. BASED UPON THE
AIRCRAFT DATA AND THE LOWER SATELLITE INTENSITY ESTIMATES...THE
INITIAL INTENSITY IS REDUCED TO 110 KT. THE EXTENSION OF AN
UPPER-LEVEL TROUGH PASSING NORTH OF IGOR IS STILL PRODUCING ABOUT
15 KT OF WESTERLY SHEAR OVER THE CYCLONE...ACCORDING TO THE LATEST
UW-CIMSS ANALYSES. THE SHIPS MODEL OUTPUT SHOWS A REDUCTION IN THE
SHEAR WITHIN THE NEXT 12 HOURS AS THIS FEATURE MOVES AWAY...WHICH
COULD ALLOW AN OPPORTUNITY FOR SOME RE-INTENSIFICATION IN THE
Despite weakening, Igor remains an intense and very, very large hurricane. To illustrate this point, here is one of the last visible images of the day, showing the sun setting over Igor over the right side of the frame. Compare his size to the state of Texas:
Karl continues to show signs of organization with his eye tightening even more the before:
This is further reflected in the IR imagry, which shows his eye becoming more apparent and surrounded by a very cold and symmetric CDO:
Also, as mentioned in the NHC Discussion for Igor above, it appears that the shear may be relaxing over him, as much of the eroded portion of his eyewall has redeveloped according to a fairly recent microwave pass:
Although he still looks somewhat ragged on IR, if this trend continues, he may be able to strengthen again, hitting a quaternary peak intensity and achieving category 4 once agian.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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