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| George, I'll take a stab at this and say that the Wind field graphic shows it missing the Azores but is time-stamped 8AM AST 8/19/06, whereas the NHC advisory is 5PM AST so something must have changed quite a bit since that last graphic. Again, like Steve said, the model is only as good as the initialization. | |
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| George, I attached the 12hr UKMET prog showing the track directly over the Azores by 0Z 9/20/06. | |
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| While I was posting this, I realized the
contradiction is still there. This prog was initialized at 1200Z which
is close to the time of that wind field graphic....and it shows the
center of Gordon passing right over the Azores...so where DID that
wind field graphic come from...a much earlier initialization ? Bill |
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| Hey George and William, I can't explain why they don't have the higher possibilities for hurricane winds going through the Azores either. The trop storm fcst map (attach 03) has 100% for the islands. In addition, I noticed this: This is from the last 5PM NHC public advisory: HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 40 MILES...65 KM...FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 175 MILES...280 KM. And here are the NHC forecast positions from the 5PM discussion: FORECAST POSITIONS AND MAX WINDS INITIAL 19/2100Z 37.9N 31.6W 75 KT 12HR VT 20/0600Z 38.1N 26.0W 65 KT 24HR VT 20/1800Z 39.0N 18.0W 55 KT...EXTRATROPICAL 36HR VT 21/0600Z 42.1N 10.0W 45 KT...EXTRATROPICAL 48HR VT 21/1800Z...ABSORBED BY A FRONTAL SYSTEM That is straight through the heart of the islands. What’s interesting is that the NHC map from 5PM this evening (01) doesn’t jive with those forecast positions. Those center positions on the map are not going through the middle of the islands, but south of them. But the 18Z NAVY (02) map shows the positions perfectly. Don’t ask me why! But it is bothersome.
01_NHC_5PM_position___forecast_track_204603W_sm.gif
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| I don't know if I see what you guys are seeing on the NHC track graphic. It looks to me that the initial position is around 38ºN, and by 2 pm Wednesday (less than 24 hours into the future) it's approaching 39ºN. | |
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| OK, Steve. My apologies! After looking ever more closely, I can see that they must be the same. It's just that the NHC map is on such a large scale, leaving the islands so tiny, that it's hard to make out detail. I missed the dot they have for Sao Miguel at 37.8N, 25.5W. Also, when I copied the NAVY map into here, it changed size and detail so that it doesn't look any much clearer. If you go to their sight and click on the map there, it gives very fine detail. I should have mentioned that. Sorry... But I'm still confused as to why they have such low probabilites for hurricane force winds at the islands. It doesn't jive with the 5PM discussion and forecast advisory. |
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| Earlier this afternoon Gordon's satellite
presentation was still remarkable for it's location. At that time
Gordon's eye was remaining visible. Here's is the latest satellite
loop from the NHC: (http://www.ssd.noaa.gov/goes/flt/t2/loop-avn.html). Gordon's is losing its organization and may not be a hurricane any more. In the loop, you can see that the deep convection has been pushed farther east than the center of the storm. Also note the low level clouds, especially in the western half of the storm. Perhaps the NHC kept the intensity forecast a little higher just for a precaution, in case the storm pulled any suprises. |
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| Hey guys, I think I might be missing something on the original questions here. The NHC graphics indicate the probability of sustained hurricane force or tropical storm force winds are based on 1 minute surface wind speed averages depending on track and intensity. The tropical storm force conditions have a larger radii than the hurricane force winds as you can seen on the cumulative distribution. This brings me to a question. Are the hurricane probabilities lower due to the intensity and track or is it due to poor model initialization or combination of both? |
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| Robert is right. Gordon is a storm that's barely a category 1 storm (and weakening) as it's moving through the Azores area, and the area of hurricane-force winds extends up to 40 miles from the center. But, in reality, the areas experiencing hurricane-force sustained winds are pretty small within that larger framework. That lends itself to lower probabilities. The probability of tropical storm-force winds is much higher, because they extend out much farther from the center and while it's not entirely certain that Gordon will remain a hurricane for long, it surely will maintain the strength of a tropical storm. | |
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| Here's the updated cumulative winds. Looks like Gordo did not, technically, make landfall. Close but no cigar. Am I correct? | |
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| Lee, you are right. It just missed. The eye
passed between the islands of Sao Miguel and Santa Maria. From the Associated Press (2 hrs 36 mins ago) "The eye of Gordon moved between the islands of Sao Miguel and Santa Maria, and was rapidly moving east, according to the National Hurricane Center in Miami." “As it stands right now it will not make land fall,” said Dave Roberts, a hurricane forecaster for the National Hurricane Center. “There are still some winds there. They definitely felt some effect, but the eye didn’t pass on land.” The full link: http://www.msnbc.msn.com/id/14907792/ |
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| Here's a map of the Azores showing Sao
Miguel and Santa Maria so you can see how close Gordon passed to the
islands...it basically "threaded the needle" between the 2
islands ! http://www.worldatlas.com/webimage/countrys/europe/azores.htm |
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| Thanks Bill! | |
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| The NHC discussion mentions that Gordon is
in the process of becoming extraptropical and merging with a cold
front: A STRONG COLD FRONT IS ALREADY VERY NEAR THE CORE OF THE TROPICAL CYCLONE AND GORDON SHOULD BECOME FULLY EXTRATROPICAL LATER TODAY. The 0z CMC (12 hr--see attached) run has a tough time finding a center of circulation for Gordon. The Vorticity image (upper right) clearly shows the cold front just to the East of the Azores but no sign of the circulation of Gordon. This shows that the core is basically imbedded in the front at this point. |
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