ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NICHOLAS DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT TUE OCT 14 2003 DVORAK SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 AND 35 KT...RESPECTIVELY. A QUIKSCAT PASS AT 2030Z CONTAINED A NUMBER OF 30 KT VECTORS OUTSIDE OF THE HEAVY RAIN AREAS. SINCE IT IS QUITE LIKELY THAT THE WINDS WITHIN THE HEAVIEST CONVECTION ARE SOMEWHAT HIGHER...THE DEPRESSION IS BEING UPGRADED TO TROPICAL STORM NICHOLAS...THE 14TH NAMED STORM OF THE YEAR. SINCE 1900...ONLY SIX SEASONS HAVE PRODUCED MORE STORMS THAN 2003...AND THERE ARE STILL SIX WEEKS LEFT IN THE SEASON. NICHOLAS IS MAINTAINING VERY COLD CONVECTION TO THE EAST OF THE CENTER...ALTHOUGH THIS CONVECTION STILL SHOWS LITTLE OR NO BANDING STRUCTURE. SHEAR ANALYSES FROM THE UNIVERSITY OF WISCONSIN/CIMSS WEB PAGE SHOWS NICHOLAS IS EMBEDDED WITHIN AN ENVIRONMENT OF WESTERLY WIND SHEAR. SOME WESTERLY OR SOUTHWESTERLY SHEAR SHOULD CONTINUE OVER NICHOLAS...BUT THIS IS NOT EXPECTED TO PREVENT GRADUAL STRENGTHENING. THE OFFICIAL FORECAST IS A BLEND OF THE SHIPS AND GFDL INTENSITY GUIDANCE. THE INITIAL MOTION IS 295/9. NICHOLAS IS SOUTH OF A MID- TO UPPER-LEVEL TROUGH IN THE WESTERLIES BUT WILL SOON BE SEPARATING FROM THIS FEATURE. WEAK MID-LEVEL RIDGING LIES TO THE NORTHWEST OF THE CYCLONE. THERE IS AN INTERESTING SPLIT IN THE MODEL GUIDANCE...WITH THE SIMPLER STATISTICAL AND BAM MODELS SHOWING A CONTINUED WEST-NORTHWEST TRACK BENEATH THIS RIDGE OVER THE NEXT FIVE DAYS. ON THE OTHER HAND...THE MODELS WITH MORE COMPLEX PHYSICS ARE FORECASTING IMMEDIATE SLOWING WITH A TURN TO THE NORTHWEST. I AM NOT SURE I UNDERSTAND WHY THE MODELS ARE SPLIT IN THIS FASHION. THE WESTERLY SHEAR AND CURRENT DISTRIBUTION OF CONVECTION WOULD TEND TO SLOW THE FORWARD SPEED AND DRAG THE TRACK TO THE RIGHT...BUT I CANNOT SAY THAT THIS IS WHAT THE GLOBAL MODELS ARE TRYING TO DO WITH NICHOLAS. THERE IS SOME INDICATION IN THESE MODELS THAT THE AFOREMENTIONED RIDGE MAY WEAKEN SOMEWHAT WITH THE APPROACH OF A SECOND MID-LATITUDE TROUGH CURRENTLY NEAR 60W. IN ANY EVENT...THE OFFICIAL FORECAST CONTINUES TO FOLLOW A GFS/UKMET/GFDL CONSENSUS. NEAR THE END OF THE FORECAST PERIOD...NICHOLAS MAY FIND ITS NORTHWARD PROGRESS BLOCKED BY WHATEVER REMAINS OF THE RIDGE. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 15/0300Z 11.6N 42.9W 35 KT 12HR VT 15/1200Z 12.2N 43.8W 40 KT 24HR VT 16/0000Z 13.1N 44.6W 45 KT 36HR VT 16/1200Z 14.0N 45.3W 50 KT 48HR VT 17/0000Z 15.0N 46.0W 55 KT 72HR VT 18/0000Z 16.5N 47.0W 60 KT 96HR VT 19/0000Z 18.0N 48.0W 65 KT 120HR VT 20/0000Z 19.0N 49.0W 65 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:50:00 UTC