Tropical Storm EMILIA
ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM EMILIA DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP062006 800 AM PDT SAT JUL 22 2006 DURING THE PAST 6 HOURS...CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE EMILIA HAS EXPERIENCED SOME MODERATE NORTHEASTERLY SHEAR WHICH HAD DISPLACED THE DEEPEST CONVECTION TO THE SOUTHWEST OF THE LOW-LEVEL CENTER. HOWEVER...CONVECTION IN THE SOUTHWESTERN QUADRANT HAS MADE A COMEBACK DURING THE PAST COUPLE OF HOURS...AND SEVERAL NARROW CONVECTIVE BANDS HAVE ALSO DEVELOPED IN THE NORTHEASTERN SEMICIRCLE. GIVEN THE RECENT AND EXPECTED CONVECTIVE REDEVELOPMENT TREND...THE INTENSITY IS BEING HELD AT 35 KT ASSUMING THAT TROPICAL STORM FORCE WINDS EXIST IN THE SOUTHWESTERN QUADRANT. USING A 12-HOUR TREND...THE INITIAL MOTION IS 335/12. THE ACTUAL PAST 6-HOUR MOTION HAS BEEN CLOSER TO 15 KT DUE TO EMILIA HAVING LOST SOME VERTICAL EXTENT WHEN THE CONVECTION BRIEFLY WEAKENED. HOWEVER...THE VERTICAL SHEAR IS EXPECTED TO DECREASE TO LESS THAN 5 KT BY 24 HOURS...WHICH SHOULD ALLOW MORE CENTRAL CONVECTION AND A DEEPER VORTEX TO REDEVELOP. THIS SHOULD CAUSE EMILIA TO BE STEERED MORE WESTWARD BY THE SUBTROPICAL RIDGE LOCATED OVER MEXICO. THE BIG CONCERN IS EXACTLY WHEN EMILIA WILL BECOME A MORE VERTICALLY DEEP CYCLONE. IF CENTRAL DEEP CONVECTION DOES NOT REDEVELOP WITHIN THE NEXT 12 HOURS...THEN A MORE SHALLOW STORM COULD SLIDE TO THE EAST OF THE OFFICIAL FORECAST TRACK AND MOVE CLOSER TO THE WEST-CENTRAL MEXICAN COAST... POSSIBLY BRINGING TROPICAL STORM FORCE WINDS VERY CLOSE TO THAT AREA. THE OFFICIAL FORECAST TRACK IS WELL TO THE RIGHT OR EAST OF THE PREVIOUS FORECAST...AND IS ALONG THE RIGHT SIDE OF THE NHC MODEL GUIDANCE ENVELOPE. THE LOW SHEAR ENVIRONMENT THAT EMILIA IS FORECAST TO MOVE INTO AFTER 24 HOURS WOULD NORMALLY FAVOR SIGNIFICANT INTENSIFICATION. HOWEVER ...LIGHT-MODERATE EAST TO SOUTHEASTERLY 300 MB WINDS ARE FORECAST TO UNDERCUT THE OTHERWISE FAVORABLE 200 MB OUTFLOW PATTERN...SO ONLY MODEST STRENGTHENING IS FORECAST...WHICH IS A BLEND OF THE LOWER GFDL FORECAST AND THE HIGHER SHIPS INTENSITY MODEL FORECAST. HOWEVER...IF THE 300 MB WIND FLOW REMAINS WEAKER THAN EXPECTED... THEN EMILIA COULD BECOME A HURRICANE IN 48 HOURS. THE SIZE OF THE WIND RADII WERE TRIMMED BACK SOMEWHAT SINCE EMILIA HAS NOT YET INTENSIFIED AND BECOME AS ORGANIZED AS PREVIOUSLY EXPECTED. FORECAST POSITIONS AND MAX WINDS INITIAL 22/1500Z 15.3N 104.6W 35 KT 12HR VT 23/0000Z 16.4N 105.5W 40 KT 24HR VT 23/1200Z 17.5N 107.0W 45 KT 36HR VT 24/0000Z 18.3N 108.2W 50 KT 48HR VT 24/1200Z 18.9N 109.4W 60 KT 72HR VT 25/1200Z 20.4N 111.4W 60 KT 96HR VT 26/1200Z 22.3N 113.8W 50 KT 120HR VT 27/1200Z 24.5N 116.0W 40 KT $$ FORECASTER STEWART NNNN