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#1 |
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Registered User
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Tropical Storm ANA
![]() TROPICAL DEPRESSION TWO SPECIAL DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009 600 AM AST TUE AUG 11 2009 FIRST LIGHT VISIBLE SATELLITE IMAGES SHOW THAT THE BROAD LOW PRESSURE AREA ASSOCIATED WITH A TROPICAL WAVE THAT WE HAVE BEEN TRACKING OVER THE FAR EASTERN TROPICAL ATLANTIC HAS ACQUIRED SUFFICENT ORGANIZED DEEP CONVECTION TO BE DESIGNATED AS A TROPICAL DEPRESSION. THE TROPICAL CYCLONE IS SITUATED OVER MARGINALLY WARM SEA SURFACE TEMPERATURES AND THE VERTICAL SHEAR IS CURRENTLY RATHER WEAK. THE OFFICIAL FORECAST SHOWS GRADUAL STRENGHENING OVER THE NEXT COUPLE OF DAYS AND IS A BLEND OF THE VARIOUS NUMERICAL GUIDANCE TOOLS. AS USUAL THERE IS CONSIDERABLE UNCERTAINTY AS TO THE STRENGTH OF THIS SYSTEM LATER IN THE FORECAST PERIOD. IF THE CYCLONE MOVES FARTHER NORTH THAN ANTICIPATED BELOW IT WILL PROBABLY ENCOUNTER STRONGER SHEAR AND NOT INTENSIFY AS MUCH AS FORECAST. ON THE OTHER HAND IF THE SYSTEM MOVES FARTHER SOUTH THAN EXPECTED LATE IN THE PERIOD...IT WILL PROBABLY BECOME STRONGER THAN ANTICIPATED HERE. INITIAL MOTION IS ABOUT 270/11. THIS TRACK IS LIKELY TO MORE OR LESS CONTINUE FOR THE NEXT 2-3 DAYS DUE TO THE FLOW SOUTH OF A FAIRLY WELL-ESTABLISHED MID-LEVEL SUBTROPICAL RIDGE. LATER IN THE PERIOD...A SLIGHT WEAKNESS IN THE RIDGE IS LIKELY TO INDUCE A MORE WEST-NORTHWESTWARD MOTION. THE OFFICIAL FORECAST IS A LITTLE SLOWER THAN THE MODEL CONSENSUS AND WELL TO THE SOUTH AND WEST OF THE BAM TRACKS. THIS IS ALSO SOUTH OF THE LATEST HWRF TRACK. FORECAST POSITIONS AND MAX WINDS INITIAL 11/1000Z 14.4N 28.6W 25 KT 12HR VT 11/1800Z 14.6N 30.1W 30 KT 24HR VT 12/0600Z 14.8N 32.3W 35 KT 36HR VT 12/1800Z 15.0N 34.6W 35 KT 48HR VT 13/0600Z 15.2N 36.8W 40 KT 72HR VT 14/0600Z 16.0N 41.2W 45 KT 96HR VT 15/0600Z 17.5N 45.5W 50 KT 120HR VT 16/0600Z 19.5N 49.5W 50 KT $$ FORECASTER PASCH |
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#2 |
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Moderator
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Fish spinner me thinks, there are two more areas which need watching though.
has to have been the quietest season for a long time. |
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#5 |
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Registered User
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TD2 is looking a lot less like a fish today (see models above), however it is struggling to reach TS status....
000 WTNT42 KNHC 130840 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009 500 AM AST THU AUG 13 2009 THE DEPRESSION HAS A RATHER MEAGER AMOUNT OF CONVECTION THIS MORNING WITH JUST A FEW CELLS AROUND THE EXPOSED CENTER. SATELLITE INTENSITY ESTIMATES ARE DROPPING...SO THE INITIAL INTENSITY IS LOWERED TO 25 KT. IF SIGNIFICANT DEEP CONVECTION DOES NOT DEVELOP SOON... THE SYSTEM COULD BE DECLARED A REMNANT LOW LATER TODAY. ASSUMING THE DEPRESSION SURVIVES...THE ENVIRONMENT OVER THE NEXT FEW DAYS IS MARGINALLY CONDUCIVE FOR SOME STRENGTHENING WITH GRADUALLY INCREASING WATER TEMPERATURES WEST OF 40W AND PERHAPS A DECREASE IN MODERATE SOUTHEASTERLY SHEAR. THE INTENSITY FORECAST IS LOWERED FROM THE PREVIOUS ONE BUT STILL SHOWS THE DEPRESSION EVENTUALLY BECOMING A TROPICAL STORM. THIS IS A PRETTY LOW CONFIDENCE INTENSITY FORECAST AS THE DEPRESSION MAY NOT EVEN SURVIVE THE DAY. THE SYSTEM HAS BEEN MOVING SLOWER DURING THE PAST FEW HOURS...AND A TWELVE-HOUR MOTION IS ESTIMATED AT 270/10. MOST OF THE GUIDANCE SUGGEST THAT THIS WESTWARD MOTION SHOULD CONTINUE FOR A DAY OR SO WITH A GRADUAL TURN TO THE WEST-NORTHWEST THEREAFTER AS A WEAKNESS DEVELOPS IN THE SUBTROPICAL RIDGE. THE GLOBAL MODELS NOW INDICATE THAT THE DEPRESSION COULD BE TOO FAR SOUTH TO BE AFFECTED SIGNIFICANTLY BY THE WEAKNESS IN THE RIDGE AND HAVE SHIFTED THE TRACK EQUATORWARD AS A RESULT. THE HWRF CONTINUES ON ITS OWN BY MOVING THE SYSTEM MORE TO THE NORTH...WHILE THE REST OF THE GUIDANCE IS PRETTY WELL-CLUSTERED ON A MORE SOUTHERN PATH. THE OFFICIAL FORECAST IS ADJUSTED SOUTHWARD AND WITH MANY RELIABLE MODELS STILL SOUTH OF THE NHC TRACK...IT WOULD NOT BE SURPRISING TO SEE THE FORECAST MOVE FARTHER SOUTH LATER ON. FORECAST POSITIONS AND MAX WINDS INITIAL 13/0900Z 14.0N 36.9W 25 KT 12HR VT 13/1800Z 14.0N 38.5W 25 KT 24HR VT 14/0600Z 14.2N 40.7W 30 KT 36HR VT 14/1800Z 14.4N 43.0W 35 KT 48HR VT 15/0600Z 14.9N 45.9W 40 KT 72HR VT 16/0600Z 16.5N 52.0W 40 KT 96HR VT 17/0600Z 19.0N 59.0W 40 KT 120HR VT 18/0600Z 22.5N 65.0W 35 KT $$ FORECASTER BLAKE |
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#6 |
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Registered User
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TD2 is now Tropical Storm Ana....
000 WTNT42 KNHC 150840 TCDAT2 TROPICAL STORM ANA DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009 500 AM AST SAT AUG 15 2009 SATELLITE IMAGES INDICATE THAT THE TROPICAL DEPRESSION HAS CONTINUED TO BECOME BETTER ORGANIZED AND IS NOW UPGRADED TO TROPICAL STORM ANA. THE STORM IS DISPLAYING IMPROVED BANDING IN THE WESTERN SEMICIRCLE ALONG WITH A BALL OF CONVECTION NEAR THE CENTER. NOAA BUOY 41041 REPORTED A MINIMUM PRESSURE OF ABOUT 1005 MB AS THE DEPRESSION PASSED VERY NEAR THE BUOY. THE INITIAL INTENSITY IS RAISED TO 35 KT FOR THIS ADVISORY IN AGREEMENT WITH DVORAK INTENSITY ESTIMATES FROM SAB AND TAFB. THE INITIAL MOTION ESTIMATE IS 270/14. THE GLOBAL MODELS ARE IN AGREEMENT THAT A DEEP-LAYER RIDGE WILL STRENGTHEN NORTH OF THE TROPICAL CYCLONE OVER THE NEXT DAY OR SO. THIS PATTERN FAVORS THE TRACK OF ANA GRADUALLY BENDING FROM A WEST TO A WEST-NORTHWEST DIRECTION WITH AN INCREASE IN FORWARD SPEED. THE ONLY SIGNIFICANT OUTLIERS TO THIS TRACK ARE THE GFDL AND GFS...WHICH BOTH WEAKEN THE SYSTEM RATHER QUICKLY...LEADING TO A MORE WESTWARD TRACK OF THE CYCLONE. IN A FEW DAYS...SOME OF THE MODELS...SUCH AS THE GFS... SHOW A WEAKNESS IN THE RIDGE OVER THE WESTERN ATLANTIC THAT COULD ALLOW THE CYCLONE TO GAIN A LITTLE MORE LATITUDE. THIS WEAKNESS APPEARS TO BE CAUSED BY THE MID- TO UPPER-LEVEL LOW CURRENTLY NEAR 25N 65W. HOWEVER...THE MAJORITY OF THE GUIDANCE SHOWS THE MID- TO UPPER-LEVEL LOW MOVING WEST-SOUTHWESTWARD WITH MINIMAL INFLUENCE ON THE STRENGTH OF THE RIDGE. GENERALLY...THE MODELS THAT HOLD ONTO ANA ARE IN GOOD AGREEMENT THROUGHOUT THE FORECAST PERIOD. THE NHC TRACK FORECAST IS SHIFTED TOWARD THE SOUTHWEST FOR THIS ADVISORY... BUT NOT AS FAR AS THE MODEL CONSENSUS. THE 0000 UTC GLOBAL MODELS GENERALLY FORECAST A MORE CONDUCIVE ENVIRONMENT FOR STRENGTHENING THAN PREVIOUS CYCLES...SHOWING A WEAKER MID-OCEANIC TROUGH AFFECTING THE SYSTEM. IN PARTICULAR...THE UKMET AND NOGAPS BUILD UPPER-RIDGING NEAR THE CYCLONE WITH LIGHT SHEAR THROUGH THE PERIOD. HOWEVER...THE ECMWF SHOWS SOME WESTERLY SHEAR DEVELOPING IN ABOUT A DAY...BUT EVEN THAT MODEL HAS LIGHTER SHEAR CONDITIONS IN A FEW DAYS. THE INTENSITY GUIDANCE RUNS THE FULL SPECTRUM THIS MORNING...WITH THE GFDL DISSIPATING THE SYSTEM...WHILE THE HWRF SHOWS A CATEGORY TWO HURRICANE BY THE END OF THE FORECAST PERIOD. GIVEN THE UNCERTAINTY IN THE UPPER-LEVEL ENVIRONMENT LATER IN THE FORECAST PERIOD...THE OFFICIAL INTENSITY FORECAST IS INCREASED CONSERVATIVELY...IN BEST AGREEMENT WITH THE SHIPS MODEL BUT BELOW THE INTENSITY CONSENSUS. A TROPICAL STORM WATCH MAY BE REQUIRED FOR PORTIONS OF THE LEEWARD ISLANDS LATER TODAY. FORECAST POSITIONS AND MAX WINDS INITIAL 15/0900Z 14.6N 46.8W 35 KT 12HR VT 15/1800Z 14.7N 49.4W 40 KT 24HR VT 16/0600Z 15.3N 52.7W 45 KT 36HR VT 16/1800Z 16.1N 56.4W 45 KT 48HR VT 17/0600Z 17.0N 60.0W 50 KT 72HR VT 18/0600Z 19.5N 67.0W 55 KT 96HR VT 19/0600Z 22.5N 73.0W 60 KT 120HR VT 20/0600Z 26.0N 78.5W 60 KT $$ FORECASTER BLAKE |
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