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Tropical Storm SONIA Forecast Discussion Number 10

2013-11-03 15:44:21| National Hurricane Center (East Pacific)

Issued at 700 AM PST SUN NOV 03 2013 000 WTPZ43 KNHC 031444 TCDEP3 TROPICAL STORM SONIA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182013 700 AM PST SUN NOV 03 2013 THE AREA OF DEEP CONVECTION THAT DEVELOPED OVERNIGHT IN ASSOCIATION WITH SONIA HAS EXPANDED THIS MORNING. EARLY MORNING VISIBLE SATELLITE IMAGES SUGGEST THAT THE CENTER IS LOCATED JUST BENEATH THE SOUTHEAST PORTION OF THE LARGE CONVECTIVE MASS. BASED ON THE SLIGHTLY IMPROVED ORGANIZATION AND DVORAK T-NUMBERS OF 2.5 AND 3.0 FROM SAB AND TAFB...RESPECTIVELY...THE INITIAL WIND SPEED IS INCREASED TO 40 KT. THE RECENT STRENGTHENING APPEARS TO BE THE RESULT OF DECREASING SHEAR AS SONIA MOVED BENEATH AN UPPER-LEVEL RIDGE AXIS OVERNIGHT. THIS RELAXATION IN SHEAR IS EXPECTED TO BE SHORT-LIVED AS SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF A MID- TO UPPER-LEVEL TROUGH WILL CAUSE A SUBSTANTIAL INCREASE IN SHEAR TONIGHT....AND NO SIGNIFICANT ADDITIONAL STRENGTHENING IS EXPECTED. SOME WEAKENING IS POSSIBLE AROUND THE TIME SONIA REACHES THE COAST AS THE SHEAR IS EXPECTED TO CAUSE THE LOW- AND MID-LEVEL CENTERS TO DECOUPLE. SONIA IS FORECAST TO DISSIPATE SHORTLY AFTER LANDFALL OVER THE MOUNTAINS OF WESTERN MEXICO. THE INITIAL MOTION IS STILL NORTHWARD OR 005 DEGREES AT 7 KT. SONIA SHOULD TURN NORTH-NORTHEASTWARD VERY SOON AS DEEP LAYER SOUTHWESTERLY FLOW STRENGTHENS AHEAD OF A MID-LATITUDE TROUGH MOVING INTO THE SOUTHWESTERN UNITED STATES AND NORTHERN MEXICO. SONIA SHOULD BEGIN TO ACCELERATE LATER TODAY AND MAKE LANDFALL ALONG THE COAST OF MAINLAND MEXICO MONDAY MORNING. THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND NO SIGNIFICANT CHANGES WERE REQUIRED FROM THE PREVIOUS NHC ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 19.9N 109.8W 40 KT 45 MPH 12H 04/0000Z 21.6N 109.1W 40 KT 45 MPH 24H 04/1200Z 23.7N 107.6W 35 KT 40 MPH 36H 05/0000Z 25.9N 106.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/1200Z...DISSIPATED $$ FORECASTER BROWN

Tags: number discussion storm tropical

 

Tropical Storm SONIA Forecast Discussion Number 9

2013-11-03 09:44:20| National Hurricane Center (East Pacific)

Issued at 100 AM PST SUN NOV 03 2013 000 WTPZ43 KNHC 030844 TCDEP3 TROPICAL STORM SONIA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182013 100 AM PST SUN NOV 03 2013 AFTER HAVING GONE THROUGH SEVERAL PULSING PHASES OF CONVECTIVE DEVELOPMENT DURING THE PAST COUPLE OF DAYS...MORE PERSISTENT AND ORGANIZED DEEP CONVECTION HAS OCCURRED SINCE THE PREVIOUS ADVISORY DUE TO A SHARP DECREASE IN THE VERTICAL WIND SHEAR. ASCAT-A AND ASCAT-B OVERPASSES AT 0421Z AND 0514Z...RESPECTIVELY...INDICATED BELIEVABLE 30-34 KT WIND VECTORS IN THE NORTHWEST QUADRANT. THESE WINDS ARE ALSO SUPPORTED BY SATELLITE INTENSITY ESTIMATES OF 35 KT FROM TAFB AND 36 KT FROM THE UW-CIMSS SATCON. AS A RESULT...THE DEPRESSION HAS BEEN UPGRADED TO TROPICAL STORM SONIA. THE VERTICAL SHEAR IS FORECAST TO REMAIN LESS THAN 10 KT FOR THE NEXT 12 HOURS OR SO...WHICH SHOULD ALLOW FOR SOME ADDITIONAL STRENGTHENING DURING THAT TIME. HOWEVER...BY 24 HOURS AND BEYOND...THE WIND SHEAR IS EXPECTED TO INCREASE FROM THE SOUTHWEST AT MORE THAN 25 KT... CAUSING RAPID WEAKENING TO OCCUR...ESPECIALLY BY 36 HOURS WHEN THE SYSTEM IS INTERACTING WITH THE MOUNTAINOUS TERRAIN OF MEXICO. ALTHOUGH A POSITION IS SHOWN AT 48 HOURS...MAINLY FOR CONTINUITY... THE SYSTEM WILL LIKELY HAVE DISSIPATED INLAND BY THAT TIME. THE INITIAL MOTION ESTIMATE IS 360/06 KT. THE TWO AFOREMENTIONED ASCAT OVERPASSES...ALONG WITH PASSIVE MICROWAVE SATELLITE IMAGERY...HAVE HELPED SIGNIFICANTLY WITH THE CENTER LOCATION THIS MORNING. HOWEVER...SINCE THE OVERALL INNER-CORE WIND FIELD IS STILL BROAD AND CONVECTION CONTINUES TO DEVELOP OVER AND NORTH OF THE ALLEGED CENTER...SOME ERRATIC MOTION IN A GENERAL NORTHWARD DIRECTION COULD OCCUR DURING THE NEXT 6 HOURS OR SO. BY 12 HOURS AND BEYOND...SONIA WILL GRADUALLY COME UNDER THE INFLUENCE OF INCREASING SOUTHWESTERLY STEERING FLOW AHEAD OF AN APPROACHING BROAD MID-/UPPER-LEVEL TROUGH THAT IS CURRENTLY PASSING 120W LONGITUDE. AS A RESULT...SONIA SHOULD BEGIN TO ACCELERATE AND TURN TOWARD THE NORTH-NORTHEAST BY THIS AFTERNOON OR EVENING...AND CONTINUE TO ACCELERATE TO THE NORTH-NORTHEAST OR NORTHEAST UNTIL LANDFALL OCCURS ON MONDAY. THE NHC MODELS ARE NOW IN EXCELLENT AGREEMENT ON THIS SCENARIO....AND THE NEW TRACK FORECAST IS SIMILAR TO BUT SLIGHTLY TO THE RIGHT OF THE PREVIOUS ADVISORY TRACK AND TO THE LEFT OF THE CONSENSUS MODEL TVCE. BASED ON THE UPDATED TRACK AND INTENSITY FORECASTS...THE GOVERNMENT OF MEXICO HAS ISSUED A TROPICAL STORM WARNING FOR THE COAST OF WEST-CENTRAL MEXICO FROM MAZATLAN TO ALTATA. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 18.8N 110.0W 35 KT 40 MPH 12H 03/1800Z 20.3N 109.7W 40 KT 45 MPH 24H 04/0600Z 22.6N 108.3W 35 KT 40 MPH 36H 04/1800Z 24.9N 106.6W 30 KT 35 MPH...INLAND 48H 05/0600Z 27.0N 105.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 72H 06/0600Z...DISSIPATED $$ FORECASTER STEWART

Tags: number discussion storm tropical

 
 

Tropical Depression EIGHTEEN-E Forecast Discussion Number 8

2013-11-03 03:34:50| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SAT NOV 02 2013 000 WTPZ43 KNHC 030234 TCDEP3 TROPICAL DEPRESSION EIGHTEEN-E DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182013 800 PM PDT SAT NOV 02 2013 THE DEPRESSION HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST FEW HOURS. THE COLDEST CLOUD TOPS HAVE MOVED FARTHER AWAY FROM THE ESTIMATED CENTER POSITION...AND THE TOPS HAVE WARMED DURING THE PAST FEW HOURS. THE LAST VISIBLE IMAGES SUGGESTED THAT THE CENTER HAD NOT BECOME ANY BETTER DEFINED...WITH MULTIPLE CLOUD SWIRLS NOTED WITHIN THE BROADER CIRCULATION. THE INITIAL INTENSITY REMAINS 30 KT BASED ON A BLEND OF THE LATEST DVORAK ESTIMATES. THE CYCLONE IS CURRENTLY EXPERIENCING MODERATE EASTERLY SHEAR...AND THE SHIPS MODEL SHOWS ONLY A BRIEF PERIOD WHERE THE SHEAR DECREASES IN THE NEXT 12 TO 18 HOURS BEFORE THE SHEAR INCREASES DRAMATICALLY AHEAD OF A LARGE MID/UPPER-LEVEL TROUGH. THE INTENSITY GUIDANCE DOES NOT SHOW MUCH IN THE WAY OF STRENGTHENING...BUT THE OFFICIAL FORECAST STILL SHOWS THE CYCLONE REACHING TROPICAL STORM STRENGTH IN THE NEXT 12-24 HOURS. WEAKENING IS EXPECTED WHEN THE CYCLONE APPROACHES MAINLAND MEXICO IN ABOUT 36 HOURS AS THE SHEAR INCREASES FURTHER. THE CENTER HAS BEEN DIFFICULT TO LOCATE DURING THE PAST FEW HOURS...BUT A BLEND OF THE LATEST FIXES AND CONTINUITY PROVIDES AN UNCERTAIN INITIAL MOTION ESTIMATE OF 320/5. THE CYCLONE SHOULD RECURVE AROUND THE WESTERN SIDE OF THE RIDGE AND AHEAD OF THE ABOVE-MENTIONED TROUGH IN THE NEXT 24 TO 36 HOURS. THIS PATTERN SHOULD LEAD TO A NORTHWARD TURN IN THE NEXT 12 HOURS...FOLLOWED BY AN ACCELERATION TOWARD THE NORTH-NORTHEAST. THE MODELS ARE IN GENERALLY GOOD AGREEMENT ON THIS SCENARIO...AND THE NHC TRACK IS LARGELY AN UPDATE OF THE PREVIOUS FORECAST AND CLOSE TO THE MIDDLE OF THE GUIDANCE ENVELOPE. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 18.3N 110.1W 30 KT 35 MPH 12H 03/1200Z 19.4N 110.3W 35 KT 40 MPH 24H 04/0000Z 21.6N 109.3W 35 KT 40 MPH 36H 04/1200Z 24.1N 107.8W 30 KT 35 MPH 48H 05/0000Z 26.5N 106.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 06/0000Z...DISSIPATED $$ FORECASTER BRENNAN

Tags: number discussion tropical depression

 

Tropical Depression EIGHTEEN-E Forecast Discussion Number 7

2013-11-02 21:38:27| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SAT NOV 02 2013 000 WTPZ43 KNHC 022038 TCDEP3 TROPICAL DEPRESSION EIGHTEEN-E DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182013 200 PM PDT SAT NOV 02 2013 VISIBLE SATELLITE IMAGES SUGGEST THAT THE CENTER OF THE CYCLONE IS CLOSER TO THE DEEP CONVECTION THAN EARLIER...ALTHOUGH IT IS STILL DIFFICULT TO PINPOINT THE EXACT LOCATION OF THE CENTER. THE INITIAL WIND SPEED IS HELD AT 30 KT...BUT THE SYSTEM COULD BE A LITTLE STRONGER. MICROWAVE AND OTHER SATELLITE DATA INDICATE THAT THE CENTER HAS BEEN MOVING TO THE WEST-NORTHWEST AT ABOUT 5 KT. THIS MOTION SHOULD BE TEMPORARY HOWEVER...AS A LARGE MID-TROPOSPHERIC TROUGH APPROACHING THE CYCLONE SHOULD TURN IT TOWARD THE NORTH AND NORTH-NORTHEAST BY LATE SUNDAY. ONLY SMALL CHANGES WERE MADE TO THE PREVIOUS NHC TRACK...AND THE NEW OFFICIAL FORECAST IS SIMILAR TO THE LATEST ECMWF AND THE MODEL CONSENSUS. THERE IS STILL AMPLE TIME FOR THIS SYSTEM TO BECOME A TROPICAL STORM. WIND SHEAR SHOULD DECREASE A LITTLE BIT DURING THE NEXT DAY OR SO...WHICH WILL PROBABLY ALLOW FOR SOME STRENGTHENING. HOWEVER...SOUTHWESTERLY SHEAR IS EXPECTED TO RAPIDLY INCREASE BY 36H...WHICH WILL LIKELY CAUSE WEAKENING WHILE THE CYCLONE APPROACHES MAINLAND MEXICO. THE OFFICIAL FORECAST IS BASICALLY THE SAME AS THE PREVIOUS ONE...WITH NO SIGNIFICANT CHANGES TO THE GUIDANCE SUITE. A TROPICAL STORM WATCH HAS BEEN ISSUED FOR MEXICO GIVEN THE SMALL... BUT NOT NEGLIGIBLE...CHANCES OF TROPICAL-STORM-FORCE WINDS OCCURRING SOMEWHERE WITHIN THE WATCH AREA. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 17.7N 109.8W 30 KT 35 MPH 12H 03/0600Z 18.5N 110.2W 35 KT 40 MPH 24H 03/1800Z 20.3N 109.9W 35 KT 40 MPH 36H 04/0600Z 22.9N 108.5W 35 KT 40 MPH 48H 04/1800Z 25.5N 107.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 05/1800Z...DISSIPATED $$ FORECASTER BLAKE

Tags: number discussion tropical depression

 

Tropical Depression EIGHTEEN-E Forecast Discussion Number 6

2013-11-02 15:53:18| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SAT NOV 02 2013 000 WTPZ43 KNHC 021453 TCDEP3 TROPICAL DEPRESSION EIGHTEEN-E DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP182013 800 AM PDT SAT NOV 02 2013 CONVECTION HAS BEEN ON THE INCREASE ON THE NORTHWESTERN SIDE OF THE DEPRESSION...BUT VISIBLE SATELLITE IMAGES STILL SHOW THAT THE CENTER OF THE CYCLONE REMAIN WELL TO THE SOUTHEAST OF THE CONVECTIVE MASS. THERE HAS BEEN SOME EXPANSION OF THE CIRRUS CLOUDS EAST OF THE CENTER...SO PERHAPS THE EASTERLY SHEAR THAT HAS BEEN AFFECTING THE DEPRESSION IS ON THE WAY DOWN. THE INITIAL WIND SPEED WILL REMAIN 30 KT AS A BLEND OF THE TAFB/SAB DVORAK ESTIMATES. THE DEPRESSION IS MOVING NORTHWESTWARD AT ABOUT 4 KT. A TURN TO THE NORTH THEN NORTH-NORTHEAST IS ANTICIPATED OVER THE NEXT COUPLE OF DAYS DUE TO AN APPROACHING CLOSED LOW. MODEL GUIDANCE REMAINS TIGHTLY CLUSTERED ON THIS TRACK...AND NO SIGNIFICANT CHANGES WERE MADE TO THE PREVIOUS FORECAST. A 72H FORECAST IS INCLUDED FOR CONTINUITY...BUT THE CYCLONE WILL LIKELY BE DISSIPATED BY THEN. IT WOULD NOT TAKE MUCH OF AN INCREASE IN WINDS FOR THE DEPRESSION TO BECOME A LOW-END TROPICAL STORM...AND THE LATEST GUIDANCE DOES HAVE A COUPLE OF MORE MODELS THAT SHOW THIS SOLUTION. THUS THE NEW FORECAST WILL CONTINUE TO SHOW MODEST STRENGTHENING. SOUTHWESTERLY WIND SHEAR IS EXPECTED TO RAPIDLY INCREASE AFTER 36H...WHICH SHOULD CAUSE THE CYCLONE TO WEAKEN WHILE ITS APPROACHES MAINLAND MEXICO. THE NEW NHC FORECAST IS NOT FAR FROM THE PREVIOUS ONE...WITHIN A FEW KNOTS OF THE MODEL CONSENSUS. GIVEN THE CURRENT LACK OF ORGANIZATION AND THE LOW CHANCES OF SIGNIFICANT STRENGTHENING...THE CYCLONE IS UNLIKELY TO CAUSE TROPICAL-STORM-FORCE WINDS OVER MEXICO. THUS...IT IS PRUDENT TO WAIT FOR ANY TROPICAL STORM WATCHES AT THIS TIME. HOWEVER INTERESTS IN BAJA CALIFORNIA SUR AND SINALOA SHOULD MONITOR THIS SYSTEM. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 17.6N 109.1W 30 KT 35 MPH 12H 03/0000Z 18.3N 109.8W 35 KT 40 MPH 24H 03/1200Z 19.6N 110.0W 35 KT 40 MPH 36H 04/0000Z 21.9N 109.2W 35 KT 40 MPH 48H 04/1200Z 24.8N 107.8W 30 KT 35 MPH...INLAND 72H 05/1200Z 28.5N 105.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 06/1200Z...DISSIPATED $$ FORECASTER BLAKE

Tags: number discussion tropical depression

 

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