ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HERNAN DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 200 PM PDT MON AUG 11 2008 HERNAN WAS DIAGNOSED AS A MARGINAL HURRICANE AT THE 18Z SYNOPTIC TIME...BUT SINCE THEN THE LOW-LEVEL AND UPPER-LEVEL CIRCULATIONS HAVE STARTED TO DECOUPLE. BASED ON THIS MOST RECENT SATELLITE TREND...HERNAN HAS BEEN DOWNGRADED TO A 60-KT TROPICAL STORM AT THE 21Z ADVISORY TIME. NOW THAT THE LOW- TO MID-LEVEL CIRCULATIONS HAVE STARTED TO DECOUPLE FROM THE UPPER-LEVEL CIRCULATION...HERNAN IS EXPECTED TO MAKE MORE OF A WESTWARD AND WEST-SOUTHWESTWARD MOTION AS IT COMES UNDER THE INFLUENCE OF THE STRONG LOW-LEVEL RIDGING TO THE NORTH OF THE CYCLONE. THIS FORECAST SCENARIO IS CONSISTENT WITH THE CONSENSUS OF ALL OF THE NHC MODELS. HERNAN OR ITS REMNANT CIRCULATION IS EXPECTED TO CROSS INTO THE CENTRAL PACIFIC BASIN ON THURSDAY. HERNAN WILL BE PASSING OVER SUB-24C SEA SURFACE TEMPERATURES FOR THE NEXT 48 HOURS...WHICH SHOULD INDUCE CONTINUED WEAKENING. HOWEVER... BY 72 HOURS...THE CYCLONE WILL BE MOVING OVER 25C AND WARMER SSTS AND ALSO BE UNDER THE INFLUENCE OF LIGHT SOUTHEASTERLY UPPER-LEVEL SHEAR...WHICH COULD ALLOW FOR SOME REDEVELOPMENT OF CONVECTION THAT WOULD HELP MAINTAIN THE SYSTEM AS A TROPICAL CYCLONE RATHER THAN A REMNANT LOW AT DAYS 4 AND 5. FORECAST POSITIONS AND MAX WINDS INITIAL 11/2100Z 19.0N 131.2W 60 KT 12HR VT 12/0600Z 18.9N 132.3W 55 KT 24HR VT 12/1800Z 18.5N 133.9W 45 KT 36HR VT 13/0600Z 18.0N 135.4W 40 KT 48HR VT 13/1800Z 17.6N 137.2W 35 KT 72HR VT 14/1800Z 16.5N 140.5W 30 KT 96HR VT 15/1800Z 16.0N 144.5W 25 KT...REMNANT LOW 120HR VT 16/1800Z 16.0N 148.5W 25 KT...REMNANT LOW $$ FORECASTER STEWART/PASCH NNNN
Alternate Formats
About Alternates -
E-Mail Advisories -
RSS Feeds
Cyclone Forecasts
Latest Advisory -
Past Advisories -
About Advisories
Marine Forecasts
Latest Products -
About Marine Products
Tools & Data
Satellite Imagery -
US Weather Radar -
Aircraft Recon -
Local Data Archive -
Forecast Verification -
Deadliest/Costliest/Most Intense
Learn About Hurricanes
Storm Names
Wind Scale -
Prepare -
Climatology -
NHC Glossary -
NHC Acronyms -
Frequently Asked Questions -
AOML Hurricane-Research Division
About Us
About NHC -
Mission/Vision -
Other NCEP Centers -
NHC Staff -
Visitor Information -
NHC Library
NOAA/
National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida, 33165-2149 USA
nhcwebmaster@noaa.gov
Disclaimer
Privacy Policy
Credits
About Us
Glossary
Career Opportunities
Page last modified: Tuesday, 21-Apr-2009 12:09:38 UTC