WTNT44 KNHC 122047
TCDAT4
TROPICAL STORM NANA DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
500 PM EDT SUN OCT 12 2008
 
ALTHOUGH THE CONVECTIVE ORGANIZATION OF THE AREA OF LOW PRESSURE
LOCATED OVER THE EASTERN ATLANTIC HAS DEGRADED SOME THIS
AFTERNOON...THE SYSTEM HAS MAINTAINED SUFFICIENT CONVECTION FOR A
LONG ENOUGH PERIOD TO CONSIDER IT A TROPICAL CYCLONE.  DURING THE
AFTERNOON...THE CENTER OF THE CYCLONE HAS BECOME EXPOSED WELL TO
THE WEST OF THE LARGE AREA OF DEEP CONVECTION DUE TO WESTERLY
SHEAR.  AN ASCAT OVERPASS FROM 12Z INDICATED MAXIMUM WINDS OF 30-35
KT.  GIVEN THE TYPICAL LOW BIAS OF THIS INSTRUMENT...THE CYCLONE IS
DECLARED A TROPICAL STORM...THE FOURTEENTH OF THE 2008 SEASON.  THE
LONG-TERM SURVIVAL OF NANA SEEMS BLEAK AS STRONG UPPER-LEVEL
WESTERLIES ARE FORECAST TO CONTINUE.  ALL THE INTENSITY GUIDANCE
SHOWS WEAKENING AND SO DOES THE OFFICIAL FORECAST.  THE OFFICIAL
FORECAST SHOWS NANA DEGENERATING INTO A REMNANT LOW IN ABOUT 48
HOURS...BUT IT WOULD NOT BE SURPRISING IF IT OCCURRED SOONER.

NANA HAS BEEN MOVING SLOWLY WEST-NORTHWESTWARD OR 290/6 KT.  THE
TRACK GUIDANCE PREDICTS A SLOW WEST-NORTHWESTWARD MOTION AROUND THE
SOUTH SIDE OF A LOW- TO MID-LEVEL RIDGE OVER THE EASTERN ATLANTIC. 
THE CYCLONE IS FORECAST TO BE NEAR THE SOUTHWESTERN PERIPHERY OF
THE RIDGE IN A COUPLE OF DAYS AND SHOULD TURN TOWARD THE NORTHWEST
AHEAD OF A DEEP-LAYER TROUGH THAT DEVELOPS OVER THE CENTRAL
ATLANTIC.  THE TRACK FORECAST IS CLOSE TO THE MIDDLE OF THE
GUIDANCE ENVELOPE...BUT IS SLOWER THAN THE MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/2100Z 16.4N  37.9W    35 KT
 12HR VT     13/0600Z 16.7N  39.0W    30 KT
 24HR VT     13/1800Z 17.0N  40.4W    25 KT
 36HR VT     14/0600Z 17.4N  41.7W    25 KT
 48HR VT     14/1800Z 17.9N  43.0W    25 KT...REMNANT LOW
 72HR VT     15/1800Z 19.0N  46.0W    20 KT...REMNANT LOW
 96HR VT     16/1800Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 130240
TCDAT4
TROPICAL STORM NANA DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
1100 PM EDT SUN OCT 12 2008
 
WESTERLY SHEAR CONTINUES TO DISPLACE THE DEEP CONVECTION TO THE EAST
OF THE CENTER.  A QUIKSCAT PASS AT 2030Z HAD BELIEVABLE 35 KT
VECTORS...SO THE INITIAL INTENSITY REMAINS 35 KT.  WITH NO
APPRECIABLE LET UP OF THE SHEAR INDICATED BY THE GLOBAL MODELS OVER
THE NEXT DAY OR TWO...NANA IS FORECAST TO DEGENERATE TO A REMNANT
LOW FAIRLY SOON.
 
THE INITIAL MOTION IS 285/7.  THIS GENERAL MOTION IS EXPECTED TO
CONTINUE TO THE SOUTH OF A LOW- TO MID-LEVEL RIDGE OF HIGH PRESSURE
OVER THE EASTERN ATLANTIC.  THIS TRACK IS IN BEST AGREEMENT WITH
THE GFS...WITH MOST OF THE REMAINING GUIDANCE A LITTLE FARTHER
NORTH.  IF NANA DOES NOT WEAKEN AS QUICKLY AS EXPECTED...IT
PROBABLY WOULD INTERACT MORE STRONGLY WITH THE UPPER-LEVEL FLOW AND
TAKE A TRACK TO THE RIGHT OF THE OFFICIAL FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 16.6N  38.8W    35 KT
 12HR VT     13/1200Z 16.8N  40.0W    30 KT
 24HR VT     14/0000Z 17.2N  41.2W    25 KT...REMNANT LOW
 36HR VT     14/1200Z 17.9N  42.5W    25 KT...REMNANT LOW
 48HR VT     15/0000Z...DISSIPATED
 
$$
FORECASTER FRANKLIN
 

WTNT44 KNHC 130833
TCDAT4
TROPICAL STORM NANA DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
500 AM EDT MON OCT 13 2008
 
NANA REMAINS IN AN ENVIRONMENT OF STRONG WESTERLY SHEAR AND THE
LOW-CLOUD CENTER IS DISPLACED WELL TO THE WEST OF THE MAIN BLOB OF
DEEP CONVECTION.  AN ASCAT PASS FROM 2332 UTC MEASURED 30-35 KT
WINDS OVER THE NORTHEAST QUADRANT OF THE CYCLONE.  GIVEN THE
DISORGANIZATION OF THE SYSTEM IT IS POSSIBLE THAT...SINCE THE TIME
OF THAT OVERPASS...NANA MAY HAVE WEAKENED BELOW TROPICAL STORM
STRENGTH.  HOWEVER...BECAUSE OF THE UNCERTAINTIES...I WILL MAINTAIN
THE INTENSITY AT 35 KT FOR NOW.  THE GLOBAL MODEL'S 200 MB WIND
FORECASTS SHOWS 25-30 KT WESTERLY WINDS OVER THE AREA FOR THE NEXT
36 HOURS OR SO...SO WE DO NOT EXPECT THE SHEAR TO LESSEN
SIGNIFICANTLY IN THE NEAR FUTURE.  NANA WILL LIKELY WEAKEN AND
DEGENERATE INTO A REMNANT LOW WITHIN 24 HOURS.

INITIAL MOTION IS ESTIMATED TO BE 285/6.  NANA OR ITS REMNANT SHOULD
CONTINUE THIS GENERAL MOTION WHILE SITUATED TO SOUTH-SOUTHWEST OF A
LOW- TO MID-LEVEL HIGH PRESSURE RIDGE OVER THE EASTERN ATLANTIC. 
THE OFFICIAL FORECAST TRACK...LIKE THE PREVIOUS ONE...IS ON THE
SOUTH SIDE OF THE GUIDANCE ENVELOPE AND LEANS TOWARD THE SHALLOW
BAM TRACK...ALBEIT NOT QUITE AS FAST AS THAT GUIDANCE.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 16.6N  39.3W    35 KT
 12HR VT     13/1800Z 17.0N  40.1W    30 KT
 24HR VT     14/0600Z 17.7N  41.3W    25 KT...REMNANT LOW
 36HR VT     14/1800Z 18.5N  42.7W    25 KT...REMNANT LOW
 48HR VT     15/0600Z...DISSIPATED
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 131444
TCDAT4
TROPICAL DEPRESSION NANA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
1100 AM EDT MON OCT 13 2008
 
AS EXPECTED...WESTERLY SHEAR HAS CONTINUED TO TAKE ITS TOLL ON NANA.
THE AREAL EXTENT OF THE CONVECTION HAS DECREASED CONSIDERABLY SINCE
YESTERDAY AND THE CENTER REMAINS EXPOSED.  DVORAK INTENSITY
ESTIMATES SUPPORT DOWNGRADING NANA TO A 30-KT TROPICAL DEPRESSION. 
THE SHEAR IS NOT EXPECTED TO DECREASE DURING THE NEXT COUPLE OF
DAYS AND NANA IS FORECAST TO DEGENERATE INTO A REMNANT LOW WITHIN 
A DAY OR SO. 

THE CYCLONE HAS BEEN MOVING ON A WEST TO WEST-NORTHWESTWARD TRACK
AT ABOUT 6 KT.  NANA OR ITS REMNANTS ARE EXPECTED TO MOVE IN A
WEST-NORTHWEST MOTION TO THE SOUTH OF A LOW- TO MID-LEVEL RIDGE
OVER THE EASTERN ATLANTIC UNTIL DISSIPATION.  THE TRACK FORECAST IS
CLOSE TO THE PREVIOUS ADVISORY AND REMAINS ALONG THE SOUTHERN SIDE
OF THE GUIDANCE ENVELOPE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 16.8N  39.8W    30 KT
 12HR VT     14/0000Z 17.1N  40.6W    30 KT
 24HR VT     14/1200Z 17.6N  41.7W    25 KT...REMNANT LOW
 36HR VT     15/0000Z 18.5N  43.0W    25 KT...REMNANT LOW
 48HR VT     15/1200Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 132037
TCDAT4
TROPICAL DEPRESSION NANA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
500 PM EDT MON OCT 13 2008
 
CONVECTION ASSOCIATED WITH NANA HAS CONTINUED TO DECREASE TODAY AND
THE REMAINING SHOWER ACTIVITY IS LOCATED VERY FAR TO THE SOUTHEAST
OF THE CENTER.  STRONG WESTERLY SHEAR IS EXPECTED TO CONTINUE AND
NANA SHOULD DEGENERATE INTO A REMNANT LOW VERY SOON.  IT IS
TEMPTING TO DECLARE NANA REMNANT LOW AT THIS TIME...HOWEVER IT
SEEMS BEST TO WAIT A FEW MORE HOURS TO MAKE SURE THAT CONVECTION
DOES NOT TRY TO REFORM. 

NANA HAS BEEN MOVING A LITTLE FASTER TOWARD THE WEST-NORTHWEST
DURING THE PAST FEW HOURS...AND THE INITIAL MOTION ESTIMATE IS 
295/8 KT.  NANA OR ITS REMNANT LOW IS EXPECTED TO CONTINUE ON A
WEST-NORTHWESTWARD MOTION UNTIL DISSIPATION AND ONLY A SLIGHT
NORTHWARD ADJUSTMENT WAS REQUIRED TO THE NEW OFFICIAL TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/2100Z 17.5N  40.6W    30 KT
 12HR VT     14/0600Z 18.1N  41.7W    25 KT...REMNANT LOW
 24HR VT     14/1800Z 18.9N  42.9W    25 KT...REMNANT LOW
 36HR VT     15/0600Z 19.9N  44.3W    20 KT...REMNANT LOW
 48HR VT     15/1800Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 140232
TCDAT4
TROPICAL DEPRESSION NANA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
1100 PM EDT MON OCT 13 2008
 
NANA CONTINUES TO PRODUCE A SMALL AREA OF DEEP CONVECTION...AND THUS
IT REMAINS A TROPICAL CYCLONE A LITTLE LONGER.  STILL...WHAT LITTLE
CONVECTION REMAINS IS DISPLACED EAST OF THE LOW-LEVEL CIRCULATION
INDICATING STRONG VERTICAL SHEAR HAS NOT ABATED.  NANA IS EXPECTED
TO EVENTUALLY SUCCUMB TO THE STRONG SHEAR AND THE OFFICIAL FORECAST
CALLS FOR THE CYCLONE TO DEGENERATE INTO A REMNANT LOW WITHIN THE
NEXT 12-24 HOURS.  DISSIPATION IS EXPECTED TO FOLLOW SHORTLY
THEREAFTER.
 
NANA HAS BEEN MOVING WEST-NORTHWESTWARD OR 295/10.  A MOTION BETWEEN
WEST-NORTHWEST AND NORTHWEST IS EXPECTED UNTIL THE CYCLONE...OR ITS
REMNANTS...DISSIPATES IN ABOUT TWO DAYS.  SINCE NANA'S TRACK HINGES
ON HOW LONG IT CAN PRODUCE DEEP CONVECTION...THE OFFICIAL FORECAST
ESSENTIALLY SPLITS THE DIFFERENCE BETWEEN THE SHALLOW AND MEDIUM
BETA ADVECTION MODELS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 17.7N  41.8W    30 KT
 12HR VT     14/1200Z 18.4N  42.7W    25 KT...REMNANT LOW
 24HR VT     15/0000Z 19.3N  44.1W    25 KT...REMNANT LOW
 36HR VT     15/1200Z 20.4N  45.6W    20 KT...REMNANT LOW
 48HR VT     16/0000Z...DISSIPATED
 
$$
FORECASTER RHOME
 

WTNT44 KNHC 140832
TCDAT4
TROPICAL DEPRESSION NANA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
500 AM EDT TUE OCT 14 2008
 
NANA HASN'T BEEN PRODUCING ENOUGH CONVECTION TO QUALIFY FOR TROPICAL
CYCLONE STATUS FOR MANY HOURS...SO IT'S TIME TO SING NA NA HEY HEY
KISS HER GOODBYE. THIS WILL BE THE LAST ADVISORY ON NANA. WITH SUCH
STRONG SHEAR FORECAST IN THE PATH OF THIS SYSTEM...REGENERATION IS
EXTREMELY UNLIKELY. A MOTION BETWEEN WEST-NORTHWEST AND NORTHWEST
IS EXPECTED UNTIL THE REMNANT LOW DISSIPATES IN A COUPLE OF DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 18.4N  43.3W    25 KT...REMNANT LOW
 12HR VT     14/1800Z 19.3N  44.7W    25 KT...REMNANT LOW
 24HR VT     15/0600Z 20.5N  46.6W    20 KT...REMNANT LOW
 36HR VT     15/1800Z 21.8N  48.5W    20 KT...REMNANT LOW
 48HR VT     16/0600Z...DISSIPATED
 
$$
FORECASTER BLAKE
 

WTNT44 KNHC 140832
TCDAT4
TROPICAL DEPRESSION NANA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142008
500 AM EDT TUE OCT 14 2008
 
NANA HASN'T BEEN PRODUCING ENOUGH CONVECTION TO QUALIFY FOR TROPICAL
CYCLONE STATUS FOR MANY HOURS...SO IT'S TIME TO SING NA NA HEY HEY
KISS HER GOODBYE. THIS WILL BE THE LAST ADVISORY ON NANA. WITH SUCH
STRONG SHEAR FORECAST IN THE PATH OF THIS SYSTEM...REGENERATION IS
EXTREMELY UNLIKELY. A MOTION BETWEEN WEST-NORTHWEST AND NORTHWEST
IS EXPECTED UNTIL THE REMNANT LOW DISSIPATES IN A COUPLE OF DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 18.4N  43.3W    25 KT...REMNANT LOW
 12HR VT     14/1800Z 19.3N  44.7W    25 KT...REMNANT LOW
 24HR VT     15/0600Z 20.5N  46.6W    20 KT...REMNANT LOW
 36HR VT     15/1800Z 21.8N  48.5W    20 KT...REMNANT LOW
 48HR VT     16/0600Z...DISSIPATED
 
$$
FORECASTER BLAKE
 

