WTNT41 KNHC 280306
TCDAT1
TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL162007
1100 PM EDT SAT OCT 27 2007
 
THE AREA OF LOW PRESSURE IN THE CARIBBEAN SEA HAS DEVELOPED ENOUGH
ORGANIZED CONVECTION TO BE CLASSIFIED AS A TROPICAL
DEPRESSION...WITH A LARGE CONVECTIVE MASS TO THE EAST AND NORTHEAST
OF THE PARTLY EXPOSED LOW-LEVEL CENTER.  SATELLITE INTENSITY
ESTIMATES ARE 30 KT FROM TAFB AND 25 KT FROM SAB...WHILE QUIKSCAT
DATA SHOWED NO RELIABLE WINDS HIGHER THAN 30 KT.  BASED ON
THIS...THE INITIAL INTENSITY IS SET AT 30 KT.  
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 290/6.  THE LARGE
CYCLONIC ENVELOPE OF THE DEPRESSION IS LOCATED SOUTH OF A
LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC...WITH AN UPPER-LEVEL
LOW OVER HAITI AND SURFACE TROUGHS OVER THE NORTHWESTERN CARIBBEAN
AND GULF OF MEXICO.  THE LARGE-SCALE MODELS GENERALLY FORECAST THE
ATLANTIC RIDGE TO GRADUALLY WEAKEN...WITH A MID/UPPER-LEVEL
SHORTWAVE TROUGH MOVING INTO THE SOUTHEASTERN UNITED STATES BY
96-120 HR.  THE TRACK GUIDANCE RESPONDS TO THIS EVOLUTION WITH A
RANGE OF POSSIBILITIES.  THE UKMET KEEPS THE SYSTEM SOUTH OF CUBA
BY 120 HR...WHILE THE NOGAPS FORECASTS IT TO REACH THE SOUTHEASTERN
GULF OF MEXICO BY THAT TIME.  THE GFS AND ECMWF FORECAST THE
CYCLONE TO TURN NORTHWARD BY 72-96 HR...THEN EITHER RECURVE OR
RE-FORM NORTHEASTWARD INTO THE NORTHERN BAHAMAS.  THE GFDL AND THE
HWRF CALL FOR A TRACK ACROSS HAITI AND THE CENTRAL BAHAMAS INTO THE
ATLANTIC.  THE TRACK FORECAST IS FURTHER COMPLICATED BY THE
GFS...ECMWF...AND NOGAPS SHOWING THE SEPARATION OF THE LOW-LEVEL
AND MID-LEVEL CENTERS BY 96-120 HR DUE TO SHEAR.  THE TRACK
FORECAST IS DOWN THE MIDDLE OF THIS SPREAD...WITH A NORTHWESTWARD
MOTION THROUGH 72 HR FOLLOWED BY A SLOW RECURVATURE INTO THE
WESTERLIES.  IT IS IN BEST AGREEMENT WITH THE GFS AND ECMWF.
 
THE COMBINATION OF THE LARGE SIZE OF THE DEPRESSION AND VERTICAL
WIND SHEAR FROM THE UPPER-LEVEL LOW SHOULD SLOW DEVELOPMENT DURING
THE FIRST 36 HR OR SO.  AFTER THAT...THE LARGE-SCALE MODELS BUILD A
LARGE UPPER-LEVEL ANTICYCLONE OVER THE WESTERN CARIBBEAN THAT COULD
PRODUCE A MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING...IF THE
CYCLONE IS UNDER IT RATHER THAN NORTH OF IT AS CURRENTLY FORECAST. 
THE GFDL AND HWRF MAKE THE SYSTEM A HURRICANE OVER THE ATLANTIC
DESPITE STRONG SHEAR.  DUE TO THE UNCERTAINTY...THE INTENSITY
FORECAST CALLS FOR GRADUALLY STRENGTHENING THROUGH 72 HR...BELOW
THAT OF THE SHIPS...GFDL..AND HWRF.  AFTER 72 HR...LITTLE CHANGE IN
STRENGTH IS FORECAST DUE TO A COMBINATION OF LAND INTERACTION AND
INCREASING SHEAR ALONG THE FORECAST TRACK.

BOTH THE TRACK AND INTENSITY FORECASTS HAVE GREATER THAN NORMAL
UNCERTAINTY AT THIS TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0300Z 15.9N  71.5W    30 KT
 12HR VT     28/1200Z 16.6N  72.6W    35 KT
 24HR VT     29/0000Z 17.7N  74.2W    40 KT
 36HR VT     29/1200Z 18.8N  76.0W    45 KT
 48HR VT     30/0000Z 19.6N  77.6W    50 KT
 72HR VT     31/0000Z 21.0N  80.0W    60 KT
 96HR VT     01/0000Z 22.5N  80.0W    60 KT...INLAND
120HR VT     02/0000Z 25.0N  78.5W    60 KT
 
$$
FORECASTER BEVEN
 

WTNT41 KNHC 280855
TCDAT1
TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL162007
500 AM EDT SUN OCT 28 2007
 
THE CENTER OF THE DEPRESSION IS DIFFICULT TO IDENTIFY ON INFRARED OR
NIGHT-VIS IMAGERY.  RECENT MICROWAVE PASSES ALSO ARE NOT
CONCLUSIVE...BUT SUGGEST THAT THE DEPRESSION IS CONTINUING ON ITS
PREVIOUS TRACK...WITH AN INITIAL MOTION ESTIMATE OF 300/6.  DEEP
CONVECTION NEAR THE CENTER LACKS ANY APPRECIABLE BANDING...AND A
RECENT ASCAT PASS DOES NOT INDICATE THAT ANY STRENGTHENING HAS
OCCURRED.  WITH AN UPPER-LEVEL LOW IMPARTING WESTERLY SHEAR OVER THE
CYCLONE...THE ENVIRONMENT DOES NOT FAVOR MUCH DEVELOPMENT IN THE
SHORT TERM.  GLOBAL MODELS SUGGEST THAT THE UPPER LOW WILL WASH OUT
IN A COUPLE OF DAYS...LEAVING THE CYCLONE UNDER A LESS HOSTILE
UPPER PATTERN...BUT THE ENVIRONMENT NEVER APPEARS TO BE IDEAL FOR
DEVELOPMENT.  IN ADDITION...THERE IS AMPLE OPPORTUNITY FOR LAND
INTERACTIONS OVER THE NEXT FEW DAYS THAT WOULD HINDER
STRENGTHENING.  THE GFDL AND HWRF INTENSITY FORECASTS...WHICH
SUGGEST A MORE VERTICALLY-CONNECTED CYCLONE THAN APPEARS TO
EXIST...ARE LARGELY BEING DISCOUNTED.  THE OFFICIAL FORECAST IS IN
GOOD AGREEMENT WITH THE LGEM.

TRACK FORECASTING OF WEAK SYSTEMS IN SHEARED ENVIRONMENTS IS
PARTICULARLY CHALLENGING...AND THE AVAILABLE MODEL GUIDANCE
REFLECTS THIS UNCERTAINTY.  THE PRIMARY SYNOPTIC PLAYERS ARE THE
UPPER-LOW ALREADY MENTIONED...A MID-LEVEL RIDGE OVER THE
SOUTHWESTERN ATLANTIC...A BROAD LOW-LEVEL CYCLONIC ENVELOPE
SURROUNDING THE DEPRESSION...AND A MID- TO UPPER-LEVEL SHORTWAVE
TROUGH FORECAST TO MOVE INTO THE SOUTHEASTERN UNITED STATES IN ABOUT
FOUR DAYS.  THE GFDL AND HWRF LIE ON THE EASTERN EDGE OF THE
GUIDANCE ENVELOPE...TAKING THE CYCLONE ACROSS HISPANIOLA AND
THROUGH THE CENTRAL BAHAMAS IN 2-3 DAYS.  THIS APPEARS TO RESULT
FROM AN OVERLY STRONG INTERACTION WITH THE UPPER LOW.  ANOTHER
SCENARIO IS FOR THE DEPRESSION TO TURN TEMPORARILY TO THE NORTHWEST
IN RESPONSE TO THE UPPER-LOW...BUT THEN BEND BACK TO THE
WEST-NORTHWEST IN A COUPLE DAYS AROUND THE BROAD LOW-LEVEL
GYRE...BEFORE BEING DEFLECTED NORTHEASTWARD WHEN THE SHORT WAVE
ARRIVES ON DAYS 4-5.  THIS IS THE SOLUTION OF THE UKMET.  ON THE
LEFT SIDE OF THE GUIDANCE ENVELOPE ARE THE BAM MODELS AND THE
GFS...WHICH TAKE A RELATIVELY WEAK AND ILL-DEFINED LOW
WEST-NORTHWESTWARD UNTIL THE MID-LATITUDE SHORT WAVE ARRIVES AND
SLOWLY RECURVES THE CYCLONE.  THIS IS THE SOLUTION FAVORED BY THE
OFFICIAL FORECAST.  IT IS WORTH REITERATING THAT THE UNCERTAINTY
LEVEL IS HIGH.
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0900Z 16.2N  72.1W    30 KT
 12HR VT     28/1800Z 17.0N  73.2W    30 KT
 24HR VT     29/0600Z 17.9N  74.6W    35 KT
 36HR VT     29/1800Z 18.9N  76.3W    35 KT
 48HR VT     30/0600Z 19.7N  77.7W    40 KT
 72HR VT     31/0600Z 21.5N  80.0W    50 KT
 96HR VT     01/0600Z 23.0N  79.0W    40 KT
120HR VT     02/0600Z 25.0N  77.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER FRANKLIN
 

WTNT41 KNHC 281459
TCDAT1
TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL162007
1100 AM EDT SUN OCT 28 2007
 
THE APPEARANCE OF THE CYCLONE ON SATELLITE IMAGERY HAS BECOME FAIRLY
IMPRESSIVE...FOR A TROPICAL DEPRESSION.  INFRARED CLOUD TOP
TEMPERATURES ARE QUITE COLD OVER A LARGE AREA...AND THERE IS EVEN A
BAND EXTENDING SOUTHWARD...GIVING THE SYSTEM A COMMA SHAPE.  THE
DEPRESSION CERTAINLY SEEMS ON THE VERGE OF BECOMING A TROPICAL
STORM...BUT THE AVAILABLE DATA AT THE MOMENT ARE INCONCLUSIVE AS TO
WHETHER OR NOT THIS HAS YET OCCURRED.  THE EASTERN EDGE OF A
QUIKSCAT PASS FROM ABOUT 1115Z ONLY CAUGHT A PORTION OF THE
CIRCULATION AND DID NOT RETRIEVE ANY RELIABLE WINDS OF TROPICAL
STORM FORCE.  DVORAK INTENSITY ESTIMATES ARE UNCHANGED SINCE 06Z
AND THE ADVISORY INTENSITY REMAINS 30 KT.  AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO DEPART SHORTLY TO
INVESTIGATE THE DEPRESSION AND GIVE US A BETTER HANDLE ON THE
INTENSITY.
 
THE DEPRESSION CONTINUES WEST-NORTHWESTWARD TO THE SOUTH OF A LOW-
TO MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC.  ALL OF THE MODELS
FORECAST THE MID-LEVEL RIDGE TO WEAKEN DURING THE NEXT DAY OR TWO AS
A SHORT WAVE TROUGH MOVES INTO THE SOUTHEASTERN UNITED STATES AND
HEIGHTS RISE FARTHER TO THE EAST.  SOME OF THE TRACK MODELS...IN
PARTICULAR THE GFDL AND HWRF...RESPOND TO THIS PATTERN CHANGE BY
FORECASTING A RELATIVELY QUICK RECURVATURE OUT OF THE CARIBBEAN VIA
EASTERN CUBA.  MOST OF THE GLOBAL MODELS...HOWEVER...FORECAST A
SLOWER MOTION GENERALLY TOWARD THE WEST-NORTHWEST AND KEEP THE
CYCLONE SOUTH OF CUBA BETWEEN 3 AND 5 DAYS.  THE NEW OFFICIAL TRACK
FORECAST FOLLOWS THE SAME PATH AS IN THE PREVIOUS ADVISORY...BUT AT
A SLIGHTLY SLOWER PACE IN DEFERENCE TO THE GLOBAL MODELS.
 
THE HUGE UNCERTAINTIES IN THE TRACK FORECAST ALSO TRANSLATE INTO A
VERY CHALLENGING INTENSITY PROGNOSIS.  IF THE OFFICIAL TRACK WERE
TO VERIFY PERFECTLY...THE CIRCULATION CENTER WOULD REMAIN OVER
WATER FOR ABOUT FOUR MORE DAYS BEFORE CROSSING CUBA.  SINCE THE
UPPER-LEVEL LOW CURRENTLY NEAR THE DEPRESSION IS FORECAST TO
DISSIPATE WITHIN A DAY OR TWO...THE RESULTING DECREASE IN WIND
SHEAR WOULD PROBABLY ALLOW FOR SOME STRENGTHENING.  IF...HOWEVER...
THE CYCLONE GOES FARTHER NORTH AND EAST...LAND INTERACTION WOULD
OCCUR SOONER AND PERHAPS FOR A LONGER PERIOD AND COULD LIMIT
STRENGTHENING.  FINALLY...A TRACK FARTHER SOUTH AND WEST COULD
PLACE THE CYCLONE WITHIN A WEAKER-SHEAR ENVIRONMENT AND ALLOW FOR
MORE STRENGTHENING THAN FORECAST.  IF THE CYCLONE DOES RECURVE
TOWARD THE WESTERN ATLANTIC IN A FEW DAYS...THE UPPER-LEVEL
WESTERLIES NORTH OF CUBA ARE FORECAST BY THE GLOBAL MODELS TO BE
STRONG AND NOT CONDUCIVE FOR THE CYCLONE TO STRENGTHEN...AT LEAST
NOT AS A TROPICAL CYCLONE.  THE NEW OFFICIAL INTENSITY FORECAST
PEAKS JUST A LITTLE HIGHER THAN THE PREVIOUS ADVISORY AND IS
BETWEEN THE LGEM AND SHIPS SOLUTIONS...AND MUCH LESS THAN THE GFDL
AND HWRF FORECASTS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/1500Z 16.5N  72.5W    30 KT
 12HR VT     29/0000Z 17.0N  73.4W    35 KT
 24HR VT     29/1200Z 18.0N  75.0W    40 KT
 36HR VT     30/0000Z 19.0N  76.5W    45 KT
 48HR VT     30/1200Z 20.0N  78.0W    50 KT
 72HR VT     31/1200Z 21.0N  79.5W    55 KT
 96HR VT     01/1200Z 22.0N  80.0W    50 KT...INLAND OVER CUBA
120HR VT     02/1200Z 24.0N  78.0W    45 KT...OVER WATER
 
$$
FORECASTER KNABB
 

