417
WTPZ44 KNHC 300231
TCDEP4
TROPICAL STORM JULIETTE DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP142007
800 PM PDT SAT SEP 29 2007
SATELLITE IMAGERY SHOWS THAT THE LOW-LEVEL CENTER OF JULIETTE IS AT
LEAST PARTLY EXPOSED ON THE EAST SIDE OF A SMALL BUT PERSISTENT
CONVECTIVE CLUSTER. SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM
TAFB AND 35 KT FROM SAB. SINCE THE SYSTEM HAS CHANGED LITTLE IN
APPEARANCE OVER THE PAST 6 HR...THE INITIAL INTENSITY REMAINS 35
KT. THE STORM IS EXPERIENCING 15-20 KT OF EASTERLY VERTICAL WIND
SHEAR...WHICH IS ALLOWING GOOD CIRRUS OUTFLOW IN THE WESTERN
SEMICIRCLE AND NONE IN THE EASTERN SEMICIRCLE.
JULIETTE HAS JUMPED A BIT NORTH OF THE PREVIOUS FORECAST TRACK AS
THE 6 HR MOTION FROM 18Z-00Z WAS 355/4. SINCE THEN...THE STORM
APPEARS TO BE MOVING 335/7. THE SYSTEM IS ON THE SOUTHWEST SIDE OF
A MID/UPPER-LEVEL RIDGE OVER MEXICO...WHICH THE LARGE-SCALE MODELS
FORECAST WILL PERSIST THROUGH THE FORECAST PERIOD. THIS SHOULD
STEER JULIETTE IN A GENERAL NORTH-NORTHWESTWARD DIRECTION FOR AS
LONG AS THE CYCLONE RETAINS VERTICAL DEPTH. THE MODEL GUIDANCE IS
TIGHTLY CLUSTERED FOR THE FIRST 36-48 HR...THEN DIVERGES BETWEEN A
WESTWARD TURN AND A NORTH-NORTHEASTWARD TURN. THE NEW FORECAST
TRACK IS SHIFTED TO THE RIGHT OF THE PREVIOUS TRACK BASED ON THE
INITIAL POSITION AND MOTION...BUT MAINTAINS CONTINUITY WITH THE
PREVIOUS FORECAST BY CALLING FOR A WESTWARD TURN AS JULIETTE
WEAKENS OVER COOLER WATERS.
THE LARGE-SCALE MODELS FORECAST EASTERLY TO SOUTHEASTERLY SHEAR TO
PERSIST OR INCREASE DURING THE NEXT 72 HR. THIS WILL ALLOW ONLY
MODEST STRENGTHENING BEFORE JULIETTE REACHES COOLER WATERS IN 36-48
HR...AND PROBABLY SPEED THE WEAKENING THEREAFTER. THE INTENSITY
FORECAST CALLS FOR 24 HR OF STRENGTHENING TO A PEAK INTENSITY OF 45
KT...FOLLOWED BY WEAKENING TO A REMNANT LOW IN 96 HR. MUCH OF THE
MODEL GUIDANCE CALLS FOR AN EARLIER DISSIPATION...SO IT IS POSSIBLE
JULIETTE WILL NOT LAST AS LONG AS FORECAST.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/0300Z 16.9N 112.1W 35 KT
12HR VT 30/1200Z 18.2N 112.7W 40 KT
24HR VT 01/0000Z 20.0N 113.8W 45 KT
36HR VT 01/1200Z 21.3N 114.6W 40 KT
48HR VT 02/0000Z 22.0N 115.4W 35 KT
72HR VT 03/0000Z 22.5N 116.5W 25 KT...DISSIPATING
96HR VT 04/0000Z 22.5N 117.5W 20 KT...REMNANT LOW
120HR VT 05/0000Z...DISSIPATED
$$
FORECASTER BEVEN
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