Skip Navigation Links
NOAA NOAA United States Department of Commerce

Tropical Storm NADINE


ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM NADINE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
500 AM AST WED SEP 12 2012

NADINE CONTINUES TO BECOME BETTER ORGANIZED WITH THE FORMATION OF A
CENTRAL DENSE OVERCAST AND AN OUTER CONVECTIVE BAND IN THE
SOUTHEASTERN SEMICIRCLE. SATELLITE INTENSITY ESTIMATES ARE 45 KT
FROM SAB AND 35 KT FROM TAFB.  IN ADDITION...RECENT AUTOMATED
DVORAK INTENSITY ESTIMATES FROM CIMSS ARE NEAR 45 KT.  THE INITIAL
INTENSITY IS INCREASED TO 40 KT...AND THIS COULD BE A LITTLE
CONSERVATIVE.

THE INITIAL MOTION IS 300/15.  NADINE IS MOVING TOWARD A SIGNIFICANT
BREAK IN THE SUBTROPICAL RIDGE OVER THE CENTRAL NORTH ATLANTIC. 
THE GLOBAL MODELS FORECAST THIS BREAK TO BECOME EVEN MORE
PRONOUNCED BY 72 HR AS A DEEP-LAYER LOW PRESSURE SYSTEM FORMS NEAR
OR NORTH OF BERMUDA.  THIS EVOLUTION SHOULD STEER NADINE GENERALLY
NORTHWESTWARD FOR 36 HR OR SO...FOLLOWED BY A TURN TOWARD THE
NORTH.  THIS PART OF THE NEW FORECAST TRACK IS SIMILAR TO THE
PREVIOUS TRACK AND LIES JUST TO THE RIGHT OF THE CONSENSUS MODELS. 
AFTER 72 HR...THE SUBTROPICAL RIDGE IS FORECAST TO BUILD ALONG
20N...LEAVING NADINE IN WESTERLY OR SOUTHWESTERLY FLOW ON THE NORTH
SIDE OF THE RIDGE.  THE TRACK GUIDANCE BECOMES MORE DIVERGENT
DURING THIS PERIOD.  THE UKMET SHOWS NADINE GOING NORTHWARD AND
BECOMING ENTANGLED WITH THE DEEP-LAYER LOW...WHILE THE GFS SHOWS AN
EASTWARD MOTION.  THE OTHER DYNAMICAL MODELS ARE SPREAD BETWEEN
THESE EXTREMES.  THIS PORTION OF THE NEW FORECAST TRACK IS SHIFTED
A LITTLE NORTH OF THE PREVIOUS TRACK...BUT LIES TO THE SOUTH OF THE
CONSENSUS MODELS AND THE CENTER OF THE TRACK GUIDANCE ENVELOPE. 
OVERALL...THE NEW FORECAST TRACK IS IN BEST AGREEMENT WITH THE
FLORIDA STATE SUPERENSEMBLE.

NADINE IS CURRENTLY IN AN ENVIRONMENT OF LIGHT VERTICAL WIND SHEAR
WITH GOOD TO EXCELLENT CIRRUS OUTFLOW IN ALL DIRECTIONS.  THE
QUESTION IS HOW LONG WILL THE FAVORABLE CONDITIONS LAST?  THE SHIPS
MODEL FORECASTS WESTERLY SHEAR OF ABOUT 15 KT TO DEVELOP WITHIN 24
HR...ALTHOUGH THE SOURCE OF THIS IS NOT READILY APPARENT IN THE GFS
MODEL FIELDS.  THE SHIPS AND LGEM MODELS SHOW NADINE BECOMING A
HURRICANE IN 36-48 HR DESPITE THE SHEAR FORECAST...SO THE NEW
INTENSITY FORECAST DOES LIKEWISE.  THERE IS AN ALTERNATIVE SCENARIO
FOR THIS PORTION OF THE INTENSITY FORECAST...WHICH IS THE SHEAR
DOES NOT OCCUR AND NADINE RAPIDLY STRENGTHENS.  THIS IS SOMEWHAT
SUPPORTED BY THE RAPID INTENSIFICATION INDEX OF THE SHIPS MODEL...
WHICH SHOWS ABOUT A 40 PERCENT CHANCE OF RAPID INTENSIFICATION
DURING THE NEXT 24 HOURS.  REGARDLESS OF WHAT HAPPENS IN THE SHORT
TERM...FROM 72-120 HR NADINE IS LIKELY TO ENCOUNTER AT LEAST 20-25
KT OF WESTERLY SHEAR NORTH OF THE SUBTROPICAL RIDGE AXIS...WHICH
SHOULD STOP INTENSIFICATION AND START A WEAKENING TREND.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0900Z 18.6N  46.6W   40 KT  45 MPH
 12H  12/1800Z 19.7N  48.5W   50 KT  60 MPH
 24H  13/0600Z 21.4N  50.6W   60 KT  70 MPH
 36H  13/1800Z 23.3N  52.6W   65 KT  75 MPH
 48H  14/0600Z 25.4N  53.8W   70 KT  80 MPH
 72H  15/0600Z 29.0N  54.0W   75 KT  85 MPH
 96H  16/0600Z 31.0N  51.0W   70 KT  80 MPH
120H  17/0600Z 32.5N  46.5W   65 KT  75 MPH
 
$$
FORECASTER BEVEN
 
NNNN