TROPICAL DEPRESSION NINETEEN DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192012
500 PM AST MON OCT 22 2012
DEEP CONVECTION ASSOCIATED WITH THE LOW PRESSURE SYSTEM OVER THE CENTRAL ATLANTIC HAS BECOME A BIT MORE ORGANIZED DURING THE DAY...AND BOTH TAFB AND SAB PROVIDED 1800 UTC DVORAK ESTIMATES OF T2.0. ADVISORIES ARE THEREFORE BEING INITIATED ON TROPICAL
DEPRESSION NINETEEN WITH 30-KT WINDS. THE DEPRESSION IS FORECAST TO BE IN AN ENVIRONMENT OF LIGHT UPPER-LEVEL WINDS FOR THE NEXT DAY OR TWO...SO SOME STRENGTHENING APPEARS LIKELY. AFTER 48 HOURS...
THE VERTICAL SHEAR IS EXPECTED TO INCREASE TO AT LEAST 30 KT...AND THE CYCLONE WILL BE MOVING OVER SUB-26C WATERS. IN ADDITION...THE GLOBAL MODELS ARE INDICATING THAT THE SYSTEM IS LIKELY TO BECOME A
FRONTAL LOW...AND A WEAK ONE AT THAT...BY 72 HOURS. THEREFORE... THE NHC INTENSITY FORECAST SHOWS A PEAK IN INTENSITY OCCURRING IN 48 HOURS WITH STEADY WEAKENING THEREAFTER. INTERESTINGLY...THE SHIPS MODEL BRINGS THE SYSTEM TO NEAR HURRICANE STRENGTH ON DAYS 3 THROUGH 5 EVEN IN THE FACE OF MORE HOSTILE CONDITIONS. GIVEN THAT THE GLOBAL MODELS DO NOT SUGGEST THAT EXTRATROPICAL LOW WILL FEED OFF OF BAROCLINIC ENERGY...THE NHC FORECAST LEANS LOWER THAN MOST OF THE HURRICANE MODELS. DISSIPATION IS ANTICIPATED BY DAY 5 WHEN THE SYSTEM IS FORECAST TO BECOME ABSORBED BY A COMPLEX AREA OF LOW PRESSURE WEST OF THE AZORES.
THE DEPRESSION IS BEING STEERED NORTHWARD ON THE EASTERN SIDE OF A MID- TO UPPER-LEVEL CUTOFF LOW...AND THE INITIAL MOTION ESTIMATE IS 350/6 KT. THE CUTOFF LOW IS EXPECTED TO WEAKEN DURING THE NEXT
COUPLE OF DAYS...AND THE TROPICAL CYCLONE SHOULD THEN BE PICKED UP BY FASTER MID-LATITUDE WESTERLIES. THERE IS NOT MUCH SPREAD IN THE TRACK GUIDANCE...AND THE OFFICIAL TRACK FORECAST IS CLOSEST TO THE GFS MODEL AND THE MODEL CONSENSUS TVCA.
FORECAST POSITIONS AND MAX WINDS