TROPICAL DEPRESSION ERIN DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013
1100 AM AST FRI AUG 16 2013

SATELLITE IMAGES INDICATE THAT ERIN HAS WEAKENED. THE STRUCTURE OF
THE CYCLONE CONSISTS OF A LOW-LEVEL CLOUD SWIRL WITH A COUPLE OF
SMALL AREAS OF CONVECTION SOUTH AND EAST OF THE CENTER. THE DVORAK
CLASSIFICATIONS HAVE FALLEN…AND ERIN IS DOWNGRADED TO A 30-KT
TROPICAL DEPRESSION FOR THIS ADVISORY. THE OBSERVED WEAKENING IS
LIKELY THE RESULT OF COOL SEA SURFACE TEMPERATURES AND STABLE AIR…
AS SEEN IN THE GOES-R PROVING GROUND AIRMASS PRODUCT. ALTHOUGH ERIN
IS EXPECTED TO MOVE OVER WARMER WATER IN A FEW DAYS…
SOUTHWESTERLY SHEAR IS ANTICIPATED TO INCREASE WHILE THE DEPRESSION
REMAINS IN A STABLE ATMOSPHERE. THE NHC INTENSITY PREDICTION CALLS
FOR LITTLE CHANGE IN STRENGTH THROUGHOUT THE FORECAST PERIOD. IT IS
POSSIBLE THAT ERIN COULD DEGENERATE TO A REMNANT LOW OR AN OPEN
TROUGH DURING THE NEXT FEW DAYS…AS SUGGESTED BY SOME OF THE MODEL
GUIDANCE.

THE DEPRESSION IS MOVING WEST-NORTHWESTWARD AT ABOUT 15 KT. THIS
GENERAL MOTION WITH SOME DECREASE IN FORWARD IS EXPECTED DURING THE
NEXT 36 HOURS WHILE THE CYCLONE FEELS SOME INFLUENCE FROM A
WEAKNESS IN THE SUBTROPICAL RIDGE. BETWEEN 36 AND 72 HOURS…LOW-
TO MID-LEVEL RIDGING IS FORECAST TO BECOME MORE PRONOUNCED TO THE
NORTH OF THE SYSTEM…CAUSING A TURN TOWARD THE WEST. BEYOND THAT
TIME…A GRADUAL TURN TO THE NORTHWEST IS PREDICTED WHEN THE WEAK
CYCLONE MOVES TOWARD ANOTHER WEAKNESS IN THE RIDGE. THE NHC TRACK
FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE
MULTI-MODEL CONSENSUS TVCA.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 16.9N 32.1W 30 KT 35 MPH
12H 17/0000Z 17.9N 34.0W 30 KT 35 MPH
24H 17/1200Z 19.1N 36.2W 30 KT 35 MPH
36H 18/0000Z 19.9N 38.2W 30 KT 35 MPH
48H 18/1200Z 20.2N 40.2W 30 KT 35 MPH
72H 19/1200Z 21.1N 44.6W 30 KT 35 MPH
96H 20/1200Z 23.5N 49.5W 30 KT 35 MPH
120H 21/1200Z 25.5N 52.5W 30 KT 35 MPH

$$
FORECASTER CANGIALOSI

INVEST 92L

SATELLITE IMAGES INDICATE THAT AN AREA OF LOW PRESSURE HAS MOVED
OFFSHORE OF THE YUCATAN PENINSULA AND OVER THE SOUTHWESTERN GULF OF
MEXICO. ALTHOUGH THE SHOWER AND THUNDERSTORM ACTIVITY IS CURRENTLY
DISORGANIZED AND LOCATED WELL TO THE EAST AND NORTHEAST OF THE LOW
CENTER…ENVIRONMENTAL CONDITIONS COULD BECOME MORE FAVORABLE FOR
DEVELOPMENT IF THE LOW MOVES TOWARD THE WEST OR WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS. INTERESTS IN THE CENTRAL AND WESTERN GULF OF MEXICO SHOULD MONITOR THE PROGRESS OF THE SYSTEM THROUGH THE WEEKEND. IF THE LOW TAKES A MORE NORTHWARD TRACK…HOWEVER…IT WOULD MOVE INTO A LESS CONDUCIVE ENVIRONMENT FOR DEVELOPMENT. THIS SYSTEM HAS A MEDIUM CHANCE…50 PERCENT…OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS…AND A HIGH CHANCE…60
PERCENT…OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 5 DAYS.
THE AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT MISSION SCHEDULED FOR
TODAY HAS BEEN CANCELLED.