Tropical Storm Melissa

[Somerset Squall]

TD14 has formed to the southwest of the Cape Verde Islands. Convection is nice and deep and concentrated over the center and the depression is set to strengthen as it moves northwestwards then northwards. The northwards motion will eventually take it over higher shear and lower sea temps which should induce weakening.

TROPICAL DEPRESSION FOURTEEN DISCUSSION NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL142007

1100 AM EDT FRI SEP 28 2007

SATELLITE IMAGES...MICROWAVE DATA AND SHIP OBSERVATIONS INDICATE

THAT THE AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE NEAR

THE CAPE VERDE ISLANDS HAS DEVELOPED INTO A TROPICAL DEPRESSION.

THE CYCLONE HAS DEEP ORGANIZED CONVECTION NEAR THE CENTER WITH WELL

ESTABLISHED OUTFLOW. A SHIP LOCATED JUST TO THE NORTH OF THE CENTER

REPORTED 29 KNOTS. BASED ON THE ABOVE INFORMATION...THE INITIAL

INTENSITY IS SET AT 30 KNOTS. THE DEPRESSION HAS THE OPPORTUNITY TO

STRENGTHEN A LITTLE DURING THE NEXT DAY OR TWO...WHILE THE SHEAR IS

LOW.

THE DEPRESSION IS LOCATED TO THE SOUTHEAST OF A RATHER STRONG

MID-LEVEL TROUGH AND ON THE WESTERN EDGE OF A MID-LEVEL RIDGE. THIS

PATTERN WOULD FAVOR A GRADUAL TURN TOWARD THE NORTHWEST AND NORTH

THROUGH THE FORECAST PERIOD. ON THIS TRACK...THE CYCLONE SHOULD

ENCOUNTER HIGHER SHEAR AND COOLER WATERS BEYOND 48 HOURS. THIS

SHOULD RESULT IN WEAKENING. THE OFFICIAL INTENSITY FORECAST IS MUCH

LOWER THAN THE SHIPS MODEL WHICH IN FACT MAKES THE DEPRESSION A

HURRICANE IN ABOUT 2 DAYS.

NUMERICAL GUIDANCE IS LIMITED AT THIS TIME BUT WE SHOULD HAVE MORE

INFORMATION FROM GLOBAL MODELS AFTER THE 12Z RUN.

FORECAST POSITIONS AND MAX WINDS

INITIAL 28/1500Z 14.1N 26.5W 30 KT

12HR VT 29/0000Z 14.4N 27.3W 35 KT

24HR VT 29/1200Z 15.0N 28.5W 40 KT

36HR VT 30/0000Z 16.0N 30.0W 40 KT

48HR VT 30/1200Z 17.0N 31.5W 35 KT

72HR VT 01/1200Z 18.5N 34.0W 30 KT

96HR VT 02/1200Z 21.0N 36.0W 25 KT

120HR VT 03/1200Z 25.0N 36.6W 20 KT...REMNANT LOW

$$

FORECASTER AVILA

Edited September 28, 2007 by Somerset Squall

[Somerset Squall]

TD14 has improved overnight and has been upgraded to Tropical Storm Melissa. Melissa has dipped south of the really strong shear and could strengthen a little as it heads west-northwest. However, ferocious shear is forecast to disspate Melissa in around 3-4days.

TROPICAL STORM MELISSA DISCUSSION NUMBER 4

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL142007

500 AM EDT SAT SEP 29 2007

DEEP CONVECTION HAS BEEN ON THE INCREASE DURING THE PAST SEVERAL

HOURS. 0319Z MICROWAVE IMAGERY INDICATED THAT THE CIRCULATION

CENTER WAS UNDER THE WESTERN PORTION OF THE CONVECTIVE CANOPY...BUT

SUBSEQUENT GOES IMAGES HINT THAT THE CONVECTION IS WRAPPING MORE

AROUND THE CENTER. SUBJECTIVE DVORAK INTENSITY ESTIMATES AT 06Z

WERE A CONSENSUS 30 KT...BUT OBJECTIVE ESTIMATES ARE HIGHER AND

PROVIDE THE BASIS FOR UPGRADING THE SYSTEM TO A TROPICAL STORM WITH

35 KT MAXIMUM WINDS.

IT IS CLEAR THAT THE DEPRESSION IS BARELY MOVING...BUT THE EXACT

INITIAL MOTION IS STILL UNCERTAIN...ESTIMATED TO BE 270/3. THE

CYCLONE IS EMBEDDED WITHIN VERY WEAK STEERING CURRENTS...LACKING A

SUBTROPICAL RIDGE TO ITS NORTH DUE TO A DEEP LAYER LOW PRESSURE

SYSTEM OVER THE NORTHEASTERN ATLANTIC. AS THAT LOW PROCEEDS

EASTWARD...ALL OF THE MODELS DEPICT SOME RIDGING TO GRADUALLY BUILD

BACK IN OVER THE TROPICAL EASTERN ATLANTIC...BUT THEY DO NOT AGREE

ON HOW THE TRACK OF THE DEPRESSION WILL RESPOND. THE HWRF PROVIDES

THE NORTHERNMOST SOLUTION...TAKING THE CYCLONE IMMEDIATELY

NORTHWESTWARD...WHILE THE ECMWF AND GFS ENSEMBLE MEAN ARE THE

SOUTHERN EXTREMES. IN GENERAL...THE MODELS SEEM TO HAVE SHIFTED

AGAIN TO THE LEFT...AND SO HAS THE OFFICIAL FORECAST...WHICH CALLS

FOR THE CYCLONE TO MOVE IN A GENERAL WEST-NORTHWESTWARD DIRECTION

THROUGHOUT THE FIVE-DAY PERIOD.

THE DEPRESSION CURRENTLY RESIDES IN A RELATIVELY WEAK-SHEAR

ENVIRONMENT JUST TO THE SOUTH OF A BELT OF STRONG UPPER-LEVEL

WESTERLIES. THE SHEAR WILL PROBABLY REMAIN WEAK ENOUGH TO ALLOW FOR

A LITTLE STRENGTHENING DURING THE NEXT 24-36 HOURS...BUT THEN IT

WILL BE ON THE INCREASE...ESPECIALLY BEYOND 48 HOURS WHEN

SIGNIFICANT WEAKENING IS EXPECTED. THE OFFICIAL FORECAST PEAKS AT

40 KT...SLIGHTLY HIGHER THAN ALL OF THE OBJECTIVE GUIDANCE...BUT

CALLS FOR THE DEPRESSION TO DISSIPATE IN LESS THAN FIVE DAYS IN THE

HOSTILE ENVIRONMENT THAT LIES AHEAD LATER IN THE FORECAST PERIOD.

FORECAST POSITIONS AND MAX WINDS

INITIAL 29/0900Z 14.1N 27.4W 35 KT

12HR VT 29/1800Z 14.4N 28.7W 35 KT

24HR VT 30/0600Z 14.8N 30.5W 40 KT

36HR VT 30/1800Z 15.5N 32.7W 40 KT

48HR VT 01/0600Z 16.2N 34.8W 35 KT

72HR VT 02/0600Z 17.5N 38.5W 30 KT

96HR VT 03/0600Z 19.0N 42.0W 25 KT...DISSIPATING

120HR VT 04/0600Z 21.0N 45.0W 20 KT...REMNANT LOW

$$

FORECASTER KNABB