Prognostic Meteorological Discussion
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FXCA20 KWBC 291646
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 PM EDT FRI MAY 29 2015

AT 15 UTC TROPICAL STORM ANDRES CENTERED NEAR 12.5N 114.6W...WITH
MAXIMUM SUSTAINED WINDS OF 60KT AND MINIMUM CENTRAL PRESSURE OF
994 HPA. THE STORM IS MOVING TO THE WEST-NORTHWEST AT 08KT. SEE
NHC BULLETIN FOR OFFICIAL FORECAST.

DISCUSSION FROM MAY 29/12 UTC: MID-LEVEL RIDGE CENTERS TO THE WEST
OF COLIMA/NAYARIT IN MEXICO. THIS IS STEERING TROPICAL STORM
ANDRES TO THE WEST-NORTHWEST. THE NHC IS FORECASTING THIS STORM TO
BECOME A HURRICANE LATER ON FRIDAY. THIS EVOLUTION IS MODULATING
THE ITCZ TO THE NORTH...YET THE ITCZ IS EXPECTED TO REMAIN FAR
OFFSHORE. STILL...CONVECTIVE INSTABILITY HAS INCREASED
SIGNIFICANTLY ACROSS MOST OF THE SOUTHWESTERN COAST OF MEXICO
WHICH WILL BE EXPERIENCING A WET PATTERN THROUGH THE WEEKEND.
EXPECTING ACCUMULATIONS OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY
THROUGH THE PERIOD. SOME ENHANCEMENT IS EXPECTED ACROSS
COLIMA/JALISCO/WESTERN MICHOACAN DURING SUNDAY INTO EARLY MONDAY
WITH ISOLATED MAXIMA OF 20-40MM/DAY.

MOISTURE TRANSPORT FROM THE PACIFIC INTO THE SIERRA MADRE
OCCIDENTAL...UNDER INTERACTION WITH BASE OF UPPER TROUGH
APPROACHING THE REGION DURING SATURDAY...WILL LEAD TO AN INCREASE
IN ACTIVITY ALONG THIS REGION. CONVECTION WILL BUILD INTO THE
MOUNTAINS OF NAYARIT/SINALOA DURING SATURDAY WITH RAINFALL MAXIMA
OF 15MM/DAY. ACTIVITY WILL BUILD FURTHER NORTH INTO THE MOUNTAINS
OF SONORA/WESTERN CHIHUAHUA DURING SUNDAY...YET EXPECTING LIGHT
ACCUMULATIONS AS MID-LEVEL RIDGE BUILDS OVER THE REGION.

NORTHEASTERN MEXICO WILL CONTINUE UNDER THE INFLUENCE OF RAPIDLY
MOVING SHORT WAVE PERTURBATIONS AND ASSOCIATED THUNDERSTORMS. A
WELL DEFINED UPPER TROUGH AND ASSOCIATED FRONT WILL ENTER THE
REGION DURING EARLY SATURDAY. ALTHOUGH THE FRONT WILL REMAIN JUST
TO THE NORTH...EXPECTING ENHANCED LOW-LEVEL MOISTURE CONVERGENCE
ESPECIALLY IN INTERACTION WITH THE MOUNTAINS. COOLER AIR ALONG
MID-UPPER TROUGH AXIS WILL ENHANCE INSTABILITY. UPPER TROUGH WILL
ALSO PROVIDE VENTILATION. THIS WILL LEAD TO A PEAK IN ACTIVITY
DURING SATURDAY INTO EARLY HOURS OF SUNDAY...WHEN EXPECTING
ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF 25-50MM WITH THE RISK
OF SEVERE CONVECTION. AMOUNTS WILL START DECREASING AFTERWARDS.

AFOREMENTIONED UPPER TROUGH WILL ALSO PLAY A ROLE IN ENHANCING
ACTIVITY ACROSS THE NORTHWESTERN CARIBBEAN/YUCATAN PENINSULA INTO
EARLY NEXT WEEK. TROUGH IS FORECAST TO DIG ACROSS LOUISIANA/GULF
COAST OF MEXICO DURING SUNDAY...AND FURTHER MORE AS IT MEANDERS
SLOWLY EASTWARD TO EXTEND ALONG THE WESTERN GULF OF
MEXICO-TEHUANTEPEC ON MONDAY. THIS WILL ENTER IN PHASE WITH
MOISTURE SURGE ARRIVING FROM THE CARIBBEAN. FURTHERMORE...THE
DEEPENING OF THE UPPER TROUGH AND VENTILATION TO THE SOUTHEAST OF
THE MAIN AXIS WILL ERODE THE CURRENT SUBSIDENCE INVERSION
ESTABLISHED OVER THE NORTHWESTERN CARIBBEAN/NORTHERN CENTRAL
AMERICA. THIS WILL LEAD TO A WET PATTERN DEVELOPING ACROSS
NORTHERN CENTRAL AMERICA/YUCATAN/GULF OF HONDURAS INTO SUNDAY AND
EARLY NEXT WEEK.

A WEAK TUTT-LOW CENTERS TO THE SOUTH OF THE CAYMAN ISLANDS AND IS
INTERACTING WITH AN EAST-WEST FETCH OF CONVECTIVE INSTABILITY THAT
EXTENDS JUST TO THE SOUTH OF CUBA. THIS WILL SUSTAIN ACTIVE
CONVECTION IN THE REGION DURING FRIDAY...WHEN EXPECTING MAXIMA OF
15-25MM/DAY OVER SOUTHEASTERN CUBA...MAXIMA OF 20-35MM/DAY ACROSS
EXTREME WESTERN CUBA...AND MAXIMA OF 15MM/DAY OVER BELIZE/EASTERN
YUCATAN. TUTT WILL GRADUALLY WEAKEN AS IT MEANDERS WESTWARD
TOWARDS THE GULF OF HONDURAS...YET LOCALLY MODERATE AMOUNTS ARE
STILL POSSIBLE. DURING SATURDAY FOCUS OF ACTIVITY WILL EXTEND INTO
NORTHEASTERN YUCATAN WHERE EXPECTING ACCUMULATIONS OF 05-10MM/DAY
AND MAXIMA OF 15-25MM/DAY. HIGHEST AMOUNTS IN THE REGION ARE TO
THEN CONCENTRATE OVER MOST OF NORTHERN YUCATAN DURING SUNDAY INTO
EARLY MONDAY.

TO THE EAST... STRONG PAIR OF TUTT LOWS EXTENDS WELL TO THE NORTH
OF THE GREATER ANTILLES NEAR 28N 61W. THESE ARE INDUCING A PAIR OF
SURFACE TROUGHS...ONE OF WHICH IS CROSSING THE CARIBBEAN EXTENDING
ACROSS HISPANIOLA INTO WESTERN VENEZUELA. ACTIVE CONVECTION IN
NORTHERN SOUTH AMERICA IS ENHANCING THE DEVELOPMENT OF THE
SUBEQUATORIAL RIDGE. AS RIDGE BUILDS WHILE TUTTS WEAKEN AND
MEANDER TO THE NORTH...EXPECTING SOUTHERN TIER OF TUTT-INDUCED
WAVE TO DETACH AND START PROPAGATING WESTWARD ACROSS THE CENTRAL
CARIBBEAN AS EARLY AS SATURDAY MORNING. PRECIPITABLE WATER
ANALYSIS SHOWS A POOL OF DEEP MOISTURE AND DEEP-LAYER CONVECTIVE
INSTABILITY SITTING OVER THE SOUTHEASTERN CARIBBEAN AND NORTHERN
COLOMBIA/VENEZUELA/GUYANA/WINDWARD ISLANDS. THIS MOISTURE POOL IS
FORECAST TO MEANDER WEST/NORTHWESTWARD THROUGH THE CYCLE...LEADING
TO A NOTICEABLE INCREASE IN CONVECTION AND ACCUMULATIONS ACROSS
THE LEEWARD ISLANDS/PUERTO RICO AND THE DOMINICAN REPUBLIC ON
FRIDAY...JAMAICA/HAITI SOUTHEASTERN CUBA AND COSTA RICA ON
SATURDAY...SOUTHEASTERN CUBA/CAYMAN ISLANDS/NICARAGUA/EASTERN
HONDURAS ON SUNDAY...AND ALL OF NORTHERN CENTRAL
AMERICA/BELIZE/YUCATAN AND WESTERN CUBA ON MONDAY. AT UPPER
LEVELS...EXPECTING AN INCREASE IN DIVERGENCE OVER THE
CENTRAL/EASTERN CARIBBEAN INTO THE NORTHEASTERN GREATER ANTILLES
TO PEAK DURING SATURDAY AND SUNDAY IN RESPONSE TO THE
INTENSIFICATION OF THE SUBEQUATORIAL RIDGE. THIS WILL INTERACT
WITH DEEP-LAYER MOISTURE TO ENHANCE THUNDERSTORMS DEVELOPMENT AND
ACCUMULATIONS. ANOTHER SIGNIFICANT FEATURE THAT WILL PLAY AN
IMPORTANT ROLE IN PRECIPITATION IS A TRADE WIND SURGE. THE SURGE
HAS SPEEDS EXCEEDING 20KT AT 950 HPA. THE EDGE OF THE SURGE WILL
EXTEND FROM SOUTHWEST TO NORTHEAST OF A LINE CROSSING
GUADELOUPE/DOMINICA BY FRIDAY EVENING...THE LEEWARD ISLANDS/VIRGIN
ISLANDS BY SATURDAY EVENING...TO EXTEND ALONG JAMAICA-SOUTHERN
HISPANIOLA-PUERTO PLATA/JUST TO THE NORTHWEST OF PUERTO RICO BY
SUNDAY EVENING. THE LEADING EDGE OF THIS SURGE WILL BE ASSOCIATED
WITH AN ENHANCEMENT OF CONVECTION DUE TO ENHANCED LOW-LEVEL
CONVERGENCE. BEHIND THE EDGE OF THIS SURGE HOWEVER...EXPECTING THE
ADVECTION OF A MUCH MORE STABLE AIRMASS THAT WILL LEAD TO A MARKED
DECREASE IN ACTIVITY AS IT MOVES FROM THE TROPICAL NORTH ATLANTIC
INTO CARIBBEAN.

IN TERMS OF ACCUMULATIONS...THROUGH EARLY SATURDAY EXPECTING
LARGEST AMOUNTS OVER PUERTO RICO AND DOMINICAN REPUBLIC WITH
MAXIMA OF 20-45MM/DAY. OVER JAMAICA/HAITI AND THE LEEWARD ISLANDS
EXPECTING MAXIMA OF 15MM/DAY. DURING SATURDAY INTO EARLY SUNDAY
EXPECTING LARGEST AMOUNTS OVER JAMAICA AND HAITI WITH MAXIMA OF
25-50MM/DAY. ACROSS PUERTO RICO/EASTERN HISPANIOLA EXPECTING STILL
MAXIMA OF 20-45MM/DAY. OVER THE LEEWARD ISLANDS EXPECTING MAXIMA
OF 15MM/DAY WITH A WEAKENING TREND AFTERWARDS. DURING SUNDAY INTO
EARLY MONDAY EXPECTING FOCUS OF STRONGEST ACTIVITY OVER JAMAICA
WITH MAXIMA OF 25-50MM/DAY. MODERATE AMOUNTS ARE ALSO EXPECTED
OVER HISPANIOLA AND SOUTHEASTERN CUBA/CAYMAN ISLANDS WITH MAXIMA
OF 20-40MM/DAY.

FURTHER SOUTH...SEASONALLY ACTIVE PATTERN OF CONVECTION IS
DOMINATING EXTREME NORTHERN SOUTH AMERICA AIDED BY THE UPPER
DIVERGENT PHASE OF THE MADDEN-JULIAN OSCILLATION. ACTIVITY IS
ORGANIZING ALONG THE ITCZ AND EMBEDDED PERTURBATIONS...WHICH WILL
ROUGHLY EXTEND OVER THE NORTHERN GUIANAS/NORTH-CENTRAL VENEZUELA
INTO NORTH-CENTRAL COLOMBIA THROUGH THE CYCLE. DURING
FRIDAY...TROUGH PROPAGATING ALONG THE ITCZ WILL ENHANCE ACTIVITY
ACROSS FRENCH GUYANA AND SURINAME TO PRODUCE ACCUMULATIONS OF
10-15MM/DAY AND MAXIMA OF 20-40MM/DAY. ANOTHER REGION OF ENHANCED
CONVECTION WILL CONCENTRATE ACROSS EASTERN/CENTRAL VENEZUELA INTO
TRINIDAD WITH MAXIMA OF 25-50MM/DAY. A THIRD REGION OF ENHANCED
ACTIVITY WILL CONCENTRATED OVER NORTHWESTERN VENEZUELA INTO
NORTHERN COLOMBIA WITH MAXIMA OF 40-80MM/DAY. DURING SATURDAY INTO
EARLY SUNDAY ACTIVITY WILL CONCENTRATE ALONG THREE TROUGHS. ONE
WILL EXTEND ACROSS SURINAME TO ENHANCE DEVELOPMENT AND PRODUCE
MAXIMA OF 20-35MM/DAY IN NORTHERN SURINAME AND FRENCH GUIANA. THE
SECOND TROUGH WILL EXTEND ALONG NORTHEASTERN VENEZUELA TO PRODUCE
MAXIMA OF 25-50MM/DAY. A THIRD REGION OF ENHANCED ACTIVITY WILL
EXTEND OVER THE ANDES OF COLOMBIA INTO LAKE MARACAIBO/WESTERN
VENEZUELA WITH MAXIMA OF 25-50MM/DAY. ON SUNDAY INTO
MONDAY...EXPECTING A SLIGHT DECREASE IN MAXIMA. ENHANCED ACTIVITY
WILL CONCENTRATE OVER THE NORTHERN GUIANAS...BUT ESPECIALLY TO THE
WEST ACROSS MOST OF VENEZUELA/GUYANA WHERE EXPECTING MAXIMA OF
25-50MM/DAY. ACROSS SOUTHERN CENTRAL AMERICA...EXPECTING A GRADUAL
INCREASE IN ACTIVITY FROM EAST TO WEST WITH AMOUNTS INCREASING
FROM MAXIMA OF 15-20MM/DAY TO 20-35MM/DAY BY MONDAY MORNING.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE

CRAIG...TTMS (TRINIDAD AND TOBAGO)
SAMUEL...MDS (SURINAME)
GALVEZ...WPC (USA)


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