Prognostic Meteorological Discussion
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FXCA20 KWBC 311834
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT FRI JUL 31 2015

DISCUSSION FROM JUL 31/12 UTC: SEASONAL MID-UPPER RIDGE IS
ESTABLISHED OVER TEXAS AND DOMINATES MOST OF NORTHERN MEXICO.
ACTIVITY IS PRIMARILY BEING CONSTRAINED TO THE WEST COAST AND
SIERRA MADRE OCCIDENTAL WHERE CONVECTIVE INSTABILITY WILL REMAIN
HIGH THROUGH THE CYCLE. A BROAD AND WEAK TUTT LIES TO THE
SOUTHEAST OF THE RIDGE OVER THE GULF OF HONDURAS AND INTO THE GULF
OF TEHUANTEPEC. THROUGH SATURDAY...TUTT WILL STIMULATE DIURNAL
CONVECTION ACROSS OAXACA. THIS WILL LEAD TO MAXIMA OF 15-20MM/DAY.
BY SATURDAY INTO SUNDAY EXPECTING AN INCREASE IN ACTIVITY ACROSS
CENTRAL/NORTHEASTERN MEXICO AS A MOISTER AND UNSTABLE AIRMASS
ARRIVES FROM THE NORTHERN GULF OF MEXICO. THIS WILL LEAD TO MAXIMA
OF 15MM/DAY IN PARTS OF NORTHERN MEXICO. TO THE SOUTHWEST
EXPECTING MAXIMA OF 20-30MM/DAY IN DIURNAL CONVECTION AND
VENTILATION IN THE NORTHERN PERIPHERY OF THE TUTT. TUTT EFFECTS ON
CONVECTION WILL PEAK DURING SUNDAY AFTERNOON AS IT INTERACTS WITH
MOIST AND UNSTABLE AIRMASS IN SOUTHWESTERN MEXICO...AND WITH
WESTERLY LOW-LEVEL WINDS ALONG THE PACIFIC COAST. THIS WILL LEAD
TO STRONG CONVECTION BETWEEN  SOUTHERN
SINALOA/JALISCO/AGUASCALIENTES SOUTH INTO MICHOACAN/COLIMA WHERE
EXPECTING MAXIMA OF 40-80MM/DAY.

VARIABLE CONDITIONS ARE EXPECTED IN CENTRAL AMERICA UNDER THE
INFLUENCE OF PASSING TROPICAL WAVE AND A TUTT TO THE NORTH. TUTT
WILL CENTER OVER THE GULF OF HONDURAS ON FRIDAY TO RETROGRESS INTO
NORTHERN GUATEMALA ON SATURDAY. BY THIS TIME...VENTILATION IN THE
SOUTHEASTERN PERIPHERY OF THE TUTT WILL ENTER IN PHASE WITH
INSTABILITY ASSOCIATED WITH ARRIVING TROPICAL WAVE. THIS WILL LEAD
TO MODERATE RAINFALL AMOUNTS IN HONDURAS/NICARAGUA/COSTA RICA.
EXPECTING MAXIMA OF 20-40MM/DAY IN SCATTERED THUNDERSTORMS. THIS
VENTILATION/INSTABILITY INTERACTION WILL MEANDER WESTWARD
FOLLOWING BOTH TUTT AND TROPICAL WAVE TO ENHANCE ACCUMULATIONS IN
GUATEMALA/EL SALVADOR/BELIZE WHERE EXPECTING MAXIMA OF 25-50MM/DAY
ON SUNDAY. THE PATTERN IN SOUTHERN CENTRAL AMERICA/NORTHWESTERN
COLOMBIA WILL BE MORE PERSISTENT IN ASSOCIATION WITH THE ITCZ AND
PLENTIFUL MOISTURE AND INSTABILITY. EXPECTING ACCUMULATIONS IN THE
ORDER OF 10-15MM/DAY AND MAXIMA OF 20-35MM/DAY IN SCATTERED
CONVECTION...WITH AMOUNTS INCREASING TO MAXIMA OF 20-45MM/DAY
DURING SUNDAY ACROSS EASTERN PANAMA/WESTERN COLOMBIA.

ACTIVE CONVECTION IN THE FAR NORTHERN BAHAMAS WILL CONTINUE MOVING
OFFSHORE LEADING TO ISOLATED MAXIMA OF 15-25MM/DAY THROUGH EARLY
SATURDAY. OTHERWISE...A TUTT CENTERS OVER THE ISLANDS AND IS
FORECAST TO MEANDER SOUTHWESTWARD THROUGH THE CYCLE TO CENTER OVER
SOUTHEASTERN CUBA DURING SUNDAY AFTERNOON. THIS WILL LEAD TO A
GRADUAL INCREASE IN DIURNAL CONVECTION IN CUBA WITH MAXIMA
INCREASING TO 15-20MM/DAY BY SUNDAY INTO MONDAY. OVER THE
BAHAMAS...ISOLATED SHOWERS AND THUNDERSTORMS WILL DOMINATE THROUGH
THE CYCLE BUT ACCUMULATIONS ARE TO LIMIT TO MAXIMA OF 15MM/DAY.

A TRANSIENT SLIGHTLY WETTER PATTERN WILL DOMINATE THE GREATER
ANTILLES...FIRST UNDER THE INFLUENCE OF THE NORTHERN TIER OF A
TROPICAL WAVE AND THEN UNDER THE INFLUENCE OF WEAK PERTURBATIONS
IN THE TRADES AND TUTT ALOFT. STILL...RAINFALL AMOUNTS WILL BE
LIMITED TO MAXIMA OF 15MM/DAY. EXPECTING ISOLATED MAXIMA OF
15-25MM/DAY OVER JAMAICA DURING SATURDAY IN ASSOCIATION WITH
PASSING TROPICAL WAVE. OTHERWISE CONVECTION WILL BE ISOLATED AND
PRODUCE GENERALLY MAXIMA OF 10MM.

MOISTURE PLUME WILL CONTINUE ENHANCING CONVECTION ACROSS THE
SOUTHERN LESSER ANTILLES MAINLY BETWEEN GRENADA/TOBAGO NORTH INTO
ST.LUCIA WITH MAXIMA OF 15-20MM/DAY THROUGH EARLY SATURDAY.
AMOUNTS ARE TO DECREASE AFTER...TO INCREASE AGAIN DURING SUNDAY
INTO EARLY MONDAY AS A NEW TROPICAL MOISTURE PLUME SETS UP. BY
THEN...EXPECTING MAXIMA TO INCREASE TO 15-20MM/DAY ONCE AGAIN.
ELSEWHERE IN THE LESSER ANTILLES EXPECTING DRIER CONDITIONS AS
PERSISTENT SUBSIDENCE INVERSION AND LIMITED MOISTURE WILL CONTINUE
SUSTAINING UNSEASONABLE DRY PATTERN. MAXIMA WILL CONSTRAIN TO
10MM/DAY WHEREVER TRADE WIND SHOWERS OCCUR.

QUIET PATTERN ESTABLISHING IN NORTHERN SOUTH AMERICA. MOST
CONVECTION IS OCCURRING IN ASSOCIATION WITH THE ITCZ/NET.
CONVECTION WILL HOWEVER CONTINUE OCCURRING IN AN ISOLATED MANNER
AND DECREASE THROUGH THE CYCLE. THROUGH EARLY SATURDAY EXPECTING
MAXIMA OF 20-35MM/DAY IN EASTERN COLOMBIA/CENTRAL VENEZUELA.
MAXIMA IS TO DECREASE TO 15MM/DAY BY SUNDAY.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
32W      35W    38W    41W    44W    46W    49W    52W       TW
78W      82W    85W    88W    92W    95W    98W   101W       TW
93W      96W    99W   102W   105W   109W   112W   115W       TW

TROPICAL WAVE ALONG 32W IS TO CONFINE TO THE ATLANTIC ITCZ.

TROPICAL WAVE IS INITIALIZED ALONG 78W AND SOUTH OF 18N. THIS WAVE
WILL PLAY AN IMPORTANT ROLE ENHANCING CONVECTION ACROSS EASTERN
CENTRAL AMERICA DURING SATURDAY AND NORTHWESTERN CENTRAL AMERICA
DURING SUNDAY. SEE ABOVE FOR ACCUMULATIONS.

TROPICAL WAVE ALONG 93W IS EXITING INTO THE OPEN WATERS OF THE
EASTERN PACIFIC. IT WILL ENHANCE ACTIVITY ALONG SOUTHERN MEXICO
SLIGHTLY TO PRODUCE MAXIMA IN THE ORDER OF 20-30MM/DAY.

SALMON...MS (ANTIGUA AND BARBUDA)
SAMUEL...MDS (SURINAME)
GALVEZ...WPC (USA)
$$




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