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Tropical Discussion
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EST FRI JAN 23 2015

DISCUSSION FROM JANUARY 23/00UTC: CONSISTENT WITH PREVIOUS
FORECASTS EXPECTING DEEP POLAR TROUGH TO MIGRATE ACROSS THE
CENTRAL TO THE EASTERN USA THROUGH SATURDAY EVENING...THEN LIFT TO
THE NORTHEAST AS IT ENTERS THE WESTERN ATLANTIC. A SECONDARY
VORTEX IS TO CLOSELY FOLLOW...EXPECTED TO PULL ACROSS THE EASTERN
USA EARLY ON MONDAY...THEN RAPIDLY DEEPEN ACROSS THE WESTERN
ATLANTIC TO THE NORTHERN CARIBBEAN ISLES. AT LOW
LEVELS...DEEPENING POLAR LOW OVER THE SOUTHEAST USA EXTENDS A
FRONT ACROSS THE GULF TO SOUTHERN VERACRUZ. THIS ALSO FAVORS
STRONG BOUNDARY LAYER WINDS OF 25-30KT ACROSS THE WESTERN GULF
INTO THE SOUTHERN STATES OF MEXICO. THROUGH FRIDAY EVENING THIS IS
TO DRIVE THE FRONT EAST AND SOUTH...WITH AXIS TO MOVE ACROSS
NORTHERN FLORIDA/GEORGIA TO CHIAPAS IN SOUTHERN MEXICO. ON
SATURDAY MORNING THE FRONT IS TO EXTEND ACROSS CENTRAL/SOUTHERN
FLORIDA-THE YUCATAN TO SOUTHERN MEXICO. DURING THE EVENING...IT
MOVES TO THE NORTHWEST BAHAMAS-WESTERN CUBA-BELIZE TO SOUTHERN
MEXICO. EARLY ON SUNDAY MORNING THE FRONT CONTINUES INTO THE
CENTRAL BAHAMAS-CENTRAL CUBA...TRAILING TO THE GULF OF
HONDURAS/BELIZE. THE FRONT IS TO THEN MEANDER OVER THE SOUTHEAST
BAHAMAS-CENTRAL/EASTERN CUBA WHILE TRAILING TO THE NORTHWEST
CARIBBEAN EARLY ON MONDAY. LATER ON MONDAY...THE FRONT IS TO
STRENGTHEN AS A SECONDARY BOUNDARY SURGES ACROSS THE SOUTHEAST USA
TO THE BAHAMAS. MEANWHILE...THE SURGING FRONT IS TO TRIGGER
SCATTERED CONVECTION ACROSS VERACRUZ WITH RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM. FRONTAL NORTHERLIES OVER
SOUTHERN MEXICO ARE TO THEN FAVOR MODERATE TO HEAVY RAINFALL
AMOUNTS...WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 35-70MM.
THROUGH SUNDAY MORNING CONVECTION BUILDS EAST ACROSS GUATEMALA TO
NORTHWEST HONDURAS...WHERE WE EXPECT RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM. AS IT ENTERS THE NORTHWEST
BAHAMAS EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM...WHILE OVER WESTERN-CENTRAL CUBA EXPECTING ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-20MM.

THE SURGING FRONT IS TO ALSO TRIGGER A PREFRONTAL SHEAR LINE AND
AN INDUCED/INVERTED TROUGH ACROSS THE CENTRAL CARIBBEAN. EARLY ON
SUNDAY THE SHEAR LINE IS TO EXTEND ACROSS EASTERN CUBA/JAMAICA TO
SOUTHERN NICARAGUA. THIS IS TO REMAIN NEARLY STATIONARY THROUGH
MONDAY MORNING...THEN SURGES ACROSS COSTA RICA TO WESTERN PANAMA
WHILE MEANDERING OVER JAMAICA LATER ON MONDAY. ALONG THIS AXIS
EXPECTING SCATTERED SHOWERS TO DEVELOP...WITH RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. MOST ACTIVE IS EXPECTED ACROSS
JAMAICA AND NORTHEAST HONDURAS/NICARAGUA ON SUNDAY...WITH ACTIVITY
OVER COSTA RICA TO SUSTAIN RAINFALL AMOUNTS OF 00-05MM/DAY AND
MAXIMA OF 10MM..

AS SUCCESSIVE POLAR PERTURBATIONS SURGE ACROSS NORTH
AMERICA...THEY ARE TO PRESS AGAINST A CELL OF THE SUBEQUATORIAL
RIDGE TO THE SOUTH. AT MID/UPPER LEVELS THE RIDGE IS TO EXTEND
WEST-TO-EAST ACROSS THE BASIN WHILE INITIALLY ANCHORING ON A
CLOSED HIGH NEAR THE CAYMAN ISLANDS. THROUGH SUNDAY EVENING/MONDAY
MORNING...THE DEEPENING POLAR TROUGH IS TO SPLIT THIS RIDGE IN TWO
CELLS...WITH ONE TO CONFINE TO MEXICO/CENTRAL AMERICA AND THE
OTHER OVER THE CENTRAL TROPICAL ATLANTIC TO THE EAST OF THE LESSER
ANTILLES. AS THE RIDGE WEAKENS ACROSS THE NORTHERN TO CENTRAL
CARIBBEAN...EXPECTING TRADE WINDS CAP  TO ERODE. THIS IS TO THEN
ALLOW FOR DEEPER MOISTURE TO POOL ACROSS THE NORTHERN CARIBBEAN
ISLES AND PORTIONS OF SOUTH AMERICA. AT LOW LEVELS... WANING CELL
OF THE SUBTROPICAL RIDGE NORTH OF THE ISLANDS IS TO GRADUALLY
YIELD TO ADVANCING POLAR TROUGH. UNDER PRESSURE FROM THE POLAR
FRONT...THIS RIDGE IS TO WEAKEN/NEARLY COLLAPSE THROUGH SATURDAY
EVENING. MEANWHILE... WEAK RIDGE PATTERN TO THE NORTH IS TO
SUSTAIN LIGHT EASTERLY TRADES ACROSS THE BASIN. LATER DURING THE
WEEKEND...AS SHEAR LINE MOVES ACROSS CENTRAL AMERICA...EXPECTING
NORTHEASTERLY WINDS TO INCREASE TO 30-40KT ACROSS NICARAGUA TO THE
EASTERN TROPICAL PACIFIC.

SOUTH OVER THE EASTERN PACIFIC...ITCZ LIES EAST ALONG 06N/07N TO
WESTERN COLOMBIA. IN A WEAK EASTERLY FLOW ACROSS THE BASIN...THE
CONVERGENCE ZONE LIES NORTH OF ITS CLIMATOLOGICAL POSITION. BUT
THIS IS LIKELY TO CHANGE LATER DURING THE WEEKEND AS STRONGER
WINDS OVER SOUTHERN CENTRAL AMERICA ARE TO DISPLACE THIS BOUNDARY
SOUTH. MEANWHILE...OVER WESTERN COLOMBIA THIS IS TO FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH SUNDAY THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM.

THE ATLANTIC ITCZ...MEANWHILE...ENTERS THE CONTINENT OVER AMAPA IN
BRASIL...THEN WEST-SOUTHWEST ACROSS THE SOUTHERN GUIANAS TO
NORTHERN BRASIL. MODELS FORECAST THIS BOUNDARY TO REMAIN NEARLY
STATIONARY OVER THE NEXT FEW DAYS. MOST ACTIVE CONVECTION IS
EXPECTED ACROSS FRENCH GUIANA TO SURINAME...WHERE DIURNAL
CONVECTION IS TO TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM. THROUGH SUNDAY DAILY MAXIMA DECREASES TO 15MM.
ACROSS GUYANA AND THE SOUTHERN WINDWARD ISLANDS EXPECTING LESSER
AMOUNTS DUE TO TRADE WIND SHOWERS/SEA BREEZE CONVERGENCE...WITH
ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. ALONG THE NEAR
EQUATORIAL TROUGH TO THE WEST...DAILY MAXIMA OVER SOUTHERN
VENEZUELA-AMAZONIA IN COLOMBIA IS TO PEAK AT 20-45MM THROUGH
SUNDAY MORNING.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
71W     74W    77W    79W    81W     DISSIPATES            EW

WANING PERTURBATION IN THE EASTERLY TRADES IS INITIALIZED ALONG
71W. LATER ON SUNDAY IT IS FORECAST TO DISSIPATE AS IT MERGES INTO
AN INDUCED/INVERTED PREFRONTAL TROUGH ACROSS THE CENTRAL
CARIBBEAN. MEANWHILE...AS IT PULLS ACROSS HISPANIOLA THIS IS TO
SUSTAIN LIGHT CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15MM...WHILE OVER JAMAICA IT IS TO SUSTAIN RAINFALL
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ACROSS NORTHWEST
VENEZUELA TO NORTHERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM.

JN BAPTISTE...MS (SAINT LUCIA)
NANDA...MDS (SURINAME)
DAVISON...WPC (USA)