988  
FXCA20 KWBC 101928  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
227 PM EST WED JAN 10 2018  
 
TROPICAL DISCUSSION FROM JAN 10/12 UTC: WEST OVER THE DOMAIN...A  
MID/UPPER LEVEL TROUGH SURGES ACROSS THE WESTERN USA TO  
TEXAS/NORTHERN STATES OF MEXICO LATER THIS EVENING/EARLY THURSDAY  
MORNING. ON FRIDAY MORNING IT MOVES ACROSS THE MISSISSIPPI VALLEY  
IN THE USA WHILE GRADUALLY AMPLIFYING ACROSS THE GULF OF MEXICO TO  
THE YUCATAN LATER IN THE DAY. AT LOW LEVELS THE DEEP POLAR TROUGH  
THIS WILL SUSTAIN A PROGRESSIVE FRONT THAT SURGES ACROSS SOUTH  
TEXAS TO THE RIO BRAVO BASIN ON THURSDAY EVENING. A NORTHERLY WIND  
SURGE OF 30-35KT OVER THE WESTERN GULF OF MEXICO WILL RAPIDLY  
DRIVE THIS BOUNDARY SOUTH ALONG THE GULF COAST TO SOUTHERN  
VERACRUZ ON FRIDAY MORNING. LATER IN THE DAY THE FRONT WILL  
CONTINUE ACROSS FLORIDA TO BELIZE/GUATEMALA. ON SATURDAY THE FRONT  
WILL THEN MOVE TO THE NORTHWEST BAHAMAS-CENTRAL CUBA INTO THE  
WESTERN CARIBBEAN/NORTHERN CENTRAL AMERICA. AS THE FRONT SURGES  
ACROSS THE GULF OF MEXICO IT IS TO INDUCE A PREFRONTAL SHEAR LINE  
OVER THE WESTERN CARIBBEAN TO NORTHEAST HONDURAS/NICARAGUA ON  
FRIDAY EVENING. THROUGH SATURDAY THIS MOVES TO THE CENTRAL  
CARIBBEAN-COSTA RICA/WESTERN PANAMA...WITH 850 HPA WINDS OVER  
NICARAGUA-EASTERN PACIFIC FORECAST TO PEAK AROUND 40-50KT. OVER  
CHIAPAS-TABASCO IN SOUTHERN MEXICO THIS WILL FAVOR RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON THURSDAY AND FRIDAY.  
SIMILAR AMOUNTS ARE EXPECTED ACROSS BELIZE-GUATEMALA ON FRIDAY.  
HIGHER AMOUNTS ARE EXPECTED BETWEEN PUERTO BARRIOS GUATEMALA AND  
TELA/SAN PEDRO SULA IN NORTHWEST HONDURAS-ISLAS DE LA BAHIA...WITH  
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON  
FRIDAY-SATURDAY. ACROSS CUBA EXPECTING RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM ON FRIDAY. THIS INTENSIFIES ON  
SATURDAY AS IT SPREADS ACROSS CENTRAL-EASTERN PORTIONS OF THE  
ISLAND WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM.  
ACROSS THE BAHAMAS EXPECTING FRONTAL CONVECTION ON FRIDAY TO  
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ON  
SATURDAY MAXIMA INCREASES TO 25-50MM. SHEAR LINE CONFLUENCE OVER  
THE CAYMAN ISLES AND PREFRONTAL TROUGH OVER JAMAICA WILL RESULT IN  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON FRIDAY  
AND SATURDAY. MOST INTENSE CONVECTION IS EXPECTED TO THE SOUTH IN  
ASSOCIATION WITH THE SHEAR LINE MOVING TO THE SOUTHERN CARIBBEAN.  
OVER COSTA RICA-WESTERN PANAMA IT IS TO TRIGGER RAINFALL AMOUNTS  
OF 50-75MM/DAY AND MAXIMA OF 125-250MM ON SATURDAY.  
 
THE AMPLIFYING POLAR TROUGH WILL PRESS AGAINST A WANING MID/UPPER  
LEVEL RIDGE THAT EXTENDS FROM CENTRAL/SOUTHERN MEXICO ACROSS THE  
GULF OF MEXICO TO THE EASTERN USA. UNDER PRESSURE...THE RIDGE  
COLLAPSES LATER ON THURSDAY/EARLY FRIDAY MORNING. EAST OF THIS  
RIDGE...A CLOSED LOW OVER SOUTH FLORIDA ANCHORS A NEGATIVELY  
TILTED SHORT WAVE TROUGH ACROSS FLORIDA-THE BAHAMAS-CUBA TO THE  
NORTHWEST CARIBBEAN. THIS TROUGH IS ENHANCING MOISTURE TRANSPORT  
ACROSS CUBA/THE CAYMAN ISLES TO THE BAHAMAS...WHERE IT SUSTAINS  
ORGANIZED DEEP CONVECTION. AS THE RIDGE TO THE WEST WEAKENS THE  
LOW IS FORECAST TO FILL TO AN OPEN TROUGH LATER ON THURSDAY. THIS  
IS TO THEN RAPIDLY LIFT TO THE NORTHEAST AHEAD OF THE  
AFOREMENTIONED LONG WAVE TROUGH MOVING TO THE EASTERN USA ON  
FRIDAY. AT LOW LEVELS...THE TROUGH ALOFT SUSTAINS A WANING FRONT  
OVER WESTERN CUBA-WESTERN CARIBBEAN. THIS BOUNDARY FRONTOLIZES  
EARLY IN THE CYCLE. MEANWHILE...THIS IS TO FAVOR A LOW LEVEL  
CONVERGENT PATTERN ACROSS CENTRAL/EASTERN CUBA-JAMAICA TO RESULT  
IN RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. OVER THE  
CENTRAL/NORTHWEST BAHAMAS EXPECTING HIGHER RAINFALL AMOUNTS WITH  
ACCUMULATION OF 20-30MM/DAY AND MAXIMA OF 50-100MM THROUGH  
THURSDAY MORNING. ON THURSDAY-FRIDAY THIS DECREASES TO 10-15MM/DAY  
AND MAXIMA OF 20-30MM.  
 
FARTHER EAST...A 250 HPA HIGH NEAR ISLA DE MARGARITA ANCHORS A  
CELL OF THE SUBEQUATORIAL RIDGE AS IT EXTENDS FROM NORTHERN SOUTH  
AMERICA ACROSS THE EASTERN CARIBBEAN TO THE WESTERN ATLANTIC. ON  
THURSDAY THE CLOSED HIGH WEAKENS TO AN OPEN RIDGE. LATER IN THE  
WEEK THIS IS TO THEN CONFINE TO THE CENTRAL-EASTERN  
CARIBBEAN/NORTHERN SOUTH AMERICA. AT 500 HPA A HIGH NORTH OF THE  
LEEWARD ISLANDS ANCHORS A SHORT WAVE RIDGE OVER THE CENTRAL  
ATLANTIC/EASTERN CARIBBEAN. THIS RIDGE FAVORS AN ELEVATED TRADE  
WINDS CAP ACROSS THE NORTHEAST CARIBBEAN THAT IS STRONG ENOUGH TO  
INHIBITING ORGANIZED DEEP CONVECTION BUT NOT STRONG ENOUGH TO  
SUPPRESS SHALLOW CONVECTIVE DEVELOPMENT. DOWNSTREAM FROM THIS  
RIDGE A TUTT MEANDERS OVER THE TROPICAL ATLANTIC WHILE CENTERING  
ON A 250 HPA LOW NEAR 17N 43W. THE LOW EXTENDS A TROUGH WEST TO  
THE EASTERN CARIBBEAN. AS IT PRESSES AGAINST THE RIDGE TO THE  
NORTH THIS IS SHEARING SHORT WAVE ENERGY WITH VORTICES SPREADING  
ACROSS THE EASTERN CARIBBEAN. INFLOW OF SHORT WAVE ENERGY IS TO  
ENHANCE CONVECTIVE DEVELOPMENT ACROSS TRINIDAD-TOBAGO...THE  
GRENADINES...BARBADOS AND THE SOUTHERN WINDWARD ISLANDS. IN THIS  
AREA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-45MM. THIS ALSO SUSTAINS A PLUME OF SHALLOW MOISTURE SPREADING  
ACROSS THE FRENCH/LEEWARD ISLES TO PUERTO RICO AND HISPANIOLA.  
ACROSS THE FRENCH/LEEWARD ISLANDS EXPECTING RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15MM. ACROSS PUERTO RICO AND HISPANIOLA  
EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON  
FRIDAY THIS DECREASES TO 00-05MM/DAY AND WIDELY ISOLATED MAXIMA OF  
10MM AS A DRYER AIR MASS ENTRAINS FROM THE EAST. HOWEVER...ON  
SATURDAY...A SECONDARY PLUME IS TO ONCE AGAIN SUSTAIN RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
 
AT LOW LEVELS...THE MODELS FORECAST A RIDGE TO BUILD ACROSS THE  
WESTERN NORTH ATLANTIC EARLY IN THE CYCLE...TO GRADUALLY BECOME  
DOMINANT FEATURE ON THURSDAY-FRIDAY. AS THE RIDGE BUILDS EXPECTING  
BRISK EASTERLY TRADES TO DOMINATE THE FLOW ACROSS THE  
EASTERN-CENTRAL CARIBBEAN...WITH 925/950 HPA WINDS TO PEAK AT  
25-30KT. THE BRISK EASTERLY TRADES WILL FAVOR GENERATION OF  
STREAMERS ACROSS THE ISLAND CHAIN TO THE EASTERN CARIBBEAN. THESE  
ARE TO AFFECT THE VIRGIN ISLES-EASTERN PUERTO RICO FROM  
TIME-TO-TIME. BUT THESE ARE TO ONLY FAVOR LIGHT RAINFALL AMOUNTS.  
OVER THE SOUTHERN CARIBBEAN THE FLOW IS CONVERGING ALONG AN ILL  
ORGANIZED CELL OF THE PANAMANIAN LOW/TROUGH OVER PANAMA-WESTERN  
COLOMBIA. THE TROUGH IS ENHANCING MOISTURE CONVERGENCE ON THE  
CAUCA VALLEY IN SOUTHWEST COLOMBIA...WHERE WE EXPECT RAINFALL  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH THURSDAY  
MORNING. ON FRIDAY-SATURDAY EXPECTING ACCUMULATION OF 05-10MM/DAY  
AND MAXIMA OF 15-25MM. ON THE ANDEAN REGION TO THE NORTH AND ALONG  
THE NORTHWEST COAST EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15MM. THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF  
15-25MM ON FRIDAY.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
62W 65W 68W 71W 74W 76W 78W DISSIPATES EW 18N  
 
AN EASTERLY WAVE ALONG 62W AND SOUTH OF 18N IS TO DISSIPATE EARLY  
ON SATURDAY. MOST ACTIVE CONVECTION WITH THIS FEATURE IS EXPECTED  
TO THE SOUTH ACROSS SOUTHERN VENEZUELA TO EASTERN COLOMBIA...WHERE  
IT IS TO TRIGGER RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF  
35-70MM. ON THURSDAY THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF  
20-40MM. AS IT MOVES ACROSS NORTHERN COLOMBIA ON FRIDAY THIS IS TO  
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
OVER JAMAICA THIS IS TO THEN SUSTAIN ACCUMULATION OF 10-15MM/DAY  
AND MAXIMA OF 20-40MM.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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