178
FXCA20 KWBC 051838
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
237 PM EDT WED AUG 05 2009
DISCUSSION FROM AUG 05/0000 UTC. AT MID/UPPER LEVELS...A LONG
WAVE RIDGE DOMINATES NORTHERN STATES OF MEXICO AND THE WESTERN
USA. AT 250 HPA IT ANCHORS ON A MEANDERING HIGH OVER NORTHERN
CHIHUAHUA/SONORA...WHILE AT 500 HPA IT CENTERS ON A HIGH OVER NEW
MEXICO/TEXAS. THE PATTERN REMAINS NEARLY UNCHANGED THROUGH 36-48
HRS. BUT...BY 60-72 HRS...THE HIGHS/RIDGES WILL START TO MIGRATE
EAST ACROSS THE MISSISSIPPI VALLEY IN THE UNITED STATES...WITH
RIDGE PATTERN TO SETTLE OVER THE EASTERN USA LATER THIS WEEK.
UNDER INFLUENCE OF THE CONTINENTAL RIDGE...A HIGH AMPLITUDE TROUGH
IS TO EXTEND SOUTH ALONG 88W/90W TO THE GULF OF MEXICO...WITH BASE
OF THE TROUGH TO AMPLIFY TO THE SOUTHERN STATES OF MEXICO BY 24-48
HRS. LATER IN THE CYCLE...AS THE HIGH MIGRATES EAST...IT WILL
PINCH OFF A CUT OFF LOW OVER THE WESTERN GULF/NORTHEAST MEXICO.
THE AMPLIFYING UPPER TROUGH IS TO TAKE ADVANTAGE OF FAVORABLE MJO
CONDITIONS ACROSS THE EASTERN PACIFIC...TO FAVOR ORGANIZED
CONVECTION ACROSS CENTRAL AND SOUTHERN STATES OF MEXICO. THE MOST
INTENSE CONVECTION IS EXPECTED ACROSS
VERACRUZ-TABASCO-CHIAPAS-OAXACA-PUEBLA-MEXICO/MEXICO DF-GUERRERO
TO MICHOACAN-JALISCO-NAYARIT. RAINFALL AMOUNTS WILL RANGE BETWEEN
15-20MM/DAY AND THE DAILY MAXIMA WILL PEAK AT 30-50MM. LOCALLY
HIGHER AMOUNTS ARE QUITE POSSIBLE DUE TO TOPOGRAPHICAL FORCING.
WE EXPECT ACTIVITY TO PERSIST THROUGH DAY 03. DIURNAL CONVECTION
ALONG THE SIERRA MADRE OCCIDENTAL WILL RESULT IN RAINFALL AMOUNTS
OF 00-05MM/DAY AND MAXIMA OF 10-15MM...TO CONCENTRATE BETWEEN
SONORA/ WESTERN CHIHUAHUA TO DURANGO/SINALOA.
THERE IS ALSO A CELL OF THE SUBTROPICAL RIDGE WITH CLOSED
CIRCULATION AT 250 HPA NEAR 25N 75W...WITH AXIS EXTENDING FROM
HISPANIOLA-CUBA NORTHWARD INTO THE WESTERN ATLANTIC. THE RIDGE
PATTERN WILL PERSIST THROUGH 60-72 HRS...WITH AXIS TO REACH
MAXIMUM AMPLITUDE EARLY THIS PERIOD. THIS FEATURE REFLECTS AT 500
HPA...WITH A SOMEWHAT WEAKER RIDGE PATTERN OVER THE BAHAMAS.
ALTHOUGH THIS IS TO FAVOR A WEAK SUBSIDENCE CAP OVER THE BAHAMAS
AND MOST OF CUBA...IT WILL NOT BE STRONG ENOUGH TO INHIBIT
ISOLATED DEEP CONVECTIVE CELLS DUE TO SEA BREEZE CONVERGENCE.
CONVECTION IS TO RANGE BETWEEN 05-10MM/DAY WITH MAXIMA TO PEAK AT
15-25MM/DAY. LOCALLY HIGHER AMOUNTS ARE POSSIBLE
A TUTT TO THE EAST STRETCHES ALONG 66W/67W TO NORTHWEST VENEZUELA.
THIS TROUGH IS TO MEANDER OVER PUERTO RICO/EASTERN HISPANIOLA TO
NORTHERN COLOMBIA/NORTHWEST VENEZUELA THROUGH AT LEAST 48-60 HRS.
BY 60-72 HRS THE TUTT IS TO CUT OFF FROM THE FLOW AND MODELS SHOW
IT TO PROGRESSIVELY DECAY. SO THE BEST DYNAMICS ARE EXPECTED
THROUGH 36-48 HRS. MODELS SHOW POSITIVE INTERACTION BETWEEN THIS
TUTT AND A TROPICAL WAVE/WIND SURGE ENTERING THE LESSER
ANTILLES...WITH BEST DYNAMICS AT FIRST OVER THE SOUTHERN
FRENCH/WINDWARD ISLANDS. ACROSS PUERTO RICO-VIRGIN ISLES AND THE
DOMINICAN REPUBLIC MOST INTENSE CONVECTION IS EXPECTED BETWEEN
30-54 HRS. MAXIMA WILL RANGE BETWEEN 35-50MM...WITH LOCALLY HIGHER
AMOUNTS OVER THE MOUNTAINS TO EXCEED 100MM. OTHER ACTIVITY IS
EXPECTED TO THE SOUTH AS THE TUTT INTERACTS WITH THE NEAR
EQUATORIAL TROUGH OVER VENEZUELA TO COLOMBIA...TO FAVOR RAINFALL
AMOUNTS OF 15-25MM/DAY AND MAXIMA OF 30-45MM/DAY.
FARTHER EAST AT 250 HPA...OVER THE TROPICAL ATLANTIC... ANOTHER
CELL OF THE SUBTROPICAL RIDGE EXTENDS EAST-TO-WEST ALONG 18N/20N
TO THE EASTERN CARIBBEAN ISLES. EARLY IN THE CYCLE IT WILL CENTER
ON A HIGH NEAR 20N 50W...THAT IS FORECAST TO RELOCATE WEST TO 20N
60W BY 72 HRS. THE CORRESPONDING MID LEVEL RIDGE LIES FARTHER
NORTH... CENTERING ON CLOSED HIGHS AT 30N 55W AND 35N 45W. THIS
RIDGE IS TO BUILD INTO THE NORTHEAST CARIBBEAN BY 48-60
HRS...BRINGING A DRYER/MORE STABLE AIR MASS TO THE NORTHEAST
CARIBBEAN LATER IN THE PERIOD. THE SUBSIDENCE CAP WILL DROP TO
700/750 HPA BY THE END OF THE CYCLE. AT LOW LEVELS THE ITCZ
EXTENDS ACROSS THE TROPICAL ATLANTIC ALONG 08N/10N...WHICH KEEPS
THE MOST ACTIVE CONVECTION JUST NORTH OF SURINAME/FRENCH
GUIANAS...WITH ACTIVITY CONCENTRATING ACROSS NORTHERN
GUYANA/ORINOCO DELTA REGION IN NORTHEAST VENEZUELA AND THE
SOUTHERN WINDWARD ISLANDS/GRENADINES... WHERE WE EXPECT RAINFALL
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM. HIGHER
AMOUNTS...HOWEVER...ARE EXPECTED WITH TROPICAL WAVES.
EASTERLY/TROPICAL WAVES (INITIALIZED AT 12Z TODAY)
INITIAL F24 F36 F48 F60 F72 F84
38W (S/16N) 41W 44W 48W 51W 54W 56W
59W (S/24N) 62W 66W 70W 74W 78W 82W
83W (S/21N) 87W 91W 94W 97W 100W 103W
98W (TROF) 100W 103W 106W 109W 112W 115W
THE WAVE ALONG 38W WILL MOVE OVER FRENCH GUIANA/SURINAME BY 66-84
HRS. MODELS...HOWEVER...KEEP THE MOST ACTIVE CONVECTION ALONG THE
ITCZ. AS IT NEARS THE SOUTHERN WINDWARD ISLANDS/GRENADINES THE
MAXIMA WILL PEAK AT 30-55MM.
THE WAVE ALONG 59W LEADS A WIND SURGE...WHICH TRAILS THIS AXIS BY
04-06 DEGREES. THE WAVE WILL ENTER THE ISLAND CHAIN THROUGH 24
HRS...AND THROUGH 36-48 HRS IT IS TO AFFECT THE VIRGIN
ISLES/PUERTO RICO...INTO THE DOMINICAN REPUBLIC THROUGH 48 HRS.
OVER THE SOUTHERN FRENCH AND WINDWARD ISLANDS WE EXPECT RAINFALL
AMOUNTS OF 10-20MM/DAY AND MAXIMA OF 30-50MM. SIMILARLY ACROSS
PUERTO RICO AND THE VIRGIN ISLANDS TO THE DOMINICAN REPUBLIC. OVER
HAITI TO JAMAICA-EASTERN CUBA EXPECT ACCUMULATION OF 05-10MM/DAY
AND MAXIMA OF 15-30MM...WHILE OVER THE CAYMAN ISLANDS IT WILL
FAVOR ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY. OVER
NORTHWEST VENEZUELA-SANTANDERES/SIERRA DE SANTA MARTA IN NORTHERN
COLOMBIA IT WILL FAVOR RAINFALL AMOUNTS OF 10-20MM/DAY AND MAXIMA
OF 30-40MM...WHILE OVER EJE CAFETERO TO THE DARIEN IN EASTERN
PANAMA EXPECT ACCUMULATION OF 15-25MM/DAY AND MAXIMA OF 35-60MM.
THE WAVE ALONG 83W IS TO FAVOR SCATTERED CONVECTION ACROSS THE
CAYMAN ISLANDS WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF
10-20MM. OVER WESTERN PANAMA TO COSTA RICA TO SOUTHERN NICARAGUA
THE MAXIMA WILL PEAK AT 35-60MM/DAY AS THE WAVE MODULATES THE ITCZ
NORTH. OVER THE CARIBBEAN PLAINS OF NICARAGUA TO NORTHEAST
HONDURAS THE MAXIMA WILL PEAK AT 15-25MM/DAY. OVER
BELIZE-GUATEMALA-THE YUCATAN-CENTRAL/WESTERN HONDURAS IT WILL
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-35MM. ON
THE SOUTHERN STATES OF MEXICO WE EXPECT ACCUMULATION OF
10-15MM/DAY AND MAXIMA OF 30-40MM BY 48-60 HRS...WHILE OVER
GUERRERO-OAXACA THE MAXIMA WILL PEAK AT 15-25MM BY 72 HRS.
A TUTT INDUCED TROUGH IS INITIALIZED ALONG 100W... SUPPORTING
SCATTERED CONVECTION OVER SOUTHERN MEXICO. AS IT MOVES WEST ACROSS
THE CENTRAL STATES OF MEXICO IT WILL FAVOR ACCUMULATION OF
15-25MM/DAY AND MAXIMA OF 35-60MM.
OUTLOOK: MEDIUM RANGE GUIDANCE SHOWS A PATTERN TRANSITION ON THE
NORTHERN PORTIONS OF THE DOMAINS...WITH THE RIDGE OVER THE WESTERN
USA RELOCATING TO THE EASTERN USA/WESTERN ATLANTIC THROUGH DAY
03-04...THEN PERSISTING THROUGH DAY 07. THIS IS TO THEN FAVOR THE
SOUTHWARD AMPLIFICATION OF A TROUGH OVER THE WESTERN
ATLANTIC...WHILE A CELL OF THE SUBTROPICAL RIDGE ESTABLISHES OVER
THE CENTRAL-EASTERN ATLANTIC. A WEAKNESS IN THE HEIGHT FIELD WILL
REMAIN BETWEEN 65-45W. THIS CHANGE IN PATTERN COINCIDES WITH AN
INCREASE IN THE MJO. THIS IS ALREADY AFFECTING THE EASTERN
PACIFIC...WHERE WE HAVE SEEN A SURGE IN ITCZ RELATED CONVECTION
DURING THE LAST COUPLE OF DAYS. CONDITIONS...AS PREDICTED BY THE
EWP/CFS...ARE TO REMAIN FAVORABLE DURING THE NEXT TWO TO THREE
WEEKS. BUT BEST DYNAMICS OVER THE TROPICAL ATLANTIC MIGHT BE
SLOWER TO MATERIALIZE...WITH MODELS NOW HOLDING BACK UNTIL THE
SECOND HALF OF AUGUST. NEVERTHELESS...THE CHANGE IN FLOW PATTERN
MIGHT BE ENOUGH TO ALLOW AN INCREASE IN TROPICAL CONVECTION ACROSS
THE ATLANTIC...AND POSSIBLY LEAD TO A HIGHER INCIDENCE IN TROPICAL
CYCLONES.
ALBERT...NWS (SAINT LUCIA)
CANALES...SMN (HONDURAS)
DAVISON....NCEP (USA)
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