Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXCA20 KWBC 261840
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 PM EDT WED JUL 26 2017

AT 15 UTC HURRICANE HILLARY CENTERED NEAR 16.4N 112.3W...WITH
MINIMAL CENTRAL PRESSURE OF 973 HPA AND MAXIMUM SUSTAINED WINDS OF
90KT. THE HURRICANE IS MOVING WEST AT 11KT. SEE NHC DISCUSSION FOR
OFFICIAL FORECAST.

TROPICAL DISCUSSION FROM JUL 26/12 UTC: A 250 HPA HIGH RIDGE OVER
NEW MEXICO ANCHORS A SHORT WAVE RIDGE ACROSS THE SOUTHWEST USA.
THIS IS DRIVING A TUTT WEST ACROSS NORTHERN MEXICO. THIS IS TO
SLOWLY PULL ACROSS CHIHUAHUA TO SONORA/NORTHERN SINALOA EARLY ON
THURSDAY...AND ACROSS THE BAJA PENINSULA LATER IN THE DAY. AS IT
RETROGRESSES ACROSS NORTHERN MEXICO THIS WILL ENHANCE DIURNAL
CONVECTION. ON THE STATES OF TAMAULIPAS-VERACRUZ AND CENTRAL
MEXICO THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM. ON THURSDAY-FRIDAY THIS DECREASES TO
05-10MM/DAY AND MAXIMA OF 15-20MM. ACROSS
COLIMA-NAYARIT-SINALOA-SONORA THIS WILL FAVOR RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 35-70MM. ON THURSDAY...AS THE TROUGH
MOVES AWAY IT DECREASES TO 10-15MM/DAY AND MAXIMA OF
20-45MM...WHILE ON FRIDAY-SATURDAY EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM.

FARTHER EAST...AT 500 HPA...A NARROW CELL OF THE SUBTROPICAL RIDGE
EXTENDS OVER THE WESTERN ATLANTIC JUST NORTH OF THE GREATER
ANTILLES. THIS IS WEAKENING UNDER PRESSURE FROM A POLAR TROUGH TO
THE NORTH. AT 250 HPA A TUTT OVERLAYS THE WANING MID LEVEL RIDGE
AXIS...WITH TROUGH EXTENDING OVER THE BAHAMAS-CUBA TO THE WESTERN
CARIBBEAN. THE TROUGH ALOFT IS TO PERSIST THROUGH SATURDAY
MORNING. MEANWHILE...AS IT MEANDERS OVER CUBA...THE TROUGH WILL
ENHANCE DIURNAL CONVECTION...WITH RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-25MM/DAY. ON THURSDAY TO FRIDAY THIS IS TO
GRADUALLY INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-30MM. THIS IS
TO ALSO ENHANCE CONVECTION ACROSS JAMAICA...TO FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM OVER THE NEXT COUPLE
OF DAYS.

FARTHER EAST...A TUTT LOW NEAR 27N 58W EXTENDS A TROUGH TO THE
SOUTHWEST ACROSS THE NORTHEAST CARIBBEAN ISLES. THIS IS ALSO
PRESSING AGAINST THE SUBTROPICAL RIDGE TO THE WEST/NORTH OF THE
ISLANDS...WEAKENING ASSOCIATED TRADE WINDS CAP OVER THE NORTHEAST
CARIBBEAN. IN RESPONSE...ATMOSPHERE HAS BECOME CONVECTIVELY
UNSTABLE. TUTT PATTERN IS TO GRADUALLY WEAKEN THROUGH SATURDAY
MORNING. AS UPPER SUPPORT WANES...EXPECTING ACTIVITY TO ALSO
WEAKEN LATER DURING THE WEEK. EARLY IN THE CYCLE THIS IS TO
SUSTAIN MODERATE CONVECTION ACROSS PUERTO RICO AND
HISPANIOLA...WITH RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-45MM. ON THURSDAY-FRIDAY THE DAILY MAXIMA DECREASES TO
20-35M...WHILE ON SATURDAY IT IS TO PEAK AT 15-20MM. OVER THE
VIRGIN ISLES-NORTHERN LEEWARD ISLANDS THIS WILL FAVOR RAINFALL
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ON THURSDAY...UNDER
INFLUENCE OF A TUTT INDUCED PERTURBATION...THIS INCREASES TO
05-10MM/DAY AND MAXIMA OF 15-25MM.

SOUTH OVER THE CARIBBEAN...AT 250 HPA...A CELL OF THE
SUBEQUATORIAL RIDGE EXTENDS EAST-TO-WEST ALONG THE CARIBBEAN COAST
OF SOUTH AMERICA TO CENTRAL AMERICA. THE RIDGE ALOFT IS VENTING
DIURNAL CONVECTION OVER NORTHERN SOUTH AMERICA AND ALONG THE NEAR
EQUATORIAL TROUGH/INTERTROPICAL CONVERGENCE ZONE. OVER COSTA
RICA-SOUTHERN NICARAGUA THIS IS TO FAVOR RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM OVER THE NEXT THREE DAYS...WHILE
ACROSS PANAMA TO NORTHERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. HIGHER AMOUNTS ARE EXPECTED
OVER CHOCO/EJE CAFETERO IN WESTERN COLOMBIA...WHERE UNDER THE
INFLUENCE OF THE PANAMANIAN TROUGH EXPECTING RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM/DAY. OVER CENTRAL VENEZUELA
INITIALLY EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM. ON FRIDAY-SATURDAY IT WILL INCREASES TO 10-15MM/DAY AND
MAXIMA OF 20-45MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96     TYPE
34W      36W    39W    41W    45W    49W    52W    56W  TUTT INDCD
55W      58W    61W    64W    67W    70W    73W    75W  TUTT INDCD
63W      66W    68W    71W    74W    76W    DISSIPATES  TUTT INDCD
74W      76W    78W    81W    84W    86W    89W    91W  TUTT INDCD
88W      90W    94W    97W    99W   103W   106W   109W     TW
102W    105W   107W   109W   110W   111W   112W   113W     EW

A TUTT INDUCED PERTURBATION IS INITIALIZED ALONG 34W AND SOUTH OF
27N. AXIS IS TO CONFINE TO THE TROPICAL ATLANTIC DURING THE NEXT
FOUR DAYS. A DRY SAHARAN AIR LAYER TRAILS THIS PERTURBATION.

DEEP TUTT TO THE NORTH OF THE ISLAND CHAIN SUSTAINS AN INDUCED
TROUGH IN THE EASTERLY TRADES...WITH AXIS ALONG 55W AND SOUTH OF
30N. THIS IS TO SUSTAIN SCATTERED CONVECTION ACROSS NORTHERN
GUIANA-NORTHEAST VENEZUELA-TRINIDAD AND TOBAGO...WITH ACCUMULATION
OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER THE LESSER ANTILLES-VIRGIN
ISLES THIS WILL FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA
OF 10MM. ON THURSDAY THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF
15-25MM WHILE SPREADING TO ACROSS PUERTO RICO EARLY ON FRIDAY.
OVER THE DOMINICAN REPUBLIC THIS IS TO THEN FAVOR RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-30MM.

A TUTT INDUCED TROUGH EXTENDS ALONG 63W TO 27N. OVER PUERTO RICO
AND HISPANIOLA THIS WILL SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-45MM EARLY IN THE PERIOD...WITH ADDITIONAL
10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY. ACROSS CUBA THIS IS
TO ALSO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM ON FRIDAY...WITH WAVE FORECAST TO DISSIPATE EARLY ON
SATURDAY MORNING.

ANOTHER TUTT INDUCED TROUGH EXTENDS ALONG 74W TO 27N. THIS WAVE
TENDS TO WEAKEN AS IT MOVES ACROSS THE YUCATAN PENINSULA ON
SATURDAY. MEANWHILE...OVER EASTERN CUBA AND JAMAICA THIS IS TO
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.
SIMILAR AMOUNTS ARE EXPECTED OVER CENTRAL-WESTERN CUBA ON
THURSDAY...INCREASING TO 10-15MM/DAY AND MAXIMA OF 20-30MM ON
FRIDAY. OVER THE YUCATAN THIS IS TO THEN TRIGGER RAINFALL AMOUNTS
OF 05-10MM/DAY AND MAXIMA OF 15-25MM ON SATURDAY.

A TROPICAL WAVE ALONG 88W AND SOUTH OF 21N IS TO SUSTAIN SCATTERED
CONVECTION ACROSS BELIZE-GUATEMALA-CHIAPAS IN SOUTHERN
MEXICO...WITH RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM THROUGH THURSDAY MORNING. ACROSS THE NORTHERN YUCATAN
PENINSULA IT IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15MM. ON THURSDAY-FRIDAY...OVER CENTRAL AND SOUTHWEST
MEXICO...THE WAVE WILL SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

AN EASTERLY WAVE ALONG 102W AND SOUTH OF 21N IS TO TRIGGER
CONVECTION ACROSS COLIMA-NAYARIT IN SOUTHWEST MEXICO...WITH
ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 35-70MM EARLY IN THE
CYCLE.

GAJADHAR...SLMS (SAINT LUCIA)
DAVISON...WPC (USA)
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.