[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171047
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUL 17 2010

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC...

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS ALONG 47/48W FROM 8N TO 19N. THE WAVE IS
FAIRLY WELL ORGANIZED WITH CYCLONIC TURNING COVERING A BROAD
AREA OF ABOUT FIVE DEGREES EITHER SIDE OF THE WAVE AXIS. A
NARROW BAND...EXHIBITING CYCLONIC CURVATURE CONSISTING OF
MODERATE CONVECTION IS DEVELOPING ON THE WEST SIDE OF THE WAVE
AXIS. THE WAVE IS MOVING W NEAR 20 KT AND REMAINS EMBEDDED
WITHIN AN AREA OF DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL
PRECIPITABLE WATER ANIMATION. 850 MB MODEL GUIDANCE SUGGEST A
VORTICITY MAXIMUM NEAR 12N48W WHERE FIRST VISIBLE SATELLITE
PICTURE OF THE DAY SHOWS A SMALL CLUSTER OF SHOWERS AND ISOLATED
TSTMS. AN EARLIER ASCAT PASS INDICATED NE WINDS OF 20 KT NEAR
THE NORTHERN END OF THE WAVE AXIS DUE TO THE PRES GRADIENT
BETWEEN THIS SYSTEM AND THE ATLC RIDGE EXTENDING ALONG 31N. THIS
WAVE WILL REACH 55W TONIGHT AND THE EASTERN CARIBBEAN SUN NIGHT
BRINGING AN INCREASE IN SHOWER AND TSTM ACTIVITY PARTICULARLY
ACROSS THE LEEWARD ISLANDS AND THEN OVER PUERTO RICO AND THE
US/UK VIRGIN ISLANDS BY MON.

TROPICAL WAVE IS MOVING ACROSS THE LESSER ANTILLES WITH AXIS
ALONG 62W S OF 17N. THIS FEATURE IS MOVING W ABOUT 15 KT. A
DIFFLUENT PATTERN ALOFT BETWEEN AN UPPER-LEVEL LOW APPROACHING
PUERTO RICO AND A RIDGE OVER THE EASTERN CARIBBEAN IS HELPING TO
INDUCE CONVECTION NEAR THE WAVE AXIS. SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS SEEN BETWEEN GUADELOUPE AND
DOMINICA. THE WAVE WILL MOVE THROUGH THE REMAINDER OF THE
EASTERN CARIBBEAN SEA THROUGH TONIGHT...THEN ACROSS THE CENTRAL
CARIBBEAN SUN AND MON.

TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 72W MOVING W
AT ABOUT 10 KT. THE WAVE EXTENDS FROM HISPANIOLA TO NEAR LAKE
MARACAIBO IN WESTERN VENEZUELA. CLUSTERS OF SCATTERED MODERATE
TO ISOLATED STRONG CONVECTION ARE OVER MUCH OF THE EASTERN
CARIBBEAN WITH THE STRONGEST ONE BETWEEN BUOY 42959 AND THE ABC
ISLANDS. THE WAVE IS ALSO ENHANCING CONVECTION JUST S OF HAITI
AND NEAR THE COAST OF COLOMBIA. THIS SYSTEM WILL MOVE INTO THE
W CARIBBEAN THIS EARLY TONIGHT.

...ITCZ...

THE ITCZ AXIS IS ALONG 10N15W 7N30W 10N44W 9N50W 12N58W.
SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 15W AND 27W.
SIMILAR CONVECTION IS NEAR 7N41W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH CONTINUES TO MOVE WWD ACROSS THE GULF WITH AXIS
ALONG 92W S OF 27N TO THE BAY OF CAMPECHE. DEEP LAYER MOISTURE
IS NOTED BETWEEN THE TROUGH AXIS AND AN UPPER-LEVEL LOW SPINNING
NEAR THE FLORIDA KEYS. SCATTERED SHOWERS AND ISOLATED TSTMS ARE
NEAR THE TROUGH AXIS WHICH IS FORECAST TO APPROACH THE TEXAS
COAST TONIGHT WHILE WEAKENING. A RIDGE FROM THE ATLC EXTENDS
ACROSS THE FLORIDA PENINSULA INTO THE EASTERN GULF. THE RIDGE
ALSO DOMINATES THE SE CONUS. A DRYER AIR MASS IS NOTED WEST OF
THE SURFACE TROUGH.

CARIBBEAN SEA...
A BROAD AREA OF LOW PRESSURE LOCATED JUST EAST OF NICARAGUA
CONTINUES TO PRODUCE DISORGANIZED SHOWERS AND THUNDERSTORMS OVER
A LARGE PORTION OF THE WESTERN CARIBBEAN SEA...BUT NONE OF THIS
ACTIVITY IS CONCENTRATED NEAR THE CENTER OF THE LOW. A SURFACE
TROUGH IS ANALYZED IN THIS AREA EXTENDING FROM 21N85W TO A 1011
MB LOW PRES LOCATED NEAR 13N83W. SIGNIFICANT DEVELOPMENT OF THIS
SYSTEM IS NOT EXPECTED DUE TO PROXIMITY TO LAND. HOWEVER...HEAVY
RAIN WILL SPREAD OVER PORTIONS OF CENTRAL AMERICA DURING THE
NEXT COUPLE OF DAYS AS THIS SYSTEM MOVES SLOWLY WESTWARD. AN
ASCAT PASS FROM 0308 UTC SHOWED THE WIND SHIFT ASSOCIATED WITH
THE TROUGH AND WEAK CYCLONIC CIRCULATION RELATED TO THE LOW
CENTER. E TO SE WINDS OF 15-20 KT CAN BE FOUND E OF THE TROUGH
AXIS. CONVECTION HAS FLARED UP EARLY THIS MORNING OVER THE
WESTERN CARIBBEAN NEAR AND EAST OF THE THE TROUGH AXIS WITH A
CLUSTER OF MODERATE TO STRONG CONVECTION BETWEEN CUBA AND
JAMAICA. ANOTHER SURFACE TROUGH PERSISTS OVER THE NE CARIBBEAN
STRETCHING FROM E PUERTO RICO NE TO NEAR 22N65W. THIS TROUGH IS
THE SURFACE REFLECTION OF AN UPPER-LEVEL LOW CENTERED NEAR
22N64W. THE SAN JUAN DOPPLER RADAR REVEALS SCATTERED TO NUMEROUS
SHOWERS WITH EMBEDDED TSTMS...MORE CONCENTRATED SE OF PUERTO
RICO. THE UPPER LOW IS FORECAST TO BRING ACTIVE WEATHER TO
PUERTO RICO AND THE VIRGIN ISLANDS TODAY.

ATLANTIC OCEAN...
ALOFT...AN UPPER-LEVEL LOW IS SPINNING NEAR THE FLORIDA KEYS
WITH THE CYCLONIC FLOW COVERING FLORIDA...CUBA AND THE BAHAMAS
MAINLY W OF 76W. AS PREVIOUSLY MENTIONED...ANOTHER UPPER LEVEL
LOW IS NEAR 22N64W HELPING TO INDUCE CONVECTION NEAR PUERTO
RICO. IN BETWEEN...THERE IS AN UPPER-LEVEL RIDGE EXTENDING S TO
NEAR THE SE BAHAMAS. A RIDGE ALSO COVERS THE TROPICAL ATLC.
AT THE SURFACE...RIDGING DOMINATES THE BASIN ANCHORED BY A
SERIES OF HIGH CENTERS LOCATED N OF THE DISCUSSION AREA. THE
STRONGEST ONE...ANALYZED 1028 MB...IS NEAR THE AZORES. PRES
GRADIENT BETWEEN THE AZORES HIGH AND LOWER PRES OVER AFRICA IS
PRODUCING AN AREA OF NLY WINDS IN THE 20 TO 25 KT RANGE BETWEEN
THE CANARY AND THE CAPE VERDE ISLANDS MAINLY E OF 20W. DRY
SAHARAN AIR LAYER ACCOMPANIED BY DUST COVERS MUCH OF THE
TROPICAL ATLC SUPPRESSING CONVECTION IN THIS REGION.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GR






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