[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 102333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 10 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 27W/28W S OF 17N MOVING W 5-10 KT.
SURROUNDING SOUNDING DATA AND MODEL FIELDS INDICATE THAT THIS
WEAK FEATURE HAS BEEN EMBEDDED IN VERY LIGHT STEERING OVER THE
PAST 24 HOURS. IT IS EXPECTED TO SPEED UP SHORTLY AS AN ELY JET
SETS UP IN THIS REGION. CURRENT SATELLITE IMAGES SHOW LITTLE
WAVE SIGNATURE...SO THE CURRENT PSN IS BASED ON SLOW FORWARD
EXTRAPOLATION WHICH AGREES WELL WITH A NEARLY STATIONARY
MOISTURE BUMP SEEN IN THE UW-CIMSS TPW LOOP.

TROPICAL WAVE IS ALONG 44W S OF 14N MOVING W 10-15 KT. THIS LOW
AMPLITUDE WAVE REMAINS WEAK CAUSING A VERY SLIGHT PERTURBATION
IN THE ITCZ. ONLY ISOLATED SHOWERS ARE ASSOCIATED WITH THIS
FEATURE.

HIGHER AMPLITUDE TROPICAL WAVE IS ALONG 65W S OF 21N MOVING W
NEAR 15 KT. THIS WAVE WAS ONE OF THE MORE OBVIOUS SYSTEMS TO
TRACK SO FAR THIS SEASON...ALBEIT IT REMAINED DEVOID OF
SIGNIFICANT CONVECTION. TODAY IT IS LESS DEFINED AS IT HAS MOVED
INTO A REGION WITH CONSIDERABLE MOISTURE PRODUCED BY SEVERAL
FEATURES. UPPER AIR TIME SECTION PLOTS INDICATE THAT THE WAVE
PASSED BARBADOS ABOUT 18 HOURS AGO. IN ADDITION...THE UW-CIMSS
TPW PRODUCT CONTINUES TO A SHOW A NARROW WWD MOVING SURGE OF
HIGHER PW. SHOWERS AND TSTMS ARE MOST ORGANIZED TO THE W OF THE
WAVE AXIS...WHICH IS LIKELY MORE RELATED TO UPPER DIFFLUENCE.

TROPICAL WAVE IS ALONG 75W S OF 19N MOVING W NEAR 15 KT. THIS
WAVE HAS BEEN CHALLENGING TO TRACK OVER THE PAST COUPLE OF DAYS.
THE UPPER PATTERN ALONG WITH THIS WAVE AND OTHER LOW-LEVEL
FEATURES HAVE PRODUCED A LARGE DISORGANIZED AREA OF SHOWERS AND
TSTMS ACROSS MUCH OF THE NRN HALF OF THE CARIB SEA...ESPECIALLY
BETWEEN 65W-80W. REFER TO THE CARIB SECTION BELOW FOR DETAILS.
BASED ON CURRENT IMAGERY...IS IT DIFFICULT TO TELL HOW MUCH OF
THIS ACTIVITY IS ASSOCIATED WITH THE WAVE ITSELF. THE UW-CIMSS
TPW PRODUCT DOES SHOW AN ENHANCED WWD MOVING MOISTURE SURGE IN
AN ALREADY HIGH TPW ENVIRONMENT. THIS IS MAIN SOURCE USED TO
TRACK THIS FEATURE.

TROPICAL WAVE IS OVER CENTRAL AMERICA ALONG 90W S OF 20N MOVING
W 10-15 KT. THIS WAVE LIES UNDERNEATH AN UPPER LOW WHICH IS
HELPING TO GENERATE SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN
90 NM OF THE AXIS. LITTLE LOW-LEVEL TURNING OR WAVE-TYPE
SIGNATURE IS EVIDENT OVER CENTRAL AMERICA...BUT SLIGHT TURNING
HAS DEVELOPED NEAR THE SRN EXTENSION OF THE WAVE OVER THE EPAC
WATERS. FOR MORE INFO REFER TO THE PACIFIC TWD...MIATWDEP.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 11N27W 10N42W 12N61W.
SCATTERED MODERATE TO STRONG CONVECTION IS NEAR AND OVER W
AFRICA FROM 9N-13N E OF 18W...ASSOCIATED WITH A LARGE TROPICAL
WAVE MAKING ITS WAY TO THE COAST. SCATTERED MODERATE IS WITHIN
150 NM S OF THE AXIS BETWEEN 20W-23W AND WITHIN 90 NM EITHER
SIDE W OF 49W.

DISCUSSION...
GULF OF MEXICO...
COMBINATION OF A STRONG UPPER HIGH OVER THE SRN U.S. AND AN
UPPER LOW ABOVE THE ERN BAY OF CAMPECHE CONTINUES TO PRODUCE
STRONG UPPER E TO NE FLOW ACROSS THE GULF. THE ATMOSPHERE HERE
IS SLIGHTLY MORE MOIST THAN IT WAS OVER THE PAST FEW DAYS...
THOUGH FAIR CONDITIONS STILL COVER THE BULK OF THE AREA.
LEFTOVER SHOWERS...FROM EARLIER CONVECTIVE ACTIVITY...IS OVER
THE NW GULF N OF 28N BETWEEN 91W-94W. SIMILAR ISOLATED SHOWER
ACTIVITY IS OVER THE BAY OF CAMPECHE CAUSED BY INSTABILITY NEAR
THE UPPER LOW AND A NEARBY TROPICAL WAVE. ISOLATED TO SCATTERED
SHOWERS AND TSTMS ARE ALSO OVER THE SE GULF...S FLORIDA AND CUBA
TRIGGERED BY A SFC TROUGH WHICH EXTENDS NWD FROM THE CARIB
ACROSS W CUBA INTO SW FLORIDA. THE SFC PATTERN REMAINS WEAK WITH
A QUASI-STATIONARY 1016 MB HIGH CENTER NEAR 28N93W. THIS WEAK
PRES GRAD IS EXPECTED TO CONTINUE FOR A FEW MORE DAYS ALLOWING
WINDS AND SEAS TO REMAIN LIGHT/LOW. THE NEXT MOISTURE SURGE
LOOKS TO MOVE INTO THE SE GULF LATE THIS WEEKEND/EARLY NEXT WEEK.

CARIBBEAN SEA...
A CONSIDERABLE AMOUNT OF MOISTURE REMAINS OVER THE CARIB THIS
EVENING. THE DIFFLUENT UPPER PATTERN ENHANCING THIS MOISTURE
CONSISTS OF AN UPPER LOW IN THE BAY OF CAMPECHE...TWO UPPER
HIGHS NEAR 18N81W AND 14N65W AND ANOTHER UPPER LOW NEAR THE
CENTRAL BAHAMAS BAHAMAS. WITHIN THIS MOIST UPPER ENVIRONMENT
THERE ARE THREE TROPICAL WAVES AND A SFC TROUGH HELPING TO
PROVIDE EVEN MORE LIFT. AS MENTIONED IN THE TROPICAL WAVES
SECTION...IT IS DIFFICULT TO DETERMINE WHICH WAVE IS GENERATING
WHAT ACTIVITY. CURRENTLY...A LARGE AREA OF DISORGANIZED
SCATTERED SHOWERS AND TSTMS ARE AFFECTING THE NRN HALF OF THE
CARIB N OF 16N BETWEEN 67W-83W. THE ACTIVITY IS STRONGEST NEAR
AND OVER THE ISLANDS OF HISPANIOLA...CUBA AND JAMAICA WHERE
SEABREEZE AND TOPOGRAPHIC LIFTS ARE LIKELY PLAYING A ROLE.
CONVECTION IS ALSO MAKING ITS WAY TOWARD THE SRN WINDWARDS AS A
WEAK IMPULSE ALONG THE ITCZ MOVES INTO THE AREA.

ATLANTIC OCEAN...
HIGH LEVEL CLOUDINESS AND EMBEDDED POCKETS OF DEEPER MOISTURE
LIE ABOVE A PORTION OF THE SW ATLC S OF 25N BETWEEN 60W-75W.
THIS IS MOSTLY ASSOCIATED WITH DIFFLUENCE ALOFT BETWEEN AN UPPER
LOW NEAR THE CENTRAL BAHAMAS AND AN UPPER HIGH OVER THE E CARIB.
A HIGH LEVEL CIRRUS DECK ALSO COVERS THE AREA N OF 27N BETWEEN
55W-67W AS MOISTURE ROUNDS THE WRN EDGE OF AN UPPER HIGH
CENTERED OFF THE MID-ATLANTIC COAST. THE UPPER PATTERN THEN
FOLDS INTO A LARGE SCALE HIGHLY ELONGATED TROUGH EXTENDING SW
ALONG 32N33W 24N52W 17N55W. RIDGING TAKES OVER E OF THERE
STRETCHING W FROM AN ANTICYCLONE OVER AFRICA ALONG 23N7W 22N22W
20N45W. THERE IS LITTLE MOISTURE ASSOCIATED WITH EITHER THE
RIDGE OR TROUGH. IN FACT...THESE UPPER FEATURES ARE ENHANCING
ABUNDANT DRY AIR ALOFT E OF 50W ALLOWING FAIR WEATHER TO
DOMINATE.

AT THE SFC...THE MAIN FEATURE IS A STATIONARY 1026 MB HIGH
CENTERED NEAR 37N34W. THIS HIGH IS PRODUCING LIGHT TO MODERATE
TRADES ACROSS THE BULK OF THE ATLC DISCUSSION AREA. A QSCAT PASS
NEAR 1930Z SHOWS A SMALL AREA OF SLIGHTLY STRONGER WINDS NEAR
THE COAST OF NW AFRICA...BUT THESE WINDS ARE MUCH WEAKER THAN
THE PAST FEW DAYS. EARLIER VIS IMAGERY AND THE CIMSS SAL
ANALYSIS SHOWS A LARGE MODEST AREA OF SAHARAN DUST BEHIND THE
TROPICAL WAVE IN THE E CARIB. THIS STABLE LOW-MID LEVEL AIR IS
PROMOTING THE WIDESPREAD FAIR CONDITIONS.

$$
CANGIALOSI


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