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Wednesday, July 15, 2009

Atlantic Hurricane Season Update



While the Pacific side of North America is working on it's fifth storm, the Atlantic Basin has yet to see one. That may be about to change as a couple of tropical waves have formed off the western coast of Africa (an image of one of them is above) and may work their way across the Atlantic in the next week or so. Or not.

The typical peak of the Atlantic Hurricane Season is from August to the end of October.

More details regarding the activity from the National Hurricane Center:

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED JUL 15 2009

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 1045 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 24W S OF 15N MOVING W NEAR 15 KT.
RECENT VISIBLE SATELLITE IMAGERY DEPICTS MID-LEVEL CYCLONIC
CIRCULATION NEAR THIS WAVE. SCATTERED MODERATE CONVECTION IS
FROM 7N-12N BETWEEN 23W-28W.

A TROPICAL WAVE IS ALONG 40W/41W S OF 16N MOVING W NEAR 15 KT.
THIS WAVE COINCIDES WITH A LOW AMPLITUDE MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. SCATTERED MODERATE CONVECTION IS FROM 11N-14N BETWEEN
38W-40W.

A HIGHLY-AMPLIFIED TROPICAL WAVE IS OVER THE SW NORTH ATLC AND E
CARIBBEAN...AND EXTENDS FROM 24N66W TO 15N68W TO 6N68W MOVING W
20-25 KT. UPPER AIR DATA FROM BARBADOS AND GUADELOUPE AT
15/0000 UTC INDICATE THAT THE WAVE IS FOLLOWED BY A STRONG
EASTERLY 700-650 MB JET...WITH CORE WINDS OF 45 KT. RECENT
SATELLITE IMAGERY SHOW A WELL-DEFINED AND HIGHLY-AMPLIFIED
INVERTED-V PATTERN EVIDENT IN THE COVERAGE OF LOW-LEVEL CLOUDS
NEAR THE WAVE...COINCIDING WITH A MAXIMUM IN TOTAL PRECIPITABLE
WATER. THE WAVE IS LEADING AN AREA OF ABUNDANT DRY LOW/MID-LEVEL
SAHARAN AIR. THIS IS CONTRIBUTING TO SUFFICIENT LOW LEVEL
ATMOSPHERIC LIFT TO SUPPORT SCATTERED SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WITHIN 180 NM E OF THE WAVE AXIS. THE DRY
AIR...ALONG WITH STABLE ATMOSPHERIC CONDITIONS BENEATH AN UPPER
LEVEL HIGH OVER THE E CARIBBEAN...ARE LIMITING THE AREAL
COVERAGE OF DEEP CONVECTION NEAR THE WAVE. THE AFOREMENTIONED
DRY AIR IS LIKELY CONTRIBUTING TO STRONG DOWNDRAFTS AND GUSTY
OUTFLOW WINDS WITH THE SHOWER AND THUNDERSTORM ACTIVITY. THE
STRONG EASTERLY JET FOLLOWING THE WAVE HAS PUSHED THE SOUTHERN
PORTIONS OF THE WAVE SUFFICIENTLY FAR TO THE WEST TO HAVE
FRACTURED THE WAVE ALONG 24N. N OF 24N...A SURFACE TROUGH IS
ANALYZED FROM 30N62W TO 24N66W...WITH SCATTERED SHOWERS WITHIN
60 NM EITHER SIDE OF THE SURFACE TROUGH. THIS TROUGH WAS
PREVIOUSLY A PART OF THE TROPICAL WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N15W 10N27W 10N37W 9N50W
9N61W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM
6N-14N E OF 22W. SCATTERED MODERATE CONVECTION IS FROM 10N-12N
BETWEEN 42W-46W. SCATTERED MODERATE CONVECTION IS ALSO FROM
8N-10N BETWEEN 53W-56W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL HIGH IS OVER THE NW GULF OF MEXICO CENTERED NEAR
28N95W WITH A SURFACE RIDGE ACROSS THE N GULF AND A 1019 MB
SURFACE HIGH OVER THE FLORIDA PENINSULA NEAR 29N82W. GENERALLY
FAIR WEATHER IS PRESENT ACROSS THE GULF. WINDS ARE LIGHT AND
VARIABLE IN THE VICINITY OF THE SURFACE RIDGE ACROSS THE N
GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING A
BROAD SWATH OF E WINDS OF 10-15 KT ACROSS THE S HALF OF THE
GULF. THESE CONDITIONS ARE FORECAST TO CONTINUE DURING THE NEXT
SEVERAL DAYS. HOWEVER...NE WINDS UP TO 20 KT ARE FORECAST TO
OCCUR DURING THE LATE AFTERNOON AND EVENING HOURS DURING THE
NEXT SEVERAL DAYS NEAR THE COAST OF THE YUCATAN PENINSULA.
LITTLE CHANGE IS EXPECTED OVER THE NEXT DAY OR TWO AS BOTH THE
UPPER AND SFC RIDGE REMAIN IN PLACE.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE
SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER
NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST
OF COLOMBIA. THE QUIKSCAT PASS AROUND 14/2315 UTC INDICATED A
LARGE AREA OF NE TO E WINDS OF 20 TO 30 KT ACROSS THE CENTRAL
CARIBBEAN. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL
DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A TROPICAL
WAVE MOVES ACROSS THE AREA. IN FACT...GALE CONDITIONS ARE
FORECAST TO BEGIN LATER TODAY THROUGH THE END OF THE WEEK...AS
THE LOW LEVEL FLOW STRENGTHENS ACROSS THE CARIBBEAN AND
INTERACTS THE LOCAL TOPOGRAPHICAL VARIATIONS NEAR THE COAST OF
COLOMBIA. INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER
THE N CENTRAL CARIBBEAN CENTERED NEAR 18N82W AND AN UPPER LEVEL
TROUGH OVER THE SW CARIBBEAN IS RESULTING IN SCATTERED SHOWERS
AND THUNDERSTORMS WITHIN 120 NM OF THE COAST OF CENTRAL AMERICA
S OF 16N. ALSO...THE TROPICAL WAVE MOVING ACROSS THE E CARIBBEAN
IS ACCOMPANIED BY...AND FOLLOWED BY...STRONGER WINDS AND A
STRONG SURGE OF SAHARAN AIR.

ATLANTIC OCEAN...
DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE IN
NORTHWESTERLY FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 30N W OF
77W. ALSO...SCATTERED SHOWERS AND ISOLATED TSTMS ARE N OF 24N
BETWEEN 66W-75W. THIS ACTIVITY IS BEING SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM 29N69W TO
25N74W. THIS ACTIVITY IS ALSO SUPPORTED BY ATMOSPHERIC
INSTABILITY ASSOCIATED WITH AN UPPER TROUGH OVER THE SW NORTH
ATLC. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS
MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH
A 1029 MB HIGH NEAR 34N48W. ACROSS THE TROPICAL N ATLC...
NORTHEASTERLY UPPER LEVEL FLOW IS IN PLACE...WITH STRONG UPPER
LEVEL DIFFLUENCE SUPPORTING THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE ALONG 40W/41W S OF 16N.

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