Tropical Weather Discussion
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000
AXPZ20 KNHC 281539
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON JUL 28 2014

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1500 UTC.

...SPECIAL FEATURES...
HERNAN WAS DOWNGRADED TO A TROPICAL STORM AT 28/0900 UTC. AT
28/1500 UTC...IT IS CENTERED NEAR 20.5N 115.9W OR ABOUT 365
NM...675 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MOVING NW
OR 305 DEGREES AT 14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS
996 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65
KT. SATELLITE IMAGERY SHOWS SCATTERED MODERATE ISOLATED STRONG
CONVECTION WITHIN 75 NM SE QUADRANT AND 60 NM NW QUADRANT. A
MODERATE SHEAR ENVIRONMENT ALONG WITH AN INCREASINGLY STABLE AIR
MASS AND DECREASING SEA SURFACE TEMPERATURE SHOULD WEAKEN HERNAN
INTO A POST TROPICAL CYCLONE IN ABOUT 48 HOURS. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...
A TROPICAL WAVE WITH AXIS ACROSS HONDURAS AND NICARAGUA EXTENDS
INTO THE EPAC TO NEAR 08N86W. SCATTERED MODERATE CONVECTION IS
NOTED WHERE THE WAVE MEETS THE MONSOON TROUGH...MAINLY FROM 05N
TO 09N BETWEEN 84W AND 86W. THIS WAVE WILL CONTINUE TO MOVE
WESTWARD REACHING NEAR 90W TUE MORNING AND 95W WED MORNING.

A SECOND TROPICAL WAVE EXTENDS FROM 17N101W TO 08N102W. A
CLUSTER OF MODERATE CONVECTION IS OBSERVED FROM 13N TO 15N
BETWEEN 99W AND 102W. THIS WAVE IS EXPECTED TO PASS 110W EARLY
TUE. A WEAK LOW PRES AREA IS FORECAST TO DEVELOP NEAR THE
SOUTHERN END OF THE WAVE AXIS BY EARLY WED.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 08N78W TO 09N85W TO 07N100W TO
09N98W. THE ITCZ AXIS CONTINUES FROM 09N98W TO 10N100W TO
07N113W TO A 1011 MB LOW PRES NEAR 11N123W TO 09N130W TO A
SECOND LOW PRES NEAR 15N135W TO 12N140W. SCATTERED MODERATE
CONVECTION IS FROM 05N TO 09N BETWEEN 84W AND 86W. SIMILAR
CONVECTION IS FROM 09N TO 11N BETWEEN 104W AND 106W...AND FROM
09N TO 12N BETWEEN 123W AND 126W.

...DISCUSSION...
AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY WITH AXIS
EXTENDING FROM 30N130W TO A BASE NEAR 15N127W. MOSTLY DRY AIR
ACCOMPANIES THIS TROUGHING GENERALLY N OF 18N BETWEEN 125W AND
135W. AN UPPER LEVEL RIDGE FOLLOWS THIS TROUGH WITH AXIS ALONG
135W/136W. NWLY FLOW ALOFT ASSOCIATED WITH THIS RIDGE CONTINUES
TO IMPACT THE LOW PRES LOCATED NEAR 15N135W. AN ANTICYCLONIC
CIRCULATION IS NOTED OVER TEXAS NEAR 31N101W WITH A RIDGE
EXTENDING SW ACROSS NW MEXICO AND SOUTHERN BAJA CALIFORNIA
PENINSULA TO JUST NE OF HERNAN. ANOTHER ANTICYCLONE IS LOCATED
NEAR 15N116W. AN UPPER-LEVEL LOW HAS DEVELOPED OVER SOUTH-
CENTRAL MEXICO AND IS CENTERED NEAR 19N98W. A TROUGH EXTENDS
FROM THE LOW TO NEAR 13N98W. A DIFFLUENT PATTERN ALOFT W OF THE
TROUGH AXIS IS HELPING TO INDUCE CONVECTION NEAR THE TROPICAL
WAVE ALONG 101W/102W.

WHILE NO SIGNIFICANT CONVECTION REMAINS NEAR A 1009 MB SURFACE
LOW NEAR 15N135W...AN EARLIER ASCAT PASS INDICATED THAT FRESH TO
STRONG WINDS PERSIST WITHIN 240 NM IN THE NORTHERN QUADRANT OF
THE LOW...BETWEEN THE LOW PRES AND THE SUBTROPICAL RIDGE N OF
THE AREA. A PAIR OF ALTIMETER PASSES ALSO INDICATED SEAS OF 8 TO
11 FT IN THIS AREA OF ENHANCED TRADES. THE FORECAST CALLS FOR
THE LOW TO WEAKEN AND THE WINDS TO DIMINISH THROUGH EARLY TUE AS
THE LOW PRES CENTER MOVES W OF 140W...BUT WITH RESIDUAL SEAS
OF 8-9 FT.

A WEAK 1011 MB LOW PRES IS WITHIN THE ITCZ AXIS NEAR 11N123W. A
SMALL CLUSTER OF MODERATE CONVECTION IS OBSERVED WITHIN 120 NM
NW QUADRANT OF LOW CENTER. THIS SYSTEM WILL MOVE GENERALLY W-NW
WITH LITTLE CHANGE.

NORTHERLY WINDS OF 15-20 KT CONTINUE TO PULSE ACROSS THE GULF OF
TEHUANTEPEC WITH SEAS OF 6-7 FT. WINDS ARE EXPECTED TO INCREASE
BRIEFLY TO 20-25 KT BY TUE MORNING LIKELY ASSOCIATED WITH AN
APPROACHING TROPICAL WAVE. SEAS ARE FORECAST TO BUILD TO AROUND
9 FT. CONDITIONS ARE EXPECTED TO IMPROVE BY LATE TUE.

WINDS ARE ALSO EXPECTED TO INCREASE TO 20-25 KT ACROSS THE GULF
OF PAPAGAYO OVERNIGHT TONIGHT INTO TUE MORNING...THEN AGAIN TUE
NIGHT INTO WED MORNING WITH SEAS TO 8 FT DURING EACH PULSE.

FINALLY...SE SWELL FROM THE SOUTHERN HEMISPHERE CONTINUES TO
IMPACT THE SOUTH-CENTRAL WATERS...GENERALLY S OF 04N BETWEEN
110W AND 120W. THIS SWELL EVENT WILL CONTINUE TO PROPAGATE
FARTHER WEST ACROSS THE FORECAST REGION WHILE SUBSIDING.

$$
GR


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