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EPAC Tropical Action 2011


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Well the majority of the circulation is over land right now in Central America. Were is not for the land interaction, this system would likely be in the process of becoming a tropical cyclone. As the low level ridge strengthens across the Atlantic basin and Eastern US, it will force the disturbance out into the East Pacific where it should develop pretty quickly under low shear and warm SSTs. By 72 hours, the GFS is projecting a very favorable upper wind flow pattern at 200mb, forecasting expanding outflow in all quadrants of the system, which may already be a tropical storm by this point.

This could become quite a formidable storm (hurricane and beyond) if this outflow regime verifies. The ECWMF eventually develops this system as well, but much later on (beyond 96 hours). I see no reason for its conservative forecast in the short term given that the circulation is already well established over Central America. It is just a matter of how quickly it can get into the East Pacific and start developing.

Cool, thanks. What about the track? Land threat or total fish?

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Cool, thanks. What about the track? Land threat or total fish?

Still a little too early to tell for now. The GFS (and ECWMF) show a powerful ridge dominating across the Central US the next 2-3 days. This will likely keep the track westward for now with a slight northward component. However, you can see in 72 hours a strong trough will be moving into the Western US. This will weaken the ridge... the question is how much? The equation becomes more complicated because its unknown how strong the current disturbance will get, with a stronger and larger system more susceptible to a weaker ridge. I think if we are ultimately dealing with a stronger system, a track closer the the Mexican coastline is more likely than the Euro solution, which keeps the system out to sea. As always though, track forecasts are tricky to forecast before the genesis of a system.

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20% at 5:00AM and sort of slow development per the GFS SE of the Gulf of Tehuantepec in about 3 days. The Euro OTOH is even slower in developing a potential Dora that makes a run near Socorro Island next weekend. We will see...

avn-l.jpg

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The GFS continues to be very adamant about immediate genesis as soon as the low over Central America moves into the East Pacific. This is not the same feature that the NHC has been keying on. The NHC lemon has some potential as well, but is much more loosely organized and hasn't totally become a separate entity from the monsoonal trough.

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Two lemons...how about some lemonaide...?

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

1100 AM PDT SAT JUL 16 2011

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

1. A BROAD LOW PRESSURE SYSTEM LOCATED ALONG THE COAST OF SOUTHEASTERN

MEXICO JUST EAST OF PUERTO ANGEL IS PRODUCING A LARGE AREA OF

CLOUDINESS AND SHOWERS OVER THE GULF OF TEHUANTEPEC AND ADJACENT

LAND AREAS. DEVELOPMENT OF THIS DISTURBANCE...IF ANY...SHOULD BE

SLOW TO OCCUR DUE TO INTERACTION WITH LAND. THIS SYSTEM HAS A LOW

CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE

NEXT 48 HOURS AS IT MOVES SLOWLY TOWARD THE WEST OR WEST-NORTHWEST.

REGARDLESS OF DEVELOPMENT... LOCALLY HEAVY RAINS COULD OCCUR OVER

PORTIONS OF SOUTHEASTERN MEXICO DURING THE NEXT COUPLE OF DAYS IN

ASSOCIATION WITH THIS SYSTEM.

2. A LOW PRESSURE SYSTEM EMERGING OFF THE COAST OF COSTA RICA IS

PRODUCING SCATTERED THUNDERSTORMS OVER PORTIONS OF CENTRAL

AMERICA AND ADJACENT PACIFIC WATERS. ONLY SLOW DEVELOPMENT IS

EXPECTED FOR THE NEXT DAY OR TWO DUE TO LAND INTERACTION...BUT

ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR MORE SIGNIFICANT

DEVELOPMENT TO OCCUR AFTER THAT TIME. THIS SYSTEM HAS A LOW

CHANCE...20 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE

NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT 5 TO 10 MPH.

LOCALLY HEAVY RAINFALL WILL BE POSSIBLE OVER MUCH OF CENTRAL

AMERICA DURING THE NEXT COUPLE OF DAYS IN ASSOCIATION WITH THIS

LARGE DISTURBANCE.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER STEWART

post-32-0-43395700-1310839201.gif

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This invest is for the southern most area off Costa Rica...

BEGIN

NHC_ATCF

invest_ep942011.invest

FSTDA

R

U

040

010

0000

201107161729

NONE

NOTIFY=ATRP

END

INVEST, EP, E, , , , , 94, 2011, DB, O, 2011071618, 9999999999, , , , , , METWATCH, , EP942011

EP, 94, 2011071512, , BEST, 0, 98N, 825W, 15, 1010, LO, 0, , 0, 0, 0, 0,

EP, 94, 2011071518, , BEST, 0, 98N, 831W, 15, 1010, LO, 0, , 0, 0, 0, 0,

EP, 94, 2011071600, , BEST, 0, 98N, 836W, 20, 1009, LO, 0, , 0, 0, 0, 0,

EP, 94, 2011071606, , BEST, 0, 99N, 841W, 20, 1009, LO, 0, , 0, 0, 0, 0,

EP, 94, 2011071612, , BEST, 0, 100N, 846W, 20, 1009, LO, 0, , 0, 0, 0, 0,

EP, 94, 2011071618, , BEST, 0, 101N, 851W, 20, 1009, LO, 34, NEQ, 0, 0, 0, 0, 1

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18Z SHIPS up to 61 kts now...

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

1100 AM PDT SUN JUL 17 2011

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

A VIGOROUS LOW PRESSURE SYSTEM LOCATED ABOUT 225 MILES SOUTH OF

EL SALVADOR IS PRODUCING WIDESPREAD CLOUDINESS AND SCATTERED

THUNDERSTORMS. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR FURTHER

DEVELOPMENT OF THIS LARGE DISTURBANCE AS IT MOVES WEST-NORTHWESTWARD

AT 5 TO 10 MPH. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF

BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER STEWART

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SHIPS has been slowly increasing the max strength over the past few days, no reason to think it won't get to hurricane strength, the models are certainly agressive enough to suggests thats probable. I'd personally go with a peak strength of say 80kts.

Steady does it!

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Sweet. A big old Cherry...

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

500 AM PDT MON JUL 18 2011

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

THUNDERSTORM ACTIVITY HAS BECOME MORE CONCENTRATED NEAR THE CENTER

OF A WELL-DEFINED LOW PRESSURE SYSTEM LOCATED ABOUT 240 MILES SOUTH

OF GUATEMALA. UPPER-LEVEL WINDS HAVE ALSO BECOME MORE CONDUCIVE FOR

DEVELOPMENT...AND A TROPICAL DEPRESSION COULD FORM LATER TODAY.

THIS SYSTEM HAS A HIGH CHANCE...90 PERCENT...OF BECOMING A TROPICAL

CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT 10 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER STEWART

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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 1

NWS NATIONAL HURRICANE CENTER MIAMI FL EP042011

800 AM PDT MON JUL 18 2011

SATELLITE IMAGERY INDICATES THUNDERSTORM ACTIVITY HAS BECOME

SUFFICIENTLY ORGANIZED NEAR THE CENTER OF THE WELL-DEFINED LOW

PRESSURE AREA LOCATED TO THE SOUTH OF GUATEMALA FOR THIS SYSTEM TO

BE DESIGNATED AS THE FOURTH TROPICAL DEPRESSION OF THE SEASON.

ALTHOUGH SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE ONLY

T1.5/25 KT...NHC ADT ESTIMATES INDICATE THE SYSTEM IS NEAR TROPICAL

STORM STRENGTH. IN ADDITION...SHIP WDE5381 LOCATED ABOUT 70 NMI

NORTH OF THE CENTER REPORTED AN EAST WIND OF 31 KT AT 06Z.

THEREFORE...THE INITIAL INTENSITY IS SET AT A CONSERVATIVE 30 KT.

THE INITIAL MOTION ESTIMATE IS 280/11. AN EXTENSIVE SUBTROPICAL

RIDGE LOCATED ACROSS MOST OF THE UNITED STATES AND EXTENDING

SOUTHWARD ACROSS THE GULF OF MEXICO AND INTO MAINLAND MEXICO IS

EXPECTED TO KEEP THE SYSTEM MOVING IN A GENERAL WEST-NORTHWESTWARD

DIRECTION THROUGHOUT THE FORECAST PERIOD. THE GFDL AND HWRF MODELS

ARE FORECASTING THE WESTERN PORTION OF THE RIDGE TO ERODE AFTER 72

HOURS...WHICH WOULD ALLOW THE CYCLONE TO TURN NORTHWESTWARD TOWARD

BAJA CALIFORNIA. HOWEVER...THESE APPEAR TO BE OUTLIER SOLUTIONS

GIVEN THE CURRENT STRENGTH OF THIS BROAD HEAT-WAVE DOME OF HIGH

PRESSURE. AS A RESULT...THE OFFICIAL FORECAST TRACK IS WELL SOUTH

OF THE GFDL/HWRF TRACKS AFTER AT 96 AND 120 HOURS...AND IS SIMILAR

TO BUT SLIGHTLY SOUTH OF THE GLOBAL MODEL CONSENSUS THROUGHOUT THE

FORECAST PERIOD.

SATELLITE IMAGERY INDICATES A WELL-DEFINED CURVED BAND OF CONVECTION

THAT IS INDICATIVE OF A DEVELOPING TROPICAL STORM. MICROWAVE AND

VISIBLE SATELLITE IMAGERY...PLUS THE AFOREMENTIONED SHIP

REPORT...ALSO SUGGEST THAT THE DEPRESSION HAS A FAIRLY TIGHT INNER

CORE WIND FIELD. ALL OF THIS WOULD INDICATE THAT RAPID

INTENSIFICATION IS A DISTINCT POSSIBILITY. HOWEVER...AN INHIBITING

FACTOR FOR THE NEXT 24 HOURS IS MODERATE NORTHERLY SHEAR...SO ONLY

STEADY STRENGTHENING IS FORECAST. BY 36 HOURS...THE SHEAR IS

EXPECTED TO DECREASE TO NEAR 5 KT...WHICH SHOULD ALLOW FOR

SIGNIFICANT INTENSIFICATION OF THE CYCLONE. THE OFFICIAL INTENSITY

FORECAST IS WELL ABOVE ALL OF THE STATISTICAL INTENSITY GUIDANCE

AND CLOSELY FOLLOWS THE GFDL AND HWRF MODELS THROUGH 96 HOURS.

AFTER THAT...RAPID WEAKENING IS FORECAST AS THE CYCLONE IS EXPECTED

TO MOVE OVER THE COLD WATER TROPICAL CYCLONE GRAVEYARD SITUATED

WEST OF 110W LONGITUDE.

FORECAST POSITIONS AND MAX WINDS

INIT 18/1500Z 10.6N 91.5W 30 KT 35 MPH

12H 19/0000Z 10.7N 93.1W 40 KT 45 MPH

24H 19/1200Z 11.3N 95.5W 55 KT 65 MPH

36H 20/0000Z 12.3N 98.7W 70 KT 80 MPH

48H 20/1200Z 13.6N 101.5W 85 KT 100 MPH

72H 21/1200Z 16.6N 106.5W 105 KT 120 MPH

96H 22/1200Z 18.8N 110.3W 100 KT 115 MPH

120H 23/1200Z 20.0N 113.0W 70 KT 80 MPH

$$

FORECASTER STEWART

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TROPICAL STORM DORA TROPICAL CYCLONE UPDATE

NWS NATIONAL HURRICANE CENTER MIAMI FL EP042011

1100 AM PDT MON JUL 18 2011

...DEPRESSION REACHES TROPICAL STORM STRENGTH...

SATELLITE IMAGES INDICATE THAT TROPICAL DEPRESSION FOUR-E

HAS STRENGTHENED AND IS NOW TROPICAL STORM DORA.

SUMMARY OF 1100 AM PDT...1800 UTC...INFORMATION

--------------------------------------------------

LOCATION...10.6N 92.3W

ABOUT 400 MI...645 KM SSE OF SALINA CRUZ MEXICO

MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H

PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/H

MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES

$$

FORECASTER STEWART

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