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Ex-Helene remnant trof


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Might just burn a name

DISCUSSION AND 48-HOUR OUTLOOK

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

AT 800 PM AST...0000 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN

WAS LOCATED NEAR LATITUDE 13.8 NORTH...LONGITUDE 52.8 WEST. THE

DEPRESSION IS MOVING TOWARD THE WEST NEAR 24 MPH...39 KM/H...AND

THIS GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH SUNDAY. ON THE

FORECAST TRACK...THE CENTER OF THE CYCLONE WILL BE NEAR THE

WINDWARD ISLANDS ON SATURDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 35 MPH...55 KM/H...WITH HIGHER

GUSTS. SOME STRENGTHENING IS POSSIBLE OVER THE NEXT DAY OR SO...AND

THE DEPRESSION COULD BECOME A TROPICAL STORM BEFORE REACHING THE

ISLANDS.

NOAA BUOY 41040...LOCATED ABOUT 50 MILES...80 KM...NORTH-NORTHWEST

OF THE CENTER OF THE DEPRESSION...RECENTLY REPORTED A SUSTAINED

WIND OF 36 MPH...57 KM/H...AND A GUST OF 40 MPH...65 KM/H.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB...29.80 INCHES.

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That's a really good question. It wouldn't be a horrible idea to cut a tiny portion of their budget by eliminating the NOGAPS.

So why bother even keeping it around?

As mentioned earlier in this thread (at least I think it was this thread), its used to initialize the TC-COAMPS, which they all seem to be raving about

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NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012

1100 PM AST FRI AUG 10 2012

WHILE THERE HAS BEEN SOME INCREASE IN DEEP CONVECTION NEAR THE

CENTER OVER THE PAST FEW HOURS...THE OVERALL CLOUD PATTERN REMAINS

RATHER SHAPELESS WITH LITTLE EVIDENCE OF BANDING. SATELLITE

ESTIMATES ARE STILL T1.5 FROM TAFB AND SAB...AND THE INITIAL

INTENSITY OF 30 KT IS BASED ON A 1-MINUTE WIND OBSERVATION AT NOAA

BUOY 41040 OF 31 KNOTS AT 2246Z. THE ENVIRONMENT IS CURRENTLY

MARGINAL FOR INTENSIFICATION...AND THE SHIPS MODEL SHOWS THE SHEAR

INCREASING ABOVE 20 KT IN THE NEXT DAY OR SO AS AN UPPER-LEVEL

TROUGH AMPLIFIES TO THE NORTHWEST OF THE CYCLONE. THE NEW NHC

FORECAST SHOWS THE DEPRESSION BECOMING A TROPICAL STORM IN 12 HOURS

WITH LITTLE CHANGE AFTER THAT TIME UNTIL DISSIPATION IN 72 HOURS.

THIS SCENARIO IS SUPPORTED BY THE GFS AND ECMWF GLOBAL MODELS...

WHICH CONTINUE TO SHOW THE CYCLONE DEGENERATING INTO A TROUGH OVER

THE EASTERN OR CENTRAL CARIBBEAN SEA IN 2 TO 3 DAYS.

THE DEPRESSION CONTINUES TO MOVE RAPIDLY WESTWARD WITH AN INITIAL

MOTION OF 275/21. THIS MOTION IS EXPECTED TO CONTINUE THROUGH

DISSIPATION AS THE TROPICAL CYCLONE IS STEERED BY THE ATLANTIC

SUBTROPICAL RIDGE TO THE NORTH. THE NEW NHC FORECAST IS AN UPDATE

OF THE PREVIOUS ONE AND IS CLOSE TO A CONSENSUS OF THE GFS AND

ECMWF MODELS.

GIVEN THE CONTINUING UNCERTAINTY AS TO WHETHER THE DEPRESSION WILL

BECOME A TROPICAL STORM...TROPICAL STORM WATCHES CONTINUE FOR PART

OF THE LESSER ANTILLES...EVEN THOUGH TROPICAL STORM CONDITIONS

WOULD REACH THOSE LOCATIONS WITHIN THE NEXT 24 TO 36 HOURS.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 13.9N 54.1W 30 KT 35 MPH

12H 11/1200Z 14.1N 57.0W 35 KT 40 MPH

24H 12/0000Z 14.3N 60.8W 35 KT 40 MPH

36H 12/1200Z 14.6N 64.7W 35 KT 40 MPH

48H 13/0000Z 14.8N 68.7W 35 KT 40 MPH

72H 14/0000Z...DISSIPATED

$$

FORECASTER BRENNAN

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I never thought NHC needs to issue warnings for a 40mph TS. Wind Advisory, Flood Watch, Gale Warning seems to cover it. TS Warning just confuses people.

I think that is a fair point. In fact, until the late 1980's, there was no such thing as tropical storm watches/warnings. They were covered by gale watches/warnings.

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Because the Navy doesn't want to spend money on upgrading it.

What are you talking about? They upgrade it fairly regularly, though they obviously have a different mission than a regular nwp shop (and much fewer resources). They do a tend to do a lot more da stuff than core model development.

Ed, I will try to find some information when I get a chance.

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Similar to last discussion. Just a snip.

TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 7

NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012

500 AM AST SAT AUG 11 2012

THERE HAS BEEN SOME ADDITIONAL INCREASE IN CONVECTION NEAR AND SOUTH

OF THE CENTER OF TROPICAL DEPRESSION SEVEN DURING THE PAST FEW

HOURS. HOWEVER...THE SYSTEM REMAINS DISORGANIZED...AND IT IS

UNCLEAR IF A CLOSED CIRCULATION STILL EXISTS DUE TO THE RAPID

WESTWARD MOTION. THE INITIAL INTENSITY REMAINS 30 KT BASED ON A

30 KT SATELLITE INTENSITY ESTIMATE FROM TAFB AND CONTINUITY FROM THE

PREVIOUS ADVISORY. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT

IS SCHEDULED TO INVESTIGATE THE SYSTEM LATER THIS MORNING.

Edit- re watches versus warnings- NHC coordinates, however, in case of foreign countries/territories, final decision on watches/warnings is by local governments and met services.

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Recon has found that TD7 is broad and ill defined, with a central pressure ~1012mb, but probably still closed, as the hurricane hunter has found a few, although weak, W wind vectors. It's also farther south than what was shown in the last advisory, closer to 13.3N. Also, clouds are warming on IR...All in all, I doubt that it will survive today.

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They also found tropical storm force SFMR winds... So this is probably TS Gordan.

They may just declare this a vigorous tropical wave. The circulation is very ill-definied and the pressure of 1012mb is really not that different than the background ambient pressure. Also no vortex message yet probably means they dont think they have found a real center yet. We shall see though, all in the eye of the subjective NHC beholder.

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REMNANTS OF SEVEN DISCUSSION NUMBER 8

NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012

1100 AM AST SAT AUG 11 2012

AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION

HAS OBSERVED SHARP WIND SHIFTS AT AN ALTITUDE OF 1000 FT...BUT IT

HAS BEEN UNABLE TO LOCATE A PERSISTENT AND WELL-DEFINED CENTER OF

CIRCULATION. THE DEPRESSION HAS THEREFORE DEGENERATED INTO A

TROPICAL WAVE...AND ADVISORIES ARE BEING DISCONTINUED AT THIS TIME.

THE WAVE WILL BE MONITORED FOR SIGNS OF REGENERATION...AND

ADVISORIES WOULD BE RE-INITIATED IF NEEDED.

THE WAVE CONTINUES TO MOVE RAPIDLY TO THE WEST AT AN ESTIMATED SPEED

OF 22 KT. THE AXIS OF THE WAVE SHOULD MOVE ACROSS THE LESSER

ANTILLES THIS EVENING AND THEN CONTINUE WESTWARD ACROSS THE

CARIBBEAN SEA DURING THE NEXT FEW DAYS. HEAVY RAINS AND WIND GUSTS

TO TROPICAL STORM FORCE ARE STILL POSSIBLE ACROSS PORTIONS OF THE

LESSER ANTILLES LATER TODAY AND TONIGHT.

WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR

THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 13.3N 58.9W 30 KT 35 MPH

12H 12/0000Z...DISSIPATED

$$

FORECASTER BERG/AVILA

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RIP TD-7

AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION

HAS OBSERVED SHARP WIND SHIFTS AT AN ALTITUDE OF 1000 FT...BUT IT

HAS BEEN UNABLE TO LOCATE A PERSISTENT AND WELL-DEFINED CENTER OF

CIRCULATION. THE DEPRESSION HAS THEREFORE DEGENERATED INTO A

TROPICAL WAVE...AND ADVISORIES ARE BEING DISCONTINUED AT THIS TIME.

THE WAVE WILL BE MONITORED FOR SIGNS OF REGENERATION...AND

ADVISORIES WOULD BE RE-INITIATED IF NEEDED.

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This isn't surprising. The global models just weren't as friendly towards TD 7 as they were Ernesto which they were fairly okay on. It's okay though... there will be more storms!

What are you talking about? You can't use global models to forecast tropical cyclones. :rolleyes: :rolleyes: :rolleyes:

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Actually looking halfway decent right now... the system has actually slowed down somewhat today and probably has a closed circulation again. I'm actually quite surprised they downgraded the system earlier today with what looked like a closed circulation on the recon observations. In fact, Ernesto had a more poorly defined circulation in several recon passes last week.

353cnes.gif

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12z Euro isn't as dismal as previous runs or like the GFS...barely avoids Central America and gets into the GoH and BoC as a weak, but trackable disturbance. Saving grace could be the rather unusual ULL to it's southwest, moving in tandem trough the Caribbean, allowing to counter the TUTT to the N/NE in the upper levels.

As for steering currents, it's only mid Aug, and it's a weak disturbance, so it should keep mostly W to WNW, so it's either CA or MX. If it gets to the BoC it might find a weakness, but I seriously doubt it, the central CONUS ridge has been strong this summer, and the disturbance should be far enough W to avoid any weakness between that and the Bermuda ridge. Also, with the NAO going strongly negative, that would probably translate to more zonal ridging in the Sern CONUS, with the trough farther N and E.

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12z Euro isn't as dismal as previous runs or like the GFS...barely avoids Central America and gets into the GoH and BoC as a weak, but trackable disturbance. Saving grace could be the rather unusual ULL to it's southwest, moving in tandem trough the Caribbean, allowing to counter the TUTT to the N/NW in the upper levels.

As for steering currents, it's only mid Aug, and it's a weak disturbance, so it should keep mostly W to WNW, so it's either CA or MX. If it gets to the BoC it might find a weakness, but I seriously doubt it, the central CONUS ridge has been strong this summer, and the disturbance should be far enough W to avoid any weakness between that and the Bermuda ridge. Also, with the NAO going strongly negative, that would probably translate to more zonal ridging in the Sern CONUS, with the trough farther N and E.

I'm looking at the latest model guidance, and both the GFS and ECMWF actually have easterly upper level flow over the Caribbean, which is in stark contract to the last several days. The TUTT doesn't dig down nearly as far south and quickly recedes. There is a decent chance TD#7 recovers under this improving upper level environment.

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I think it has a decent chance (~50%) of re-developing in the W. Caribbean or BOC.

Upper pattern in the BOC days 5-7 looks favorable on the GFS and Euro.

This WRF run agrees:

http://www.myfoxhurricane.com/custom/models/wrf_caribbean.html

12z Euro isn't as dismal as previous runs or like the GFS...barely avoids Central America and gets into the GoH and BoC as a weak, but trackable disturbance. Saving grace could be the rather unusual ULL to it's southwest, moving in tandem trough the Caribbean, allowing to counter the TUTT to the N/NE in the upper levels.

As for steering currents, it's only mid Aug, and it's a weak disturbance, so it should keep mostly W to WNW, so it's either CA or MX. If it gets to the BoC it might find a weakness, but I seriously doubt it, the central CONUS ridge has been strong this summer, and the disturbance should be far enough W to avoid any weakness between that and the Bermuda ridge. Also, with the NAO going strongly negative, that would probably translate to more zonal ridging in the Sern CONUS, with the trough farther N and E.

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I'm looking at the latest model guidance, and both the GFS and ECMWF actually have easterly upper level flow over the Caribbean, which is in stark contract to the last several days. The TUTT doesn't dig down nearly as far south and quickly recedes. There is a decent chance TD#7 recovers under this improving upper level environment.

Yep, that, and the troughing/ULL to it's SW, over Nern SA...which is forecasted to move in tandem with ex TD7, though it's not ideal, as it won't help much venting the storm, it's probably better than having westerly winds. Next 24hrs will probably be the worst shear wise, then they should slowly improve.

post-29-0-41244200-1344716558_thumb.gif

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Agreed. It looks better now than it did for most of the past 3 days.

Also, Barbados, at 13.1N, 59.5W (a little bit SW of the center) has reported winds with a westerly component the past 3 hours:

METAR TBPB 111800Z 19012KT 9999 VCSH SCT010CB SCT034 BKN260 28/26 Q1011

METAR TBPB 111900Z 24016KT 8000 -SHRAVCSH BKN008CB SCT010 24/24 Q1011

METAR TBPB 112000Z 33004KT 9999 VCSH SCT008CB SCT036 BKN260 25/24 Q10

Another personal wx station confirms this, and also has had gusts of ~30 mph several times today:

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=ISTGEORG3&day=11&month=08&year=2012

Actually looking halfway decent right now... the system has actually slowed down somewhat today and probably has a closed circulation again. I'm actually quite surprised they downgraded the system earlier today with what looked like a closed circulation on the recon observations. In fact, Ernesto had a more poorly defined circulation in several recon passes last week.

353cnes.gif

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I've looked at the recon data and I'm very surprised TD#7 was downgraded. Lets look at a few recon passes. This was this morning, where you can see a slightly elongated, but obvious surface circulation. Maybe it wasn't well defined enough to get the VDM, but I'd find hard to dispute that this is a surface circulation.

6tcr4o.png

Now compare this with Ernesto. This was actually the first flight into the system before it was upgraded to a tropical storm.

11vt9hk.png

The main different I see is that the winds on the N side of Ernesto were much stronger, but in terms of the circulation organization, they are not all that different, with very few westerly wind barbs under 10 knots. In fact the first recon flight int Ernesto didn't generate a VDM either. In my opinion the organization of TD#7 is on par with how Ernesto looked at this point, so its unclear to be me why the NHC would downgrade.

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