Post Tropical Cyclone Helene: Dissipated Over Mexico

[srainhoutx]

TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
500 PM AST THU AUG 09 2012

LOW CLOUD MOTIONS FROM ANIMATION OF SATELLITE IMAGERY INDICATE THAT
THE AREA OF LOW PRESSURE ACCOMPANYING A TROPICAL WAVE OVER THE
CENTRAL TROPICAL ATLANTIC HAS DEVELOPED A WELL-DEFINED LOW-LEVEL
CIRCULATION. THERE IS SUFFICIENT ORGANIZED DEEP CONVECTION TO
WARRANT THE DESIGNATION OF THE SYSTEM AS A TROPICAL CYCLONE AT THIS
TIME. THE CURRENT INTENSITY ESTIMATE IS 30 KT PENDING OBSERVATIONS
FROM NOAA DATA BUOY 41041...WHICH THE CYCLONE SHOULD PASS NEAR OR
OVER A FEW HOURS FROM NOW. THE SYSTEM IS EXPECTED TO MOVE THROUGH
AN ATMOSPHERIC ENVIRONMENT THAT IS MARGINALLY FAVORABLE FOR
STRENGTHENING...AS THE LGEM GUIDANCE INDICATES SHEAR IN THE 15 TO 20
KT RANGE LATER IN THE FORECAST PERIOD. MOREOVER...THE ECMWF AND GFS
MODELS SUGGEST THAT THE SYSTEM COULD OPEN UP INTO A WAVE IN A FEW
DAYS. THE OFFICIAL INTENSITY FORECAST CALLS FOR ONLY SLOW
STRENGTHENING...AND MORE OR LESS FOLLOWS THE LATEST LGEM GUIDANCE.

A STRONG MID-LEVEL RIDGE IS SITUATED TO THE NORTH OF THE DEPRESSION
AND THE CYCLONE IS MOVING RAPIDLY WESTWARD AT AROUND 17 KT. AN
EVEN FASTER FORWARD MOTION OVER THE NEXT SEVERAL DAYS IS INDICATED
BY THE GLOBAL MODELS...AND BY THE OFFICIAL FORECAST. THE GFDL AND
HWRF MODELS SUGGEST A MORE NORTHWESTWARD TRACK IN THE LATTER PART
OF THE FORECAST PERIOD. THAT SCENARIO SEEMS LESS LIKELY GIVEN THE
STRENGTH OF THE RIDGE FORECAST BY THE GFS AND ECMWF AT THIS TIME.

FORECAST POSITIONS AND MAX WINDS

INIT 09/2100Z 13.7N 43.8W 30 KT 35 MPH
12H 10/0600Z 13.6N 46.3W 30 KT 35 MPH
24H 10/1800Z 13.5N 50.0W 35 KT 40 MPH
36H 11/0600Z 13.5N 53.7W 40 KT 45 MPH
48H 11/1800Z 13.8N 57.4W 40 KT 45 MPH
72H 12/1800Z 14.6N 64.0W 45 KT 50 MPH
96H 13/1800Z 15.5N 70.5W 50 KT 60 MPH
120H 14/1800Z 16.5N 77.0W 55 KT 65 MPH

$$
FORECASTER PASCH

[Gene Norman]

Must say I was more than a little surprised at the initial track, but it seems to be a trend with NHC this year. Model consensus would have favored a more northerly one. Interesting that the 10 pm track starts going in that direction. Since the GFS has done so well this season, I'll stick with it. Tonight's run shows Gordon gone by the weekend and Helen strengthening to a hurricane, but a "fish storm", disturbing only fish in the middle of the ocean. Nice to see some east coast troughing return as was the case the past few seasons.

[wxman57]

Well, I'm a bit surprised at the NHC's more westerly track (diverging from consensus) but for different reasons. I think the more westerly track is more likely. The consensus models appear to be more to the north because of the inclusion of the UKMET and NOGAPS models which take the depression across the extreme NE Caribbean then off to the NW. These two models are almost certainly wrong, given the strong ridge building north of the depression.

And in the longer range, the Euro an GFS build a ridge westward across Florida and the Gulf, all the way to Mexico. They were quite right with the pattern in advance of Ernesto, and I think they're right again. This would suggest a continued westerly movement toward either the southern Yucatan or Nicaragua/Honduras.

Next question is intensity. Indications are that the depression will be fighting the same battle with shear and dry air as Ernesto, perhaps even more so. It could well dissipate or open up to a wave after entering the Caribbean.

[wxman57]

I just measured a 1-hr movement of 28 kts and 3-hr of 27 kts. Can't survive moving that quickly.

[wxman57]

No way this is even close to being a TS, and it probably won't be a TS when it enters the Caribbean.

P.S. Movement between 14Z and 15Z 270 deg at 36 kts.

[Andrew]

You can write this thing off right now until it slows down. If it is moving 36knots there is no way convection can be maintained. It is going to have to slow down a lot. Based on steering currents TD 7 isn't going to slow down anytime soon (at least until it gets into the Mid Caribbean).

[srainhoutx]

TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
500 PM AST FRI AUG 10 2012

DEEP CONVECTION HAS INCREASED SINCE THIS MORNING...BUT THE OVERALL
STRUCTURE HAS NOT IMPROVED. IN FACT...THE LOW-LEVEL CIRCULATION
MAY BE ELONGATING...AND IT IS HARD TO TELL IF THE CENTER IS
EVEN CLOSED ANYMORE. THE CYCLONE IS BEING KEPT AS A 30-KT
DEPRESSION BASED ON DVORAK ESTIMATES OF T1.5 FROM TAFB AND SAB.
THE EVIDENCE APPEARS TO BE MOUNTING THAT SIGNIFICANT
INTENSIFICATION WILL NOT TAKE PLACE. THE DEPRESSION WILL BE MOVING
INTO A HIGHER-SHEAR ENVIRONMENT SOON...AND THE LGEM AND SHIPS
MODELS SHOW VERY LITTLE CHANGE IN STRENGTH FOR THE FIRST 48 HOURS
OR SO. THE GFS AND ECMWF HAVE ALSO BEEN IN CONSISTENT AGREEMENT
THAT THE CYCLONE WILL DEGENERATE INTO AN OPEN WAVE IN 2 TO 3 DAYS
OVER THE EASTERN CARIBBEAN SEA. GIVEN THE CURRENT FRAGILE STATE OF
THE DEPRESSION...AND THE UNFAVORABLE CONDITIONS THAT LIE AHEAD...
THE NEW NHC FORECAST BRINGS THE CYCLONE TO A 35-KT TROPICAL STORM
BEFORE IT REACHES THE LESSER ANTILLES AND THEN SHOWS DISSIPATION
INTO A TROUGH OVER THE CARIBBEAN SEA BY DAY 3.

THE DEPRESSION CONTINUES TO MOVE RAPIDLY TO THE WEST...NOW WITH AN
ESTIMATED MOTION OF 270/21 KT. A FAST WESTWARD MOTION IS EXPECTED
TO CONTINUE OVER THE NEXT FEW DAYS WHILE THE SYSTEM LIES TO THE
SOUTH OF THE SUBTROPICAL RIDGE. THE GFS AND ECMWF SOLUTIONS ARE IN
BETTER AGREEMENT THAN THEY HAD BEEN...AND THE NHC TRACK FORECAST IS
NEAR A CONSENSUS OF THOSE TWO MODELS UNTIL DISSIPATION IN 72 HOURS.

THERE IS STILL A LOT OF UNCERTAINTY REGARDING WHETHER OR NOT THE
DEPRESSION WILL EVEN BECOME A TROPICAL STORM. THE VARIOUS
GOVERNMENTS IN THE LESSER ANTILLES HAVE THEREFORE DECIDED TO ISSUE
TROPICAL STORM WATCHES FOR THEIR RESPECTIVE ISLANDS...EVEN THOUGH
TROPICAL STORM CONDITIONS WOULD REACH THOSE LOCATIONS WITHIN THE
NEXT 36 HOURS.

FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 13.7N 51.9W 30 KT 35 MPH
12H 11/0600Z 13.9N 54.8W 30 KT 35 MPH
24H 11/1800Z 14.2N 58.5W 35 KT 40 MPH
36H 12/0600Z 14.5N 62.3W 35 KT 40 MPH
48H 12/1800Z 14.7N 66.3W 35 KT 40 MPH
72H 13/1800Z...DISSIPATED

$$
FORECASTER BERG/BRENNAN

[wxman57]

Agree with the latest NHC forecast, except the part about it becoming a TS before it dissipates.

[biggerbyte]

I would not write off TD7 just yet. Ernie hit it rough, and many were calling for his demise, yet he did make it far enough west to get his act together. It is going to be a tough trek for TD7, so we'll see. If the models are correct, if anything were left, this system will just stay well south like Ernesto. That is a whole lot of big ifs in this post. After the Debbie fiasco, I do not know how anyone would not be skepticle.

[srainhoutx]

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

[srainhoutx]

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1045 AM EDT SAT 11 AUGUST 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 12/1100Z TO 13/1100Z AUGUST 2012
TCPOD NUMBER.....12-085

I. ATLANTIC REQUIREMENTS
1. TROPICAL DEPRESSION SEVEN
FLIGHT ONE - TEAL 72 -
MISSION DELAYED 6 HOURS FROM TASKED MISSION ON TCPOD 12-084
A. 12/1800Z
B. AFXXX 0207A CYCLONE
C. 12/1630Z
D. 13.3N 68W
E. 12/1700Z TO 12/2200Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: PSBL FIX MISSION NEAR 14N AND 74W
IF SYSTEM BECOMES A THREAT.

3. REMARK: 12/0000Z-0600Z MISSION WAS CANCELLED BY NHC 11/1500Z.

[srainhoutx]

The 12z Euro is a bit more bullish on some development with Ex 07 today. While the GFS never develops the wave again, it is a tad interesting to see one of the more reliable global models 'sniffing' a chance at seeing some strengthening in the Bay of Campeche. We will see...

[biggerbyte]

TD7 remnant is far from being gone for good. Still too early to tell if we can get a TS out of this system, but it is not out of the question at this point.

Definately stay tuned.

[srainhoutx]

12Z Tracks & Intensity:

[srainhoutx]

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1045 AM EDT MON 13 AUGUST 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 14/1100Z TO 15/1100Z AUGUST 2012
TCPOD NUMBER.....12-087

I. ATLANTIC REQUIREMENTS
1. REMNANTS OF TROPICAL DEPRESSION SEVEN
FLIGHT ONE --TEAL 72--
A. 14/1700Z
B. AFXXX 0207A INVEST
C. 14/1300Z
D. 15.5N 83.0W
E. 14/1630Z TO 14/1930Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

[srainhoutx]

THE REMNANTS OF TROPICAL DEPRESSION SEVEN ARE MOVING OVER THE
CENTRAL CARIBBEAN SEA AND PRODUCING DISORGANIZED SHOWERS AND
THUNDERSTORMS FROM THE CENTRAL CARIBBEAN NORTHWARD TO HISPANIOLA
AND JAMAICA. UPPER-LEVEL WINDS ARE EXPECTED TO GRADUALLY BECOME
MORE CONDUCIVE FOR REGENERATION OVER THE NEXT DAY OR SO AS THE
SYSTEM MOVES TOWARD HONDURAS...BELIZE...AND THE YUCATAN. THIS
SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A TROPICAL
CYCLONE AGAIN DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD NEAR
20 MPH. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULED
TO INVESTIGATE THE DISTURBANCE TUESDAY AFTERNOON...IF NECESSARY.

[Portastorm]

Sadly, the GFS runs it into Nicaragua. It does make a bit of a late comeback before crashing and burning into land. Could get a TS warning in Nicaragua out of ex-7 if GFS is right.

Which run? 12z?

There seems to be a diversity of opinion in the professional meteorology community about TD #7 and it's ultimate impact. Some are saying Texas, some are saying Central America.

[TexasBreeze]

It's racing towards C. America and will landfall real soon I think.

[srainhoutx]

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0910 AM EDT TUE 14 AUGUST 2012
SUBJECT: PLAN OF THE DAY (TCPOD)
VALID 15/1100Z TO 16/1100Z AUGUST 2012
NUMBER.....12-088

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
3. REMARKS: FLIGHT INTO THE REMNANTS OF TD #7 FOR
14/1700Z CANCELED BY NHC AT 14/0930Z

[srainhoutx]

The latest microwave pass suggests that the vort max located just SW of Jamaica is becoming the more dominant feature as ex TD 7 moves into the NW Caribbean. The area of convection further S appears to be loosing convection and the vorticity has decreased. Just perhaps the GFS has been right all along with this moisture and vorticity becoming active in the Bay of Campeche all along. We will see...