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TD Erin


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000
WTNT45 KNHC 150238
TCDAT5

TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013
1100 PM AST WED AUG 14 2013

ASCAT DATA FROM EARLIER THIS EVENING INDICATED THAT THE AREA OF LOW
PRESSURE NEAR THE CAPE VERDE ISLANDS HAS AN INNER CORE REGION OF
LIGHT WINDS SURROUNDED BY A BAND OF STRONGER WINDS NEAR 30 KT...BUT
THE CENTER APPEARS SUFFICIENTLY WELL DEFINED TO FIT THE DEFINITION
OF A TROPICAL CYCLONE. DVORAK INTENSITY ESTIMATES WERE ONLY T1.0
FROM TAFB AND SAB AT 0000 UTC...BUT GIVEN RECENT CONVECTIVE TRENDS
AND THE OVERALL STRUCTURE...ADVISORIES ARE BEING INITIATED ON
TROPICAL DEPRESSION FIVE.

THE DEPRESSION IS CURRENTLY IN AN ENVIRONMENT THAT IS CONDUCIVE FOR
STRENGTHENING...CHARACTERIZED BY LOW WIND SHEAR...WARM SSTS...AND A
MOIST AIR MASS. THIS ENVIRONMENT...HOWEVER...WILL BECOME A LITTLE
LESS FAVORABLE IN A FEW DAYS WHEN THE CYCLONE IS EXPECTED TO REACH
SLIGHTLY COOLER SSTS AND A MORE STABLE ENVIRONMENT. IN ADDITION...
THE DEPRESSION IS LIKELY TO BE CUT OFF FROM ITS DEEP MOISTURE
SOURCE TO THE SOUTH IN ABOUT 3 DAYS. THEREFORE...MODEST
STRENGTHENING IS INDICATED IN THE OFFICIAL FORECAST THROUGH THE
FIRST 48 HOURS WITH SOME WEAKENING BY THE END OF THE FORECAST
PERIOD. THIS FORECAST IS VERY NEAR THE INTENSITY CONSENSUS.

THE DEPRESSION IS LOCATED ON THE SOUTHERN PERIPHERY OF A NARROW
MID-LEVEL RIDGE...AND IT HAS AN INITIAL MOTION OF 290/12 KT. THE
RIDGE IS EXPECTED TO BE RATHER WEAK FOR THE NEXT FEW DAYS DUE TO A
CLOSED MID- TO UPPER-LEVEL LOW LOCATED SOUTH OF THE AZORES...AND
THIS PATTERN SHOULD KEEP THE CYCLONE ON A WEST-NORTHWESTWARD
TRAJECTORY THROUGH THE FIRST 3 DAYS. ONCE WEAKENING BEGINS IN 4 TO
5 DAYS...LOWER-LEVEL FLOW WILL TAKE OVER AND SHOULD STEER THE
SYSTEM ON A MORE WESTERLY TRACK. WITH THE EXCEPTION OF THE GFDL
MODEL...WHICH SHOWS A SLOWER AND MORE NORTHERLY SOLUTION...THE
OTHER TRACK MODELS ARE IN DECENT AGREEMENT THROUGH 5 DAYS. THE NHC
TRACK FORECAST IS THEREFORE VERY CLOSE TO THE MODEL CONSENSUS TVCA.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 14.0N 23.5W 30 KT 35 MPH
12H 15/1200Z 14.5N 25.2W 35 KT 40 MPH
24H 16/0000Z 15.1N 27.9W 40 KT 45 MPH
36H 16/1200Z 15.7N 30.6W 45 KT 50 MPH
48H 17/0000Z 16.5N 32.9W 50 KT 60 MPH
72H 18/0000Z 17.5N 37.0W 50 KT 60 MPH
96H 19/0000Z 17.5N 41.5W 45 KT 50 MPH
120H 20/0000Z 17.5N 46.0W 40 KT 45 MPH

$$
FORECASTER BERG/STEWART

post-442-0-85928800-1376535099_thumb.gif

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BULLETIN
TROPICAL STORM ERIN INTERMEDIATE ADVISORY NUMBER 2A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013
800 AM AST THU AUG 15 2013

...DEPRESSION BECOMES TROPICAL STORM ERIN WEST-SOUTHWEST OF THE
SOUTHERN CAPE VERDE ISLANDS...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...14.5N 25.6W
ABOUT 65 MI...100 KM WSW OF BRAVA IN THE CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

 
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Erin will be an interesting test of the relative skill (or lack thereof) of the models and the NHC at forecasting strength of tropical systems. The conditions ahead of it are fair but not particularly hostile. It certainly has a better chance than Dorian had. I like the NHC forecast of a steady perhaps slightly weakening tropical storm, but I could see Erin surprising on the up or downside too. 

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Weenieism watch

 

Glass quarter full optimism, what is left of Erin will be Northeast of the Greater Antilles at hour 192 per 6Z GFS.  Post truncation GFS doesn't regenerate it.  Moisture wise, not in a very favorable place, but it is forecast under an upper ridge with light winds over the remnant but 35 knot knot 250mb winds just North of it which could help with upward motion.  (Proper placement of remnant vorticity obviously important, to be South of the shear and not in the shear)  And decent enough heat potential if it does get convectively active again, it might be able to modify/overcome somewhat dry air.

 

2013226at.jpg

 

And by staying weak, even degenerating back into a wave, it has a much better chance of getting within striking range of the US East Coast

 

 

Big picture Euro MJO forecast looks decent enough, maybe MV or Phil or one of the other Albany heavies will weigh in on whether this might encounter favorable or unfavorable shorter period conditions, CCKWs and all that when it gets towards the Bahamas.

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Euro turns the remnants of Erin into the C Atlantic around 60W. Just FYI, Ed.

 

I read the NHC discussion this morning.  (And first thing I do this time of year after waking up while drinking coffee is hit PSU tropical 4 panels and Euro 240 hour 850 mb vorticity forecasts.  I skip NavGem and Canadian if in a rush)  All depends on how fast it weakens, I suppose.  But I am sort of assuming the NHC forecast track is close and the intensity forecast is a touch optimistic.

 

Euro does seem to be winning the overall war on 92L.

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A small tidbit favoring my natural see the silver lining in any situation optimism.

 

 

0

00
WTNT45 KNHC 151440
TCDAT5

TROPICAL STORM ERIN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 AM AST THU AUG 15 2013

THE SATELLITE PRESENTATION OF THE CYCLONE HAS CONTINUED TO IMPROVE
OVER THE PAST FEW HOURS. INFRARED IMAGERY SHOWS VERY COLD CLOUD
TOPS SITUATED NEAR AND TO THE SOUTH OF THE ESTIMATED CENTER
POSITION...WITH A SMALL BANDING FEATURE EXTENDING TO THE SOUTHWEST.
THE INITIAL INTENSITY OF 35 KT IS SUPPORTED BY A BLEND OF THE
LATEST OBJECTIVE AND SUBJECTIVE DVORAK ESTIMATES AND A 1102 UTC
ASCAT-A PASS THAT SHOWED WINDS OF 32 KT. ERIN IS EXPECTED TO BE IN
AN ENVIRONMENT THAT SUPPORTS SOME STRENGTHENING DURING THE NEXT
COUPLE OF DAYS WITH SSTS OF 26-27C...LOW SHEAR...AND A MOIST
ENVIRONMENT. BY DAY 3...THE SYSTEM WILL BE MOVING INTO A DRIER AND
MORE STABLE ATMOSPHERIC ENVIRONMENT...WHICH SHOULD RESULT IN
WEAKENING. THE GLOBAL MODELS AND THE HWRF SHOW A WEAK OR
DISSIPATING SYSTEM BY DAY 5...HOWEVER THE SHIPS AND LGEM SHOW
LITTLE CHANGE IN INTENSITY OR EVEN STRENGTHENING. THE OFFICIAL
FORECAST LEANS A LITTLE TOWARD THE WEAKER SOLUTION AT DAYS 4 AND 5.

THE AFOREMENTIONED ASCAT PASS WAS ALSO HELPFUL IN LOCATING THE
CENTER OF ERIN...WHICH IS A LITTLE SOUTH AND WEST OF PREVIOUS
ESTIMATES
. BASED ON A SOUTHWESTWARD ADJUSTMENT OF THE CENTER
POSITION THE INITIAL MOTION ESTIMATE IS 285/13. ERIN IS CURRENTLY
BEING STEERED BY A NARROW SUBTROPICAL RIDGE TO ITS NORTH...AND THE
GUIDANCE IS IN GOOD AGREEMENT ON THIS MOTION CONTINUING FOR THE
NEXT COUPLE OF DAYS. BY DAY 3...THE SPREAD IN THE GUIDANCE
INCREASES. ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE THE GFDL...
GFDL ENSEMBLE MEAN...ECMWF AND UKMET SHOW A NORTHWESTWARD OR
WEST-NORTHWESTWARD MOTION. THE FIM...GFS...GFS ENSEMBLE MEAN AND
HWRF ALL SHOW A WESTWARD TRACK...CONSISTENT WITH A SHALLOWER SYSTEM
BEING STEERED BY THE LOW-LEVEL FLOW. THE NHC FORECAST AT DAYS 3
THROUGH 5 CONTINUES TO FOLLOW THIS SOUTHERN CAMP OF MODELS AND IS
LARGELY AN UPDATE OF THE PREVIOUS NHC TRACK.



FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 14.4N  26.5W   35 KT  40 MPH
12H  16/0000Z 15.0N  28.6W   40 KT  45 MPH
24H  16/1200Z 15.7N  31.2W   45 KT  50 MPH
36H  17/0000Z 16.7N  33.5W   45 KT  50 MPH
48H  17/1200Z 17.4N  35.8W   50 KT  60 MPH
72H  18/1200Z 18.0N  40.0W   50 KT  60 MPH
96H  19/1200Z 18.0N  44.5W   45 KT  50 MPH
120H  20/1200Z 18.0N  49.0W   35 KT  40 MPH

$$
FORECASTER BRENNAN

 

 

EDIT TO ADD:

 

Looks like the 12Z GFS gets the Erin remnants far enough North if there is anything there at all it is being captured by a small disturbance passing by to its North in 7 1/2 days.

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