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East Pacific Hurricane Season 2013


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HURRICANE COSME DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032013
800 AM PDT TUE JUN 25 2013

CONVENTIONAL SATELLITE IMAGERY SHOWS THAT COSME HAS BECOME BETTER
ORGANIZED DURING THE PAST FEW HOURS...WITH A WELL-DEFINED
CONVECTIVE BAND PATTERN AND OCCASIONAL APPEARANCES OF AN EYE.
SATELLITE INTENSITY ESTIMATES FROM BOTH TAFB AND SAB ARE NOW 65 KT.
IN ADDITION...A RECENT AMSU OVERPASS SHOWED AN ALMOST-CLOSED
EYEWALL WITH AN ACCOMPANYING INTENSITY ESTIMATE OF 67 KT.  BASED ON
ALL OF THE ABOVE...COSME IS UPGRADED TO A HURRICANE.

COSME HAS JOGGED A LITTLE TO THE RIGHT SINCE THE LAST ADVISORY WITH
A 12-HOUR MOTION OF 305/16.  OTHER THAN THAT...THERE IS LITTLE
CHANGE TO THE TRACK FORECAST PHILOSOPHY.  COSME IS EXPECTED TO TURN
WEST-NORTHWESTWARD AND WESTWARD DURING THE NEXT 48-72 HOURS ALONG
THE SOUTHWESTERN PERIPHERY OF A WESTWARD-EXPANDING MID-LEVEL
SUBTROPICAL RIDGE OVER NORTHERN MEXICO AND THE SOUTHWESTERN UNITED
STATES.  AFTER THAT TIME...COSME SHOULD BE STEERED GENERALLY
WESTWARD BY THE LOW-LEVEL TRADE WIND FLOW AS IT WEAKENS.  THE NEW
FORECAST TRACK IS PARALLEL TO...BUT NORTH OF...THE PREVIOUS TRACK
BASED ON THE CURRENT POSITION AND MOTION.  THE NEW TRACK LIES NEAR
THE CENTER OF THE TRACK GUIDANCE ENVELOPE...WHICH IS MORE TIGHTLY
CLUSTERED THAN NORMAL.

COSME IS IN A LIGHT/MODERATE SHEAR ENVIRONMENT...AND THE NEW
FORECAST TRACK HAS IT REACHING 26C SEA SURFACE TEMPERATURES IN
ABOUT 12 HOURS.  THE INTENSITY FORECAST THUS SHOWS SOME
STRENGTHENING DURING THE FIRST 12 HOURS...FOLLWED BY STEADY
WEAKENING OVER DECREASING SSTS.  THE CYCLONE IS EXPECTED TO WEAKEN
TO A TROPICAL STORM IN 24-36 HOURS...A TROPICAL DEPRESSION IN ABOUT
72 HOURS...AND SUBSEQUENTLY DECAY INTO A REMNANT LOW IN ABOUT 96
HOURS.  THE NEW INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS
FORECAST.

THE EXTENSIVE 12-FT SEAS RADII IN THE EASTERN SEMICIRCLE PROVIDED BY
THE TAFB IS THE RESULT OF LONG-FETCH SOUTHERLY CROSS-EQUATORIAL
FLOW GENERATING LARGE SWELLS...WHICH WILL AFFECT MUCH OF THE PACIFIC
COAST OF MEXICO AND THE BAJA PENINSULA DURING THE NEXT COUPLE OF
DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 17.7N 110.7W   65 KT  75 MPH
12H  26/0000Z 18.2N 112.7W   75 KT  85 MPH
24H  26/1200Z 18.9N 114.9W   70 KT  80 MPH
36H  27/0000Z 19.6N 117.2W   55 KT  65 MPH
48H  27/1200Z 20.4N 119.8W   45 KT  50 MPH
72H  28/1200Z 21.5N 125.0W   30 KT  35 MPH
96H  29/1200Z 21.5N 130.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  30/1200Z 21.5N 134.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER BEVEN

 

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Cosme has weakened to a TS over colder waters.  Looks to me on the last 2-3 frames of visible satellite that the center is jogging a bit south of the forecast track, which could potentially keep it a TS slightly longer than NHC projects.  Still, probably just delaying the inevitable (and could easily 'correct' back north in the next frame). 

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Over the past couple of days, the Globals have been fairly consistent in developing tropical cyclone in the EPAC. The GFS and Euro both suggest a general NW to NNW motion with the Euro hinting a possible approach to Cabo San Lucas in about 8-10 days.

96E has a better chance than Cosme ever did...

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post-378-0-33131400-1372431741_thumb.gif

1. AN AREA OF DISTURBED WEATHER SEVERAL HUNDRED MILES SOUTHWEST OFACAPULCO MEXICO HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING. UPPER-LEVEL WINDS ARE FORECAST TO BECOME MORE CONDUCIVE FORDEVELOPMENT OVER THE NEXT COUPLE OF DAYS...AND THIS SYSTEM HAS AMEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE DURINGTHE NEXT 48 HOURS AS IT MOVES SLOWLY NORTHWESTWARD OR NORTHWARD.
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It's interesting to compare a 96 h ECMWF forecast for Cosme made pre-genesis verifying close to the time of peak intensity (left), to a 120 h ECMWF forecast for what may become Dalila (right).  The forecast MSLP suggested a broad wind field for Cosme, which verified nicely.  The forecast for 96E suggests a much tighter core.

 

We'll see ;)

 

post-378-0-66627800-1372437912_thumb.png

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000
NOUS42 KNHC 281709
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0110 PM EDT FRI 28 JUNE 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 29/1100Z TO 30/1100Z JUNE 2013
TCPOD NUMBER.....13-028 AMENDMENT

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

II. PACIFIC REQUIREMENTS -- ADDED
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
3. ADDITIONAL DAY OUTLOOK: POSSIBLE FIX OF A DEVELOPING
HURRICANE OFF MEXICO'S WEST COAST NEAR 18.0N 106.0W

AT 01/1800Z.

 

 

 

 

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:P

I am keepin' an eye on it. Adam said there's a tiny (but real) chance it could get interestin'.

But like I said on the iCyclone Facebook page, hurricane landfalls on Mexico's Pacific coast in July are exceedingly rare-- only three since 1949.

I tend to agree. Close but no cigar. The Western Ridge should turn  any future Dalila NW away from landfall. Sappy love songs come to mind with that name anyway... :)

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I tend to agree. Close but no cigar. The Western Ridge should turn  any future Dalila NW away from landfall. Sappy love songs come to mind with that name anyway... :)

 

:lmao:

 

 

Either way, pretty good agreement in the models from ECMWF to HWRF that Dalila will be a small, reasonably-well organized TC that has a good shot at being the best eye candy so far this season - in either basin. 

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A majority of the statistical model guidance, and the GFS, showed 96E peaked as a Category 2 hurricane in 3-4 days. Now none of them show the storm becoming a hurricane.

 

Wazzup with that. I know sea surface temperatures are expected to decrease towards the end of the period, but that much of an intensity reduction while the storm is forecast to be in favorable conditions for the next 3-4 days (before said SSTs decrease)?

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Meh...

 

TROPICAL STORM DALILA DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042013
800 AM PDT SUN JUN 30 2013

SATELLITE IMAGES SHOW THAT THE COVERAGE AND INTENSITY OF DEEP
CONVECTION HAS DIMINISHED SOMEWHAT OVER THE PAST FEW HOURS...AND
BANDING FEATURES ARE NOT YET WELL-DEFINED.   THE CURRENT INTENSITY
ESTIMATE IS HELD AT 35 KT IN AGREEMENT WITH DVORAK ESTIMATES FROM
TAFB AND SAB.  DALILA IS EXPERIENCING SOME SOUTHERLY SHEAR...BUT
THE ENVIRONMENT SHOULD BE FAVORABLE FOR SOME STRENGTHENING OVER THE
NEXT 48 HOURS OR SO.  THE OFFICIAL WIND SPEED FORECAST IS A LITTLE
ABOVE THE STATISTICAL-DYNAMICAL GUIDANCE AND CLOSE TO THE INTENSITY
MODEL CONSENSUS.

RECENT CENTER FIXES SUGGEST THAT THE MOTION IS NOW NORTH-NORTHWEST
OR NEAR 340/8.  A MID-LEVEL RIDGE EXTENDING SOUTHEASTWARD FROM A
STRONG HIGH PRESSURE AREA OVER THE SOUTHWESTERN U.S. IS EXPECTED TO
INDUCE A GRADUAL TURN TOWARD THE LEFT DURING THE NEXT FEW DAYS.
THE OFFICIAL TRACK FORECAST IS ONLY A LITTLE TO THE SOUTH OF THE
PREVIOUS ONE BEYOND 48 HOURS...AND IS NEAR THE NORTHERN EDGE OF THE
TRACK GUIDANCE MODEL ENVELOPE.

GIVEN THE UNCERTAINTIES IN SIZE AND TRACK...THE TROPICAL STORM
WARNING AND WATCH HAVE BEEN EXTENDED NORTHWARD ALONG THE
SOUTHWESTERN COAST OF MEXICO.  

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 15.5N 103.2W   35 KT  40 MPH
12H  01/0000Z 16.4N 103.9W   40 KT  45 MPH
24H  01/1200Z 17.3N 104.7W   50 KT  60 MPH
36H  02/0000Z 18.0N 105.6W   55 KT  65 MPH
48H  02/1200Z 18.6N 106.4W   60 KT  70 MPH
72H  03/1200Z 19.0N 108.0W   60 KT  70 MPH
96H  04/1200Z 19.0N 109.5W   50 KT  60 MPH
120H  05/1200Z 19.0N 112.0W   40 KT  45 MPH

$$
FORECASTER PASCH
 

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To be honest, the lack of strengthening so far today and the decrease in the intensity forecast are both a bit strange.  Both mid-level and deep-layer wind shear are low, at or below 10 kt per CIMSS analyses.  There is somewhat stronger shear NW / ahead of Dalila but the area of higher shear appears to be "retreating" towards the NW.  There is also some dry air ahead of Dalila but with the shear out of the south there shouldn't be much getting into the system.  Even the CPC velocity potential plots still look favorable for ventilation of outflow. 

 

The biggest detractor on SHIPS is somewhat warm temps at 200 mb, but with so much else going for it, I don't see any obvious reasons why Delila won't exceed current NHC forecasts and become a hurricane. 

 

Aside: I will be out of town the next 10 days with little free time to update the subtitle.  Srain / Adam could you help out here when necessary (keep Josh happy)?  K thx. 

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I'm reading the latest discussion on Dalila and I had a question.

 

SATELLITE IMAGERY DURING THE PAST FEW HOURS REVEALS THAT THE CLOUDPATTERN OF DALILA IS DETERIORATING FAST. AN SSMI/S MICROWAVEPASS...AROUND 0000 UTC...SHOWED THAT THE LOW-LEVEL CENTER ISREMOVED FROM A SHRINKING AREA OF DEEP CONVECTION. FURTHERMORE...LATEST AVAILABLE SCATTEROMETER DATA SUGGEST THAT THE WINDS COULD BELOWER THAN INDICATED. HOWEVER...SINCE I INHERITED A 60-KNOTSTORM...I WOULD RATHER LOWER THE WINDS GRADUALLY...AND THE INITIALINTENSITY IS SET AT 50 KNOTS. IT APPEARS THAT DRY AND STABLE AIR ISALREADY AFFECTING THE CIRCULATION...AND THE SHIPS MODEL FORECASTSINCREASING SHEAR. THE OFFICIAL FORECAST CALLS FOR A GRADUALWEAKENING...BUT THIS PROCESS COULD OCCUR FASTER THAN FORECAST.

 

Why does Avila want to "lower the winds gradually?"  I understand that estimating wind speed isn't necessarily easy and/or particularly accurate without a recon mission or something, but he seems to be saying "I think it's a 40/45-knot storm and I'm calling it 50 knots."

 

It's a fairly irrelevant storm, it's not an important difference anyway, and I'm certainly not trying to attack the NHC :lmao: but as an amateur I'd like to understand the logic of the pros, especially if there's a scientific reason.  Is it simply not feasible to expect a storm to spin down that fast in open water?

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I'm reading the latest discussion on Dalila and I had a question.

 

 

Why does Avila want to "lower the winds gradually?"  I understand that estimating wind speed isn't necessarily easy and/or particularly accurate without a recon mission or something, but he seems to be saying "I think it's a 40/45-knot storm and I'm calling it 50 knots."

 

It's a fairly irrelevant storm, it's not an important difference anyway, and I'm certainly not trying to attack the NHC :lmao: but as an amateur I'd like to understand the logic of the pros, especially if there's a scientific reason.  Is it simply not feasible to expect a storm to spin down that fast in open water?

 

Avila is a long time veteran and and often likes to add in his own prior experience before trusting remote sensing (like ASCAT) for the intensity of TCs in the EPAC. I think this is a fair move given that Dalila is still over warm SSTs and could re-fire substancial convection. It is also worth noting that intensity can and often is adjusted in the best track if it is later discovered the intensity was assessed incorrectly. Just because Dalila is assessed at 50 knots operationally doesn't mean that it couldn't be revised to 40/45 knots later on for the same time period. 

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