TROPICAL DISTURBANCE 92L / TROPICAL STORM ERIN FORECAST SYNOPSIS…AUG. 15, 2013…ISSUED 11:35 A.M. EDT…PHFC

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Good day everyone!

Things have changed over the past 24 hours in regard to conditions forecast for the upper level wind pattern.  Analysis of the current wind shear pattern shows a big shift in the upper level anticyclone we saw over INVEST 92L during the past 12 hours.  As a result, the upper level feature is over the Yucatan Peninsula, in turn placing 92L under about 15 knots of mid to upper level shear.  This has caused the disturbance to become less organized overnight, however current satellite loop images indicate an increase in thunderstorm activity once more, and the system may become just slightly better organized prior to crossing into the Yucatan Peninsula.  The NHC has changed the probability of this becoming a tropical cyclone during the next 48 hours to MEDIUM (50%), with a HIGH chance (60%) over the next 5 days.

NHC GRAPHICAL TROPICAL WEATHER OUTLOOK

92L / WATL SATELLITE LOOP IMAGES


The disturbance continues to move toward the WNW, and I expect this motion to continue today into tomorrow, with more of a track toward the NW to NNW once it emerges into the GOMEX.  Based on the 12Z dynamic model guidance, I prefer a blend of the TVCN and OFCI track at this time, based off of the current run of the PSU e-WALL forecast steering maps.

12Z DYNAMIC MODEL GUIDANCE
12zatcfearlyinvest2best.gif.92L

As far as strength, once this disturbance enters the GOMEX, the current wind shear forecast from the GFS indicates only a small window of opportunity for further organization, as upper level winds become more conducive in about 24 hours through 36 hours.  Thereafter, upper level winds are forecast to become marginal at best.  Given these parameters, it now appears this my struggle to reach depression status in the GOMEX, and at the moment, I would have to agree with the GFS and FIM Experimental model at this becoming an open wave prior to affecting the Gulf Coast states.  The CMC I believe is too over zealous in developing a tropical storm.  However, as a caution, one does not turn their back on a system in the GOMEX in that as quickly as we have just seen the forecast pattern change to less favorable upper level conditions, it could as easily change the other way.  Remember, this current change happened in less than 24 hours.  I have included the 96 hour accumulated rainfall map from the FIM model.  Regardless of development, residents along the Gulf Coast from LA to AL should be aware that a flooding potential exists.

CMC
00zggem500mbHGHTPMSLtropical102.gif.AUG 15

FIM MODEL PRODUCTS

I will continue to monitor this disturbance for any significant changes.

Tropical Low INVEST 93L has been upgraded to Tropical Storm Erin…our second Cape Verde system of the season.  Satellite loop imagery indicates cloud tops over the LLC have cooled, and a CDO is developing, along with banding features.

As of the 11:00 a.m. EDT advisory from the NHC, the following was available on Erin:

11:00 AM AST Thu Aug 15
Location: 14.4°N 26.5°W
Moving: WNW at 15 mph
Min pressure: 1006 mb / 29.71 in
Max sustained: 40 mph

TROPICAL STORM ERIN HURREVAC TRACKING MAPS
ERIN 72

ERIN 120 FCST

TROPICAL STORM ERIN SATELLITE LOOP IMAGES / EATL LOOP

Based on analysis of current wind shear, a textbook upper level anticyclone is centered directly over Erin at the moment.  The wind shear forecast indicates upper level winds to remain generally favorable during the next 72-96 hours, and further strengthening should occur.

CURRENT WIND SHEAR EATL

The forecast discussion from the NHC 11:00 a.m. advisory indicates Erin to traverse waters of 26-27C over the next few days, so I am calling for slow strengthening than per NHC forecast discussion, as a stable stratocumulus deck lies just NW and on the edge of the northern banding.  The only negating factor I see right now as forecast, is Erin may run into dry air in about 4-5 days.  Other than that, she should have a somewhat favorable upper level wind pattern as seen in the shear forecast maps.

NHC FORECAST DISCUSSION INTENSITY FORECAST

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

Based on analysis of the forecast steering maps, and various satellite loop imagery channels, I have to concur with the NHC forecast track on Erin, as ridging appears stronger and a little more expansive based on satellite loop imagery.  As far as the dynamic model guidance, I prefer the OFCI / TV15 forecast track, which is the official track from the NHC.

ERIN 12Z DYNAMIC MODEL GUIDANCE
12zatcfearlyinvest2best.ERIN

I will be monitoring Erin closely as she approaches the northern Lesser Antilles in 5 days, for any significant changes to the pattern that may allow for strengthening at that time, save any dry air intrusion,  as upper level winds are forecast to be favorable at that time in the 
forecast period.

Have a blessed day!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS 
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)
CoCoRaHS OBSERVER

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About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
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6 Responses to TROPICAL DISTURBANCE 92L / TROPICAL STORM ERIN FORECAST SYNOPSIS…AUG. 15, 2013…ISSUED 11:35 A.M. EDT…PHFC

  1. Monty says:

    Thanks Storm. Latest runs have Erin heading further North…like you don’t know that…interesting next few days shaping up for Erin and 92L. Do you think Erin can survive a more Northerly track?

  2. originallt says:

    Thank you Storm. Kind of surprised that the NHC really brings Erin down in strength in 4-5 days. Climatologically it should become more favorable. Even in your last paragraph you say you will be monitoring Erin for any significant changes that might occur in the days ahead that will or would allow for strengthening as it approaches the Windward Islands. Thanks again, LT.

  3. stefanie says:

    Thanks Storm. Good news 92l isn’t as bad…yet. I never turn my back on them in the Gulf until they get where they’re going. Another Humberto won’t take me by surprise again. lol. Hope Erin doesn’t get bad for anyone. Things got busy in a hurry. Have a good day too. 🙂

  4. TexasHurricane says:

    Thanks Storm! You would think this time of year the conditions would be great for development, but as we can see with 92L, conditions aren’t fully there just yet.

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