INVEST 99L FORECAST SYNOPSIS…ISSUED AUG. 12, 2017…7:35 P.M. EDT

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(T. F. “Storm” Walsh III)

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STORM W’s SEASONAL HURRICANE FORECAST
TOTAL STORMS: 14-16
HURRICANES:       6-8
MAJ. HURRICANES: 3-4

CURRENT TOTALS
STORMS: 6
HURRICANES: 1
MAJ. HURRICANES: 0

U.S. LANDFALLS: 2

Good evening  all!

To save time, I’ve cut out some graphics due to the late nature of the evening.

The current GTWO from the NHC now designates  a HIGH (70%) probability of cyclone formation during the next 5 days for INVEST 99L

NHC 5 DAY GRAPHICAL TROPICAL WEATHER OUTLOOK (GTWO) LINKED FOR TEXT


As of the 18Z ATCF BTK report, the following was available on INVEST 99L:

2:00 PM EDT Sat Aug 12
Location: 23.5°N 69.5°W
Moving: WNW at 9 mph
Min pressure: 1012 mb / 29.88 in
Max sustained: 30 mph

Recent satellite loop imagery indicates INVEST 99L may be getting slowly better organized, showing expanding convection, and some very slight banding features.  However, INVEST 99L still lacks a closed off LLC.  It is noted that a westerly wind component is missing south of the “center”.  Once a true west sustained wind becomes established, 99L will most likely be classified a tropical depression.

NOAA INVEST 99L FLOATER LOOP (CLICK IMAGE)

RAMSDIS VIS/IR LOOP (CLICK IMAGE)

Based on model guidance from the ECMWF Cyclone Probability Forecast, 99L has a 100% probability of reaching depression status during the next 24 hours.  At the moment, I have to concur, as an upper level anticyclone and low shear is currently over the disturbance, and an outflow channel is currently established.  Analysis of the wind shear forecast from the both the ECMWF and GFS indicate upper level winds may remain conducive over the next 24 to possibly 36 hours.  Thereafter, the GFS indicates upper level winds to become marginal to non conducive, and opens the system back to a wave by 48 hours or so.  The ECMWF is a little more generous, with the upper level pattern remaining somewhat conducive after 48-60 hours, but does induce some shear between 36 and 42 hours into the period, from 12Z today.  The NAVGEM seems to take the GFS side on the shear pattern.  Based on this analysis, I do believe we will see a tropical depression within the next 24-36 hours.  Thereafter, it’s up in the air as to whether or not we see “GERT” develop.  It will depend on the wind shear forecast, and which model is handling the forecast the best.  I’ll be looking closer at this tomorrow.

ECMWF CYCLONE PROBABILITY GUIDANCE


CIMSS WIND SHEAR AND UPPER LEVEL WIND PATTERN FOR INVEST 99L

INVEST 99L is currently moving to the WNW at around 9 mph, based on a 12 hour average, showing the system moving 0.7 degrees N, and 1.5 degrees W from 06Z to 18Z

Based on analysis of current and forecast steering maps, 99L is coming up on a weakness in the subtropical ridge, and should turn more NW, then northerly and eventually NE as it rides around this weakness.  Based on this, I concur at the moment with the 18Z dynamic model guidance, showing 99L recurving in a few days.

INVEST 99L 18Z DYNAMIC GUIDANCE

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

Elsewhere, I am currently monitoring a tropical wave in the CATL, and another just exiting the African continent.  Here’s where we get to test the GFS upgrade.  A quick look at modeling indicates the ECMWF keeping the wave just exiting Africa, a weak system, allowing it to come further west, while the GFS depicts a 105 mph CAT 2 hurricane by day 7 from the 18Z run.  This will definitely be a good test.  Both the ECMWF and GFS do indicate fairly favorable upper level conditions during this time, with the GFS being bullish with a well established upper level anticyclone over the feature the whole trip across the Atlantic.   I will be monitoring both areas closely for any significant changes.

RAMSDIS METEOSAT FLOATER LOOP

GFS 7 DAY FORECAST

Given the late nature of the evening, I will not get fully into this, however I DO BELIEVE, we should FINALLY see action start to ramp up, I mean POSSIBLY busy, as a current combination of various forecast parameters SHOULD come into play, regarding the MJO, Kelvin Waves, 200 mb Vertical Velocity Potential, and lowering of MSLP normalized anomalies over the Atlantic MDR and Africa.  IF all the players come to fruition, I am going to go out on a limb, and target from the 20th (second 10 days in Aug.), onward, to the end of the first week of Sep.  Here’s an interesting article from the AMETSOC. regarding the MJO and increase in activity.  Click on the link.

On the Madden–Julian Oscillation–Atlantic Hurricane Relationship
http://journals.ametsoc.org/doi/full/10.1175/2009JCLI2978.1

Elsewhere…I am not expecting tropical storm development during the next 5-7days.

Have a blessed EVENING!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
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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