TROPICAL DEPRESSION ELEVEN / INVEST 99L FORECAST SYNOPSIS…ISSUED 12:15 A.M. EDT…SEP. 28, 2015

TROPICAL STORM FORMATION: T.D. ELEVEN, 99L (30%)

ALL forecasts contained on this site,  are based on my analysis and knowledge of various forecast tools, including information contained in NHC products, and are not copies from any other entity.

*NOTE: In the TROPICAL STORM FORMATION line above, probabilities are for during the next 5 day period.  My personal probability will be listed as either NONE, MONITORING or PROBABLE.  This does not necessarily mean something will develop, but that certain forecast conditions are likely to be present, for development.  Once NHC products become available, then the appropriate probability and percentage will be used.

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Current Storm Total for 2015:

TOTAL STORMS: 9
HURRICANES: 2
INTENSE HURRICANES: 1
U.S. LANDFALLS: 2

StormW’s Seasonal Forecast:

TOTAL STORMS:             8
HURRICANES:                   3
INTENSE HURRICANES: 1

Good day everyone!

One depression gone…another one develops.  INVEST 98L has been upgraded to a Tropical Depression…designated T.D. ELEVEN late yesterday evening.  As of the 11:00 a.m advisory from the NHC, the following was available on T.D. ELEVEN

11:00 AM AST Mon Sep 28

Location: 27.8°N 69.6°W
Moving: WNW at 5 mph
Min pressure: 1006 mb / 2971 in
Max sustained: 35 mph

HURREVAC NHC TRACKING MAPS
HURREVAC.ELEVEN

HURREVAC.ELEVEN72

The depression has been undergoing 20-25 knots of wind shear, which has left the LLC exposed just on the NNW edge of the convection and slight banding features, based on current satellite loop imagery.  Based on the current winds shear forecast 200 mb streamline product, and the GFS / UKMET shear prognosis from the HFIP modeling, I’m  forecasting upper level winds to become somewhat ore favorable in about 36 – 42 hours from 06Z, based on the 200 mb streamline forecast showing an improvement in upper level outflow, albeit marginal, and reduction in shear magnitude averaging 15-16 knots.  Based on this premise, if the modeling is accurate, I agree with the NHC intensity forecast, and the depression could be upgraded to Tropical Storm Joaquin.  Shear magnitude at the moment is forecast to remain somewhat favorable up to approximately 72 from 06Z this morning, so this is a short window of opportunity for this scenario to occur.  Thereafter, the system will become sheared once again, and other environmental factors would preclude further intensification.

RGB satellite loop imagery displays the LLC very well, and analysis reveals the WNW motion in the NHC advisory.  Based on forecast steering layers analysis, I expect this motion to continue for the next 36-42 hours, prior to moving more toward the NW.  This is reflected in the NHC forecast track, and is inline with the ATCF 12Z dynamic guidance.

T.D. ELEVEN SATELLITE LOOP IMAGERY
avn0ELEVEN-lalo

rgb0TD ELEVEN-lalo

12Z ATCF DYNAMIC GUIDANCE
TD11L 12Z DYNAMIC GUIDANCE

The system is forecast to merge with a front and become post tropical by 96 hours in the forecast period.

Elsewhere, INVEST 99L remains a sheared system this morning.  In fact, latest satellite loop imagery seems t0 indicate the LLC has become much less defined than it was a few hours ago.

INVEST 99L SATELLITE LOOP IMAGERY
avn099L-lalo

GOMEX RGB LOOP IMAGERY
rgbGOMEX-l

The area is still under 20-30 knots of wind shear, and the current wind shear forecast indicates shear to remain in place. I do not foresee this becoming a depression.

INVEST 99L SHEAR MAP
tccaptureshear99L

The INVEST is moving toward the NNE at around 8-10 mph, and I expect this motion to continue during the next 72 hours.  This is indicated in the 12Z dynamic guidance.  However, based on recent satellite motion, I prefer a track just right of the TVCN/TVCC consensus. 

12Z DYNAMIC GUIDANCE
99L 12Z DYNAMIC GUIDANCE

The main hazard appears to be the possibility of heavy rainfall over portions of the west Florida coastline during the next 48 hours.  Current Doppler radar information indicates total storm precipitation values of 2-4 inches in the heaviest rain areas.

The following is the 72 hour precipitation totals forecast from the NAM and GFS models

NAM
nam_namer_072_precip_ptot
GFS
gfs_namer_072_precip_ptot

Elsewhere, a large tropical wave is located in the central Atlantic.  Upper level winds are currently somewhat favorable over the area, however the current wind shear forecast indicates upper level winds to become unfavorable during the next 24-36 hours.  I am not expecting development of this area.

CATL SATELLITE LOOP IMAGERY
avncatl-l

Global models continue to hint at a weak coastal storm developing off the eastern seaboard in about 3-5 days.  Analysis suggests that the remnant of T.D. ELEVEN, along with energy from INVEST 99L will trigger this.  I will continue to monitor the area during the next 72 hours.

Elsewhere, Tropical Storm formation is not expected during the next 7 days.

Have a blessed day!

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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4 Responses to TROPICAL DEPRESSION ELEVEN / INVEST 99L FORECAST SYNOPSIS…ISSUED 12:15 A.M. EDT…SEP. 28, 2015

  1. originallt says:

    Thanks, Storm. Looks like very complicated set up over the eastern US and off shore the next 4-5 days or so. I’ll be checking in here to see your thoughts. At least it’s getting interesting, and we sure could use the rain up here!

  2. dellamom says:

    thank you, Storm. I really, really don’t like the dark orange line slicing Lake Pontchartrain in half, but at least there is no hint of this becoming anything large. I hope the rains from it do not overwhelm anyone. I also hope TD11 does not bring reminders of Sandy to the New York area. I will be watching closely.

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