TROPICAL DEPRESSION IDA / INVEST 98L / INVEST 99L FORECAST SYNOPSIS…ISSUED 8:20 P.M. EDT…SEP. 26, 2015

TROPICAL STORM FORMATION: IDA, 98L (40%), 99L (40%)

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.

Please refer to the link for the Storm Prediction Center in the box at the top of the page, just below the Hurricane Hunter graphics.

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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 evening everyone!

I am going to touch briefly on IDA and INVEST 98L.

Yes, believe it or not, IDA is still around.  The following was available on the depression at 5:00 p.m. from the NHC

5:00 PM AST Sat Sep 26

Location: 24.4°N 47.1°W
Moving: NW at 8 mph
Min pressure: 1006 mb / 29.71 in
Max sustained: 35 mph

NHC TRACKING MAP203243W5_NL_sm

IDA FLOATER SATELLITE LOOP
avn0IDA-lalo

Based on analysis of current wind shear from CIMSS, wind shear values appear to be only around 10-15 knots.  Albeit the shear forecast indicates upper level winds to remain slack for approx the next 48 hours, I have to agree with the NHC on the intensity, in that although intensity guidance indicates some strengthening,  there is a vast amount of dry air over the system and and west of it.  Based on the amount of dry air, I do not foresee strengthening occurring.  I would be awful surprised if strengthening were to happen

Based on forecast steering, the depression should continue on the NHC forecast track during the next 3-5 days.

INVEST 98L is located several hundred miles SSW of Bermuda, over the western Atlantic.  This area has recently developed a surface low, but is still producing disorganized cloudiness and showers at the moment.  Convection has increased over the past few hours.

INVEST 98L SATELLITE LOOP

avn098L-lalo

Upper level winds are forecast to become non conducive over the next 48 hours, which should preclude any further development of this area after that.  Based on forecast steering currents, this INVEST, should continue to move on pretty much a NNW motion.

The area I’ve been monitoring over the Yucatan Peninsula has been designated INVEST 99L.  Based on the 18Z ATCF FTP product, the following was available on INVEST 99L:

2:00 PM EDT Sat Sep 26
Location: 19.0°N 88.2°W
Moving: NNE at 5 mph
Min pressure: 1008 mb / 29.77 in
Max sustained: 30 mph

INVEST 99L FLOATER SATELLITE LOOP IMAGERY
avn099L-lalo

rgb099L-lalo

RAMSDIS FLOATER
tropical_ge_4km_ir4_floater_2

Analysis of the recent wind shear product from CIMSS, indicates INVEST 99L to be under about 20-25 knots of wind shear, which is exposing the low level circulation, having blown the convection to the east.  Within the next 48 hours however, a small, narrow area may become somewhat more favorable for development…however the exact track of the INVEST will determine whether or not it will be able to take advantage of this.  This will be a very brief relaxation in the upper level winds over the small area.  Thereafter, upper level winds will increase, along with shear values due to the strong upper level trof over TX, which is progged to move NE in tandem with the system.  This should pretty much keep our system sheared.

Based on the wind field from the GFS, this, should development take place, remain sub-tropical, with the maximum winds away from the center to the E and NE.  Based on the GFS 10M wind forecast, winds with this may be only on the order of 30 mph.  The GFS pretty much dissipates this right at landfall.

GFS 10M WIND FORECAST
gfs 10m wind 45

gfs 10m wind 69

Based on my analysis of the current forecast steering layers maps, the INVEST should continue to move on a somewhat northward motion for the next 24 hours, before moving more on a NNE path.  Although this is pretty much preliminary, this should be the motion unless steering currents make a big change.  This motion is reflected in the 18Z dynamic model guidance, in which I am partial to the TVCN/TVCC guidance.

ATCF 18Z INVEST 99L DYNAMIC GUIDANCE
99L 18Z DYNAMIC GUIDANCE

Rainfall could be an issue with this, mainly from the “center”, eastward.  The following is the 72 hour GFS total precipitation forecast:

GFS 72 HOUR PRECIPITATION TOTAL
GFS 72 HOUR PRECIP

I will continue to monitor this area for any significant changes, and will try and have an update sometime late morning.

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

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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4 Responses to TROPICAL DEPRESSION IDA / INVEST 98L / INVEST 99L FORECAST SYNOPSIS…ISSUED 8:20 P.M. EDT…SEP. 26, 2015

  1. originallt says:

    Thanks, Storm. A lot of “messy” little systems out there.

  2. dellamom says:

    Thank you Storm. As you have pointed out, even non-tropical systems can be hazardous. Prayers to all in the path of this system. Thank you for sharing your wisdom and access to the forecasting tools available through this site. I know it is costly.

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