TROPICAL STORM IAN / INVEST 93L / INVEST 95L FORECAST SYNOPSIS…ISSUED SEP. 13, 2016…12:25 P.M. EDT

TROPICAL CYCLONE FORMATION: T.S. IAN / INVEST 95L (50%) / INVEST 93L (40%)

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.
(T. F. “Storm” Walsh III)

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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:

TOTAL STORMS: 9
HURRICANES: 4
MAJOR HURRICANES: 1
U.S.LANDFALLS: 3

StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
HURRICANES: 6-7
INTENSE HURRICANES: 3-4

Good day everyone!

We’ll begin close to home today.

THIS IS A SPECIAL UPDATE REGARDING  INVEST 93L.  The NHC updated the probability on 93L in the 2:00 P.M. Tropical Weather Outlook.  Evidently, the center of circulation is not that far inland, and has become better organized, not unlike the disturbance that dropped all the rain over the Gulf coast states a few weeks ago.  The NHC has upgraded the probability for cyclone development to MEDIUM (40%).

The following text from the NHC TWO from 2:00 P.M:

Surface observations, satellite images, and radar data indicate that an area of low pressure is located just inland near Daytona Beach, Florida. This system continues to produce a large area of showers and thunderstorms, with winds to tropical storm force along or just offshore of portions of the northeast Florida coast. This system is very close to having the organization required of a tropical cyclone, and advisories could be initiated later this afternoon. The low is expected to move north-northwestward at 10 to 15 mph today, near and parallel to the northeast coast of Florida. Regardless of development, strong gusty winds will continue over portions of the northeast Florida coast today, and heavy rains will continue to spread over central and northern Florida today and tonight. Please consult your local National Weather Service office for additional information on this system, including possible warnings.
* Formation chance through 48 hours…medium…40 percent
* Formation chance through 5 days…medium…40 percent

I have added the NWS WARNING and HAZARDS Display which is linked.  Just click on your area.

NWS WARNINGS DISPLAY
us

The area which was INVEST 93L a few days ago, was dropped from the database, but was re-designated a little over 24 hours ago.  The following information was available on  93L in the ATCF BTK 12Z product:

8:00 AM EDT Tue Sep 13
Location: 28.1°N 80.8°W
Moving: NW at 13 mph
Min pressure: 1010 mb / 29.83 in
Max sustained: 35 mph

Recent satellite loop imagery and Doppler radar loop indicate the center has moved closer toward the mid peninsula with what appears to be a slight west jog, and just about due west of Cape Canaveral.  Current and forecast steering indicates INVEST 93L should continue on a general NW  motion over the next 24 hours.  At around 36 hours, the steering flow shift briefly toward the west, then back to the NNW.  Based on this, and the current motion, the chance for this to enter the NE GOMEX has decreased.  The last available dynamic guidance was at 0600Z, which indicates a forecast track toward the NW.  I concur with this at the moment, and I am in agreement at this time with  the consensus models TVCN/TVCC.  It was noted in forecast steering, that steering currents collapse over Florida after 48 hours, so there may be a chance of this stalling, which in turn could increase rainfall totals.

93L SATELLITE LOOP IMAGERY
avn0-lalo-93l

rgb0-lalo-93l

MELBOURNE FLORIDA DOPPLER RADAR LOOP
codnexlab-1km-s_florida-rad-20160913-1310-100-100-raw

ATCF 06Z DYNAMIC GUIDANCE
93l-06z-dynamic

The LLC was closer to the convection at the beginning of analysis, but has since shifted west of the convection.  Being this is over the Florida peninsula now, I am not expecting development of this INVEST.  However, this appears to be much like the disturbance that dropped all the rain over LA/TX, and MS not too long ago, where the center had remained just along the coast, and was able to maintain structure and draw in ample moisture from the Gulf.  The center of this is over land, however, much moisture is being drawn in from the Atlantic, across the state.  This should lead to more rainfall over the state during the next 3 days or so.  I will continue to monitor this situation for any changes.

Elsewhere, Tropical Storm IAN has had no change in strength, and remains sheared.  As of the 11:00 a.m. advisory from the NHC, the following was available on IAN:

11:00 AM AST Tue Sep 13
Location: 25.4°N 52.3°W
Moving: NNW at 13 mph
Min pressure: 1005 mb / 29.78  IN
Max sustained: 45 mph

HURREVAC NHC TRACKING MAP
hurrevac-ian-error

IAN continues to undergo 40-45 kts of SWLY shear, which has the LLC exposed well SW of the heavy convection.  This wind shear is forecast to remain through today.  Based on analysis of the current wind shear forecast maps from both the GFS and ECMWF, shear is expected to relax within the next 24-30 hours, with an improvement in the upper level pattern closer to the center of the storm.  Should this occur, it would allow for IAN to become better organized, and some further slight strengthening could occur.  Based on this, I have to concur with the current NHC intensity forecast.  It is still unclear to me, given the NHC criteria for naming a depression or tropical storm, as to WHY the NHC has designated this system a tropical storm.

IAN FLOATER SATELLITE LOOP
avn0-lalo-ian

rgb0-lalo-ian

IAN continues to move NNW through a break in the subtropical ridge, and I expect this motion to continue for the next 24-48 hours, with a slowing in forward speed as a shortwave trof approaches.  As this occurs, it should allow for a breif northward motion, before a turn more toward the NE occurs. By that time, wind shear should begin to increase, and by 96 hours, IAN should become a frontal feature. I will continue to monitor IAN for any significant changes.

Elsewhere, Tropical Disturbance INVEST 95L was located just near the African coast, SE of the Cabo Verde islands.  The disturbance has been somewhat disorganized most of the early morning, however it appears in the last couple frames of satellite loop imagery it may be trying to become slightly better organized.  The current wind shear product from CIMSS indicates an upper level anticyclone is currently over the system, and an upper level outflow pattern may be developing, based on the upper level winds product.

RAMSDIS METEOSAT FLOATER 95L
tropical_met_4km_ir4_floater

tropical_met_4km_visir2_floater

CIMSS CURRENT EATL WIND SHEAR
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The current wind shear forecast from both the GFS and ECMWF indicate the upper level pattern to be conducive for further slow development over the next 48-72 hours, maintaining an upper level anticyclone over or in close proximity to the disturbance, with shear values fluctuating between 48-72 hours, when shear values will briefly become less favorable, before relaxing slowly.  Based on this, together with current forecast track thinking, based on my analysis of the current forecast steering layers maps, we should see some further development as stated, with the possibility of this development slowing, or briefly stopping if the shear forecast pans out, followed by some more possible slow development after that.  The last guidance on this system was at 0600Z as well, at which time, the more accurate intensity models bring 95L to tropical storm strength.  Given the above mentioned parameters, I cannot rule this out.

NHC designates a MEDIUM (50%) probability of cyclone development during the next 5 days

NHC 5 DAY TROPICAL WEATHER OUTLOOK
two_atl_5d0

Based on information contained in the ATCF BTK 12Z product, the following was available on INVEST 95L:

8:00 AM EDT Tue Sep 13
Location: 13.3°N 20.5°W
Moving: W at 13 mph
Min pressure: 1010 mb / 29.83 in
Max sustained: 25 mph

INVEST 95L has been moving toward the west, however in the past few hours there has been a slight shift in latitude…it is unknown if this is a tend beginning to occur, or just some wobbling of the center, being in the slightly disorganized state at the moment.  In any case, I expect more of a motion toward the WNW to begin sometime today, as the disturbance begins to feel the effects of a weakness in the ridge, north of the Cabo Verde islands at the moment.  Based on my analysis of current steering layers forecast maps, I expect a WNW motion to be the case during the course of the next 4-5 days.  Shortly thereafter,  I am looking for a bend more toward the west, as the subtropical ridge begins to shift the weakness in the ridge further toward the west, with the ridge axis building north of INVEST 95L.  The steering forecast maps only go out to 144 hours, so beyond day 6, I have no steering information to work with.  My forecast motion is also inline with the most recent dynamic guidance, and is also shown in the GFS and ECMWF Ensemble guidance, which after days 5-6, a turn more to the NW is forecast.  Although since the system is not developed yet, guidance should be considered preliminary, however this is the current forecast idea at the moment.

ATCF INVEST 95L 06Z DYNAMIC GUIDANCE (BOTTOM RIGHT TRACK)
95l-06z-dynamic

GFS / ECMWF ENSEMBLE GUIDANCE
gefs_al95_2016091306

eps_al95_2016091300

Elsewhere, Tropical Storm formation is not expected during the next 5-7 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 STORM IAN / INVEST 93L / INVEST 95L FORECAST SYNOPSIS…ISSUED SEP. 13, 2016…12:25 P.M. EDT

  1. dellamom says:

    Thank you, Storm. Prayers for soggy Florida and Georgia from waterlogged Louisiana.

  2. Debi Dantoni says:

    Thank you,,, Storm. Deeply appreciated,,, Debi On Sep 13, 2016 11:26 AM, “WEST CENTRAL FLORIDA HURRICANE and SEVERE WEATHER FORECAST CENTER” wrote:

    > palmharborforecastcenter posted: “TROPICAL CYCLONE FORMATION: T.S. IAN / > INVEST 95L (50%) Disclaimer: This site is not affiliated with the National > Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National > Weather Service. ALL forecasts herein are the result of my analy” >

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