TROPICAL DEPRESSION HARVEY REMNANT / INVEST 92L FORECAST SYNOPSIS…ISSUED AUG. 20, 2017…5:15 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: 8
HURRICANES: 2
MAJ. HURRICANES: 0

U.S. LANDFALLS: 2

Good evening  all!

Tropical s Storm HARVEY has been downgraded to a Tropical Wave. INVEST 92L is just barley hanging on and is located approximately a couple hundred miles NNE of the DOMREP.  A Tropical Wave remains near 25.0N;47.0W.  As of the 2:0 p.m. TWO from the NHC, TW HARVEY was designated at a HIGH (70%) probability of regeneration and cyclone development during the next 5 days.  INVEST 92L a LOW (30%) probability, and the CATL Wave a LOW (10%) probability.

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

As of the 18Z ATCF BTK report, the following was available on the remnant, or Tropical Wave “HARVEY”

2:00 PM EDT Sun Aug 20
Location: 13.8°N 76.7°W
Moving: W at 20 mph
Min pressure: 1007 mb / 29.74 in
Max sustained: 35 mph

Recent satellite loop imagery indicates in the last few frames, that the cloud pattern appears to be expanding, and there appears to be some improvement in overall symmetry.  This is noted in both IR and Water Vapor loop images.

HARVEY FLOATER SATELLITE LOOP (CLICK ON IMAGES)

HARVEY WATER VAPOR LOOP

Since HARVEY was down graded, there are no advisories or forecast discussion for me to compare to my analysis.  Analysis of the GFS and ECMWF still indicate they don’t do much of anything while HARVEY is in the Caribbean, but the ECMWF does indicate a possible T.D. or very weak T.S. upon second landfall.  I am still finding it bizarre that neither model strengthens this prior to it making landfall in Belize.  That scenario just doesn’t match what both models show as a favorably or conducive upper level wind pattern, indicating and upper level anticyclone over it, and to remain with the system.

HARVEY CURRENT SHEAR AS OF 1800Z

GFS AND ECMWF WIND SHEAR FORECAST

ECMWF

The modeling from the NOAA.RUC site indicates wind shear magnitude is forecast to remain light, and pretty much below 10 knots during the next 120 hours

Based on my analysis of water vapor imagery, current wind shear analysis, and wind shear forecast, I believe HARVEY will once again become a Tropical Depression within the next 24 -36 hours, if not going directly to Tropical Storm status, should he miss Honduras.  I cannot determine, if he does strengthen, whether or not he could rapidly intensify.  But as stated, given the expanding cloud pattern, and upper pattern, I do believe he will make a comeback.

HARVEY continues to move toward the West at 20mph, and I expect this motion to continue for about the next 24 hours, from 12Z.  After that, I expect a turn more to the WNW as a weakness will be present in the extreme NW GOMEX, based on the current run of the forecast steering layers maps. Based on these maps, the flow will fluctuate, but a WNW should be the general consensus from 24-60 hours.  Thereafter, model guidance is split, however based on the steering pattern by 84-96 hours, there could be a more northerly component.  Based on this discrepancy between the guidance modeling, I prefer a compromise between the TVCA dynamic consensus model, and the CMC at the moment.

HARVEY 18Z MODEL TRACK GUIDANCE

Even though there has been a slight shift in track guidance, given that HARVEY is still organizing, I still feel Texas may not be directly hit.  This can change, however until first landfall is made, and we see what’s left after it enters the BOC, an accurate track cannot be determined from the BOC onward.

Elsewhere, INVEST 92L continues to be poorly organized.

INVEST 92L FLOATER SATELLITE LOOP

As of the 18Z ATCF BTK report, the following was available on INVEST 92L

2:00 PM EDT Sun Aug 20
Location: 22.5°N 69.0°W
Moving: WNW at 22 mph
Min pressure: 1007 mb / 29.74 in
Max sustained: 35 mph

INVEST 92L had been undergoing wind shear for the past 24 hours.  However the wind shear tendency over the past 24 hours has been declining, and the latest wind shear map indicates shear values have reduced to around 10-15 kts over the INVEST.  Water vapor imagery, and current shear map indicates the ULL to the NW of 92L appears to be dissipating, hence the reduction in shear.  This may also decrease the amount of dry air that has been around the system.  This system is a little trickier as far as whether or not it will regain composure and eventually become organized.  Based on current MTCSWA (Multiplatform Tropical Cyclone Surface Winds Analysis), 92L is lacking any closed LLC.  This would tend to indicate it may remain a wave for the next few days.  However, IF it does survive, my thoughts are, that it may begin to organize once reaching the Bahamas, mainly Central Bahamas.  My reasoning for this is the same as for HARVEY.  IF this INVEST survives, modeling indicates shear magnitude values to fall to below 10 kts, through the next 120 hours (5 days).  This could allow for the INVEST to become better organized, since it won’t be tilted, or barley tilted.  Albeit the upper pattern is not forecast to be optimal, the GFS indicates the shear pattern to become more favorable as the INVEST reaches the Bahamas.

GFS WIND SHEAR FORECAST BAHAMAS

Based on this, it will have to be a wait and see for now, however some type of organization cannot be totally ruled out as of yet, in the Bahamas. 

INVEST 92L is moving to the WNW, and I expect this motion to continue during the next 24-36hours.  As the INVEST approaches the Western Bahamas and FL. East coast, there are discrepancies in the model guidance. Some take it into FL., while others re-curve it.  Based on the premise of the system still being weak, and the fact low level steering forecast maps indicate a small ridge my be north of the system, I believe INVEST 92L may slow, and could come into FL, before any type of re-cruse could occur.  Again, given this is a poorly defined system, guidance will most likely change, so track guidance as shown, should be considered preliminary.

INVEST 92L 18Z EARLY GUIDANCE

To save time and space, the CATL wave is not of a concern at the moment, and may very well dissipate over the next few days.  However, I will continue to monitor it.

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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