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Well, Dejavu…after dropping 99L for a brief early this morning, the NAVY ATCF system has once again begun running model data on the system. Satellite loop imagery indicates convection has greatly increased since early this morning, although conditions are not quite favorable at the moment. As of the 18Z ATCF BTK update, the following information was available on INVEST 99L:
LOCATED: 17.1N…85.3 W
MOTION: WNW 10 MPH
MAX SUSTAINED: 30 MPH
PRESSURE: 1009 MB / 29.80 IN.
Based on analysis of the current wind shear product from CIMSS, INVEST 99L is currently under about 20 knots of NWLY wind shear. However, IF the center is located where the report states, 99L is moving into an area where wind shear has been on the decrease, and is only about 10 knots.
The most current wind shear forecast which was from 12Z this morning, indicates zonal shear will be marginal over the next 24 hours, and as this disturbance begins to cross into the Yucatan Peninsula, upper level winds may become more conducive for further development. Based on this analysis, some better organization should begin just prior to coming ashore over the Yucatan Peninsula, and once it enters the BOC / SW GOMEX, should begin to organize a little quicker. Once in the SW GOMEX, this system will have to be monitored closely.
The system, based on what I can make out in satellite loop imagery (various channels), but mainly based on the current steering layer mean, is moving to the WNW. Based on this and analysis of the current forecast steering layers maps from the PSU e-WALL site, I expect this motion to continue during the next 24-30 hours. Based on this, if the “center” is located where the ATCF and NHC say it is, I believe it will enter the GOMEX further north than shown in the NHC 5 day graphical tropical weather outlook. Right now, model guidance will definitely change over the next 48 hours, as the center seems not too well defined, so the initialization of the center is suspect at the moment. However, although there are only 2 dynamic guidance models available at the moment, the trend over the past 6 hours from 12Z to 18Z has been to the right. This seems logical at the moment, given the current steering flow, unless riding currently noted over the northern GOMEX bends 99L back westward somewhat. So, putting this all together, the system could come further north in the GOMEX than what is projected…this too will depend on where the center relocates after clearing the Yucatan Peninsula and exiting into the SW GOMEX.
The area of disturbed weather I have been monitoring in the EATL near 10.0N…36.0W, appears to be getting slowly better organized. This area is moving toward the west near 15 mph, and I expect this motion to continue during the next 48 – 60 hours. Shortly thereafter, a more WNW motion could occur as the disturbance gets far enough west to begin to feel the effects of a weakness in the subtropical ridge, forecast to be located near 28N…70W.
RAMSDIS CATL LOOP
Analysis of the current wind shear product indicates upper level winds are somewhat conducive for further development, and the zonal shear forecast indicates upper level winds to remain fairly conducive during the next 72 – 84 hours. After this, upper level winds are forecast to become unfavorable for further development. Regardless, I will continue to monitor this area for any significant changes during the next 72 hours. I would expect this to be designated INVEST 90L in about 24 hours, should the current trend continue
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST / SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
OFFICIAL SKYWARN SPOTTER (ADVANCED)