UPDATE..9:30 P.M. EDT AUG. 16, 2013:
92L appears to be trying to come back at the moment. There has been a quick change in the upper pattern, and a small upper level anticyclone is almost over head. Shear has been dropping over the past few hours, and this is what may be allowing for thunderstorms to move closer to the LLC. The LLC is noted reforming NE of where it has been…and closer to the convection. If this trend continues, we may see some organization of this disturbance once again. Model Track guidance graphics were messed up on the 00Z run, however if the center is in fact reforming, I believe the models will have to shift right, and this may place the disturbance further north along the Texas coast, possibly near LA once again.
Good day everyone!
Satellite loop imagery this morning indicates INVEST 92L has an exposed LLC, which is clearly defined near 21.4N…91.3W. The NHC indicates in the 8:00 a.m. EDT Tropical Weather Outlook, that INVEST 92L has a 50% (MEDIUM) chance of becoming a tropical cyclone during the next 48 hours, and a 60% (HIGH) chance over the next 5 days.
In addition to the exposed center of circulation, 92L is sitting in nothing but dry air, which covers the GOMEX. The last available wind shear forecast from the GFS (sites are down again) indicates upper level winds to become more conducive for development, with an upper level anticyclone over the central GOMEX for the next 48-60 hours. This COULD allow for 92L to become better organized, however, unless moisture conditions improve, the NHC may have to lower their expectations. Should by chance development occur, best estimate right now for strength appears to be a depression at best.
Beginning yesterday evening on the 00Z run of the model guidance, track models began shifting left with the track of 92L…this being due to a weaker system than anticipated, along with the western portion of the subtropical ridge nosing westward into the GOMEX, and pushing this more toward the west. As of the 12Z dynamic model guidance, and based on the recent changes in the forecast steering maps, I prefer right now, a track blend of the TVCC / TVCN and TV15 consensus modeling. This may change somewhat, depending on whether or not 92L recovers. Based on these parameters, the “center” could cross the coast anywhere from Brownsville, to Corpus Christi within the next 96-120 hours, which will depend on forward speed. The system is currently quasi-stationary.
Albeit the new guidance swings this westward, it is suggested that a piece of energy at mid levels may be guided NE, in which case rainfall would still affect the areas mentioned yesterday. Flooding is very possible over the areas seen in the total precipitation accumulation map provided.
I will continue to monitor 92L for any changes that may occur over the next 72 hours.
Satellite imagery indicates that Tropical Storm Erin is a bit less organized today, and has been downgraded to a depression as of the 11:00 a.m. EDT advisory from the NHC. As of the 11:00 a.m. EDT advisory from the NHC, the following information was available on Erin:
11:00 AM AST Fri Aug 16
Location: 16.9°N 32.1°W
Moving: WNW at 17 mph
Min pressure: 1008 mb / 29.77 in
Max sustained: 35 mph
Erin continues to move toward the WNW, with no change in strength. Based on forecast steering maps, and 12Z dynamic model guidance, I expect his motion to continue for the next 24-30 hours due to a weakness in the subtropical ridge. Forecast steering indicates the ridge to build back briefly, which should allow her to turn more toward the west, as shown in track guidance, which concurs with the NHC forecast track. Forecast steering layers maps this morning did indicate however, another weakness in the ridge at around 72 hours out in the forecast period, which would allow for a more WNW to NW motion. In fact, looking at the weakness, there is the possibility Erin may re-curve in about 5 days or so. Again, this is always subject to change, being that far into the forecast period…as we have just seen with 92L.
Based on forecast conditions ahead of Erin, I agree with Dr. Beven in his 5:00 a.m. discussion, in that Erin could possibly become an open wave, due to entering a stable, dry environment. Given this, I agree with the NHC forecast intensity.
Elsewhere, I am currently monitoring an area of disturbed weather in the CATL near 45W Longitude, that has taken on some cyclonic rotation over the past few hours. Based on the last update available on the wind shear forecast, upper level winds may remain conducive for development over the next 48-54 hours. Based on that information, I will continue to monitor that disturbance for the next 72 hours, with the premise of further slow organization.
Analysis of satellite loop imagery over western Africa indicates a rather large MCS about to emerge into the EATL just south of the Cape Verde Islands. This, and the next MCS directly behind it will have to be monitored for slow development, as upper level winds may remain conducive for development of both of these areas during the next 96 hours. I have provided satellite loop imagery, as well as a still with the areas circled.
I still expect an increase in activity come the 3rd week of the month, as the MJO forecast in both the OLR forecast anomalies, and the Dynamic Models MJO index forecast indicating a return of the MJO to Octants 8 and 1 over the next 7 days.. However, one thing that has me kind of stumped is, albeit we are in a Neutral ENSO pattern with a cold bias, the shear we have see in the Caribbean, and lack of instability in both the Caribbean and Atlantic basins, puts me more in mind of an El Nino phase. It is noted however, that shear is just now coming into the range of climatology, however instability remains below climatology. I still contribute this to the POSITIVE NAO phase we have been in on and off, and STRONGER Subtropical ridge, which is now showing signs of coming to a weaker average. In fact, there appears to be somewhat of a correlation between the NAO forecast, and THDV graphs albeit slightly lagged.
MJO OLR ANOMALY FORECAST
I will be out of the office tomorrow, but will most likely update on Sunday.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)