Mon Jun 11 2018 02:52 PM
Mid June NW Carib - W Gulf Trofiness

SW Atlantic Visible & Lightning June 11, 2018 1845z
Image Credit: Weathernerds.Org

A tropical wave over Venezuela and a surface trof east of Nicaragua interacting with an upper-level trof that is sagging into the SW Atlantic is resulting in an area of disturbed weather today. Additionally, there is a possibility of a monsoonal gyre setting up in this region over the next several days, and NHC has now placed 20% odds of tropical cyclogenesis within 5 days - primarily favoring the NW Caribbean to SW Gulf of Mexico.

The operational GFS has been most bullish forecasting development in the Gulf this week, with the experimental Parallel GFS and individual members less so. However, there has been some genuine buy-in from those, including more recently additional support from several other global models.

This region is climatologically favorable for tropical cyclone formation this time of year, and the way things are setting up, 20% could be conservative.. even if development does not occur within 5 days, chances for tropical cyclone formation in this general area may persist for the remainder of the month.

Steering currents suggest that should a TC develop, it would likely be steered inland from roughly Tampico, Mx to Louisiana (and just to emphasize the point, there isn't much yet to hang a forecasting hat on to help pinpoint any eventual track).

Regardless of development, this pattern often results in blustery tropical downpours from eastern Mexico into Texas. A messy and/or slow moving system could exacerbate associated flooding risks.

The area of disturbed weather in the western Caribbean has become a little better organized this Tuesday morning, June 12, and is now being tracked as an Invest (tag 91L). The title has been updated accordingly. -Ciel

Edit #2 Another trof that came up behind what was earlier tagged 91L (a trof + wave interacting with an upper-level low) has begun to merge a little with the prior features. It is unclear at this time as to whether it will be distinguished with an all-new Invest tag, but because this region in general has been a mess since the start, and overall is what we have been tracking, will merge these features into one thread. The title will be updated with subsequent Invest tags and TC numbers if warranted. - Ciel

Thu Jun 14 2018 08:43 AM
Re: Invest 91L Lounge

Fri Jun 15 2018 03:08 AM
Re: Invest 91L Lounge

"91L" looks like a tricky bugger for official sources.

On one hand, there is an abundance of model support for a sticky area of low pressure to take up residence in the far western to southwestern GOM.. a region favorable for near-land organization.. for the next several days, and maybe longer ... Plus, there is already a preexisting (albeit very weak) trof of low pressure in the general vicinity (91L). On the other hand, model support for TC genesis is subtle and fleeting at best, not to mention, shear remains very high.

And now add to the mix the formation of a Tropical Depression, 04E, just off the coast of western Mexico, and close enough to 91L to impart even more shear over the already embattled trof. But wait, 04E, or a portion of it, may, emphasize may, even get drawn up into the southerly flow in the western GOM and merge with whatever is left of 91L.

Some models, including the ECMWF, hint at development of a tropical low just along the eastern Mexico and/or Texas coast and/or inland over south Texas sometime between late this weekend and late next week. It certainly looks like there will be enough moisture around to facilitate such an evolution.

As of this entry, NHC has removed even the 10% outline for 91L, but the feature and this region remain something to be watched - primarily for the potential of a stubborn trof and/or tropical low to develop and produce days of rains, possibly heavy, from Mexico to the southern U.S.

As of 06/15 0z model runs, the following forecast a marginal TC or a noteworthy Low in the western GOM and/or southern U.S. within the next 7 days:

CMC - 1004 mb TD off the coast of Corpus Christi 12z Sunday 6/17. Moves inland by 0z Monday and runs NW then N through the state. 1008mb low over the Dallas metroplex by 0z Tuesday.

ICON - 1006 mb Low center over roughly Brownsville, TX 03z Tuesday with offshore winds to tropical storm force. Pushes further inland over deep south Tx, where it becomes absorbed in the much larger trof over Mexico, while helping to draw up copious moisture from the Gulf and into the southern U.S. through the end of next week.

ECMWF - 1005mb Low center near Tampico, MX 0z Wednesday that becomes part of a much larger, broad trof over Mexico by next weekend, continuing to help send tropical moisture up into the southern U.S.

HWRF* - 1007mb Low center just south of TX/LA border 21z Sunday. Offshore winds to tropical storm force south of Louisiana.
*NOT a genesis model.

HMON* - 1007mb Low center near Tampico, MX 09z Monday.
*NOT a genesis model.

Given that Texas is currently running below average precipitation-to-date, rains will initially be welcome, and unlikely to result in much flooding. But if moderate to heavy rains persist, as looks very possible, an enhanced flood risk would be expected.

Sat Jun 16 2018 03:27 AM
Re: Mid June NW Carib - W Gulf Trofiness

Some operational 0z June 16 model runs

GFS - No TC. Trof only, crossing W GOM into TX over this weekend

ECMWF - TD along MX coast south of Brownsville, TX by 0z Thursday. Deepens and slides south. Possible Cat 1 by next weekend near Tampico, MX

CMC - Possible TD just offshore of Galveston, TX by 12z this Sunday. Moves inland as a weak Low and near Dallas metro by 12z Monday.

NAVGEM - Possible TD just southeast of Brownsville, TX by 0z Thursday. Deepens and remains in the same general location through the end of model run. 995mb TS on 12z Saturday June 23rd.

ICON - 1009mb Tropical Low over or near Corpus Christi, TX by 15z Monday. Drifts around some and deepens to 1002mb by 09z Wednesday. Exits the state into Oklahoma by Friday.

Fri Jun 22 2018 12:35 AM
S Tx Heavy Rain and Flooding Event: June 18-21, 2018

Between Monday June 18 and Thursday June 21, south to southeast Texas was inundated with round after round of moderate to torrential rainfall associated with the final incarnation of what was originally tracked as "91L."

On more than one occasion this tropical system attempted to develop a well-defined surface circulation while mostly inland, but this was not to be. Nonetheless, the impacts throughout south to southeast Texas were often nearly indistinguishable from that of a slow-moving or stationary TD.

NWS Corpus Christi has a good summary of the event as experienced in their region:
South Texas Heavy Rain and Flooding Event: June 18-21, 2018

Rockport, TX, which was severely to catastrophically damaged during Hurricane Harvey just last year, appears to have picked up some of the most rainfall in this region as of 7AM Thursday, with 16.33 inches officially.

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