Tropical Storm Harold

[WxWatcher007]

The area of disturbed weather that we've tracked for a while from a tropical wave has been designated Invest 91L. I did a little deep dive before the designation. Sorry for cross posting so much. 

Gulf Disturbance
I tagged yesterday's disturbance with 60% odds of eventual development when it was moving through the Bahamas and Florida, and now that it has reached the eastern Gulf I am even more bullish given today's satellite appearance. 

To be clear: this one needs some work and there's not a lot of time to do it. That said, the quick convective burst and indications that it's trying to form into a low makes it worth an invest tag to me. 

The environment overall looks favorable. There is very little shear present and that should remain the case as this moves west. 

 

Once again, we obviously know that the SSTs are not an issue, with literally some of the warmest water on Earth in the Gulf and a deep reservoir of OHC. 

Moisture looks solid not great, but given where the vorticity is trying to tighten and the convective bursts we're seeing, I don't think drier continental air is a limiting factor yet. We'll see. 

I think time is the greatest limiting factor here, but kind of like Hanna a few years ago, if this can get a good organizational burst today/tonight that could bode well for another named storm to develop as this enters the western Gulf and the TX/Mexico border early Tuesday. Again, not a lot of time, and nothing can happen until there's a legitimate low, which we do not have yet. 

[Ed, snow and hurricane fan]

GFS keeps Houston completely dry, so I'm less weenied than I would otherwise be for a invest in the Gulf.  But the initial deep steering model looks like what 91L becomes goes for almost a complete ride around the death ridge.

[Normandy]

Sleeper system potentially considering its current organizational trend.  Like the idea of a strong TS landfall out of this 

[WxWatcher007]

Looks like it is sharpening nicely so far today. Dev odds should come up at 2pm. 

[WxWatcher007]

Western Gulf of Mexico (AL91):
Showers and thunderstorms have increased this afternoon in 
association with an area of disturbed weather located in the eastern 
Gulf of Mexico. Additional development of this system is possible as 
it moves westward at about 15 to 20 mph, and a tropical depression 
could form as it approaches the western Gulf of Mexico coastline by 
Tuesday.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 7 days...medium...60 percent.

[Ed, snow and hurricane fan]

I see no modeling that gets 91L above a TS, but my mind wouldn't be blown if it makes it to a 65 knot hurricane.  Vis shows good outflow in all quads but the S.  Not Weenie-casting, if I were it'd be headed for my house with 3 or 6 inches of drought busting rain (if just a Cat 1), or a major S of Port Lavaca with Reed Timmer and Josh Morgerman chasing it.  With at least outer bands raining on my yard.

 

None of that will happen with 91L.

 

[WxWatcher007]

4 minutes ago, Ed, snow and hurricane fan said:

I see no modeling that gets 91L above a TS, but my mind wouldn't be blown if it makes it to a 65 knot hurricane.  Vis shows good outflow in all quads but the S.  Not Weenie-casting, if I were it'd be headed for my house with 3 or 6 inches of drought busting rain (if just a Cat 1), or a major S of Port Lavaca with Reed Timmer and Josh Morgerman chasing it.  With at least outer bands raining on my yard.

 

None of that will happen with 91L.

 

You all need the rain. It has been a brutal summer there. 

[Stx_Thunder]

WPC Excessive Rainfall risk upgraded for Day 3 outlook over Lower TX coast today:

https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php

* WPC currently going 3 - 5 in. (isolated 7 in. totals) in slight risk area if Invest 91L becomes a TC before landfall, in ERO discussion.

[WxWatcher007]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Sun Aug 20 2023

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Active Systems:
The National Hurricane Center is issuing advisories on Tropical 
Depression Six, located several hundred miles east of the northern 
Leeward Islands, on Tropical Storm Emily, located about 1000 miles 
west-northwest of the Cabo Verde Islands, and on newly formed 
Tropical Storm Franklin, located over the eastern Caribbean Sea.

1. Western Gulf of Mexico (AL91):
Showers and thunderstorms have increased this evening, and are 
becoming better organized in association with a trough of low 
pressure located in the eastern Gulf of Mexico. Environmental 
conditions appear favorable for development of this system as it 
moves westward at about 15 to 20 mph across the central Gulf of 
Mexico. A tropical depression or storm is likely to form as it 
approaches the western Gulf of Mexico coastline by Tuesday. 
Interests in the western Gulf of Mexico should monitor the progress 
of this system. Tropical storm watches or warnings may be necessary 
on Monday for portions of the southern Texas and northern Mexico 
coastlines.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 7 days...high...70 percent.

2. Eastern Tropical Atlantic:
A large area of disorganized showers and thunderstorms over the 
far eastern tropical Atlantic is associated with a tropical wave 
located near the Cabo Verde Islands. Environmental conditions appear 
conducive for gradual development of this system, and a tropical 
depression is likely to form later this week while it moves 
west-northwestward across the eastern tropical Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...high...70 percent.

[Floydbuster]

My gut tells me this could be a hurricane. I had a similar vibe from both Erika 2003 and Hanna 2020, and both became Category 1 hurricanes.

[WxWatcher007]

It’s gradually getting its act together, still. I’m thinking PTC at 11am because this is still a little broad. Would need to organize a little faster though imo to have a reasonable shot to maximize potential. First viz will be telling.
 

Western Gulf of Mexico (AL91):
Showers and thunderstorms are showing signs of organization 
in association with a broad area of low pressure located over the 
central Gulf of Mexico.  Environmental conditions appear conducive 
for development of this system, and a tropical depression or 
tropical storm is likely to form before it reaches the western Gulf 
of Mexico coastline on Tuesday. Interests in southern Texas and 
northern Mexico should monitor the progress of this system as 
tropical storm watches or warnings are likely to be issued later 
today.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 7 days...high...80 percent.

[WxWatcher007]

Really want to see what recon finds during the early afternoon, but this looks to be organizing at a solid pace currently. Not sure I see any westerlies yet, but with convection trying to fire near the MLC if this does get a robust LLC it could pick up the organizational pace. 

 

 

[WxWatcher007]

Yep, PTC 9 coming at 11am. Expecting to see watches/warnings up for the coast. 

[hlcater]

Looking closed on visible now

[WxWatcher007]

12z GFS with its strongest run yet. All systems go as soon as this closes off. 

[NorthHillsWx]

I think a 50-60kt landfall is what I’d be expecting at this time based off current trends 

[Windspeed]

I think a 50-60kt landfall is what I’d be expecting at this time based off current trends 

It's got perhaps 30 hrs left before landfall? If it can get a core established, it has a shot at minimal cane. That obviously would require a pretty impressive period of RI. But with the favorable upper environment and SSTs being so high, I'd say chances of RI are decent if that core can get established by this evening. Even if that doesn't occur, it should still be an intensifying TS into landfall.

[olafminesaw]

Smol

[wxmx]

 

Looks like a well defined LLC

[WxWatcher007]

Recon en route. 

[WxWatcher007]

Not a bad look, but again, needs an inner core to overachieve. 

[WxWatcher007]

 

[lantanatx]

As someone sitting about 5 miles inland on Baffin Bay - what do you think this will do? Any new thoughts?

[WxWatcher007]

32 minutes ago, lantanatx said:

As someone sitting about 5 miles inland on Baffin Bay - what do you think this will do? Any new thoughts?

Everything kind of seems on track. It has organized enough to make achieving TS status more likely than not, but we haven’t seen the kind of developing inner core to suggest this significantly overperforms. 

That said, this is when the models suggested a little take off would occur, so I’ll be watching radar and IR to see how quickly things are moving in terms of spiral banding and a tight LLC.  Interestingly, 18z SHIPS increased odds for modest RI. Not seeing any evidence of that right now. 

The fast movement should make this a quick hitter with beneficial rain.

 

[WxWatcher007]

Nice convective bursts happening near the apparent center, but it's hard for me to tell since we're outside of radar range and don't have visible whether this is actually organizing a core. Microwave may be a bit dated so I didn't include. Looking forward to recon later. The convective bursts may be enough to get this named at 35kts. 

[WxWatcher007]

Tropical Depression Nine Discussion Number   3
NWS National Hurricane Center Miami FL       AL092023
1000 PM CDT Mon Aug 21 2023

Satellite imagery indicates that the depression is becoming better
organized.  Deep convection has been increasing near the mid-level
center, with the apparent low-level center displaced on the south
side of the convective mass.  The latest satellite classifications
still support an intensity of 30 kt, and an Air Force Reserve
Hurricane Hunter is scheduled to be in the area overnight for a
more detailed look at the wind field.

The depression is moving fairly quickly to the west-northwest at 16
kt on the south side of a strong mid-level ridge located over the
central United States.   This general motion should continue through
landfall tomorrow by midday.  The guidance has shifted a bit to the
north on this cycle, and the NHC forecast follows the recent 
trends. 

The system should strengthen soonb through landfall over the warm 
Gulf waters, though its time is limited.  It should be noted that
the cyclone moves inland between the 12- and 24-hour points so it is
possible that the system gets a little stronger than the forecast
intensity values below.  No noteworthy changes were required to the
last NHC wind speed forecast.

KEY MESSAGES:

1. Heavy rainfall from Tropical Depression Nine is expected across 
South Texas through early Wednesday, and may produce areas of flash 
and urban flooding. Across portions of northern Coahuila and 
northern Nuevo Leon in Mexico, flash flooding with possible 
landslides in mountainous terrain is expected Tuesday through 
Wednesday.

2. Coastal flooding is possible along the south Texas coast
tonight through Tuesday evening.

3. Tropical storm conditions are expected in the warning area and
are possible in the watch area beginning early Tuesday.


FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 25.7N  93.3W   30 KT  35 MPH
 12H  22/1200Z 26.3N  96.0W   40 KT  45 MPH
 24H  23/0000Z 27.3N  99.5W   30 KT  35 MPH...INLAND
 36H  23/1200Z 29.0N 103.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  24/0000Z...DISSIPATED

$$
Forecaster Blake

[WxWatcher007]

Recon in the air now. If I’m awake I’ll post what they find. Good time to head in. 

[WxWatcher007]

It’s much better convectively organized on satellite, but that west side still looks odd to me. Recon is starting to sample so we’ll see soon. 

[WxWatcher007]

Rain contaminated higher gusts but there are some FL and SFMR obs that look clean enough at minimal TS strength IMO. Still a lot more to sample. 

[WxWatcher007]

LLC is displaced SW of the convective bursts. Lowest extrapolated pressure so far 1004.4mb at ~2,500ft. We’ll see if the first pass is enough for the NHC to upgrade.