Two African waves, 92L and 93L, worth watching
An African wave is near 13°N 35°W, about 700 miles west-southwest of the Cape Verde Islands. This system, (Invest 92L), is moving west to west-northwest at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands early next week. Recent visible satellite loops show that 92L has less heavy thunderstorm activity near where it is trying to develop its circulation center than yesterday. Water vapor satellite loops that a large area of dry air lies just to the west of 92L, but the atmosphere in the immediate vicinity of 92L is moist. Even so, the decline of heavy thunderstorm activity since yesterday implies that dry air is probably working its way into 92L. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 15 knots affecting 92L. Sea surface temperatures are 26.5° - 27°C, which is very close to the 26.5°C threshold usually needed to support a tropical storm.
Figure 1. Morning satellite photo of Invest 92L and Invest 93L.
Forecast for 92L
Low to moderate wind shear of 5 - 15 knots is predicted along 92L's path over the coming three days, which should allow the storm to organize, assuming it can shut out any incursions of dry air that might intrude. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show weak development or no development of 92L, and NHC gave 92L a 30% chance of developing into a tropical depression by Saturday morning in their 8am outlook. A steady west to west-northwest motion for 92L is predicted by all of the models, which would put the storm in the vicinity of the northern Lesser Antilles Islands by Sunday. On Saturday and Sunday, 92L is expected to enter a region where an upper-level low pressure system will bring high wind shear of 20 knots to the storm, which should slow development. This upper-level low is also expected to turn 92L more to the northwest, so the storm is likely to pass north of the Lesser Antilles, though may pass close enough to give heavy rains to the northernmost islands. It is too early to know if 92L will recurve out to sea and potentially threaten Bermuda, or continue to the northwest towards the U.S. East Coast.
93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.
Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.
Jeff Masters
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Locally the strong heat ridge remains in place with yesterday being the tenth straight day at or above 100%u2026we will do it again today and likely again Friday. The streak to break the 1980 record is 14 and to tie it would be on Sunday. It would appear that the ridge may weaken just enough over the weekend to drop 1-3 degrees off the high temperature which would support 98-101 across the region, so it is in question if the current 100 degree streak will be broken or tied.
Heat:
Below is some comparison data to the summer of 1980 (hottest summer ever for TX) and 2011 for the number of days at or above 100:
College Station: 43 (1980), 38 (2011)
Huntsville: 43 (1980), 45 (2011)
Conroe: 22 (1980), 27 (2011)
BUSH IAH: 32 (1980), 21 (2011)
Hobby: 8 (1980), 6 (2011)
Dallas: 69 (1980), 47 (2011)
Waco: 63 (1980), 59 (2011)
Austin Mabry: 32 (1980), 57 (2011), record year is 69 in 1925
Del Rio: 56 (1980), 63 (2011), record year is 78 in 1953
San Antonio: 31 (1980), 33 (2011), record year is 59 in 2009
Number of consecutive days at or above 100 degrees:
Dallas: 42 (1980), 40 (2011)
Waco: 42 (1980), 42 (2011) *Today will break this record*
BUSH IAH: 14 (1980), 10 (2011)
So far for August of 2011, most of the climate sites in SE TX are on their way to breaking their hottest monthly temperature FOR ANY MONTH by 2-3 degrees!
Drought:
Things are bad and getting worse by the day with respect to water supply, vegetation, and agricultural impacts. The impacts to agriculture and livestock are approaching severe levels with cattle running out of drinking water from drying creeks and ponds. Vegetation has stopped growing and died in many ranch areas with feed being trucked into from the central plains for cattle. We are really getting into a bad situation quickly and we desperately need widespread rainfall. The majority of irrigation currently is just to keep vegetation alive at this point and with increasing water conservation measures likely vegetation already stressed is going to suffer even more.
Houston has now gone 198 days between 1.0 inch rainfall events breaking the previous record of 192 days from 1917-1918
Only 6.36 inches of rain has fallen in the last 191 days for the City of Houston (IAH) making this by far the driest Feb-Aug 10 period ever. This breaks the previous record by an astounding 6.25 inches of rainfall%u2026that is an amazing record!!! At Hobby Airport for the same time period the record is being broken by 5.17 inches!
The period from August 2010 to August 2011 is now the driest 1-year period ever for the City of Houston.
Water Supply:
For the first time since the drought of 1988 the City of Houston is going to be requesting emergency releases from Lake Conroe to help stabilize the rapid fall that is occurring on Lake Houston (the primary water supply for the City of Houston). This is only the third time ever this action has been required. Water intake pipes on Lake Houston are getting dangerously low to becoming exposed and causing damage to the water supply system. With this action likely next week, the City of Houston will move to Stage 2 water conservation (mandatory water restrictions). This is going to have a significant impact on the lake levels at Conroe as releases begin, and the lake will begin to fall due to the releases that are going to be required to help stop the rapid decline on Lake Houston.
Lake Somerville and Lake Texana are now close to 50% of their capacity and falling. Lake Somerville has lost an astounding 11% of its capacity in the last 3 weeks!
Outlook:
I have really no good news, as any rains over the next 48 hours will likely be focused west of SE TX. 14 day outlook continues to feature below normal rainfall unless something can develop and threaten from the tropics.
NOAA issued a La Nina Watch this week suggesting that the return of cooling in the central Pacific may once again result in La Nina conditions this fall-winter-spring%u2026.if this happens rainfall will average below normal through much of this winter and this drought will only worsen if we do not get some kind of tropical system in the next 2 months.
The tropics are starting to get interesting. The next 60 days or so could be crazy, especially with the approach of the upward motion of the MJO.
Invest92
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
12z Early Cycle NHC model tracks
Invest93
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
Enhanced Infrared (IR) Imagery (4 km Mercator)
Invest 92L and Invest 93L to watch 8/11/11
Blog update:
Tropical Tidbit for Thursday, August 11th, with Video
Not much hope in my view of any cv wave threatening the US over the next 1-2 weeks- the ridge in the Rockies and the eastern trough show no signs of shifting in the near future on the ensembles or op models. Unless it stays fairly weak its up and out.
Also I was doing a mail out for UNICEF at work tonight. It's about the crisis in the Horn of Africa that you did a blog about a few weeks ago. It anyone would like a copy. WUmail me and I'll get you a pdf copy of it.
Cheers AussieStorm
That little patch east of Galveston Bay is in the D2-D3 range due to heavy rains that fell in July. It it already shrinking rapidly and being replaced with D3/D4 drought conditions.
Meanwhile, the town I live in west of Houston has officially recorded no rain, not even a trace, in the last two months.
Morning Mate, How the weather in Alaska today?
Yea on the SW side of Galveston Bay were right back in it and getting worse by the day. Thank God for the rain we got or we would be in your situation
If it pans out then this disturbance could become our 3rd possible TD/TS to develop.
Too cold lol. It's amazing how experiencing 85 degrees for the first time will spoil a person's tolerance of the cold that comes with autumn. I'll get back into it, but 40 degrees is chilly for me right now.
Agreed!!
52.2°F here right now. getting down to 46°F overnight.
EURO has a huge 500mb trough off east coast next 10 days. Hard to see a US impact from anything out of the deep tropics.
You guys are moving upward in temperature for early spring now, right? Or not because August is technically the equivalent of our February?
August is our last month of winter, once we hit September temps start the very much welcome upward trend.
An example: "'The Island,' a resort on Lake Travis, is normally a peninsula surrounded almost completely by water. The level of the Lake has dropped, and now it now sits on dry land, as do the neighboring boat docks."
that leaves me speechless.
No, 92L came off Africa a few days ago.
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