Saturday, September 18, 2010
The upper level steering flow thus far in the season has thankfully kept such storms as hurricane Alex, tropical storm Hermine, and Hurricane Karl, south of the border, all making landfall in northern Mexico. However, long range computer models have been hinting that things might really start to ramp up across the western Caribbean sea later in the week...an area that has seen very little tropical activity so far and is therefore a prime region for rapid development should a system develop locally or move into that area.
An indice that hurricane forecasters monitor closely throughout the season is called the MJO or Madden-Julian Oscillation. It tracks the 30-60 day fluctuation of rising and sinking air, most notable across the Indian and Western Pacific oceans. The two scientists found that there was a pulse of increased thunderstorm development and tropical cyclone development that begins in the Indian Ocean and then moves east across Indonesia, into the western Pacific, central Pacific, and then into the eastern Pacific ocean. What was also found out is that about 8-10 days after the MJO reaches the eastern Pacific, there was a significant increase in tropical development across the Gulf of Mexico and Caribbean sea.
The latest projections indicate that we will be seeing a MJO pulse moving into the eastern Pacific which will likely be a positive factor, helping to increase the potential for development across the western Caribbean over the next week or so. This pattern looks to be getting picked up by the global models as well as they are now forecasting the development of a tropical system in the western Caribbean sea late next weekend and early next week (9/26 through 9/28) depending on which model you are looking at. Right now, since it is so far out in the future, it would be pointless to try and determine where such a system might go but the consistency among the models is a good indication that we will likely see activity start to ramp up as we head into the latter part of September and first week of October.
12z GFS Model
Monday, August 16, 2010
Conditions will remain favorable for at least scattered afternoon and evening shower and thunderstorm activity as we see deep moisture remain in place...being pulled around the western side of the remnant low from TD 5.
The remnants of TD 5 are showing much less organization this evening with the low level center becoming completely exposed to the northeast of the convection. The latest surface maps also shows the pressure gradient at the surface might be weakening, as seen with some westerly winds being noted north of the center (opposed to easterly winds which would be expected from a stronger closed low). It might try and re-form a center under some of the convection seen south of the Mississippi coast over the next 12-20 hours or so, however it is quickly running out of time to do much as it continues off to the west. With the system having not strengthened much today, am still not expecting very much in the way of an impact to our local weather other then to keep moisture levels high, and bring the occasional disturbance across the area helping develop local showers and thunderstorms.
Satellite and surface obs showing the weakening pressure gradient (The circled winds were being influenced by the system earlier today...not any more):
18z Model Guidance on remnant's of TD 5:
Latest surface analysis this morning indicates a very weak frontal boundary (more like a wind shift line) is currently located across north
Morning and model soundings show that the atmosphere across the region is extremely moist and unstable with precip water values in the 2.2 - 2.3'' range, a K-index around 40 (numbers above 30 would tend to indicate scattered to numerous convection), and convective temps in the lower 90s. The only fly in the ointment for some cooling rain would be some capping indicated in the GFS model soundings for this afternoon. The isolated showers that developed earlier this morning across
Of greater interest is the remnant low from TD 5 which is now out over open water south of the
Surface map showing gulf Low, Satellite imagery, and 12z Model Tracks
Sunday, August 15, 2010
Wind direction will be the main challenge....if the weak front can make it as far south as the Houston area, we will likely see more northeasterly and potentially easterly winds; however, as we will be on the western side of the low forecast to slowly develop over the northern Gulf, our winds may turn more north-northwesterly, to possibly westerly depending on the future track and strength of the low. A stronger low and more westerly track would give us a much more northwesterly wind flow....a weaker low and a further easterly track might not have much influence on our local winds at all, keeping them more northeast should the front make it down here.
The 12z models have some timing differences but do generally agree in bringing northerly winds, changing to northeast then east-southeast through the day Monday across the Houston area. The NAM shows southwesterly winds during the morning turning north-northwesterly towards noon then back around to the southeast by the late afternoon and evening. The GFS keeps weak northwesterly winds across the region during the morning turning northeast to east by the afternoon. Therefore it looks like the best window for easterly winds will be 18-00z Monday. Otherwise we will likely see northerly winds during the day which could bring down pollution from the Dallas area. All in all, it looks like an interest few days.
12z Forecasting Sounding for Hobby Airport showing how winds change during the day.
Tuesday, July 6, 2010
The small area of low pressure that moved inland in south-central LA yesterday is now located to the northeast of the Lake Charles area and is starting to take on more semi-tropical characteristics. As this low moves west, very deep tropical moisture, marked by precip water values in the 2.4-2.6'' range will spread into southeast Texas from east to west this afternoon and evening. Current thinking is that we will see scattered shower and thunderstorm activity on the west side of the low this afternoon before things transition over to more of a nocturne core rain event overnight tonight. Right now, it looks as if areas east of I-45 will have the greatest likelihood of seeing these core rains. Tomorrow, the surface low will be off to the northwest of the region allowing for a deep moisture tap to setup across the area. Expect widespread showers and thunderstorms to develop with heavy rain. With the moist ground conditions, the flooding threat will be high, especially in areas of poor drainage.
Invest 96L currently impacting the Yucatan peninsula and is forecast to move off into the southern Gulf of Mexico over the next 24 hours. At this time the system is not showing any signs of significant organization in the shower and thunderstorm activity and therefore the NHC has given the system about a 30 percent chance of development. The latest models have backed down on trying to develop a well defined low with the system, although upper level winds will be favorable for the development so this will need to be watched closely over the next few days. Will be watching for several scenarios to possibly play out as far as the rainfall threat is concerned. Models indicate that the tropical wave, or possible surface reflection should reach the middle-Texas coast Thursday with a significant amount of moisture advection on the northeast side of the system. Therefore, they really hammer the middle to upper Texas coast and southeast Texas with a significant amount rain late Wednesday and Thursday. If the system manages to close off into a low, then the heaviest rains could be focused closer to where the center crosses the coastline...which would be more toward the middle-lower Texas coast. Needless to say, there is still a good bit of uncertainty as to how this system will impact the region; therefore it will be important to monitor the latest forecasts over the next few days concerning the development of the system.
Look for additional updates throughout the week concerning the tropical and heavy rainfall threats to the region.
Friday, July 2, 2010
Storm Total Precip through 6:30am
Wednesday, June 30, 2010
Alex continues to have a very organized appearance on the latest high res visible sat imagery with a very well defined but small eye emerging as he nears the coast. Surface pressure has dropped once again and is currently at 959mb so it looks like Alex is really trying to complete the eye-wall replacement cycle which began late this morning. Latest radar data shows that the cyclone is once again developing a well defined inner eye which could mean that it is just about finished with the replacement cycle and a further increase in surface wind speeds are possible before landfall. Alex remains a very large storm with tropical storm force winds extending out up to 200 miles from the center. It looks like however, that the sustained hurricane force winds should remain south of the Brownsville area.
Local radars continue to show showers moving inland from the gulf as deep tropical moisture remains in place across the area. Rain chances will remain high through the weekend and even deeper moisture arrives later tonight. Locally heavy rainfall will remain the main threat; however there could be a very isolated tornado in any of the heavier convective bands that might develop and push onshore. Widespread 1-2 inches of rain with isolated 2-4 inches seem like a good bet through Friday evening.
KBRO Storm Total Precip