ATL: DON - Remnant - Discussion

[vaffie]

This morning's Houston National Weather Service Office Discussion

000
FXUS64 KHGX 270920
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
420 AM CDT WED JUL 27 2011

...MONITORING A TROPICAL DISTURBANCE IN THE NW CARIBBEAN...

.DISCUSSION...
THE REALITY IS THAT THERE WILL BE QUITE A BIT OF MOISTURE AND
ENOUGH OF A WEAKNESS IN THE UPPER LEVEL RIDGE TO AT LEAST SUPPORT
SOME THUNDERSTORM ACTIVITY ACROSS SE TX TODAY AND TOMORROW. POPS
WILL STILL RANGE FROM 20 TO 30 PERCENT EACH DAY AND REMAIN HOT
WITH MAX TEMPS REACHING THE LOW 100S INLAND. HEAT INDEX VALUES
WILL PROBABLY REACH CLOSE TO 107F IN A FEW LOCATIONS.

BUT THE MAIN TOPIC OF DISCUSSION IS THE TROPICAL DISTURBANCE IN
THE NW CARIBBEAN. IR SATELLITE REPRESENTATION LOOKS FAIRLY DECENT
WITH DEEP CONVECTION AROUND WHAT APPEARS TO BE A CENTER OF
CIRCULATION. NHC GIVES THIS A 70 PERCENT CHANCE OF BECOMING A
T.D. BUT THINK THE ODDS ARE THAT THIS SYSTEM IS ON ITS WAY TO
BECOMING A TROPICAL SYSTEM. AIRCRAFT RECON WILL FLY INTO THE
SYSTEM LATER TODAY AND DATA WILL LIKELY DETERMINE THE STATUS OF
THE SYSTEM. THE TRACK FORECAST OF THIS SYSTEM IS OF PARTICULAR
INTEREST BECAUSE QUITE A FEW OF THE TROPICAL MODEL GUIDANCES
BRING THE SYSTEM TO THE UPPER TX COAST. THERE IS STILL SOME
SPREAD AMONG THE GUIDANCE BUT THE NAM/GFS SEEM TO BRING THE
SYSTEM TOWARDS THE TX COAST AS WELL. FUTURE MODEL GUIDANCE SHOULD
HELP WITH THE TRACK FORECAST AS THEY WILL BENEFIT FROM A MORE
DEVELOPED SYSTEM. RIGHT NOW THE FORECAST FOR FRIDAY WILL BE ON
THE CONSERVATIVE SIDE GIVEN UNCERTAINTY SURROUNDING THE
DEVELOPMENT OF THE SYSTEM AND HOW MODEL GUIDANCE HANDLE WEAK
SYSTEMS RATHER POORLY. THAT SAID A MORE NW TRACK MAKES MORE SENSE
AS THE UPPER LEVEL RIDGE SHOULD BE LOCATED OVER THE CAROLINAS BY
THU NIGHT. RIDGES AT 700/850MB WILL ALSO BE LOCATED IN THIS
GENERAL AREA WITH A WEAKNESS OVER THE NW GULF THROUGH TX. GIVEN
THE FLOW AROUND THE RIDGE...THINK THIS SYSTEM FOR NOW WILL TRACK
AROUND THE RIDGE IN THE GENERAL DIRECTION OF THE TX COAST. THE
INTENSITY OF THE SYSTEM WILL BE CLOSELY WATCHED. RIGHT NOW THE
SYSTEM HAS WARM WATERS TO PASS THROUGH IN THE NW CARIB AND S
GULF. SHEAR IS ALSO QUITE WEAK BUT AS NOTED IN UPPER AIR
SOUNDINGS AND ANALYSIS...THERE IS QUITE A BIT OF EASTERLY SHEAR
ACROSS THE NORTHERN HALF OF THE GULF. THE SHEAR IS FORECAST BY
BOTH THE NAM/GFS TO WEAKEN SOME BUT THE MAIN QUESTION WILL BE HOW
MUCH EFFECT THE SHEAR HAS ON THE SYSTEM AND ITS INTENSITY.

WITH ALL THAT SAID...POPS WERE INCREASED TO AROUND 50 PERCENT FOR
FRIDAY BUT COULD CERTAINLY GO HIGHER DEPENDING ON THE TRACK OF THE
SYSTEM. MAX TEMPS WERE DROPPED A COUPLE DEGREES MORE IN LINE WITH
SOME OF THE GUIDANCE BUT SHOULD THE SYSTEM IMPACT SE TX...MAX
TEMPS WILL LIKELY BE IN THE 80S WHICH WOULD BE A WELCOME BREAK
FROM THE HEAT. RAINFALL AMOUNTS ARE CONSERVATIVELY A 0.50 TO 1.00
INCH BUT HEAVY RAINFALL WILL BE A GROWING THREAT DEPENDING ON THE
TRACK. ALSO KEPT POPS AROUND 30 PERCENT OVERNIGHT AND 20 PERCENT
ON SATURDAY FOR ANY LINGERING ACTIVITY AFTER THE SYSTEM MOVES
INLAND.

IF THE TROPICAL DISTURBANCE TAKES A MORE SOUTHERN TRACK AND
RAINFALL MISSES SE TX...DROUGHT CONDITIONS WILL REALLY WORSEN. BY
SAT/SUN THE UPPER LEVEL RIDGE EXPANDS INTO THE PLAINS AND
STRENGTHENS. THE RIDGE WILL REMAIN IN PLACE MON/TUE NEXT WEEK AND
BE STRONG ENOUGH TO INHIBIT THUNDERSTORM ACTIVITY. MAX TEMPS
WILL BE BACK IN THE UPPER 90S/LOW 100S. HEAT INDEX VALUES WILL
NEED TO BE WATCHED FOR POSSIBLE HEAT ADVISORIES. SE TX COULD VERY
WELL HAVE HEAT INDEX VALUES TOPPING OUT NEAR 110F. MIN TEMPS WILL
ALSO BE ON THE WARM SIDE WITH NOT A LOT OF OVERNIGHT COOLING.

39

&&

.AVIATION...
PW VALUES ARE A BIT LOWER TODAY THAN YESTERDAY. NUMERICAL
GUIDANCE IS QUITE BULLISH WITH PRECIP TODAY DESPITE THE LOWER PW
VALUES. WILL MAINTAIN CB`S IN THE TAFS. MAINLY VFR TODAY OUTSIDE
AREAS OF CONVECTION. 43

&&

.MARINE...
WEDNESDAY AND THURSDAY WILL BE RELATIVELY QUIET WITH OFFSHORE
WINDS OVERNIGHT BECOMING ONSHORE DURING THE DAY. A TROPICAL
DISTURBANCE WILL APPROACH THE WESTERN GULF OF MEXICO ON FRIDAY.
THIS FEATURE HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION OR
WEAK TROPICAL STORM. TPC HAS GIVEN THIS FEATURE A 70 PERCENT
CHANCE OF FURTHER DEVELOPMENT. WINDS AND SEAS ON FRIDAY ARE A BIT
SKETCHY AND MUCH IS DEPENDENT ON HOW THE SYSTEM EVOLVES. FOR
NOW...WENT WITH THE ECMWF WHICH HAS SSE WINDS AT 10 TO 15 KTS. 43

&&

.FIRE WEATHER...
RH VALUES DROPPED INTO THE 30`S YESTERDAY. THE LOW RH COUPLED
WITH HIGH TEMPERATURES AT OR ABOVE 100 DEGREES AND SLIGHTLY
STRONGER WINDS WILL SET THE STAGE FOR ELEVATED FIRE WEATHER
CONDITIONS TODAY...ESPECIALLY WEST OF A PALACIOS TO KATY TO
MADISONVILLE LINE. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 102 77 102 77 98 / 10 10 20 10 30
HOUSTON (IAH) 99 78 99 77 94 / 30 20 30 20 50
GALVESTON (GLS) 93 83 93 81 90 / 30 20 20 30 50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

DISCUSSION...39
AVIATION/MARINE...43

[vaffie]

6z Model Guidance

When you look at this map of models, keep in mind the following: the BAMS, BAMM and BAMD are not dynamic, meaning that they do not take into account future weather conditions in predicting paths, so they can be removed from view. The SHIP path is based on the BAM models so it can also be discounted. LBAR and CLP5 are based on history/climatology, so they can also be discounted. That therefore means that no dynamic model is right now predicting Louisiana or Mexico (at this time--of course things can change) and therefore only one (HWRF) is predicting anything south of Padre Island. When you take all of this into account, there is remarkable and surprising consensus (even before the storm has formed) at this point of time for landfall between Corpus Christi and Beaumont, with the highest likelihood being it affecting some part of Galveston Island. Time to wake up, Southeast Texas!


The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Air Force Met]

There have been failed high chance disturbances before; I am not concerned at all.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

We'll agree to disagree. I think we will see at least a TD later today.

BTW...to me it looks like the globals have been tweaked to not spin up tropical lows as quickly...and it looks as if they were tweaked too far the wrong way...so that is probably not a great rule to use this early into the season.

[southerngale]

Hi, vaffie. I just thought I'd point out that while it's not on that map, the Euro shows a Deep South Texas landfall, near Corpus, I believe. Whether it's right or not remains to be seen, but it's a respectable model that should be taken into consideration. The NHC definitely uses it.

[vaffie]

Hi, vaffie. I just thought I'd point out that while it's not on that map, the Euro shows a Deep South Texas landfall, near Corpus, I believe. Whether it's right or not remains to be seen, but it's a respectable model that should be taken into consideration. The NHC definitely uses it.

Excellent point! I typically pay more attention to the Euro than any of the others, except when there is a consensus of 3 biggies-in this case GFS, GFDL, CMC. But these things shift often. By afternoon they may all point to Lake Charles or Padre Island, so one never knows.

[GCANE]

New hot-tower firing up

[cycloneye]

Here is this morning's discussion of 90L by our friend Rob Lightbown of Crown Weather Services:

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org. For Official Information please refer to the NHC and NWS products.


http://www.crownweather.com/?page_id=4557

Invest 90-L Likely To Become A Tropical Depression Or A Tropical Storm By Late Today; Potentially A Threat To The Middle Or Lower Texas Coast As A Upper-End Tropical Storm Or A Hurricane On Friday Night
Rob Lightbown on July 27, 2011, 5:59 am

It is looking more and more likely that a tropical disturbance, Invest 90-L, located over the northwestern Caribbean will be our fourth named storm of the 2011 Hurricane Season. It’s name would be Don. As of this morning, Invest 90-L was located just south of the western tip of Cuba and it continues to organize and strengthen with a low-level circulation potentially developing about 125 miles east of Cancun, Mexico. Reconnaissance aircraft are scheduled to fly out and investigate Invest 90-L this afternoon and I suspect that they will find at the very least a tropical depression and very possibly a tropical storm.

It should be noted that this is a small system in its overall size and this is one of the main reasons none of the global models “see it” and thus continue to insist no development, while real-time observations suggest otherwise. So, I am throwing out all of the global models and going more with the track model guidance like the consenus TVCC and TVCN track models. Also, I fully expect Invest 90-L to be our next named storm and Don has the potential to be a threat to the middle and lower Texas coast by Friday night. Everyone from the Houston/Galveston area southward to Brownsville should closely monitor this system.

Invest 90-L is currently tracking west-northwestward at a forward speed of 15 mph and I fully expect this track to continue. The current synoptic setup over the Gulf of Mexico and northwest Caribbean consists 90L of a weakness in a large ridge of high pressure. This weakness has been caused by a trough of low pressure along the US East Coast and has caused Invest 90-L to slow down in forward speed. This ridge of high pressure is forecast to strengthen by later this week and this should prevent any significant northward turns of this system.

The latest track model guidance has some differences over the next few days. The latest TVCN consensus model forecasts a general west-northwest to northwest track and forecasts landfall near Port Lavaca and Port O’ Connor on Friday night. The latest GFDL model forecasts landfall near Galveston and Houston as a Category 1 hurricane on Friday night. The latest HWRF model forecasts landfall near Corpus Christi as a Category 1 hurricane on Saturday morning.

Given the overall strength of the ridge that is forecast by many of the global models, I think the GFDL model may be too far north and a track more towards the west-northwest seems reasonable. This would take this system, I think, onshore very near Port Aransas on Friday night.

As for strengthening, I think a fairly steady pace of strengthening seems likely from today through Friday. At this point, I think Invest 90L/Don will be an upper end tropical storm or a low end Category 1 hurricane when it makes landfall on Friday night. It should be emphasized that this system will encounter fairly favorable environmental conditions over the next couple of days and it will need to be watched very closely for more rapid intensification.

Everyone along the Texas coast from Galveston/Houston southward to Brownsville should closely monitor the progress of this system. I think given the trends this morning it is likely that we will have a tropical depression or a tropical storm by the end of today.

[NDG]

Based on Cancun radar loop along with a recent west wind reported in Cozumel, 90L's COC appears to be just to the east of the tip of the Yucatan Peninsula. It might have finally the closed circulation we have been waiting for.

[BobHarlem]

Based on Cancun radar loop along with a recent west wind reported in Cozumel, 90L's COC appears to be just to the east of the tip of the Yucatan Peninsula. It might have finally the closed circulation we have been waiting for.

I've been looking at the longer version of that loop at http://flhurricane.com/imageanimator.php?101 and it does appear it's heading for the Yucatan, but I don't spot anything that would say it's a closed circulation.

[NDG]

Based on Cancun radar loop along with a recent west wind reported in Cozumel, 90L's COC appears to be just to the east of the tip of the Yucatan Peninsula. It might have finally the closed circulation we have been waiting for.

I've been looking at the longer version of that loop at http://flhurricane.com/imageanimator.php?101 and it does appear it's heading for the Yucatan.

With a definite WNW track during the night.

[GCANE]

[GCANE]

Well defined mid-level PV anomaly.

Those hot towers will help to get circulation down to the surface.


http://rammb.cira.colostate.edu/product ... 270502.jpg

[Thunder44]

Based on Cancun radar loop along with a recent west wind reported in Cozumel, 90L's COC appears to be just to the east of the tip of the Yucatan Peninsula. It might have finally the closed circulation we have been waiting for.

http://smn.cna.gob.mx/radares/cancun/cancun.php

The west wind was only 5mph. Now it's calm:

http://weather.noaa.gov/weather/current/MMCZ.html

Also buoy 42056 is now reporting SE winds about 15.5kts. That's not a sign of closed circulation.


http://www.ndbc.noaa.gov/station_page.php?station=42056

[AHS2011]

Anyone have an initial prediction of maximum wind speeds of soon-to-be Don?

[tolakram]

5:50 am SE ( 140 deg ) 15.0 kts
5:40 am SE ( 136 deg ) 14.8 kts
5:30 am SE ( 128 deg ) 14.6 kts
5:20 am ESE ( 118 deg ) 9.1 kts
5:10 am SE ( 127 deg ) 5.4 kts
5:00 am SSE ( 148 deg ) 2.9 kts


http://www.ndbc.noaa.gov/station_page.php?station=42056

Steady increase in wind speeds during the hour.

[cycloneye]

80%

The plane is a go departing at 11:30 AM EDT.

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT WED JUL 27 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE NEAR THE
YUCATAN CHANNEL CONTINUES TO BECOME BETTER ORGANIZED...AND RADAR
DATA FROM MEXICO SUGGESTS THAT A CIRCULATION COULD BE FORMING ABOUT
50 MILES NORTHEAST OF CANCUN. IF CURRENT TRENDS CONTINUE...A
TROPICAL DEPRESSION COULD DEVELOP LATER TODAY. INTERESTS IN THE
NORTHEASTERN YUCATAN PENINSULA...AS WELL AS THE CENTRAL AND WESTERN
GULF OF MEXICO...SHOULD MONITOR THE PROGRESS OF THIS SYSTEM AS IT
MOVES WEST-NORTHWESTWARD NEAR 15 MPH. THIS SYSTEM HAS A HIGH
CHANCE...80 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE THIS SYSTEM LATER TODAY.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN

[Weatherfreak000]

There have been failed high chance disturbances before; I am not concerned at all.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

You will be proven wrong shortly. Btw, you have been around here for a while, you should know which battles to pick and when.

When 95% of the members and probably the same percentage of pro mets like 90L.....it's time to throw in the towel bro. lol.

[cycloneye]

Per 8 AM TWO,the plane will go to investigate 90L,so stay tuned to this thread from 11:30 AM EDT when the plane departs.

[Weatherfreak000]

Models still trending towards the TX/LA border. Big questions still about the strength of the ridging and frankly the strength of future Don.

[NDG]

06z GFDL, continues to have problems

WHXX04 KWBC 271142
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER

NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR

TROPICAL DEPRESSION INVEST 90L

INITIAL TIME 6Z JUL 27

DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT
REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD
NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC
OFFICIAL FORECAST.


FORECAST STORM POSITION

HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)

0 21.0 85.3 290./ 8.9
6 21.3 86.3 291./ 9.5

STORM DISSIPATED AT 6 HRS AT THE ABOVE PSN.