KATC StormTeam 3 Weather BLOG

Hurricane Dean brushed the Jamaican coast as a strong category 4 hurricane and now that it is moving away from the island and into very warm Caribbean waters, Cat 5 strength may be very possible over the next 24 hours.  The track still runs WNW into the Yucatan and re-emerging into the Bay of Campeche as a Cat 1 hurricane.  Beyond that, Cat 2 strength is forecast for a second landfall along the northern coast of Mexico.

Fortunately the upper level low that was over the Bahamas Friday, moved west over the Gulf as forecast.  This allowed the big ridge of high pressure over the western Atlantic to run parallel to Dean keeping it on a westward track.  Since the upper level low is still moving west, the ridge will continue to steer Dean west, then WNW into Mexico sometime Wednesday.

Another area of concern is now located a few hundered miles north of the Virgin Islands.   Invest 92 is a tropical wave located a few hundred miles north of the Virgin Islands.  High wind shear is in the area, but that is expected to weaken, possibly giving Invest 92 a chance for development.   Since there isn’t much data going into the models right now, none have a good handle on the system.  Models are running in all directions now, but after a few more runs, and with more data put into the computer, they should come more into agreement by tomorrow or Wednesday.  The more dependable models are steering this toward the Atlantic coast of Northern Florida, Georgia, and the Carolinas right now, but again this is very early in the game, and the confidence in the models is very, very low.

Right now the computer models are beginning to get a little more clustered together as they agree the storm will be south of Louisiana. Southern Texas and Northern Mexico now looks to be the target for Dean’s eye about mid-next week. Many are feeling a bit more relieved since the forecast has shifted but I still think everyone should keep their attention on what’s going on.

The TUTT low or upper low that will be moving ahead of Dean will increase our rain chances Monday and Tuesday as it passes us just offshore. We can expect heavy rain off and on to begin the week with slightly cooler temperatures. After the hurricane makes landfall our weather will dry out quickly by the end of the week and temperatures will heat up.

Here is the last discussion from the Hurricane Center:

…OUTER FRINGES OF HURRICANE DEAN LASHING THE SOUTH COAST OF
HISPANIOLA…

A HURRICANE WARNING REMAINS IN EFFECT FOR THE SOUTH COAST OF THE
DOMINICAN REPUBLIC FROM BARAHONA WESTWARD TO THE HAITI-DOMINICAN
REPUBLIC BORDER…AND FOR THE SOUTHWESTERN PENINSULA OF HAITI FROM
THE HAITI-DOMINICAN REPUBLIC BORDER TO PORT-AU-PRINCE. A HURRICANE
WARNING IS ALSO IN EFFECT FOR JAMAICA. A HURRICANE WARNING MEANS
THAT HURRICANE CONDITIONS ARE EXPECTED WITHIN THE WARNING AREA
WITHIN THE NEXT 24 HOURS.  PREPARATIONS TO PROTECT LIFE AND
PROPERTY SHOULD BE RUSHED TO COMPLETION.

A TROPICAL STORM WARNING IS STILL IN EFFECT ALONG THE SOUTH
COAST OF THE DOMINICAN REPUBLIC FROM CABO ENGANO WESTWARD TO
BARAHONA…AND FOR COAST OF HAITI NORTH OF PORT-AU-PRINCE TO THE
NORTHERN HAITI-DOMINICAN REPUBLIC BORDER.  A TROPICAL STORM WARNING
IS ALSO EFFECT FOR PORTIONS OF CUBA…FROM THE PROVINCE OF CAMAGUEY
EASTWARD TO THE PROVINCE OF GUANTANAMO.  A TROPICAL STORM WARNING
MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED WITHIN THE
WARNING AREA WITHIN THE NEXT 24 HOURS.

A HURRICANE WATCH REMAINS IN EFFECT FOR THE CAYMAN ISLANDS. A
HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN
THE WATCH AREA…GENERALLY WITHIN 36 HOURS.

INTERESTS ELSEWHERE IN THE WESTERN CARIBBEAN…INCLUDING
WESTERN CUBA AND THE YUCATAN PENINSULA…SHOULD CLOSELY MONITOR THE
PROGRESS OF DEAN.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA…PLEASE MONITOR
PRODUCTS ISSUED BY YOUR LOCAL WEATHER OFFICE.

AT 500 PM AST…2100Z…THE EYE OF HURRICANE DEAN WAS LOCATED
NEAR LATITUDE 16.1 NORTH…LONGITUDE 70.2 WEST OR ABOUT 455 MILES…
735 KM…EAST-SOUTHEAST OF KINGSTON JAMAICA AND ABOUT 165 MILES…
270 KM…SOUTH OF SANTO DOMINGO IN THE DOMINICAN REPUBLIC.

DEAN IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH…30 KM/HR…
AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 24
HOURS. ON THIS TRACK…THE CORE OF THE HURRICANE WILL CONTINUE TO
MOVE SOUTH OF HISPANIOLA TODAY AND WILL BE NEAR JAMAICA ON SUNDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 150 MPH…240 KM/HR…WITH
HIGHER GUSTS.  DEAN IS AN EXTREMELY DANGEROUS CATEGORY FOUR
HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE.  SOME FLUCTUATIONS
IN INTENSITY ARE LIKELY DURING THE NEXT 24 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 70 MILES…110 KM…FROM
THE CENTER…AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 230
MILES…370 KM. PUNTA CANA IN THE DOMINICAN REPUBLIC HAS BEEN
EXPERIENCING TROPICAL STORM FORCE WIND GUSTS FOR THE PAST SEVERAL
HOURS.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 930 MB…27.46 INCHES.

STORM TOTAL RAINFALL AMOUNTS OF 5 TO 10 INCHES CAN BE EXPECTED OVER
JAMAICA…WITH MAXIMUM AMOUNTS OF UP TO 20 INCHES POSSIBLE.  AMOUNTS
OF 4 TO 6 INCHES ARE POSSIBLE OVER SOUTHERN HAITI WITH MAXIMUM
TOTALS OF 10 INCHES POSSIBLE. THE REMAINDER OF THE DOMINICAN
REPUBLIC…HAITI AND EASTERN CUBA…COULD RECEIVE 2 TO 4 INCHES OF
RAIN WITH MAXIMUM AMOUNTS UP TO 7 INCHES POSSIBLE.  ADDITIONAL RAIN
ACCUMULATIONS OF 1 TO 2 INCHES ARE POSSIBLE OVER PUERTO RICO…WITH
ISOLATED STORM TOTAL AMOUNTS OF 5 INCHES. THESE RAINS COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUDSLIDES.

COASTAL STORM SURGE FLOODING OF 7 TO 9 FEET ABOVE NORMAL TIDE
LEVELS…ALONG WITH LARGE AND DANGEROUS BATTERING WAVES…IS
POSSIBLE NEAR THE CENTER OF DEAN IN THE HURRICANE WARNING AREA.

REPEATING THE 500 PM AST POSITION…16.1 N…70.2 W.  MOVEMENT
TOWARD…WEST-NORTHWEST NEAR 18 MPH.  MAXIMUM SUSTAINED WINDS…150
MPH.  MINIMUM CENTRAL PRESSURE…930 MB.

Today we have more questions then answers with regard to the future path of Dean.  Hurricane Dean acquired major hurricane status this afternoon with continued strengthening to near Category 5 status possible this weekend.  The NHC forecast track has stayed the course today in spite of the model guidance envelope growing larger at the end of the 5 day forecast period.  I have gotten a lot of emails today with regard to the models and specifically the 12z GFDL which was an “outlier model” right of the envelope (into Louisiana).  Since then the 18z GFDL has shifted back toward the mid-Texas coast.  Please do not get hung up on individual model tracks or runs…that’s why we look at dozens of models and what’s happening in reality!  The model divergence early next week is due to the upper low that is just east of Florida.  This feature will remain the wildcard as it treks westward across the Gulf.  If the upper low moves quickly enough the ridge of high pressure that will follow it would keep Dean moving toward Mexico or the Lower Texas Coast.  But if Dean moves at its continued forward speed we could wind up with an interaction with the upper low that would certainly usher the storm more northward.  The best call today would be for Dean to approach the lower Texas coast in about 5 days…but there is high uncertainty and lower than normal confidence levels for early next week.  We may also have to consider that Dean will be well-developed and possibly a fairly large storm in 3 days, so sometimes “mass in motion tends to stay in motion” which would keep the hurricane on a more westward track.  Do check out the model plotting utility at tropicalatlantic.com.  Models update every 6 hours and will likely change all over the place over the next few days.  Make sure you already have Google Earth downloaded on your computer otherwise it won’t work (I got about a dozen emails from viewers who had problems getting it to work…most didn’t have Google Earth installed). It is a cool utility but remember these are models!!!  Also keep in mind that any storm that’s aimed as far north as the Mid-Texas Coast will present some sort of weather threat to Acadiana so we might expect at least some sort of coastal flooding especially across Cameron Parish by mid-next week.  Have a good weekend and keep it tuned to KATC for updates…

As hurricane Dean moves away from the Lesser Antilles, it has slowed in forward speed but the intensity has increased to 105mph.  This is a solid Category 2 hurricane, and it is forecast to become a Major Hurricane (Cat 3 or Higher) later tonight.  The official word from the NHC brings Dean to near Category 5 status early Monday half way between Jamaica and the Yucatan.  After skimming the tip of the Yucatan the forecast brings it back into the Gulf of Mexico on a West-Northwest journey toward the Texas/Mexico border.  This is a very small shift to the north compared to the earlier tracks from the NHC this morning.  We are still watching an upper level low near the Bahamas that might be the deciding factor in the track of Dean beyond 72 hours.  Remember the 4 day forecast has a margin of error of over 225 miles and the 5 day error margin is over 300 miles.  So from the 5 day plot from the NHC we could see Dean striking on Day 6 anywhere from Tampico, Mexico to Cameron, Louisiana.

Hurricane Dean pounded the Lesser Antilles this morning as a Category 2 hurricane.  Now it is emerging into the Caribbean and is expected to intensify.  Low wind shear, and warm water temps should boost the strength over the next couple of days.  The National Hurricane Center official forecast brings it to near Jamaica Sunday evening and near the Yucatan late Monday night as a strong Category 4 hurricane.  Most of the models have been clustered near the official forecast.  There is one feature that might have an influence on Dean beyond the 72 hour forecast.  An upper level low is spinning near the Bahamas at the time of this post.  It is expected to drift westward over Florida and eventually into the Gulf of Mexico.  This feature may tend to break down a high pressure ridge centered over the southeastern U.S..  If that happens the hurricane would tend to be pulled toward the north, shifting the official track from the Texas/U.S. border toward the upper Texas coast.  More of a “Rita Path”.  If the upper level low continues to move west into Texas, the high pressure ridge would re-build, keeping Dean on a westerly track toward northern Mexico.  Many things can happen over the weekend, including the possibility of an earlier landfall on the island of Hispanola, Cuba or Jamaica.  Once we get to Sunday night we should have a pretty good idea on the heading. 

 For me, I don’t mind seeing the models pointing at Louisiana 5 or 6 days out, because the models will most likely change over time.  It’s when Louisiana is pegged within 48-72 hours in the models…that’s when I get nervous.

 
One extra note on computer models.  Rob obviously knows I’m a big Google Earth geek.  Which is why he shared this link with me.  You can now plot the hurricane models on Google Earth.  Open Google Earth, click on this link Full Model Plots.  Either save or open the file, and when you return to Google Earth, you can click on your Temporary Places icon, and then check the box next to NHC models for Atlantic.  You can toggle on Dean and Erin, early or late model runs, etc.  Play around with it, it’s fun!  Only the models available will be plotted, and when new storms come around, those models will be available too.  Just remember, pay attention to official forecasts, and local officials for the true details on Dean. 

The model runs are tools we use to make forecast decisions, our forecasts are based on many other factors besides the model runs.  Experience counts too, like Rob said, this was his 5th Erin to forecast.  This is my 4th Dean, names recycle every 6 years.  Although I’m not as “OLD” as Rob, (Just Kidding Rob) Erin and Dean are my 248th and 249th named storm to track since my weather career began! 

Plenty of tropical moisture was abound today thanks in part to the remnants of Erin.  Fortunately our tropical moisture was quite disorganized today with a few squally showers making for dramatic skies this afternoon.  Activity will diminish tonight but will probably fire back up for tomorrow.  The main heavy rain threat will continue across much of the Texas Coast back to the Hill Country so unfortunately bad news for the moisture-laden Lone Star State.  Rain chances should decrease Saturday but could go back up as early as Sunday and into early next week as the upper low we have been talking about over the Bahamas drifts westward into the Gulf. 

All eyes, incoming emails and weather-lab phone calls have been focused on Dean today.  As Dave alluded to in the previous post there is ample opportunity for this system to become a major storm and stay intense to the Yucatan Peninsula.  It is still too early to tell where this system will ultimately make landfall but by Sunday we’ll have a good feel on whether the Yucatan will take a direct hit or a glancing blow.  The bottom line is that Dean is expected to moving at a good clip so even if the center would cross a good part of the peninsula it would probably emerge in the southern Gulf only about 30% weaker and in less than 24 hours.  Then there would be some opportunity for re-strengthening prior to a second landfall.  Today the hurricane models were consistently clustered with this system moving through the Caribbean, near or just south of Jamaica, and then approaching the Yucatan Monday.  After this point there is some divergence with possible landfalls mid-week from the northern Mexican Coast through much of the Texas coast with the median somewhere around the lower Texas coast.  This is to be expected more than 5 days out so for now we’ll just watch the forecast trends…a lot of the computer model data is available for all of us to see, just don’t read too much into any one model.  I would expect more solid model data over the next day or two as hurricane hunter data and the NHC’s G-IV fly missions in and around the storm.  This will give us better initialized data for the models and thus, hopefully, more accurate forecasts.          

Tropical Storm Erin lashed the Texas coast this morning as a minimal tropical storm near Corpus Christi.  Heavy rains and gusty winds will continue today.  Flood watches and warning are posted over much of South Texas.  Heavy rains most of the summer have kept the grounds saturated and most additional rain from Erin will cause flooding.  Thankfully it appears that as Erin breaks apart, it should continue to move inland.  A stalled system like Tropical Storm Allison in 2001 proved to be costly, and deadly.

 Dean was upgraded to hurricane status early this morning.  It has continued to intensify and as of this posting it is nearing Category 2 strength.  Most models bring Dean into the Caribbean Sea.  There are two areas where we may see some rapid intensification (Pressure Drops of over 42 millibars in 24 hours).  We usually look for warm waters of 80 degrees or more to sustain a tropical system.  In some cases that layer of warm water is confined to the surface or only a few feet down.  A relatively new observation called the Tropical Cyclone Heat Potential (TCHP) shows how warmer water going deeper below the surface along with other factors may be an early indicator of rapid intensification.  With hurricanes Katrina, Rita, and Wilma there was a “loop current” in the Southern Gulf of Mexico between the Yucatan and Cuba northward toward Louisiana.  All three hurricanes experienced a burst of energy when passing over these areas.   Katrina and Rita barely budged this warm water, and by the time Wilma hit it the intensification was unprecedented.  Eventually Wilma dropped to 882 mb shattering the old record of 888 mb set by Gilbert in 1988.  It also knocked Rita down from 3 to 4, and kicked Katrina out of the top 5.  There are three areas in the Caribbean, (figure 1) one south of Haiti, and another near Jamaica, and still another area between the Yucatan and Cuba that may intensify Dean.  In the Gulf, that “loop current” is back, although not as prominent as it was in 2005. (figure 2). 

 Besides all of this TCHP stuff, the usual “low wind shear”, “higher humidities”, “no Saharan dust”, “No Upper Level Troughs” factors are there, so there really isn’t anything to inhibit the systems development.  The only thing I see that could “kill” it would be if the track went over the Dominican Republic, Haiti or Cuba.  Land, especially with high elevations would weaken the storm rapidly.

                                                                                                                                                                                                                         The official National Hurricane Center track keeps the center over water, intensifying to Category 4 status by Monday morning.  Eventually the track takes it toward the Yucatan, but the 5th day forecast drops the intensity down to Category 1 before a Yucatan landfall.  Considering that is an area where the TCHP was very high, and only a slight increase in upper level winds by day 5, I’m not sure what the NHC sees to drop the intensity that low.  In my opinion the hurricane would sustain itself, if not intensify by that point.

The weather story today was Erin as it heads toward the Texas coast.  Tropical Storm Erin remains fairly disorganized this evening but could strengthen prior to landfall tomorrow along the mid-Texas coast.  Most of the weather with Erin will be confined to Texas from Houston on southwestward but we could see a few squally showers and storms here tomorrow and perhaps again on Friday.  The strong hot ridge of high pressure over the SE US will usher this system to the northwest with very dry air to the northeast making for a difficult local forecast.  Many times I have seen the dry air surrounding a tropical system win out, but if Erin remains disorganized, we will likely some healthy storms especially across the coastal parishes and extreme Southwest Louisiana.  But if Erin increases in intensity overnight it may consolidate the shower activity closer to the center of circulation and draw more stable air into Acadiana so rain chances tomorrow and Friday are indeed a bit of a hedge.  Typical summer weather is expected into the weekend with highs in the low-mid 90s and slight afternoon rain chances. 

Meanwhile Dean should become a hurricane later tonight or tomorrow and is expected to become a major hurricane while trekking through the Caribbean.  Guiding influences will be the sub-tropical ridge north of the storm and an upper low that is currently over the Bahamas.  The ridge should keep Dean moving in a westerly to west-northwesterly direction through the next 5 days bringing the system to the Northwest Caribbean Monday.  The longer range models are now pushing Dean closer to the Yucatan and eventually Mexico and/or south Texas by Wednesday/Thursday of next week.  But as we say…a lot can happen between now and then.  The upper low will be the wildcard over the next few days and we’ll watch its path closely.  This upper low is expected to drift westward from the Bahamas through the Gulf over the weekend perhaps allowing for better rain chances here early next week.  The upper low itself may not have much of a direct steering influence on Dean but could pave the way for the eventual path of least resistance for the storm to follow.  Hopefully the sub-tropical ridge will be strong enough to keep the upper low and Dean south of the region.  But when we are talking about any system skirting around the periphery of a ridge there is always a strong possibility for the system to curve more northward.  Current intensity forecasts bring Dean to Category 4 status with 135mph winds in the NW Caribbean by Monday, and if the storm stays over open water there is no reason to believe that Dean storm can’t be a little stronger 5 days down the road.  This weekend would be a very good time to get your hurricane plan and supplies in place, just in case…if we don’t need them next week, there’s at least eight more weeks of peak hurricane season to follow. 

Tropical storm Erin, formally TD #5 is moving westward in the Gulf of Mexico.  A reconnaissance aircraft has determined that it has now reached tropical storm strength.  Erin should continue to move toward the west bringing heavy rain and gusty winds to coastal Texas south of Galveston.  Impacts for Acadiana should be minimal, and maybe even welcomed!  Extra showers and storms, along with breezy conditions may help to break the current heat wave for the next couple of days. 

 Dean has strengthened as well, now with 60mph winds.  Dean is expected to reach hurricane status before reaching the Windward Islands.  The extended forecast brings Dean into the central part of the Caribbean Sea, possibly reaching Category 3 strength in 5 days!  Extended models bring Dean anywhere from Honduras to the East coast and all points in between including the Gulf Coast.  Stay tuned!

Dean is now a solid Tropical Storm in the Atlantic Ocean moving toward the Caribbean.  Most long range models do bring Dean into the northern Caribbean near Jamaica by the end of the weekend as a Category 3 hurricane.  Beyond that, the Gulf or the East Coast could be on the move. 

Tropical Depression #5 formed late last night in the Gulf.  It is expected to become Tropical Storm Erin either today or tomorrow.  This system should continue to the west into Southern Texas.  Impacts will be minimal for us here in Acadiana.  It may be a bit breezy and there may be a few more storms for Thursday.  These extra storms might keep the temps down a bit.