TD 8 forms; 97L a potential threat to the Caribbean and U.S.
Tropical Depression Eight formed last night near the coast of Honduras, and is headed westwards towards a landfall in Belize on Saturday. TD 8 is a small storm, so will impact a relatively small area of northern Honduras, northern Guatemala, all of Belize, and southern portions of Mexico's Yucatan Peninsula. TD 8 has just enough room between its center and the coast of Honduras to intensify into a moderate strength tropical storm with 50 - 60 mph winds before landfall. It is very unlikely TD8 has the time or room to intensify into a hurricane; NHC gave the storm just a 7% chance of making it to hurricane strength in their 11am EDT wind probability forecast. Should TD8 make it to tropical storm strength, it would be called Harvey.
Figure 1. Morning satellite image of TD 8.
Invest 97L likely to become a tropical storm next week, could threaten the U.S.
A tropical wave near 14°N 48°W, about 800 miles east of the Lesser Antilles Islands, is moving westward near 20 mph. This wave, designated Invest 97L by NHC yesterday, has seen a marked increase in its heavy thunderstorm activity this morning, but dry air to the north and west is slowing development. An impressive amount of large-scale spin is obvious in visible satellite loops, but the storm is at least a day away from forming a well-defined surface circulation. Ocean temperatures are about 28.5°C, about 2°C above the threshold needed to support a tropical storm, and wind shear is low, 5 - 10 knots.
Figure 2. Morning satellite image of the tropical wave 97L.
The computer models have shown an unusual amount of agreement in developing 97L over the past few days, and all the ingredients seem to be in place for a tropical storm to form by Monday or Tuesday as 97L crosses the Northeast Caribbean. The atmosphere is expected to be moister over the Caribbean, wind shear will remain a low 5 - 10 knots, and sea surface temperatures will increase to near 29°C. The main impediment for development will likely be two-fold: too much dry, stable air, and proximity to land.
As seen in Figure 3, there has been an unusual amount of dry, stable air in the Atlantic this year, due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. This stable air has been largely responsible for the fact that none of our seven tropical storms so far this year has made it to hurricane strength, despite the presence of sea surface temperatures that are the 3rd warmest on record across the tropical Atlantic. Tropical Storm Emily in early August encountered problems with dry air when it crossed the Northeast Caribbean, and 97L may have similar difficulties.
Figure 3. Vertical instability of the atmosphere during 2011 in the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Observed vertical instability (blue line) has been much lower than the climatological average from previous years (black line), due to an unusual amount of dry air in the atmosphere, inhibiting tropical storm development this year. Image credit: NOAA/CIRA.
Encounters with land will be another potential major problem for 97L. Most of the computer models take 97L near or over Puerto Rico Sunday night, then very close to or over mountainous Hispaniola Monday night through Tuesday. It is unlikely that 97L will be stronger than a 55 mph tropical storm when it encounters these islands, and passage over the islands could severely disrupt the storm. However, if 97L takes a path just south or north of Hispaniola, the potential exists for the storm to intensify into a hurricane.
There will be moderate wind shear of 10 - 20 knots to the north of the islands early next week, so a path just to the south of the Dominican Republic and Haiti would be more likely to let 97L intensify into a hurricane. A west-northwest motion is likely for 97L through Wednesday, which would bring the storm to the vicinity of Jamaica-Central Cuba-the Central Bahamas on Wednesday. On Wednesday and Thursday, the models agree that a trough of low pressure will dip down over the Eastern U.S., which is likely to turn 97L to the north. The exact timing and strength of this trough varies considerably from model to model, and will be critical in determining where and when 97L will turn to the north. The best model for predicting the timing and strength of such troughs over the past two years has been the ECMWF (European Center model), and this model currently brings 97L into the Florida Keys on Thursday night next week. You can view ECMWF forecasts on our wundermap with the model layer turned on. The European Center does not permit public display of tropical storm positions from their hurricane tracking module of their model, so we are unable to put ECMWF forecasts on our computer model forecast page that plots positions from the other major models.
Remember that a 7-day forecast by even our best model will be off by an average of over 700 miles, so it is too early to tell what part of the U.S. might be most at risk from a strike by 97L. This weekend would be a good time to go over your hurricane preparedness.
Figure 4. Morning satellite image of Invest 98L off the coast of Africa.
Invest 98L near the coast of Africa
A tropical wave near the coast of Africa, a few hundred miles southeast of the Cape Verde Islands, is moving west to west-northwestward at 10 - 15 mph. This wave, designated Invest 98L by NHC yesterday, is large and well-organized, with a modest amount of spin and heavy thunderstorm activity. 98L will bring strong, gusty winds and heavy rains to the Cape Verde Islands today and Saturday as the storm skirts to the south. So far this morning, top sustained winds measured in the islands were 24 mph at Mindelo. Water temperatures are warm, near 27 - 28°C, and wind shear is low, 5 - 10 knots, so 98L should continue to organize today. NHC gave the storm a 50% chance of developing into a tropical depression in their 8am advisory. Once 98L passes to the west of the Cape Verde Islands, it has a long stretch of ocean to cross before it could affect any other land areas. Approximately 70 - 80% of all tropical cyclones that pass this close to the Cape Verde Islands end up curving out to sea and not affecting any other land areas, according to Dr. Bob Hart's excellent historical probability of landfall charts. The latest set of long-range model runs go along with this idea, but it is too early to be confident of this.
Jeff Masters
Reader Comments
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As I have said all day it really does depend on where the surface low forms. After we actually know where it is we will have a better idea, but if it were to develop right where the new convection is popping now, I would favor southeast Florida, likely after playing around with Hispaniola.
Looks like Cuba's in for it too.
San Antonio NWS office I believe.
This position is north of where the GFS was showing it on the last run, correct?
Dr Steve Lyons.
Link
Let me tell you.... that video was downloaded.... and filed...
Anybody post the TWO yet? 97L @ 70%. Looks like they expect a TD tomorrow sometime...
Goodnight.
But they are the experts, they know what they are doing.
I posted two maps however, i am assuming your talking about the initial point, it's pretty darn close.
Yeah me, someone else did on the previous page...
Though i think it shouldn't form until late tomorrow, or Early sunday or so....
He's a real expert specially with Hurricane forecasting...
Yes, very thank you.
No problem ;-)
I will.
000
WTNT33 KNHC 200546
TCPAT3
BULLETIN
TROPICAL STORM HARVEY INTERMEDIATE ADVISORY NUMBER 5A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082011
100 AM CDT SAT AUG 20 2011
...CENTER OF HARVEY APPROACHING THE BAY ISLANDS OF HONDURAS...
SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...16.3N 85.6W
ABOUT 60 MI...95 KM E OF ISLA ROATAN HONDURAS
ABOUT 200 MI...320 KM ESE OF BELIZE CITY
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.35 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...
NONE.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE BAY ISLANDS OF HONDURAS
* THE COAST OF HONDURAS FROM PUNTA PATUCA WESTWARD
* THE COAST OF BELIZE
* THE SOUTHEASTERN COAST OF THE YUCATAN PENINSULA FROM PUNTA GRUESA
SOUTHWARD TO CHETUMAL
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE COAST OF GUATEMALA
HURRICANE CONDITIONS ARE EXPECTED ALONG A PORTION OF THE COAST OF
BELIZE.
A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN
THE NEXT 24 HOURS.
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN THE NEXT 24
HOURS.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.
DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM CDT...0600 UTC...THE CENTER OF TROPICAL STORM HARVEY WAS
LOCATED NEAR LATITUDE 16.3 NORTH...LONGITUDE 85.6 WEST. HARVEY IS
MOVING TOWARD THE WEST NEAR 9 MPH...15 KM/H. A GENERAL WESTWARD TO
WEST-NORTHWESTWARD MOTION IS EXPECTED DURING THE NEXT COUPLE OF
DAYS. ON THE FORECAST TRACK...THE CENTER OF HARVEY WILL PASS NEAR
OR OVER THE BAY ISLANDS OF HONDURAS THIS MORNING AND MOVE ACROSS THE
COAST OF BELIZE THIS AFTERNOON OR TONIGHT.
MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS EXPECTED...AND HARVEY IS FORECAST TO
BECOME A HURRICANE BEFORE REACHING THE COAST OF BELIZE.
TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 40 MILES...65 KM
FROM THE CENTER.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB...29.35 INCHES.
HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL-STORM-FORCE WINDS ARE EXPECTED OVER THE BAY ISLANDS
AND ALONG THE NORTHERN COAST OF HONDURAS THIS MORNING...AND OVER THE
COAST OF BELIZE AND THE SOUTHEASTERN YUCATAN PENINSULA OF MEXICO BY
THIS AFTERNOON. HURRICANE-FORCE WINDS ARE EXPECTED ALONG A PORTION
OF THE COAST OF BELIZE BEGINNING THIS AFTERNOON OR TONIGHT.
TROPICAL-STORM-FORCE WINDS ARE POSSIBLE ALONG THE NORTHEASTERN
COAST OF GUATEMALA LATER TODAY.
RAINFALL...HARVEY IS EXPECTED TO PRODUCE TOTAL RAINFALL
ACCUMULATIONS OF 3 TO 6 INCHES ACROSS HONDURAS...GUATEMALA...
BELIZE...AND THE YUCATAN PENINSULA OF MEXICO...WITH POSSIBLE
ISOLATED MAXIMUM AMOUNTS OF 10 INCHES. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUDSLIDES...ESPECIALLY OVER
HIGHER TERRAIN.
STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 2
TO 4 FEET ABOVE NORMAL TIDE LEVELS ALONG THE COAST NEAR AND TO THE
NORTH OF WHERE HARVEY MAKES LANDFALL. NEAR THE COAST...THE SURGE
WILL BE ACCOMPANIED BY LARGE AND DAMAGING WAVES.
NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...400 AM CDT.
$$
FORECASTER BERG/STEWART
It also looks like it's not following the model predictions in terms of forward direction.
That's not completely unexpected?
Yeah man...I couldn't crash without listening to Repent Walpurgis...
It will be ok Gro. Maybe I'll be neighborly and invite you up for a glass of water in the down time. I live on a hospital grid thank god.
99L is attatched to 98L basically, and with them being interconnected they're killing each other off...
If you're talking about 97L then, Yes that is very true...
in puerto rico it was named San Felipe
Huracán San Felipe –Cruzó la isla de sureste a noroeste el 13 de septiembre de 1928. Con vientos sobre 160 mph y de categoría 5 ocasionó 300 muertes.
Hurricane San Felipe crossed the island (puerto rico) from southeast to northwest 13th september (1 day before my bday! but like 80 years before lol) 1928. Winds over 160mph and 300 deaths.
You need an iPhone; you can keep posting until the cell towers fail...and of course we would miss you
Really miss those days of good music...
a lil bit of drama there ;)
Link
Looks to me like they have a program in play; they looked at the model consistency and worked out when they were going to bump and to what, well in advance. It seems pretty logical to me, if you were actually looking at the most valid parts of those runs and not just the exciting finales...
Another week worth of runs...No need to get worried or concerned about 97L just yet. The current set of models 00z dont really look good for any circulation in terms of it being severly disrupted.
I'll be out of power too though. I lost it during Bonnie, so imagine if the GFS were to verify lol.
I heard my GrandFather tell stories about how the winds would suck up the grass from the ground...
Rompio el anenometro a 160mph.... Se cree que llego a 175 mph...
Even if it makes final landfall somewhere else, FL is going to get this. IMO.
I have a 15kw automatic Briggs & Stratton generator. It really came in handy. The best investment I ever made, besides Microsoft. It truly was a life saver. We were 3 weeks without power after Wilma. I was able to give ice and water and food to the whole neighborhood. We kept an elderly neighbor with us because we had portable air-condtioners. Everyone charged their cell phones. It was nice in a way because we all got to know each other. I had never met my next door neighbors of ten years.
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