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
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00z nam 72 hours out sim. radar reflectivity look at that well defined eye...
PARTY FOUL!!! YOU ARE BANNED! LOL
Does the NHC control the wind speed of the storm? just joking sorry for the sarcasm.
Over DomRep, and of course, Haiti.....
Hope not!
Should begin over the next half hour or so.
PR be prepared
Location: 16.2°N 85.2°W
Max sustained: 60 mph
Moving: W at 9 mph
Min pressure: 994 mb
11:00 PM EDT Fri Aug 19
Location: 16.2°N 85.2°W
Max sustained: 60 mph
Moving: W at 9 mph
Min pressure: 994 mb
I'm going to be rediculous for the moment and take Punta Gorda, FL
00z nam 84 hours out...
Shouldn't there be a comma in there somewhere? :|
just sayin'
LOL
TIA
edit: disregard, I forgot I had you on ignore
------------------------------
AT 1100 PM EDT...0300 UTC...THE CENTER OF TROPICAL STORM HARVEY WAS
LOCATED NEAR LATITUDE 16.2 NORTH...LONGITUDE 85.2 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 LATE TONIGHT OR EARLY SATURDAY
AND MOVE ACROSS THE COAST OF BELIZE SATURDAY AFTERNOON OR SATURDAY
NIGHT.
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT THE MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 60 MPH...95
KM/H...WITH HIGHER GUSTS. ADDITIONAL STRENGTHENING IS EXPECTED AND
HARVEY IS NOW FORECAST TO BECOME A HURRICANE BEFORE REACHING THE
COAST OF BELIZE.
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082011
1100 PM EDT FRI AUG 19 2011
DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT THIS
EVENING INDICATE THAT THE CENTER OF HARVEY WAS LOCATED JUST NORTH
OF THE COAST OF HONDURAS. THIS WAS A LITTLE SOUTH AND EAST OF THE
EARLIER ESTIMATES AND REQUIRED A RELOCATION ON THE 0000 UTC
INTERMEDIATE ADVISORY. THE AIRCRAFT ALSO REPORTED A MAXIMUM 700 MB
FLIGHT-LEVEL WIND OF 53 KT AND BELIEVABLE SFMR WINDS OF 45-50 KT. A
DROPSONDE THAT JUST MISSED THE CENTER MEASURED A MINIMUM PRESSURE
OF 997 MB WITH 32 KT AT THE SURFACE. THIS SUGGESTS THAT THE MINIMUM
PRESSURE IS AROUND 994 MB... A DROP OF ABOUT 11 MB SINCE THIS
MORNING. THESE DATA SUPPORT AN INITIAL INTENSITY OF 50 KT.
ENVIRONMENTAL CONDITIONS ALONG THE FORECAST TRACK ARE CONDUCIVE FOR
ADDITIONAL STRENGTHENING. HARVEY WILL BE TRAVERSING VERY WARM
WATER AND SHEAR IS EXPECTED TO REMAIN LIGHT. THE ONLY INHIBITING
FACTOR IS ITS CLOSE PROXIMITY TO LAND. THE OFFICIAL FORECAST
ASSUMES THAT HARVEY WILL MOVE A LITTLE NORTH OF DUE WEST AND
BE FAR ENOUGH OFFSHORE TO TAKE ADVANTAGE OF THE FAVORABLE
ENVIRONMENT. THE NEW INTENSITY FORECAST IS NEAR THE UPPER END OF
THE GUIDANCE...IN CLOSEST AGREEMENT WITH THE STATISTICAL SHIPS AND
LGEM MODELS. THE NEW FORECAST NOW CALLS FOR HARVEY TO BECOME A
HURRICANE BEFORE REACHING THE COAST OF BELIZE IN ABOUT 24 HOURS.
AFTER LANDFALL...STEADY WEAKENING IS PREDICTED AND HARVEY IS LIKELY
TO BECOME A REMNANT LOW OVER SOUTHERN MEXICO IN 2-3 DAYS.
BASED ON THE AIRCRAFT FIXES THE INITIAL MOTION IS 275/8...A LITTLE
SLOWER THAN PREVIOUSLY ESTIMATED. HARVEY SHOULD CONTINUE MOVING
WESTWARD TO WEST-NORTHWESTWARD TO THE SOUTH OF A LOW- TO MID-LEVEL
RIDGE ALONG THE NORTHERN COAST OF THE GULF OF MEXICO. THE TRACK
MODELS ARE IN FAIRLY GOOD AGREEMENT ON THIS SCENARIO. HOWEVER...
THE 0000 UTC GUIDANCE SHIFTED A LITTLE SOUTHWARD...PRIMARILY DUE TO
THE SOUTHEASTWARD RELOCATION OF THE CENTER. THIS REQUIRED A
SOUTHWARD ADJUSTMENT OF THE NHC TRACK AND THE NEW OFFICIAL FORECAST
REMAINS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
FORECAST POSITIONS AND MAX WINDS
INIT 20/0300Z 16.2N 85.2W 50 KT 60 MPH
12H 20/1200Z 16.4N 86.6W 55 KT 65 MPH
24H 21/0000Z 16.8N 88.5W 65 KT 75 MPH...INLAND
36H 21/1200Z 17.3N 90.7W 40 KT 45 MPH...INLAND
48H 22/0000Z 17.7N 93.0W 25 KT 30 MPH...INLAND
72H 23/0000Z 18.5N 96.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 24/0000Z...DISSIPATED
$$
FORECASTER BROWN/BLAKE
INIT 20/0300Z 16.2N 85.2W 50 KT 60 MPH
12H 20/1200Z 16.4N 86.6W 55 KT 65 MPH
24H 21/0000Z 16.8N 88.5W 65 KT 75 MPH...INLAND
36H 21/1200Z 17.3N 90.7W 40 KT 45 MPH...INLAND
48H 22/0000Z 17.7N 93.0W 25 KT 30 MPH...INLAND
72H 23/0000Z 18.5N 96.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 24/0000Z...DISSIPATED
$$
FORECASTER BROWN/BLAKE
Strengthening in a quick pace. could probably reach 80 MPH before landfall.
99L has moves WSW and the actual track should be adjusted...
Looks like pre-season is about to end...hope NHC has its game face on.
timestamp
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