Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/29/19

Area Forecast Discussion
National Weather Service Key West FL
947 PM EDT Wed Aug 28 2019 DISCUSSION...In the middle and upper levels(700-200 MB), latest available satellite imagery overlaid with model streamline analysis as of 900 pm, like 24 hours prior, depicts a complex middle and upper level flow pattern over the Southeastern United States including Florida and the Florida Keys, with the axis of a east to west oriented ridge above 500 mb extending in the Central Gulf from along 90W to across to across Central Florida thence northeast to near 30N 75W. East of that feature, a (TUTT) tropical upper tropospheric trough cell is migrating slowly westward and is now located just north of the Dominican Republic near 22N 70W. Of course, southeast of that feature is strengthening Hurricane Dorian, which was located at 8 pm to be at 19.2N 65.7W or about 60 miles NNE of San Juan, Puerto Rico. At the surface and in the middle levels(Surface to 700 mb), latest available marine and land surface observations and analysis as of 900 pm, details decoupled Tropical Depression #6 which at 5 pm was located about 165 miles ESE of Cape Hatteras, NC. This system trails a trough axis south southwestward into the Central Bahamas. As was the case 24 hours ago, there is a near 1015 mb meso- hi pressure center located over the SE Gulf of Mexico. Latest CIRA data suggests deep moisture, typical at this time of year, surrounds the Florida Keys with PWAT at 1.75 to 2.00 inches, but rises to between 2.00 and 2.25 inches upstream of the Keys across all of the Northern and Central Bahamas in association with aforementioned approaching TUTT cell and the low level trough. The evening sounding illustrated PWAT at about 1.80 inches with still gentle to moderate northwest to north flow from off of the surface up to 500 mb, then continuing to be light to gentle all the way to 150 mb. .CURRENTLY...As of 900 pm, skies are partly cloudy across all of the Florida Keys and surrounding waters. Radar still detects isolated to widely scattered showers and isolated storms still exist along boundaries, mainly concentrated attm across the Eastern Florida Straits, but like last night, this was the remnants of clusters of showers and storms that moved off the Mainland from the seabreeze in the moist gentle to moderate northwesterly flow. Temperatures across the islands remain in the upper 80s with sticky dewpoints in the upper 70s. C-man stations along the Florida Reef are still recording NW winds between 10 and 15 knots, but with gusts between 15 and 20 knots. Island sensors are recording NW winds between 10 and 15 mph. .SHORT TERM...Overnight and Thursday, as the trough over the Bahamas continues to slide westward overnight towards the Keys, increasing moisture upstream of the Keys and surrounding waters will work its way westward, with PWAT rising to between 2.00 and 2.25 inches by 12Z. As such, HRRR and the Caribbean HRRR both agree additional showers and storms will redevelop later tonight again along boundaries upstream of both the Upper Florida Keys, as well as over the Extreme Southeastern Gulf of Mexico upstream of both the Middle and Lower Keys. The configuration of the ridge to our southwest and the approaching surface/low level trough will continue to allow for gentle to moderate winds this evening and overnight and early Thursday morning. The confluent flow will drive boundaries, showers and storms across the Keys and all surrounding waters. As such, we are carrying 50% chances for 12 hour pops for scattered showers and storms, above the 35% climo pops for the date. && .MARINE...Gentle to moderate breezes will continue overnight and Thursday morning. Winds and seas will be higher in and near some of these showers and storms. Hurricane Dorian is expected to track northwest overnight through Friday morning. && .AVIATION...Mainly VFR conditions will prevail at the island terminals for the next 24 hours, but there will be periods of shower and thunderstorm activity near each terminal. For example, convection will blossom over the Southeast Gulf after midnight and then move to the southeast toward EYW and MTH during the late night and morning hours. These showers should dissipate by mid-day Thursday, and the overall trend is reflected with VCSH in the TAFs. Then afternoon thunderstorms over the Everglades on Thu afternoon will slide to the southwest toward the Middle and possibly the Lower Keys during the late afternoon and early evening. && .TROPICAL...Now is the time to make sure you have a hurricane plan. Now is the time to have your supplies ready. Do not wait to make a plan and gather supplies when under increased stress. Portions of the Florida Keys are presently inside the forecast cone as of 900 pm. Remain up-to-date with the latest forecast either through or At 800 PM AST (0000 UTC), the eye of Hurricane Dorian was located by an Air Force Reserve Unit Hurricane Hunter aircraft near latitude 19.2 North, longitude 65.7 West. Dorian is moving toward the northwest near 13 mph (20 km/h), and this general motion is expected to continue through Friday. On this track, Dorian should move over the Atlantic well east of the southeastern and central Bahamas on Thursday and Friday. Looking ahead please consider these factors! (from CLR, previous Forecaster Discussion) The expected NW to WNW turn by strengthening Hurricane Dorian will take place Friday evening or Saturday morning east of the Bahamas. This turn is critical. How far west will the surface trough make it into the Gulf of Mexico? How quickly will the subtropical ridge build to the north of Dorian? Dorian`s eventual landfall location along the Florida east coast will depend upon the timing and degree of WNW turn Friday evening/Saturday morning. For now, the official track takes Dorian into north-central Florida. The average error for the day 5 forecast point is nearly 200 miles, and Dorian is not an easy forecast to resolve. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Tropical...Futterman Aviation/Nowcasts/Statements/Warnings....Haner Social Media...SDR Upper Air/Data Collection......DR/NB Visit us on the web at Follow us on Facebook and Twitter at:
Area Forecast Discussion
National Weather Service Phoenix AZ
430 PM MST Wed Aug 28 2019 .UPDATE... Updated Aviation && .SYNOPSIS... Very hot temperatures are expected again today with portions of south-central Arizona once again reaching excessive heat thresholds. Yet another period of excessive heat is expected on Friday and Saturday with most lower desert locations across seeing highs at or above 110 degrees. Storm chances return to the higher terrain of south-central Arizona again this afternoon and evening. Storm chances may expand westward later in the holiday weekend with isolated thunderstorms possibly even reaching southeast California. && .DISCUSSION... Latest streamline analysis indicates the center of the mid-tropospheric anticyclone is centered just east of Yuma, which places much of Arizona in a weak westerly flow. Across northern Sonora, latest satellite imagery reveals a broad area of vorticity, which is associated with cooler temperatures aloft across southeastern Arizona. Morning CAMs indicate convection is expected to be favored in these areas as well as along the Mogollon Rim and higher terrain east of Phoenix late this afternoon. Latest trends in the HRRR, local CAMs and HREF suggest a relatively high likelihood of an outflow boundary propagating northwestward through the Phoenix area this evening. The boundary should be capable of producing 30 mph gusts which will likely generate at least patchy blowing dust across Pinal and Maricopa Counties. Official precipitation chances across the lower deserts remain on the high end of guidance but generally less than 20 percent, mainly owing to a pocket of warm air aloft and weak mid-level lapse rates across central Arizona. Latest ACARS soundings indicate MLCAPE between 500 and 1000 J/kg, along with 100-200 J/kg of CIN. Consequently, it will generally take increasing moisture convergence between the terrain-driven westerly flow and a strong outflow boundary to overcome the inhibition. Nevertheless, a few air mass thunderstorms even within the Phoenix metro area cannot be ruled out, given the excessive heat, seasonably high low-level dewpoints and subsequent instability. The Excessive Heat Warning will expire this evening. With a high temperature most likely reaching at least 110 deg in Phoenix, this will make 28 days at or above 110 deg, moving this year into fourth place all-time. && .PREVIOUS DISCUSSION... Over the next several days, convective activity will generally fall on the low-grade monsoon end of the spectrum. Most of the thunderstorms that develop will focus across the high terrain east of Phoenix or down into southeast Arizona in areas southeast of Casa Grande. Models continue to depict occasional inverted trofs rotating around the high, but the high itself remains rather strong each day and centered across the central portions of the state; this tends to shunt the disturbances/inverted trofs to the south and they track mainly through northwest Mexico or far southern/southeast Arizona. On Thursday, an increase in clouds/humidity from the east plus slight weakening of the high and 850mb temps dropping to around 29C support high temps falling below heat warning thresholds for one day. Guidance has been very consistent lately in calling for the excessive heat to quickly rebound Friday into Saturday. ECMPHX ensemble guidance from the ECMWF actually calls for higher temps in Phoenix Fri/Sat than the currently ongoing heat event. NAEFS percentiles for 850mb temps keeps the 90+ percentile area going across the central deserts again on Friday and Saturday, and 850mb temps climb to near 31C by Saturday afternoon. With the high centered to the west of Phoenix, a drier north/northeast steering flow sets up and 500mb heights again reach or exceed 594dm. Surface dewpoints over the lower deserts are forecast to fall in to the upper 40s to low 50s during the afternoon hours. Everything supports another bout of excessive heat and the Excessive Heat Warning that was issued earlier for much of our lower deserts will continue. This warning includes much of southwest Arizona and far southeast California as well as south-central Arizona and the Phoenix area. Operational as well as ensemble guidance continues to suggest that better chances for monsoon activity will develop Sunday into the early part of next week. The upper high finally shifts further to the north and east and a deeper east to southeast steering flow sets up that is able to import healthy amounts of moisture westward and all the way into the southern California deserts. As such POPs Sunday into Tuesday reflect conditions climbing into the moderate grade with 10-20 percent POPs in the deserts and chance numbers over the high terrain. One of the better chances may be Sunday afternoon and evening as an inverted trof looks to be moving west and around the high, increasing storm chances over the southern part of Arizona. Of course, as clouds and humidity rise (along with potential for actual rain and rain-cooled outflows) high temperatures will finally drop off to near seasonal normal levels. && .AVIATION...Updated at 2330 UTC. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Large forecast uncertainty into this evening is tied to maintenance (or lack there of) of storms and outflows progressing north and west from E/SE AZ. Moderate to high confidence exists that a better defined boundary will progress into the Phoenix metro in the 03Z-05Z time frame causing an abrupt wind shift some where between an easterly and southerly direction. Lower confidence exists regarding wind gust speeds and propagation of dust along this boundary where lofted dust and a brief period of lower slantwise visibilities may be the more common impact. The lowest confidence exists with respect to the potential for TS to be maintained or re-develop over/near terminal sites. Recent HRRR iterations are probably most aggressive though even this output generally only shows decaying storms. Chances of an actual TS within a terminal footprint is probably only 10-20% at best. If storms can form in the metro, resulting wind directions will become extremely variable with stronger gusts potential for multiple wind shifts. EVentually, a general easterly component should settle over terminals beyond midnight as any activity wanes during the overnight. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns through Thursday afternoon under clear skies. Some measure of southerly winds will be maintained with potential for some variability at KIPL through the evening/overnight. Gusty winds at KBLH should decrease during the evening with less gusty character Thursday afternoon. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Saturday through Wednesday: The Monsoon High will migrate north of the area and towards the Four Corners by early next week. This will result in an easterly flow, which will be favorable for increasing relative humidities and at least isolated storms each day, particularly across eastern Arizona. Meanwhile, above normal temperatures are expected Saturday, though a cooling trend is anticipated through the middle of next week. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning until 8 PM MST this evening for AZZ534- 537-538-540>546-548>551-553>556-559-560-562. Excessive Heat Warning from 10 AM Friday to 8 PM MST Saturday for AZZ530>532-534-536>538-540>546-548>551-553>556-559-560- 562. CA...Excessive Heat Warning from 10 AM Friday to 8 PM PDT Saturday for CAZ563-566-567-569-570. && $$ DISCUSSION...Hirsch AVIATION...MO FIRE WEATHER...Hirsch